(19)
(11)EP 1 843 167 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
15.11.2017 Bulletin 2017/46

(21)Application number: 07075508.7

(22)Date of filing:  03.10.2003
(51)Int. Cl.: 
G01S 19/37  (2010.01)
H04B 1/707  (2011.01)

(54)

Spread spectrum signal processing

Verarbeitung eines Spreizspektrumsignals

Traitement de signaux à étalement de spectre


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PT RO SE SI SK TR

(30)Priority: 15.10.2002 SE 0203047

(43)Date of publication of application:
10.10.2007 Bulletin 2007/41

(62)Application number of the earlier application in accordance with Art. 76 EPC:
03748840.0 / 1554599

(73)Proprietor: Qualcomm Technologies International, Ltd.
Cambridge, Cambridgeshire CB4 OWZ (GB)

(72)Inventors:
  • Normark, Per-Ludvig
    832 54 Frösön (SE)
  • Stählberg, Christian
    747 93 Alunda (SE)

(74)Representative: Slingsby Partners LLP 
1 Kingsway
London WC2B 6AN
London WC2B 6AN (GB)


(56)References cited: : 
WO-A-01/77705
US-A- 5 897 605
US-A- 5 808 582
US-A1- 2002 027 949
  
  • BRAASCH M S ET AL: "GPS receiver architectures and measurements" PROCEEDINGS OF THE IEEE, IEEE. NEW YORK, US, vol. 87, no. 1, 1 January 1999 (1999-01-01), pages 48-64, XP002362516 ISSN: 0018-9219
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

THE BACKGROUND OF THE INVENTION AND PRIOR ART



[0001] The present invention relates generally to processing of spread spectrum signals by means of vector based algorithms. More particularly the invention relates to a method of receiving spread spectrum signals according to the preamble of claim 1 and a signal receiver according to the preamble of claim 28. The invention also relates to a computer program according to claim 26 and a computer readable medium according to claim 27.

[0002] Spread spectrum technology is becoming increasingly important in many areas, of which cellular communication systems and global navigation satellite systems (GNSS) represent two important examples. Moreover, the large variety of transmission standards creates a demand for hybrid- or general-purpose receivers. For instance, both the cellular standards cdma2000 and WCDMA involve transmission of spread spectrum signals. However, due to differences in the air interfaces one and the same terminal cannot be used in the two systems. Instead, a dedicated terminal must be employed in each system. Alternatively, a dual mode terminal must be designed, which includes two separate transceiver chains. Correspondingly, a navigation receiver adapted for one GNSS, say the Global Positioning System (GPS; U.S. Government), is not able to receive signals from a satellite that belongs to a different GNSS, such as the Galileo system (the European programme for global navigation services) or the Global Orbiting Navigation Satellite System (GLONASS; Russian Federation Ministry of Defense).

[0003] In order to make this possible, a multi-mode receiver must be designed. However, including multiple receiver chains in a single device is not only expensive, it also renders the unit bulky and heavy, particularly if more than two signal formats are to be processed. Therefore, a programmable software receiver solution is desired whose signal processing principles may be altered according to which signals that shall be received and processed.

[0004] Various software solutions are already known for processing GNSS signals. The patent document WO02/50561 is one example in which a GPS receiver tracking system for guiding missiles is described. The receiving station here includes one or more processing stages for receiving and processing GPS data. A control signal controls whether a quantity of processing stages should be increased or decreased in response to the result of a correlation operation. The tracking and recovery of timing information is entirely performed in software. However, the processing involves real-time calculation of relatively complex Fourier transforms, and therefore requires considerable processing resources. Thus, a receiver of this type is not particularly suitable for small sized units, such cellular phones or portable GNSS-receivers.

[0005] The article "TUPM 12.4: Software Solution of GPS Baseband Processing", ULSI Laboratory, Mitsubishi Electric Corporation, IEEE, 1998 by Asai T., et al. outlines the principles for a software GPS receiver using an embedded microprocessor, which enables signals from up to eight satellites to be demodulated at around 40 MIPS (millions of / or Mega Instructions Per Second). A 2 MHz GPS baseband signal is here fed to the software radio receiver, which performs spectrum despreading and mixing; synchronous demodulation, satellite acquisition and tracking; as well as phase compensation. An algorithm is proposed through which the intermediate frequency (IF) signal is 1-bit sampled and where downconversion is performed before despreading. Resulting data in the form of 32 samples are continuously processed in parallel. A DRAM (Dynamic Random Access Memory) stores a particular C/A (Coarse Acquisition) code table for each satellite from which signals are received. All other data and instructions are stored in a cache memory in order to accomplish a high-speed processing. Although this strategy is declared to result in a reasonably efficient implementation, the document lacks a specific description as to how the dispreading and the correlation should be effected in order to, in fact, obtain this effect.

[0006] Akos. D. et al., "Tuning In to GPS - Real-Time Software Radio Architectures for GPS Receivers", GPS World, July 2001 describes a receiver architecture through which IF signal samples are fed directly from a radio front-end to a programmable processor for continued processing. The article mentions the possibility of using single instruction multiple data (SIMD) instructions to process multiple data samples in parallel. However, portability- and flexibility problems are recognized, and again, there is no teaching as to how an efficient parallel processing could actually be accomplished.

[0007] Dovis, F. et al., "Design and Test-Bed Implementation of a Reconfigurable Receiver for Navigation Applications", Electronics Department, Politecnico di Torino, Navigation Signal Analysis and Simulation Group, Spring of 2002 relates to the design of a reconfigurable GNSS receiver which is capable of fusing data from two or more different GNSS:s. The document sketches an architecture which, in addition to a radio front-end, includes a Field Programmable Gate Array (FPGA) and a Digital Signal Processor (DSP). The authors address various computational load issues. However, they do not present an algorithm which fulfills the identified requirements.

[0008] Hence, the prior art includes a number of examples of software-based GNSS-receivers. Nevertheless, there is yet no distinct teaching of a highly efficient solution which is suitable for implementation in software and has capabilities that are at least in par With those of today's ASIC-based solutions for receiving and processing spread spectrum signals in real-time (ASIC = Application Specific Integrated Circuit).

[0009] US 2002/0027949 discloses a GPS receiver having a fast time to lock onto a GPS signal by storing a time period of an incoming GPS signal in memory and comparing the signal memory against locations in a replica memory having stored GPS signal replicas.

SUMMARY OF THE INVENTION



[0010] The object of the present invention is therefore to provide a solution for receiving and processing spread spectrum signals, which solves the problems above and thus to present a truly software adapted strategy that may be implemented in a physically small and power efficient device.

[0011] According to one embodiment of the invention, there is provided a signal receiver for receiving and decoding spread spectrum signals as claimed in claim 1.

[0012] According to a second embodiment of the invention, there is provided a method for receiving and decoding spread spectrum signals as claimed in claim 32. Other preferred features of the invention are set out in the appended claims.

[0013] According to one aspect of the invention the object may be achieved by a method of receiving spread spectrum signals, which is characterized by comprising a preparation for the correlation step, wherein the preparation takes place before the receiving the continuous signal. This preparation involves pre-generating a multitude of code vectors, which each represents a particular code sequence of the at least one signal source specific code sequence. Moreover, according to the invention, the correlation step involves multiplying at least each vector in a sub-group of the code vectors with at least one vector, which is derived from the data word.

[0014] This strategy is advantageous because the proposed vector approach makes it possible for a digital processor (e.g. a micro-processor) to process multiple signal samples in parallel during each clock cycle and thus make very efficient use of the processor. Furthermore, by pre-generating the code vectors valuable processing capacity is saved, which in turn renders it possible to deal with a sufficient amount of input data per time unit in order to, for example track navigation signals that are transmitted by the satellites in a navigation satellite system.

[0015] According to a preferred embodiment of this aspect of the invention, each code vector represents a particular signal source specific code sequence, which is sampled at the basic sampling rate and quantised with the quantising process that is used to produce the level-discrete sample values. Preferably, the code vectors are also further adapted to the format of the incoming data signal in a way which renders the following processing efficient.

[0016] According to another preferred embodiment of this aspect of the invention, the at least one signal source specific code sequence represents so-called pseudo random noise. This type of code sequences is beneficial in environments where two or more different signals are modulated onto the same carrier frequency. Namely, the different pseudo random noise signals are orthogonal (or at least almost orthogonal) to each other. Consequently, a first information signal spread by means of a first pseudo random noise signal causes a minimal deterioration of a second information signal which is spread by means of a second pseudo random noise signal, and vice versa.

[0017] According to another preferred embodiment of this aspect of the invention, the receiving step involves down conversion of an incoming high-frequency signal to an intermediate frequency signal. The high-frequency signal is presumed to have a spectrum which is symmetric around a first frequency and the intermediate frequency signal is presumed to have a spectrum which is symmetric around a second frequency, which is considerably lower than the first frequency. Hence, the receiving step transforms the information carrying signal to a baseband which is technically more easy to handle than the band at which the original incoming signal is located.

[0018] According to another preferred embodiment of this aspect of the invention, the method includes the following steps. First, a maximum frequency variation of the second frequency due to Doppler-effects is determined. Then, a Doppler frequency interval around the second frequency is defined. The Doppler frequency interval has a lowest frequency limit equal to the difference between the second frequency and the maximum frequency variation, and a highest frequency limit equal to the sum of the second frequency and the maximum frequency variation. After that, the Doppler frequency interval is divided into an integer number of equidistant frequency steps, and subsequently a frequency candidate vector is defined for each frequency step. This way of dividing the spectrum is advantageous because it provides a flexible modeling of the intermediate carrier frequency and its variations.

[0019] According to another preferred embodiment of this aspect of the invention, an integer number of initial phase positions is determined for the frequency candidate vector. The integer number thus represents a phase resolution, such that a relatively high number corresponds to a comparatively high phase resolution, whereas a relatively low number corresponds to a comparatively low phase resolution. Furthermore, a carrier frequency-phase candidate vector is defined for each combination of carrier frequency candidate vector and initial phase position. The different frequency-phase candidate vectors are beneficial, since they allow the determination of a very accurate estimate of frequency- and phase characteristics of a received signal, which in turn vouches for a demodulated signal having a high quality.

[0020] According to yet another preferred embodiment of this aspect of the invention, the number of elements in each carrier frequency-phase candidate vector is determined. Subsequently, the carrier frequency-phase candidate vectors are stored according to a data format, which is adapted to performing multiplication operations between the data word and a segment of a carrier frequency-phase candidate vector. This adaptation is advantageous because thereby several signal samples may be processed in parallel by means of comparatively simple operators. Preferably, the adapting of the data format involves adding at least one element to each segment of the carrier frequency-phase candidate vector, such that the segment attains a number of elements which is equal to the number of elements in each of the at least one vector that is derived from the data word. Hence, it is namely possible to process a segment of the carrier frequency-phase candidate vector together with one of the at least one vector by either a so-called Single Instruction Multiple Data (SIMD)-operation or a logical XOR-operation.

[0021] According to still another preferred embodiment of this aspect of the invention, the method also includes the following steps. First, a maximum variation of the code rate due to Doppler-effects is determined. Then, a Doppler rate interval is defined around a center code rate. The Doppler frequency interval has a lowest code rate limit equal to the difference between the center code rate and the maximum code rate variation, and a highest frequency limit equal to the sum of the center code rate and the maximum code rate variation. In analogy with the intermediate frequency spectrum, the Doppler rate interval is divided into an integer number of equidistant code rate steps, and a code rate candidate is defined for each code rate step. In further analogy with the intermediate frequency, an integer number of possible initial code phase positions is determined for each code rate candidate. The integer number thus represents a code phase resolution, such that a relatively high number corresponds to a comparatively high code phase resolution, whereas a relatively low number corresponds to a comparatively low code phase resolution. Typically, the spread spectrum code modulation is less sensitive to distortion caused by Doppler effects than the frequency modulation. Therefore, the code rate steps may be relatively large. However, a certain degree of Doppler shift estimation is desirable to attain a demodulated signal of high quality.

[0022] According to yet another preferred embodiment of this aspect of the invention, a set of code vectors is generated for each signal source specific code sequence by sampling each code rate-phase candidate vector with the basic sampling rate, and thus produce a corresponding code vector. Again, this simplifies a parallel processing of several signal samples by means of comparatively simple operators.

[0023] According to still another preferred embodiment of this aspect of the invention, a modified code vector is generated on basis of each code vector by: copying a particular number of elements from the end of an original code vector to the beginning of the modified code vector, and copying the particular number of elements from the beginning of the original code vector to the end of the code vector. This extension of the code vector is highly advantageous because it allows extraction of tracking parameters through early-, prompt- and late techniques by performing a simple translation of local copies of the signal source specific code sequence.

[0024] According to still another preferred embodiment of this aspect of the invention, a set of modified code vectors is stored for each signal source specific code sequence. Each modified code vector here contains a number of element, which represent a sampled version of at least one full code sequence. As mentioned above, the modified code vector also includes a repetition of the beginning and the end of the sequence. A particular modified code vector is defined for each combination of code rate candidate and code phase position. These pre-generated modified code vectors save considerable processing capacity in the processor, since they need not be calculated in real time, but may simply be acquired from a memory.

[0025] According to yet another preferred embodiment of this aspect of the invention, the data format of the modified code vectors is adapted with respect to the data format of the at least one vector that has been derived from the data word, such that a modified code vector and one of the at least one vector may be processed jointly by a SIMD-operation or an XOR-operation. Naturally, this is advantageous from a processing efficiency point-of-view.

[0026] According to yet another preferred embodiment of this aspect of the invention, the method involves an initial acquisition phase and a subsequent tracking phase. The acquisition phase establishes a set of preliminary parameters which are required for initiating a decoding of signals that are received during the tracking phase. The parameters may include: a modified code vector, a carrier frequency candidate vector an initial phase position, a code phase position and code index, which denotes a starting sample value for the modified code vector. A successful acquisition phase thus results in that at least one signal source specific code sequence is identified and that this signal is possible to track by the receiver (i.e. may be continued to be received).

[0027] According to still another preferred embodiment of this aspect of the invention, the tracking in turn, involves the following steps. First, based the tracking characteristics, a prompt pointer is calculated for each modified code vector. The prompt pointer indicates a start position for the code sequence. The initial prompt pointer value is set equal to the code index. Then, at least one pair of early- and late pointers is assigned around each prompt pointer. The early pointer specifies a sample value which is positioned at least one element before the prompt pointer's position, and correspondingly, the late pointer specifies a sample value being positioned at least one element after the prompt pointer's position. These pointers are used to maintain the tracking of the received signal by a repeated repositioning of the pointers around a correlation maximum value, such that the prompt pointer is positioned as close as possible to this value, the early pointer is positioned in time somewhat prior to this value and the late pointer is positioned in time somewhat after this value. An important advantage attained by this strategy is that one and the same vector may be re-used in order to represent different delays. Thus, valuable memory space and processing capacity is saved.

[0028] According to still another preferred embodiment of this aspect of the invention, the tracking involves the following further steps.

[0029] First, a sequence of incoming level-discrete sample values is received. Then, data words are formed from the sample values, such that each data word contains a number of elements which is equal to the number of elements in each carrier frequency-phase candidate vector. After that, a relevant set of carrier frequency-phase candidate vectors is calculated for the data word, and a pre-generated in-phase representation respective a quadrature-phase representation of the vector is acquired for each carrier frequency-phase candidate vector in the relevant set. Subsequently, each data word is on one hand multiplied with a in-phase representation of the carrier frequency-phase candidate vector in the relevant set to produce a first intermediate-frequency-reduced information word, and on the other hand multiplied with a quadrature-phase representation of the carrier frequency-phase candidate vector in the relevant set to produce a second intermediate-frequency-reduced information word. The intermediate-frequency-reduced information words thus constitute a respective component of the vectors mentioned above that have been derived from the incoming data words. This multiplied strategy is advantageous because it enables a very efficient usage of the capacity of a general-purpose microprocessor.

[0030] According to yet another preferred embodiment of this aspect of the invention, XOR- or SIMD-operations are used to perform the multiplication between the data word and the in-phase representation of the carrier frequency-phase candidate vector respective between the data word and the a quadrature-phase representation of the carrier frequency-phase candidate vector.

[0031] According to another preferred embodiment of this aspect of the invention, the tracking involves the further steps of: correlating the first intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the prompt pointer to produce a first prompt-despread symbol string, correlating the first intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the early pointer to produce a first early-despread symbol string, correlating the first intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the late pointer to produce a first late-despread symbol string, correlating the second intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the prompt pointer to produce a second prompt-despread symbol string, correlating the second intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the early pointer to produce a second early-despread symbol string, and correlating the second intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the late pointer to produce a second late-despread symbol string. Preferably, a resulting data word is then derived for each set of the despread symbol strings. This may, for example be performed either by performing the relevant adding operation, or by looking up a pre-generated value in a table based on the bit pattern of the despread symbol strings depending on whether the resulting data words contain packed or un-packed information. Data of high quality may thus be obtained with a minimum of real time calculations, which is advantageous from a processing point-of-view.

[0032] According to yet another preferred embodiment of this aspect of the invention, either XOR- or SIMD-operations are used also to perform the multiplication between the intermediate-frequency-reduced information words and the modified code vectors, since again, this is advantageous from a processing point-of-view.

[0033] According to another preferred embodiment of this aspect of the invention, certain pieces of information are propagated in connection with completing the processing of a current data word and initiating the processing of a subsequent data word. Preferably, this propagated information includes: a pointer which indicates a first sample value of the following data word, a group of parameters that describe the relevant set of carrier frequency-phase candidate vectors, the relevant set of code vectors, and the prompt-, early-, and late pointers. Hence, based on the propagated information, the subsequent data word may be processed immediately.

[0034] According to a further aspect of the invention the object is achieved by a computer program directly loadable into the internal memory of a computer, comprising software for performing the above proposed method when said program is run on a computer.

[0035] According to another aspect of the invention the object is achieved by a computer readable medium, having a program recorded thereon, where the program is to make a computer perform the above proposed method.

[0036] According to another aspect of the invention the object is achieved by the signal receiver as initially described, which is characterized in that the proposed computer program is loaded into the memory means, such that the receiver will operate according to the above-described method.

[0037] Consequently, the invention offers an excellent instrument for receiving and decoding any type of spread spectrum signals in a general software radio receiver. For instance, one and the same receiver may be used to track navigation satellite signals of different formats. These signals may even be received in parallel, such that a first signal is received on a first format while one or more other signals are received on a second or third format.

[0038] Moreover, the proposed solution permits one and the same receiver to be utilized for completely different purposes, such as communication in a cellular system.

BRIEF DESCRIPTION OF THE DRAWINGS



[0039] The present invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.
Figure 1
shows a spectrum graph over an exemplary spread spectrum signal from which information may be extracted according to the invention,
Figure 2
shows a spectrum graph over a frequency down-converted signal corresponding to the spectrum shown in figure 1,
Figure 3
is an enlarged version of figure 2 in which a Doppler shifting of the spectrum is illustrated,
Figure 4
illustrates how a data signal is modulated onto a signal source specific code sequence according to an embodiment of the invention,
Figure 5
depicts a three-dimensional graph over carrier frequency-phase candidate vectors to be used as initial correlators according to an embodiment of the invention,
Figure 6
shows an alternative representation the carrier frequency-phase candidate vectors in figure 5,
Figures 7-8
show graphs which illustrate how a code index and a code phase are defined for a received signal according to an embodiment of the invention,
Figures 9a,b
illustrate how a modified code vector is generated based on an original code vector according to an embodiment of the invention,
Figure 10
depicts a three-dimensional graph over code rate-phase candidate vectors to be used as subsequent correlators according to an embodiment of the invention,
Figure 11
illustrates how a set of code sequence start pointers is assigned to a modified code vector according to an embodiment of the invention,
Figure 12
illustrates how data words are formed from a sequence of incoming level-discrete sample values according to an embodiment of the invention,
Figure 13
illustrates how the data words of figure 12 are correlated with various pre-generated vectors according to an embodiment of the invention,
Figure 14
illustrates how multiple pairs of pointers may be assigned according to an embodiment of the invention,
Figure 15
shows a proposed signal receiver, and
Figure 16
illustrates, by means of a flow diagram, the general method of processing spread spectrum signals according to the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION



[0040] In order to realize a truly software based signal processing solution in real-time at high sampling rates, such as those required in a GNSS, the architecture of the microprocessor system must be utilized very efficiently. The present invention uses an approach, which involves a form of parallel processing based on pre-generated code vector representations. The invention thereby strikes a balance between processing speed and memory usage, which compensates for the capacity deficit of a general purpose microprocessor in relation to an ASIC. The details of this solution will become apparent from the below disclosure.

[0041] Figure 1 shows a spectrum graph over an exemplary spread spectrum signal from which information may be extracted according to the invention. For example, the signal may be a GPS C/A-signal in the L1-band with a carrier frequency fHF of 1,57542 GHz. This means that the signal's spectrum is symmetrical around the carrier frequency fHF. Moreover, the signal has at least 98% of its energy distributed within a 2 MHz wide frequency band BWHF around the carrier frequency fHF. Therefore, it is generally sufficient if the spread spectrum signal is downconverted to an intermediate frequency fIF at around 1 MHz in order to enable further signal processing at a lower frequency.

[0042] Figure 2 shows a spectrum graph over such a frequency downconverted signal, whose spectrum is symmetrical around an intermediate frequency fIF, which is considerably lower than the carrier frequency fHF, for example fIF = 1,25 MHz. Due to movements of the transmitter (i.e. typically a satellite in orbit) and the receiver (i.e. typically a mobile GNSS-receiver) a Doppler shift may occur in the received signal, which is proportional to the relative velocity between the transmitter and the receiver. A maximum Doppler shift fD is defined which in the GNSS case normally is approximately 10 kHz. Thus, the entire spectrum may be shifted within an interval 2fD, such that the center frequency falls any where between fIF+fD (corresponding to a maximum positive Doppler shift) and fIF-fD (corresponding to a maximum negative Doppler shift). For illustrative purposes the interval 2fD, has been severely exaggerated in the figure 2. The figure also indicates a phase variation interval ϕD (along an independent axis ϕ) around the intermediate frequency fIF. The phase variation interval ϕD demonstrates the fact that the phase position of the received signal is initially unknown to the receiver, and thus constitutes a calibration parameter. The effects of this parameter will be further elucidated below with reference to figure 5.

[0043] An enlarged version of the spectrum in figure 2 is shown in figure 3. The intermediate spectrum may, due to possible Doppler effects, be shifted such that its center frequency lies in the interval 2fD from fIF-min=fIF-fD to fIF-max=fIF+fD. The potential maximum shifted spectra are here indicated with a respective dashed line. The diagram in figure 3 also shows a Nyquist frequency rS/2 corresponding to a minimal sampling rate rS which, when used for sampling the intermediate frequency signal, will result in a non-aliased discrete spectrum. Provided that fD = 10 kHz, fIF = 1,25 MHz, BWHF = 2 MHz and the intermediate frequency signal is lowpass filtered through an analog filter having a 2,5 MHz wide passband, the minimal sampling rate rS becomes 5 MHz (i.e. two times the highest frequency component after the analog filter).

[0044] Figure 4 illustrates schematically how a data signal D is modulated onto a signal source specific code sequence CS on the transmitter side according to an embodiment of the invention. According to a preferred embodiment of the invention, the signal source specific code sequence CS constitutes so-called pseudo random noise. The data signal D here contains a data symbol sequence [+1, -1, -1, +1, -1], and has a relatively low symbol rate, say 50 Hz. The signal source specific code sequence CS, however, has a relatively high symbol rate (or more correctly chipping rate). For instance, a signal source specific code sequence CS in the form of a GPS C/A code may have a chipping rate of 1,023 MHz and contain 1023 chips per period. Each chip, ch, is either +1 or -1. Hence, the C/A code repeats itself one per ms. The data signal D is modulated onto (or spread by) the signal source specific code sequence CS by multiplying each data symbol with the code sequence CS. The data symbol +1 thereby results in an unaltered code sequence CS, whereas the data symbol -1 results in an inverted code sequence CS.

[0045] If a data signal D having a rate of 50 Hz is spread by means of a signal source specific code sequence CS having a chipping rate of 1,023 MHz, this results in 20 entire code sequences CS per data symbol. Namely, the period time for one data symbol is 20 ms, whereas the period time for the code sequence is only 1 ms.

[0046] Figure 5 depicts a three-dimensional graph over different carrier frequency-phase candidate vectors. As mentioned above, the intermediate frequency spectrum may be Doppler shifted. Therefore, the particular frequency of the received signal is initially unknown within a Doppler frequency interval from fIF-min to fIF-max. Moreover, the phase position of the received signal is beforehand unknown to the receiver. In order to enable an estimation of the actual intermediate carrier frequency, the Doppler frequency interval fIF-min - fIF-max is divided into an integer number of equidistant frequency steps. Of course, the larger the number of steps is, the more accurately the intermediate carrier frequency may be estimated. In this example, a step size Δf of 20 Hz is chosen. In some applications, however, a much larger step size Δf may provide a sufficient frequency accuracy, whereas in other applications (where relatively high accuracy is needed) a considerably smaller step size Δf may be required. In any case, a Doppler frequency interval fIF-min - fIF-max of 20 kHz and a step size Δf of 20 Hz requires 1000 steps, where a first step includes the frequencies from fIF-min to fIF-min+Δf, a second steep includes the frequencies from fIF-min+Δf to fIF-min+2Δf, and so on up to a last step including the frequencies from fIF-min+999Δf to fIF-max.

[0047] A frequency candidate vector FIF-C is defined for each frequency step. In order to estimate an initial phase position of the intermediate carrier frequency, an integer number of initial phase positions ϕ0, ..., ϕ7 are determined. The illustrated example shows eight such positions ϕC. This gives a phase resolution of π/4. For each frequency candidate vector fIF-C, eight different phase positions ϕ0, ..., ϕ7 are thus defined which each represents a particular phase shift from 0 to 7π/4. A combination of a certain carrier frequency candidate vector FIF-C and a particular initial phase position ϕC is referred to as a carrier frequency-phase candidate vector. Figure 5 shows all such vectors (i.e. eight) for the first step, where fIF-C = fIF-min, and the second step, where fIF-C = fIF-min+Δf.

[0048] Additionally, figure 5 includes an axis LC along which the number of sample values (or length) of the frequency candidate vector fIF-C is indicated. The LC number is preferably a power of 2 because this generally renders the implementation more simple. The number of sample values in each frequency candidate vector fIF-C is set in consideration of tne available memory space, the desired frequency resolution and the desired phase resolution. If, in the example above, a length of 512 samples is chosen and each sample requires one byte, the total (uncompressed) memory demand would be 3,9 MB (i.e. 1000 frequencies × 8 phase positions × 512 B = 4096000 B = 3,9 MB).

[0049] Figure 6 shows an alternative representation the carrier frequency-phase candidate vectors V(fIF-C, ϕC) in figure 5. Here, the vectors V(fIF-C, ϕC) range from the carrier frequency fIF-C=fIF-min (say 1,24 MHz) to fIF-C=fIF-max (say 1,26 MHz), from the phase shift position ϕC0 (say 0) to ϕC7 (say 7π/4), all have a length LC of sn samples (say 512) and are represented in a cube. Hence, a particular frequency-phase candidate vector V(fIF-C, ϕC) is given by a cuboid segment in the cube which is parallel with the LC-axis, and ranges from LC=s1 to LC=Sn.

[0050] After having generated all the carrier frequency-phase candidate vectors V(fIF-C, ϕC), the vectors are stored in a digital memory with a comparatively short access time, such that they may be readily accessed during a later acquisition and/or tracking phase. Preferably, the carrier frequency-phase candidate vectors V(fIF-C, ϕC) are stored according to a data format which is adapted to performing multiplication operations between incoming data words (representing one or more received signals) and segments of carrier frequency-phase candidate vectors V(fIF-C, ϕC). The vectors may either include packed samples or they may contain samples that are unpacked to a smallest manageable unit in the microprocessor, such as a byte. Further details regarding the data format issues will be discussed below.

[0051] Figure 7 shows a graph over an exemplary code sequence CS, which has been received, downconverted and sampled according to an embodiment of the invention. After subsequent removal of the intermediate frequency component, the code sequence CS either attains the signal value +1 or -1, and the symbols are altered at a chipping rate of for example 1,023 MHz. At the receiver side, the code sequence CS is sampled with a sampling rate rS of for example 5 MHz. The sampling instances are indicated by means of dots on the code sequence signal CS along an axis sl. As is apparent from the figure there are approximately four sample values per chip period. Hence, the requirements of the Nyquist theorem are clearly fulfilled. However, the samples are not capable of determining the transition instances with a sufficient accuracy, i.e. where the code sequence signal CS changes from representing one chip symbol to representing another one chip symbol. Therefore, a so-called code phase must be determined. Moreover, a particular sample value at which the code sequence starts must also be established.

[0052] Figure 8 shows a graph, which illustrates the sample value at which the code sequence CS starts (the so-called code index CI) and how a code phase, Cph, is defined in relation to this sample value. An initial segment of the code sequence signal. CS in figure 7 is therefore represented in figure 8.

[0053] A first sample instance is here presumed to occur shortly prior to the actual start of the code sequence CS signal period. Hence, a corresponding sample value s1 belongs to the end of the preceding period. This is illustrated by means of the line representing the code sequence signal CS being dashed. A subsequent sample instance, however, overlaps the code sequence CS period. The corresponding sample value s2 is defined as the code index CI. The actual beginning of a code sequence signal is determined in a preceding acquisition phase and typically involves correlation between the received signal and a local copy of the code sequence CS.

[0054] The distance between the start of the code sequence signal CS and the code index CI, in turn, is defined as the code phase Cph, and thus represents a measure of the translation (or skew) between the sample instances si and the chip transitions. The sampling interval between two consecutive sample instances si is divided into an integer number of possible initial code phase positions in order to estimate the code phase Cph. In this example, ten 0.1-steps ranging from 0.0 to 0.9 are defined, where a first step 0.0 would indicate that code sequence signal CS starts at the code index CI, and a last step 0.9 would indicate that code sequence signal CS starts almost at the preceding sample value s1. The figure 8 shows a code phase Cph of 0.4, i.e. a situation where the code sequence signal CS starts approximately in the middle between two consecutive sample instances si.

[0055] In analogy with the carrier frequency-phase candidate vectors V(fIF-C, ϕC), code rate-phase candidate vectors may now be defined for each signal source specific code sequence CS and combination of code rate CR, code index CI and code phase Cph. Nevertheless, according to a preferred embodiment of the invention, a modified code vector is first produced based on each original code vector.

[0056] Figures 9a and 9b illustrate how this may be performed. A code vector CV in figure 9a contains a number of sample values, say 5000. Preferably, the number of sample values is selected in relation to sampling rate such that a full code sequence period is recorded. In the above example, with a sampling rate rS of 5 MHz, this means that the 5000 samples cover exactly one full code sequence CS period (which has a duration of 1 ms and contains 1023 chips, since the chipping rate is 1,023 MHz).

[0057] A modified code vector CVm is now generated on basis of the original code vector CV by copying a particular number of elements Ee (e.g. two) from the end of the original code vector CV to the beginning of the modified code vector CVm. Correspondingly, a particular number of elements Eb (e.g. two) from the beginning of the original code vector CV are copied to the end of the code vector CVm, i.e. after the elements Ee. Figure 9b shows the resulting modified code vector CVm. Since, in this example, each chip symbol is sampled at approximately four instances, two sample values are equivalent to about one half chip period. Thereby, the above copying of the elements Ee and Eb allows a one-half-chip shifting of the code vector CV during a correlation operation between the code vector CV and the received data. This will be discussed further below with reference to figure 11.

[0058] Figure 10 depicts a three-dimensional graph over different code rate-phase candidate vectors CVm(CRC-C, Cph) which represent a signal source specific code sequence CS(i). Analogous to the intermediate carrier frequency, the nominal code rate CRC for the code rate candidate vector CRC-C may also vary due to Doppler effects from a lowest value CRmin to a highest value CRmax. However, since the code rate (or chipping rate) is comparatively high, the rate variation here becomes rather small.

[0059] For example, a Doppler shift of 10 kHz at the intermediate carrier frequency is equivalent to a shift in a nominal code rate CRC at 1,023 MHz of merely 6,5 Hz. Namely, the Doppler shift in respect of the code rate is generally equal to the ratio between the carrier frequency and the code rate (1575,42 MHz / 1,023 MHz = 1540; a Doppler shift of 10 kHz at the intermediate carrier frequency thus corresponds to 10000/1540 ≈ 6,5 Hz). The code rate candidate vector CRC-C may attain a value anywhere in a Doppler rate interval between CRmin = 1022993,5 Hz and CRmax = 102306,5 Hz. The Doppler rate interval CRmin - CRmax is divided into an integer number of equidistant code rate steps ΔCR, say 13. In this example, each interval CRmin, CRmin+ΔCR, ..., CRmax thus spans 1 Hz. According to a preferred embodiment of the invention, the code rate step size is adaptive, e.g. determined on basis of the sampling frequency and the desired resolution.

[0060] In figure 10, the three-dimensional graph (or cube) contains a set of code rate-phase candidate vectors CVm(CRC-C, Cph), where the code rate ranges from CRC-C=CRmin to CRC-C=CRmax, the code phase ranges from Cph=0.0 to Cph=0.9, and each vector has a length LCVm of sm samples (for example 5004). Hence, a particular code rate-phase candidate vector CVm(CRC-C, Cph) is given by a cuboid segment CVm(CRmin+2ΔCR, 0.4) which is parallel with the LCVm -axis and ranges from LCVm=s1 to LCVm =sm.

[0061] After having generated all the code rate-phase candidate vectors CVm(CRC-C, Cph), these vectors are stored in a digital memory with a comparatively short access time, such that they may be readily accessed during the acquisition and/or tracking phase. Preferably, the code rate-phase candidate vectors CVm(CRC-C, Cph) are stored according to a data format which is adapted to correlation operations to be performed between a vector that has been derived from incoming data words and a segment of a the code rate-phase candidate vectors CVm(CRC-C, Cph). For example, the code rate-phase candidate vectors CVm(CRC-C, Cph) may include packed samples or they may contain samples that are unpacked to a smallest manageable unit in the microprocessor, such as a byte. Further details regarding these data format issues will be discussed below with reference to figure 13.

[0062] During tracking of a spread spectrum signal, i.e. a continued reception of the signal and demodulation of the data contained therein, it is necessary to update relevant tracking parameters for the signal. Normally, the tracking phase is preceded by a so-called acquisition phase during which a set of preliminary parameters are established that are required for initiating the signal decoding. A successful acquisition phase thus results in that at least one signal source specific code sequence is identified and a data signal transmitted by means of this sequence is possible to demodulate. The tracking characteristics that may be associated with a signal source specific code sequence include: a modified code vector CVm (which defines a carrier frequency candidate vector fIF-C and an initial phase position ϕC), a code phase position, Cph, and a code index, CI. In order to maintain an adequate timing of the correlating operations in the receiver, a set of pointers are required which indicate the start position of the code sequence in relation to the modified code vector and are updated repeatedly, preferably between each correlation.

[0063] Figure 11 illustrates one such set of pointers that are assigned to a modified code vector CVm. A prompt pointer PP indicates a current estimate of the code sequence start position. This pointer PP is initially set equal to the code index CI. Adequate PP-pointer positions for any subsequent segments of the received data are obtained by retrieving appropriate modified code vectors CVm from the digital memory where such pre-generated are stored. Between each segment, the code rate candidate vector CRC-C as well as the initial code phase Cph is updated. Additionally, at least one pair of early- and late pointers PE and PL respectively is assigned on each side of the prompt pointer PP, where the early pointer PE specifies a sample value being positioned at least one element before the prompt pointer's PP position, and the late pointer PL specifies a sample value being positioned at least one element after the prompt pointer's PP position. Each correlation is then performed with the presumption that the code sequence starts at the PP-position, at the PE-position as well as at the PL-position. If the correlation over the PP-position results in a higher correlation value than over any of the other positions, and at the same time the PE- and PL-pointers are balanced (i.e. the correlation over these positions result in equal values), this is interpreted as an optimal setting of the tracking parameters. Should, however, this not be true the sampled data must be repositioned in relation to the PP-, PE- and PL-pointers, such that the correlation peak again coincides with the PP-pointer's position. An un-calibrated pointer positioning may thus be detected via a difference between the correlation value over the PE-pointer position and the correlation value over the PL-pointer position, while the correlation over the PP-position still results in the highest correlation value. In this case, the potentially highest correlation value (corresponding to the optimal PP-positioning) lies somewhere between the current PP-position and the current PE-position or between the current PP-position and the current PL-position depending on which of the PE- and PL-pointer positions that results in the highest correlation value. A pointer updating normally takes place between each segment. A second or third pair of PE- and PL-pointers outside the first pair of pointers further enhances the possibilities of accomplishing an accurate adjustment of the tracking. Depending on the value of the received symbol, an optimal setting PP-pointer may, in fact, also be equivalent to the correlation over the PP-position resulting in a lower correlation value than over any of the other pointer positions. Namely, this is true if a negative valued data bit is received. However otherwise, the same principles apply.

[0064] In any case, the PP-, PE- and PL-pointers may only be positioned within certain intervals in the modified code vector CVm. The PP-pointer may be set anywhere within a first interval 111, the PE-pointer within a second interval 112 and the PL-pointer within a third interval 113. All the pointers are always set together, such that their relative distances remain unchanged. A limit value PL-min for the PL-pointer typically coincides with the first element of the modified code vector CVm. Namely, outside this range a meaningful correlation cannot be performed. As a consequence of this and the fact that the pointers are set jointly PP-, PE- and PL, a corresponding limit value PE-min for the PE-pointer is also defined.

[0065] Figure 12 illustrates how data words d(1), d(2), ..., d(N) are formed from a sequence 1210 of incoming level-discrete sample values according to an embodiment of the invention. The data words d(1), ..., d(N) are formed such that each data word d(k) contains a number of elements which is equal to the number of elements sn in each carrier frequency-phase candidate vector. For instance, the length of these vectors may be 512 sample values (as in the example described above with reference to the figures 5 and 6). Given that each sequence 1210 contains 5000 sample values, the number N of data words becomes 10 (5000/512≈9,76 means that the last quarter of the tenth data word d(10) is empty). According to the invention, the elements in a current data word d(k) are processed jointly (i.e. in parallel). Then, the processing of a subsequent data word d(k+1) is initiated, and any processing parameters obtained during the processing of the current data word d(k) that are required when processing the subsequent data word d(k+1) are propagated as input data to the processing of the latter. These processing parameters preferably include: a pointer pd which indicates a first sample value of the subsequent data word d(k+1), a group of parameters which describe the relevant set of carrier frequency-phase candidate vectors V(fIF-C, ϕC) (i.e. a carrier frequency candidate vector fIF-C representing an in-phase version and a carrier frequency candidate vector fIF-C representing a quadrature-phase version), the relevant set of code vectors CVm, and prompt-, early-, and late pointers PP, PE, and PL respectively.

[0066] Figure 13 illustrates how the data words of figure 12 are correlated with various pre-generated vectors according to an embodiment of the invention. First, a relevant set of carrier frequency-phase candidate vectors V(fIF-C, ϕC) is calculated for the data word d(k). This set is normally obtained in a preceding acquisition phase (or, if the data word d(k) is not the first word to be processed, during the processing of a previous word).

[0067] Thereafter, for each carrier frequency-phase candidate vector V(fIF-C, ϕC) in the relevant set, a pre-generated in-phase representation fIFI, and a quadrature-phase representation fIFQ of the vector V(fIF-C, ϕC)) respectively is acquired. Both these representations are found in the digital memory where the pre-generated carrier frequency-phase candidate vectors V(fIF-C, ϕC) are stored because they are merely one quarter period delays of one and the same vector, and the memory holds initial phase position representations for an entire period, see figure 6.

[0068] Then, in order to eliminate the influence of the carrier frequency component, the data word d(k) is multiplied with the in-phase representation fIFI of the carrier frequency-phase candidate vector V(fIF-C, ϕC) in the relevant set. As a result thereof, a first intermediate-frequency-reduced information word SIF-I(k) is produced. Correspondingly, the data word d(k) is also multiplied with the quadrature-phase representation fIFQ of the carrier frequency-phase candidate vector V(fIF-C, ϕC) in the relevant set, and a second intermediate-frequency-reduced information word SIF-Q(k) is produced.

[0069] Preferably, the multiplication between the data word d(k) and the in-phase representations fIFI respective the quadrature-phase representation FIFQ of the carrier frequency-phase candidate vector V(fIF-C, ϕC) are performed by means of XOR- or SIMD-operations (i.e. 1-bit and multiple-bits multiplications respectively). This is namely possible if the data word d(k) and the vector V(fIF-C, ϕC) have compatible data formats.

[0070] Subsequently, the first intermediate-frequency-reduced information word SIF-I(k) is multiplied with a modified code vector CVm-P, which has been retrieved from the digital memory where these pre-generated vectors are stored, and starts at a position indicated by the prompt pointer PP. A first prompt-despread symbol string ΛIP(k) is produced as a result of this operation. The first intermediate-frequency-reduced information word SIF-I(k) is also multiplied with a modified code vector CVm-E(k), which starts at a position indicated by the early pointer PE. A first early-despread symbol string ΛIE(K) is produced as a result of this operation. The first intermediate-frequency-reduced information word SIF-I(k) is likewise multiplied with a modified code vector CVm-L(k), which starts at a position indicated by the late pointer PL, and a first late-despread symbol string ΛIL(k) is produced. Moreover, the second intermediate-frequency-reduced information word SIF-Q(k) is multiplied with a modified code vector CVm-P(k), which starts at a position indicated by the prompt pointer PP, and a second prompt-despread symbol string ΛQP(k) is produced. Correspondingly, the second intermediate-frequency-reduced information word SIF-Q(k) is multiplied with a modified code vector CVm-E(k), which starts at a position indicated by the early pointer PE, and a second early-despread symbol string ΛQE(k) is produced. Likewise, the second intermediate-frequency-reduced information word SIF-Q(k) is multiplied with a modified code vector CVm-L(k), which starts at a position indicated by the late pointer PL, and a second late-despread symbol string ΛQL(k) is produced.

[0071] After that, a resulting data word DR-IE(k), DR-IP(k), DR-IL(k), DR-QE(k), DR-QP(k) and DR-QL(k) may be derived from the each of the despread symbol strings ΛIP(k), ΛIE(k), ΛIL(k), ΛQP(k), ΛQE(k) and ΛQL(K) respectively by adding the elements in the respective string together. If the strings represent un-packed data, the processor may simply perform the relevant adding operation to obtain the resulting data word DR(k). If however, the strings represent packed data, the resulting data word DR(k) is, according to a preferred embodiment of the invention, derived by looking up a pre-generated value in a table 1310 based on the bit pattern given by the respective despread symbol string ΛIP(k), ΛIE(k), ΛIL(k), ΛQP(k), ΛQE(k) and ΛQL(k).

[0072] According to a preferred embodiment of the invention, in addition to the individual data words DR-IE(k), DR-IP(k), DR-IL(k), DR-QE(k), DR-QP(k) and DR-QL(k), corresponding accumulated data words are produced, such that after having generated a data word DR(k), the sum of all data words DR(1) to DR(k) is also obtained. Hence, when the data word d(N) has been processed, the resulting sum DR(1) to DR(N) is also at hand.

[0073] Moreover, the resulting data words represent payload information. For instance, based on the set of resulting data words DR-IE(k), DR-IP(k), DR-IL(k), DR-QE(k), DR-QP(k) and DR-QL(k) a demodulated piece of information of a transmitted data symbol sequence D as shown in figure 4 may be derived. In a steady state operation, basically only one of the resulting data words, say DR-IP(k), actually carries the information.

[0074] According to a preferred embodiment of the invention, the multiplications involved in the multiplications between the intermediate-frequency-reduced information words SIF-I(k) and SIF-Q(k) respectively and the modified code vectors CVm-P(k), CVm-E(k); CVm-L(k) are all performed by means of XOR- or SIMD-operations. This is possible if the intermediate frequency information words SIF-I(k); SIF-Q(k) and the modified code vectors CVm-E(k), CVm-P(k); CVm-L(k) have compatible data formats.

[0075] It was mentioned above with reference to figure 11 that more than one pair of early- and late pointers may be assigned to the prompt pointer in order to accomplish an improved tracking. Figure 14 illustrates how two pairs of such pointers PE1; PL1 and PE2; PL2 respectively are assigned around a prompt pointer PP according to an embodiment of the invention. The horizontal axis here represents a code shift CS and the vertical axis shows a normalised correlation factor. An optimal positioning of the prompt pointer PP is thus equivalent to a normalised correlation value of 1. The more the sampled data is shifted in either direction from this position, the lower the correlation value becomes down to substantially zero for a shift of one chip or more. The algorithm is perfectly balanced when (as illustrated in the figure) both the pointers PE1 and PL1 of a first pair produce a first shifted correlation result, both the pointers PE2 and PL2 of a second pair produce a second shifted correlation result, the first shifted correlation result is larger than the second shifted correlation result and both the first and the second shifted correlation results are smaller than the correlation result obtained at the prompt position PP. Said correlation results are preferably generated according to a process corresponding to what has been described above with reference to figure 13. Based on the correlation results for the pointer positions PP, PE1, PL1, PE2 and PL2 a (if necessary new) set of modified code vectors CVm-E(k), CVm-P(k); CVm-L(k) is selected, which is deemed to be optimal.

[0076] Figure 15 shows a signal receiver 1500 for receiving navigation data signals transmitted in a navigation satellite system according to an embodiment ot the invention. The receiver 1500 includes radio front end unit 1510, an interface unit 1520 and a digital processor unit 1530.

[0077] The radio front end unit 1510 is adapted to receive a continuous radio signal SHF, and in response thereto produce a corresponding electrical signal SIF which has a comparatively high frequency. The interface unit 1520 is adapted to receive the electrical signal SIF, and in response thereto, produce a sequence of sample values that represents the same information as the electrical signal SIF and is divided into data words d(k). The digital processor unit 1530 is adapted to receive the data words d(k), and in response thereto, demodulate a data signal. The digital processor unit 1530, in turn, includes a memory means 1535, which is loaded with a computer program that is capable of controlling the steps of the proposed procedure when the program is run in the processor unit 1530.

[0078] In order to sum up, the general method of processing spread spectrum signals according to the invention will now be described with reference to a flow diagram in figure 16.

[0079] A preparation step 1600 pre-generates code vectors which each represents a signal source specific code sequence that is intended to be received (or at least possible to receive) and demodulated in the receiver. The step 1600 is performed before the signal reception is initiated.

[0080] A step 1610 then receives a continuous signal of a comparatively high frequency. A following step 1620 samples the continuous signal at a basic sampling rate, whereby a resulting sequence of time discrete signal samples is produced. Each sample is also quantised (either with a relatively low-resolution, such as with 1 bit per sample value, or with a relatively high resolution depending on the application and the number of data bits per samples delivered from the radio front end unit 1510), such that a corresponding level-discrete sample value is obtained. Subsequently, a step 1630 forms data words from the sample values, where each data word includes one or more consecutive sample values. After that, a step 1640 carries out correlation operations between the information in the data words and at least one of the pre-generated representations of a signal source specific code sequence. The correlation step involves correlating at least each vector in a sub-group of the code vectors with at least one vector that has been derived from a data word. A following step 1650 produces data as a result of the correlation performed in step 1640. Then, a step 1660 investigates whether the sampled sequence has ended, i.e. whether there are any more data words to process. If more sampled data to process is found, the procedure returns to the step 1640. Otherwise, the procedure loops back to the step 1610 again for continued reception of the incoming signal. Naturally, such signal is preferably also received during execution of the steps 1620 to 1660. The sequential procedure illustrated in figure 16 is merely applicable to a specific received signal segment. Preferably, all the steps are actually 1610 to 1660 are actually performed in parallel.

[0081] The process steps, as well as any sub-sequence of steps, described with reference to the figure 16 above may be controlled by means of a programmed computer apparatus, such as a microprocessor located in a GNSS-receiver. Moreover, although the embodiments of the invention described above with reference to the drawings comprise computer apparatus and processes performed in computer apparatus, the invention thus also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source and object code such as in partially compiled form, or in any other form suitable for use in the implementation of the process according to the invention. The carrier may be any entity or device capable of carrying the program. For example, the carrier may comprise a storage medium, such as a ROM (Read Only Memory), for example a CD (Compact Disc) or a semiconductor ROM, or a magnetic recording medium, for example a floppy disc or hard disc. Further, the carrier may be a transmissible carrier such as an electrical or optical signal which may be conveyed via electrical or optical cable or by radio or by other means. When the program is embodied in a signal which may be conveyed directly by a cable or other device or means, the carrier may be constituted by such cable or device or means. Alternatively, the carrier may be an integrated circuit in which the program is embedded, the integrated circuit being adapted for performing, or for use in the performance of, the relevant processes.

[0082] The term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components. However, the term does not preciude the presence or addition of one or more additional features, integers, steps or components or groups thereof.

[0083] The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.


Claims

1. A signal receiver (1500) for receiving and decoding spread spectrum signals and adapted to receive and decode spread spectrum signals via a two stage process comprising an initial acquisition phase and a subsequent tracking phase, the signal receiver (1500) comprising:

an interface unit (1520) adapted to receive an electrical signal representative of a continuous radio signal and in response thereto produce a sequence of consecutive quantised sample values divided into data words comprising a plurality of sample values; and

a digital processor unit (1530) adapted to receive the data words, characterised in that

the digital signal processor unit (1530) is adapted to generate multiple carrier frequency phase candidate vectors and code vectors to be of a format compatible with the data words produced by the interface unit or a vector derived from a data word respectively such that a correlation operation can be performed by steps including multiplying multiple samples in parallel;

the digital processor unit (1530) is further adapted to, when the signal receiver is performing the tracking phase, perform the correlation operation in response to receiving the data words by multiplying a received data word with a carrier frequency-phase candidate vector to decode the data word and multiplying a vector derived from the decoded data word with a code vector, the carrier frequency-phase candidate vector and code vector being one of the multiple vectors generated by the digital processor unit (1530) prior to performing the correlation operation; and

the signal receiver (1500) is adapted to perform the correlation operation by performing steps including multiplying multiple samples in parallel.


 
2. A signal receiver (1500) as claimed in claim 1, wherein the digital processor unit (1530) is further adapted to perform the correlation operation on each of a sequence of data words received from the interface unit (1520), the digital processor unit (1530) being further adapted to generate multiple vectors for use in the correlation operation with one data word while performing the correlation operation on a previously received data word.
 
3. A signal receiver (1500) as claimed in claim 1, wherein the digital processor unit (1530) is adapted to generate the multiple vectors prior to the continuous radio signal being received by a receiver (1510).
 
4. A signal receiver (1500) as claimed in any of claims 1 to 3, wherein the digital processor unit (1530) is adapted to multiply the multiple samples in parallel by means of an XOR operation.
 
5. A signal receiver (1500) as claimed in any of claims 1 to 3, wherein the digital processor unit (1530) is adapted to multiply the multiple samples in parallel by means of a SIMD operation.
 
6. A signal receiver (1500) as claimed in any preceding claim, wherein the digital processor unit (1530) is adapted to generate each of the multiple vectors to be of a format compatible with the data words produced by the interface unit (1520) or the vector derived from the data word by generating the multiple vectors such that the number of sample values comprised in each vector is equal to the number of sample values in each data word produced by the interface unit (1520) or vector derived from the data word respectively.
 
7. A signal receiver (1500) as claimed in any preceding claim, wherein the receiver (1510) is adapted to receive a continuous radio signal having a relatively high frequency and a frequency spectrum that is symmetric about a first frequency and form an intermediate signal having a relatively low frequency and a frequency spectrum that is symmetric about a second signal from the continuous radio signal.
 
8. A signal receiver (1500) as claimed in claim 7, wherein the digital processor unit (1530) is adapted to generate one or more carrier frequency candidate vectors by:

determining a maximum frequency variation of the second frequency due to Doppler effects;

defining a Doppler frequency interval around the second frequency, the Doppler frequency interval having a lower frequency limit equal to the difference between the second frequency and the maximum frequency variation and a higher frequency limit equal to the sum of the second frequency and the maximum frequency variation;

dividing the Doppler frequency interval into an integer number of equidistant frequency steps; and

defining a frequency candidate vector corresponding to each frequency step.


 
9. A signal receiver (1500) as claimed in claim 8, wherein the digital processor unit (1530) is adapted to generate one or more carrier frequency-phase candidate vectors by:

determining an integer number of initial phase positions for the one or more carrier frequency candidate vectors; and

defining a carrier frequency-phase candidate vector for each combination of a carrier frequency candidate vector and an initial phase position.


 
10. A signal receiver (1500) as claimed in claim 9, wherein the digital processor unit (1530) is adapted to add at least one element to each segment of a carrier frequency-phase candidate vector such that each segment contains the same number of samples as a data word produced by the interface unit (1520).
 
11. A signal receiver (1500) as claimed in any preceding claim, wherein the code vectors are each representative of at least one signal source specific code sequence.
 
12. A signal receiver (1500) as claimed in claim 11, wherein the at least one signal source specific code sequence is pseudo random noise.
 
13. A signal receiver (1500) as claimed in any preceding claim, wherein the digital processor unit (1530) is adapted to generate one or more code rate candidates representative of at least one signal source specific code sequence by:

determining a maximum variation of a code rate due to Doppler effects;

defining a Doppler rate interval around a centre code rate, the Doppler frequency interval having a lower code rate limit equal to the difference between the centre code rate and the maximum code rate variation and a higher code rate limit equal to the sum of the centre code rate and the maximum code rate variation;

dividing the Doppler rate interval into an integer number of equidistant code rate steps; and

defining a code rate candidate in respect of each code rate step.


 
14. A signal receiver (1500) as claimed in claim 13, wherein the digital processor unit (1530) is adapted to generate one or more code rate-phase candidates by:

determining an integer number of possible initial code phase positions for the one or more code rate candidates;

defining, for each signal source specific code sequence, a code rate-phase candidate for each combination of a code rate candidate and an initial code phase position.


 
15. A signal receiver (1500) as claimed in claim 14, wherein the interface unit (1520) is adapted to produce the sequence of sample values by sampling the electrical signal at a basic sampling rate and the digital processor unit (1530) is adapted to sample each code rate-phase candidate at the basic sampling rate, whereby a corresponding code rate-phase candidate vector is produced.
 
16. A signal receiver (1500) as claimed in claim 15, wherein the digital processor unit (1530) is adapted to generate a modified code vector from a code rate-phase candidate vector by:

copying a number of elements from the end of the code rate-phase candidate vector to the beginning of the modified code vector; and

copying a number of elements from the beginning of the rate-phase candidate vector to the end of the modified code vector.


 
17. A signal receiver (1500) as claimed in claim 16, wherein the signal receiver (1500) comprises a memory (1535), the digital processor unit (1530) being adapted to store a set of modified code vectors corresponding to each signal source specific code sequence in the memory (1535), wherein:

each modified code vector comprises a number of elements representative of a sampled version of at least one full code sequence of the respective signal source specific code sequence; and

a respective modified code vector is defined for each combination of code rate candidate and code phase position.


 
18. A signal receiver (1500) as claimed in claim 1, wherein the digital processor unit (1530) is adapted to, when the signal receiver (1500) is performing the initial acquisition phase, establish a set of preliminary parameters required to initiate decoding of signals received by the signal receiver (1500) during the subsequent tracking phase.
 
19. A signal receiver (1500) as claimed in claim 18, wherein the digital processor unit (1530) is adapted to, when the signal receiver is performing the initial acquisition phase, identify a signal source specific code sequence that was used to form the signal received by the signal receiver (1500).
 
20. A signal receiver (1500) as claimed in claim 18 or 19, wherein the digital processor unit (1530) is adapted to, when the signal receiver (1500) is performing the initial acquisition phase, associate a set of preliminary parameters with the signal source specific code sequence, the preliminary parameters including:

a modified code vector;

a carrier frequency candidate vector;

an initial phase position;

a code phase position; and

a code index denoting a starting sample value for the modified code vector.


 
21. A signal receiver (1500) as claimed in any of claims 1 or 18 to 20, wherein the modified code vector comprises a number of beginning elements copied from a number of end elements of an original code vector and a number of end elements copied from a number of beginning elements of the original code vector, and wherein the digital processor unit (1530) is adapted to, when the signal receiver (1500) is performing the subsequent tracking phase:

calculate a prompt pointer indicative of a code sequence start position for each modified code vector, the initial prompt pointer being equal to the code index; and

assign, around each prompt pointer, at least one pair of early and late pointers, where the early pointer specifies a sample value being positioned at least one element before the prompt pointer's position and the late pointer specifies a sample value positioned at least one element after the prompt pointer's position.


 
22. A signal receiver (1500) as claimed in any of claims 1, or 18 to 21, wherein the digital processor unit (1530) is adapted to, when the signal receiver (1500) is performing the subsequent tracking phase, calculate a relevant set of carrier frequency-phase candidate vectors for a data word received from the interface unit and acquire, for each carrier frequency-phase candidate vector in the relevant set, an in-phase representation and a quadrature phase-representation.
 
23. A signal receiver (1500) as claimed in 22, wherein the digital processor (1530) is adapted to, when the signal receiver (1500) is performing the subsequent tracking phase:

multiply each data word with the in-phase representation of the carrier frequency-phase candidate vector in the relevant set to produce a first intermediate-frequency-reduced information word, and

multiply each data word with the quadrature-phase representation of the carrier frequency-phase candidate vector in the relevant set to produce a second intermediate-frequency-reduced information word.


 
24. A signal receiver (1500) as claimed in claim 23, wherein the digital processor unit (1530) is adapted to, when the signal receiver (1500) is performing the subsequent tracking phase:

multiply the first intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the prompt pointer to produce a first prompt-despread symbol string,

multiply the first intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by an early pointer to produce a first early-despread symbol string,

multiply the first intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by a late pointer to produce a first late-despread symbol string,

multiply the second intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the prompt pointer to produce a second prompt-despread symbol string,

multiply the second intermediate-frequency-reduced information word with a modified code vector starting at a position indicated by the early pointer to produce a second early-despread symbol string, and

multiply the second intermediate-frequency-reduced information word with a modified code vector starting at a positon indicated by the late pointer to produce a second late-despread symbol string.


 
25. A signal receiver (1500) as claimed in claim 24, wherein the digital processor unit (1530) is adapted to derive, for each despread symbol string, a resulting data word.
 
26. A signal receiver (1500) as claimed in claim 25, wherein the digital processor unit (1530) is adapted to derive the resulting data words by looking up a respective pre-generated value in a table.
 
27. A signal receiver (1500) as claimed in any of claims 22 to 25, wherein the digital processor unit (1530) is adapted to perform the multiplication between the data word and the in-phase representation of the carrier frequency-phase candidate vector respective between the data word and the quadrature-phase representation of the carrier frequency-phase candidate vector by means of at least one of a SIMD-operation and an XOR-operation.
 
28. A signal receiver (1500) as claimed in any of claims 22 to 27, wherein the digital processor unit (1530) is adapted to perform the multiplication between the intermediate-frequency-reduced information words and the modified code vectors by means of at least one SIMD-operation or XOR- operation.
 
29. A signal receiver (1500) as claimed in any of claims 22 to 28, wherein the digital processor unit (1530) is adapted to perform the multiplication between the intermediate-frequency-reduced information words and the modified code vectors by means of at least one of a SIMD-operation and an XOR-operation.
 
30. A signal receiver (1500) according to any one of the claims 18 to 29, wherein the digital processor unit (1530) is adapted to propagate, in connection with completing the processing of a current data word and initiating the processing of a subsequent data word:

a pointer indicating a first sample value of the subsequent data word,

a group of parameters describing the relevant set of carrier frequency-phase candidate vectors,

the relevant set of code vectors, and

prompt-, early-, and late pointers.


 
31. A computer program directly loadable into the internal memory (1535) of a signal receiver (1500),
characterised in that
the computer program comprises software adapted to control the signal receiver (1500) to operate as a signal receiver (1500) according to any of claims 1 to
 
32. A method for receiving and decoding spread spectrum signals via a two-stage process comprising an initial acquisition phase and a subsequent tracking phase, the method comprising:

receiving (1610) a continuous signal;

forming (1630) a plurality of data words by sampling the continuous signal to produce a sequence of sample values, each data word comprising a plurality of consecutive quantised sample values;

the method characterised by:

generating (1600) multiple carrier frequency-phase candidate vectors and code vectors, each vector being generated to be of a format compatible with the data words or vectors derived from the data words such that a correlation operation can be performed by steps including multiplying multiple samples in parallel; and

performing (1640), during the tracking phase, a correlation operation by multiplying each of the plurality of data words with a carrier frequency-phase candidate vector to decode the data word and multiplying a vector derived from the decoded data word with a code vector, the carrier frequency-phase candidate vector and code vector being one of the generated multiple vectors, the correlation operation including multiplying multiple samples in parallel.


 


Ansprüche

1. Ein Signalempfänger (1500) zum Empfangen und Decodieren von Spreizspektrumsignalen und zum Empfang und Decodieren von Spreizspektrumsignalen über ein zweistufiges Verfahren ausgelegt, eine anfängliche Erfassungsphase und eine nachfolgende Verfolgungsphase umfassend, wobei der Signalempfänger (1500) Folgendes aufweist:

eine Schnittstelleneinheit (1520), die ausgelegt ist, ein elektrisches Signal zu empfangen, das für ein kontinuierliches Funksignal repräsentativ ist, und in Reaktion darauf eine Folge von aufeinanderfolgenden quantisierten Abtastwerten zu erzeugen, die in Datenwörter unterteilt sind, die eine Vielzahl von Abtastwerten umfassen, und

eine digitale Prozessoreinheit (1530), die zum Empfangen der Datenwörter ausgelegt ist, dadurch gekennzeichnet, dass

die digitale Signalprozessoreinheit (1530) angepasst ist, um mehrere Trägerfrequenzphasen-Kandidatenvektoren und Codevektoren zu erzeugen, die von einem Format sind, das mit den von der Schnittstelleneinheit erzeugten Datenworten oder einem aus einem jeweiligen Datenwort abgeleiteten Vektor kompatibel ist, sodass ein Korrelationsvorgang durch Schritte ausgeführt wird, wobei mehrere Abtastungen parallel multipliziert werden;

die digitale Prozessoreinheit (1530) ist ferner ausgelegt, den Korrelationsvorgang, wenn der Signalempfänger die Verfolgungsphase ausführt, in Reaktion auf den Empfang der Datenwörter durch Multiplizieren eines empfangenen Datenwortes mit einem Trägerfrequenzphasen-Kandidatenvektor auszuführen, um das Datenwort zu decodieren und um einen aus dem decodierten Datenwort abgeleiteten Vektor mit einem Codevektor zu multiplizieren, wobei der Trägerfrequenzphasen-Kandidatenvektor und der Codevektor jeweils einer der von der digitalen Prozessoreinheit (1530) erzeugten mehreren Vektoren ist, bevor die Korrelationsoperation durchgeführt wird, und

der Signalempfänger (1500) ausgelegt ist, den Korrelationsvorgang durch Ausführen von Schritten auszuführen, wobei mehrere Abtastungen parallel multipliziert werden.


 
2. Signalempfänger (1500) nach Anspruch 1, wobei die digitale Prozessoreinheit (1530) ferner ausgelegt ist, den Korrelationsvorgang auf jede der von der Schnittstelleneinheit (1520) empfangenen Sequenz von Datenwörtern auszuführen, wobei die digitale Prozessoreinheit (1530) ferner dazu ausgelegt ist, mehrere Vektoren zur Verwendung in dem Korrelationsvorgang mit einem Wort zu erzeugen, während der Korrelationsvorgang auf einem zuvor empfangenen Datenwort ausgeführt wird.
 
3. Signalempfänger (1500) nach Anspruch 1, wobei die digitale Prozessoreinheit (1530) zur Erzeugung von mehreren Vektoren vor dem Empfang des kontinuierlichen Funksignals von einem Empfänger (1510) ausgelegt ist.
 
4. Signalempfänger (1500) nach einem der Ansprüche 1 bis 3, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, die mehrere Abtastungen parallel mittels einer XOR-Operation zu multiplizieren.
 
5. Signalempfänger (1500) nach einem der Ansprüche 1 bis 3, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, die mehrere Abtastungen parallel mittels einer SIMD-Operation zu multiplizieren.
 
6. Signalempfänger (1500) nach einem der vorhergehenden Ansprüche, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, jeden der mehreren Vektoren so zu erzeugen, dass dessen Format mit den von der Schnittstelleneinheit (1520) erzeugten Datenwörter oder mit dem aus dem Datenwort abgeleiteten Vektor durch Erzeugen der mehreren Vektoren kompatibel ist, sodass die Anzahl der in jedem Vektor enthaltenen Abtastwerte der Anzahl der Abtastwerte jedem der von der Schnittstelleneinheit (1520) erzeugten Datenwörter oder dem von dem jeweiligen Datenwort abgeleiteten Vektor entspricht.
 
7. Signalempfänger (1500) nach einem der vorhergehenden Ansprüche, wobei der Empfänger (1510) ausgelegt ist, ein kontinuierliches Funksignal mit einer relativ hohen Frequenz und einem Frequenzspektrum, das um eine erste Frequenz symmetrisch ist, zu empfangen und ein Zwischensignal mit einer relativ niedrigen Frequenz und einem Frequenzspektrum zu bilden, das um ein zweites Signal des kontinuierlichen Funksignals symmetrisch ist.
 
8. Ein Signalempfänger (1500) nach Anspruch 7, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen oder mehrere Trägerfrequenzkandidatenvektoren durch Folgendes zu erzeugen:

Bestimmen einer maximalen Frequenzänderung der zweiten Frequenz aufgrund von Dopplereffekten;

Definieren eines Dopplerfrequenzintervalls um die zweite Frequenz, wobei das Dopplerfrequenzintervall eine untere Frequenzgrenze aufweist, die gleich der Differenz zwischen der zweiten Frequenz und der maximalen Frequenzänderung ist, und eine höhere Frequenzgrenze, die gleich der Summe der zweiten Frequenz und der maximalen Frequenzvariation ist;

Teilen des Dopplerfrequenzintervalls in eine ganzzahlige Anzahl äquidistanter Frequenzschritte; und

Definieren eines Frequenzkandidatenvektors, der jedem Frequenzschritt entspricht.


 
9. Signalempfänger (1500) nach Anspruch 8, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen oder mehrere Trägerfrequenzphasen-Kandidatenvektoren durch Folgendes zu erzeugen:

Bestimmen einer ganzzahligen Anzahl von Anfangsphasenpositionen für den einen oder die mehreren Trägerfrequenzkandidatenvektoren; und

Definieren eines Trägerfrequenzphasen-Kandidatenvektors für jede Kombination eines Trägerfrequenzkandidatenvektors und einer Anfangsphasenposition.


 
10. Signalempfänger (1500) nach Anspruch 9, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, zu jedem Segment eines Trägerfrequenzphasen-Kandidatenvektors mindestens ein Element hinzuzufügen, sodass jedes Segment die gleiche Anzahl von Abtastungen als ein von der Schnittstelleneinheit (1520) erzeugtes Datenwort enthält.
 
11. Signalempfänger (1500) nach einem der vorhergehenden Ansprüche, wobei die Codevektoren jeweils für mindestens eine signalquellenspezifische Codesequenz repräsentativ sind.
 
12. Signalempfänger (1500) nach Anspruch 11, wobei die mindestens eine signalquellenspezifische Codesequenz einem Pseudozufallsrauschen entspricht.
 
13. Signalempfänger (1500) nach einem der vorangehenden Ansprüche, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen oder mehrere Coderatenkandidaten, die für mindestens eine signalquellenspezifische Codesequenz repräsentativ ist, durch Folgendes zu erzeugen:

Bestimmen einer maximalen Variation einer Coderate aufgrund von Dopplereffekten,

Definieren eines Dopplerratenintervalls um eine zentrale Coderate, wobei das Dopplerfrequenzintervall eine untere Coderatengrenze aufweist, die gleich der Differenz zwischen der mittleren Coderate und der maximalen Coderatenvariation ist, und eine höhere Coderatengrenze, die gleich der Summe der mittleren Coderate und der maximalen Coderatenvariation ist,

Aufteilen des Dopplerratenintervalls in eine ganzzahlige Anzahl von äquidistanten Coderatenschritten, und

Definieren eines Coderatenkandidaten in Bezug auf jeden Coderatenschritt


 
14. Signalempfänger (1500) nach Anspruch 13, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen oder mehrere Coderatenphasenkandidaten durch Folgendes zu erzeugen:

Bestimmen einer ganzzahligen Anzahl von möglichen Anfangscodephasenpositionen für den einen oder die mehreren Coderatenkandidaten;

Definieren, für jede signalquellenspezifische Codesequenz, eines Coderatenphasenkandidaten für jede Kombination von einem Codenratenkandidaten und einer Anfangscodephasenposition.


 
15. Signalempfänger (1500) nach Anspruch 14, wobei die Schnittstelleneinheit (1520) ausgelegt ist, die Sequenz von Abtastwerten durch Abtasten des elektrischen Signals mit einer Basisabtastrate zu erzeugen und die digitale Prozessoreinheit (1530) ausgelegt ist, jeden Coderatenphasenkandidaten mit der Basisabtastrate abzutasten, wobei ein entsprechender Coderatenphasen-Kandidatenvektor erzeugt wird.
 
16. Signalempfänger (1500) nach Anspruch 15, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen modifizierten Codevektor aus einem Coderatenphasen-Kandidatenvektor durch Folgendes zu erzeugen:

Kopieren einer Anzahl von Elementen von dem Ende des Coderatenphasen-Kandidatenvektors zum Anfang des modifizierten Codevektors, und

Kopieren einer Anzahl von Elementen vom Beginn des Ratenphasen-Kandidatenvektors zum Ende des modifizierten Codevektors.


 
17. Signalempfänger (1500) nach Anspruch 16, wobei der Signalempfänger (1500) einen Speicher (1535) umfasst und wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen Satz modifizierter Codevektoren entsprechend jeder signalquellenspezifischen Codesequenz in dem Speicher (1535) zu speichern, wobei:

jeder modifizierte Codevektor eine Anzahl von Elementen, die für eine abgetastete Version von mindestens einer vollständigen Codesequenz der jeweiligen signalquellenspezifischen Codesequenz repräsentativ sind, umfasst, und

ein jeweiliger modifizierter Codevektor für jede Kombination von einem Coderatenkandidaten und einer Codephasenposition definiert ist.


 
18. Signalempfänger (1500) nach Anspruch 1, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, wenn der Signalempfänger (1500) die anfängliche Erfassungsphase ausführt, einen Satz vorläufiger Parameter festzulegen, die erforderlich sind, um eine Decodierung von Signalen, die von dem Signalempfänger (1500) während der nachfolgenden Verfolgungsphase empfangen werden, einzuleiten.
 
19. Signalempfänger (1500) nach Anspruch 18, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, bei Ausführung der anfänglichen Erfassungsphase durch den Signalempfänger eine signalquellenspezifische Codesequenz zu identifizieren, die verwendet wurde, um das von dem Signalempfänger (1500) empfangene Signal zu bilden.
 
20. Signalempfänger (1500) nach Anspruch 18 oder 19, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, bei Ausführung der anfänglichen Erfassungsphase durch den Signalempfänger (1500) einen Satz von vorläufigen Parametern der signalquellenspezifischen Codesequenz zuzuordnen, wobei die vorläufigen Parameter Folgendes umfassen:

einen modifizierten Codevektor,

einen Trägerfrequenzkandidatenvektor,

eine anfängliche Phasenlage,

eine Codephasenposition und

einen Codeindex, der einen Startabtastwert für den modifizierten Codevektor angibt.


 
21. Signalempfänger (1500) nach einem der Ansprüche 1 oder 18 bis 20, wobei der modifizierte Codevektor eine Anzahl von Anfangselementen umfasst, die von einer Anzahl von Endelementen eines ursprünglichen Codevektors, sowie eine Anzahl von Endelementen, die von einer Anzahl der Anfangselemente des ursprünglichen Codevektors kopiert wurden, und wobei
die digitale Prozessoreinheit (1530) zu Folgendem ausgelegt ist, wenn der Signalempfänger (1500) die nachfolgende Verfolgungsphase ausführt:

Berechnen eines Aufrufzeigers, der eine Codesequenzstartposition für jeden modifizierten Codevektor ausweist, wobei der Anfangsaufrufzeiger gleich dem Codeindex ist, und

Zuordnen von mindestens einem Paar früher und später Zeiger um jeden Aufrufzeiger, wobei der frühe Zeiger einen Abtastwert spezifiziert, der mindestens ein Element vor der Position des Aufrufzeigers positioniert ist, und der späte Zeiger einen Abtastwert spezifiziert, der mindestens ein Element nach der Position des Aufrufzeigers positioniert ist.


 
22. Signalempfänger (1500) nach einem der Ansprüche 1 oder 18 bis 21, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, einen relevanten Satz von Trägerfrequenzphasen-Kandidatenvektoren, wenn der Signalempfänger (1500) die nachfolgende Verfolgungsphase ausführt, für ein von der Schnittstelleneinheit empfangenes Datenwort zu berechnen, und um für jeden Trägerfrequenzphasen-Kandidatenvektor in dem relevanten Satz eine In-Phasendarstellung und eine Quadraturphasendarstellung zu erfassen.
 
23. Signalempfänger (1500) nach Anspruch 22, wobei der digitale Prozessor (1530) für Folgendes ausgelegt ist, wenn der Signalempfänger (1500) die nachfolgende Verfolgungsphase ausführt:

Multiplizieren jedes Datenwortes mit der In-Phasendarstellung des Trägerfrequenzphasen-Kandidatenvektors in dem relevanten Satz, um ein erstes, um die Zwischenfrequenz reduziertes Informationswort zu erzeugen, und

Multiplizieren jedes Datenwortes mit der Quadraturphasendarstellung des Trägerfrequenzphasen-Kandidatenvektors in dem relevanten Satz, um ein zweites, um die Zwischenfrequenz reduziertes Informationswort zu erzeugen.


 
24. Signalempfänger (1500) nach Anspruch 23, wobei die digitale Prozessoreinheit (1530) für Folgendes ausgelegt ist, wenn der Signalempfänger (1500) die nachfolgende Verfolgungsphase ausführt:

Multiplizieren des ersten, um die Zwischenfrequenz reduzierten Informationswortes mit einem modifizierten Codevektor, der an einer Position beginnt, die durch den Aufrufzeiger angezeigt wird, um eine erste aufrufentspreizte Symbolfolge zu erzeugen,

Multiplizieren des ersten, um die Zwischenfrequenz reduzierten Informationswortes mit einem modifizierten Codevektor, der an einer Position beginnt, die durch einen frühen Zeiger angegeben ist, um eine erste frühentspreizte Symbolfolge zu erzeugen,

Multiplizieren des ersten, um die Zwischenfrequenz reduzierten Informationswortes mit einem modifizierten Codevektor, der an einer Position beginnt, die durch einen späten Zeiger angegeben ist, um eine erste spätentspreizte Symbolfolge zu erzeugen,

Multiplizieren des zweiten, um die Zwischenfrequenz reduzierten Informationswortes mit einem modifizierten Codevektor, der an einer Position beginnt, die durch den Aufrufzeiger angezeigt wird, um eine zweite aufrufentspreizte Symbolfolge zu erzeugen,

Multiplizieren des zweiten, um die Zwischenfrequenz reduzierten Informationswortes mit einem modifizierten Codevektor, der an einer Position beginnt, die durch den frühen Zeiger angezeigt wird, um eine zweite frühentspreizte Symbolfolge zu erzeugen, und

Multiplizieren des zweiten, um die Zwischenfrequenz reduzierten Informationswortes mit einem modifizierten Codevektor, der an einer Position beginnt, die durch den späten Zeiger angezeigt wird, um eine zweite spätentspreizte Symbolfolge zu erzeugen.


 
25. Signalempfänger (1500) nach Anspruch 24, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, für jede entspreizte Symbolfolge ein resultierendes Datenwort abzuleiten.
 
26. Signalempfänger (1500) nach Anspruch 25, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, die resultierenden Datenwörter abzuleiten, indem ein jeweiliger vorgenerierter Wert in einer Tabelle nachgeschlagen wird.
 
27. Signalempfänger (1500) nach einem der Ansprüche 22 bis 25, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, die Multiplikation zwischen dem Datenwort und der In-Phasendarstellung des Trägerfrequenzphasen-Kandidatenvektors jeweils zwischen dem Datenwort und der Quadraturphasendarstellung des Trägerfrequenzphasen-Kandidatenvektors mittels mindestens einer SIMD-Operation und einer XOR-Operation auszuführen.
 
28. Signalempfänger (1500) nach einem der Ansprüche 22 bis 27, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, die Multiplikation zwischen den um die Zwischenfrequenz reduzierten Informationswörtern und den modifizierten Codevektoren mittels mindestens einer SIMD-Operation oder einer XOR-Operation auszuführen.
 
29. Signalempfänger (1500) nach einem der Ansprüche 22 bis 28, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, die Multiplikation zwischen den um die Zwischenfrequenz reduzierten Informationsworten und den modifizierten Codevektoren mittels mindestens einer SIMD-Operation und einer XOR-Operation auszuführen.
 
30. Signalempfänger (1500) nach einem der Ansprüche 18 bis 29, wobei die digitale Prozessoreinheit (1530) ausgelegt ist, sich in Verbindung mit der Fertigstellung der Verarbeitung eines aktuellen Datenwortes auszubreiten und die Verarbeitung eines nachfolgenden Datenwortes zu initiieren:

Einen Zeiger, der einen ersten Abtastwert des nachfolgenden Datenwortes angibt.

Eine Gruppe von Parametern, die den relevanten Satz von Trägerfrequenzphasen-Kandidatenvektoren beschreiben,

den relevanten Satz von Codevektoren, und

Aufruf-, frühe und späte Zeiger.


 
31. Ein in den internen Speicher (1535) eines Signalempfängers (1500) direkt ladbares Computerprogramm, dadurch gekennzeichnet, dass
das Computerprogramm Software umfasst, die ausgelegt ist, den Signalempfänger (1500) zu steuern, um als Signalempfänger (1500) nach einem der Ansprüche 1 bis zu arbeiten.
 
32. Verfahren zum Empfangen und Decodieren von Spreizspektrumsignalen über ein zweistufiges Verfahren, eine anfängliche Erfassungsphase und eine nachfolgende Verfolgungsphase umfassend, wobei das Verfahren Folgendes umfasst:

Empfangen (1610) eines kontinuierlichen Signals,

Bilden (1630) einer Vielzahl von Datenwörtern durch Abtasten des kontinuierlichen Signals, um eine Folge von Abtastwerten zu erzeugen, wobei jedes Datenwort eine Vielzahl von

fortlaufenden quantisierten Abtastwerten umfasst:

Verfahren gekennzeichnet durch:

Erzeugen (1600) von mehreren Trägerfrequenzphasen-Kandidatenvektoren und Codevektoren, wobei jeder Vektor so erzeugt wird, dass er einem Format entspricht, das mit den aus den Datenwörtern abgeleiteten Datenwörtern oder Vektoren kompatibel ist, sodass ein Korrelationsvorgang durch Schritte ausgeführt werden kann, die parallele Multiplikation mehrerer Abtastungen umfassen, und

während der Verfolgungsphase Ausführen (1640) eines Korrelationsvorgangs durch das Multiplizieren jedes der Vielzahl der Datenwörter mit einem Trägerfrequenzphasen-Kandidatenvektor zum Decodieren des Datenwortes und Multiplizieren eines aus dem decodierten Datenwort abgeleiteten Vektors mit einem Codevektor, wobei der Trägerfrequenzphasen-Kandidatenvektor und der Codevektor einer der erzeugten mehreren Vektoren sind, und wobei der Korrelationsvorgang das parallele Multiplizieren mehrerer Abtastwerte umfasst.


 


Revendications

1. Récepteur de signaux (1500) pour la réception et le décodage de signaux à étalement de spectre et adapté pour recevoir et décoder des signaux à étalement de spectre via un processus à deux étapes comprenant une phase d'acquisition initiale et une phase ultérieure de suivi, le récepteur de signaux (1500) comprenant :

une unité d'interface (1520) adaptée pour recevoir un signal électrique représentatif d'un signal radio continu et en réponse à celui-ci, produire une séquence de valeurs d'échantillons quantifiées successives divisée en des mots de données comprenant une pluralité de valeurs d'échantillons ; et

une unité de processeur numérique (1530) adaptée pour recevoir les mots de données, caractérisé en ce que

l'unité de processeur numérique de signaux (1530) est adaptée pour générer de multiples vecteurs candidats de fréquence-phase de porteuse et vecteurs de code pour être sous un format compatible avec les mots de données produits par l'unité d'interface ou un vecteur dérivé respectivement d'un mot de données de sorte qu'une opération de corrélation peut être effectuée par étapes incluant la multiplication en parallèle de multiples échantillons ;

l'unité de processeur numérique (1530) est adaptée en outre, lorsque le récepteur de signaux est en train de réaliser la phase de suivi, pour effectuer l'opération de corrélation en réponse à la réception des mots de données en multipliant un mot de données reçu avec un vecteur candidat de fréquence-phase de porteuse pour décoder le mot de données et la multiplication d'un vecteur dérivé du mot de données décodé avec un vecteur de code, le vecteur candidat de fréquence-phase de porteuse et le vecteur de code étant un parmi les multiples vecteurs générés par l'unité de processeur numérique (1530) avant d'effectuer l'opération de corrélation ; et

le récepteur de signaux (1500) est adapté pour effectuer l'opération de corrélation en réalisant des étapes incluant la multiplication de multiples échantillons en parallèle.


 
2. Récepteur de signaux (1500) selon la revendication 1, dans lequel l'unité de processeur numérique (1530) est adaptée en outre pour effectuer l'opération de corrélation sur chacune d'une séquence de mots de données reçue de l'unité d'interface (1520), l'unité de processeur numérique (1530) étant en outre adaptée pour générer de multiples vecteurs destinés à être utilisés dans l'opération de corrélation avec un mot de données tandis que s'exécute l'opération de corrélation sur un mot de données reçu précédemment.
 
3. Récepteur de signaux (1500) selon la revendication 1, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer les multiples vecteurs avant que le signal radio continu soit reçu par un récepteur (1510).
 
4. Récepteur de signaux (1500) selon l'une quelconque des revendications 1 à 3, dans lequel l'unité de processeur numérique (1530) est adaptée pour multiplier les multiples échantillons en parallèle aux moyens d'une opération XOR.
 
5. Récepteur de signaux (1500) selon l'une quelconque des revendications 1 à 3, dans lequel l'unité de processeur numérique (1530) est adaptée pour multiplier les multiples échantillons en parallèle aux moyens d'une opération SIMD.
 
6. Récepteur de signaux (1500) selon l'une quelconque revendication précédente, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer chacun des multiples vecteurs pour être sous un format compatible avec les mots de données produits par l'unité d'interface (1520) ou le vecteur dérivé du mot de données en générant les multiples vecteurs de sorte que le nombre de valeurs d'échantillons compris dans chaque vecteur est égal au nombre de valeurs d'échantillons dans chaque mot de données produits par l'unité d'interface (1520) ou le vecteur dérivé du mot de données respectivement.
 
7. Récepteur de signaux (1500) selon l'une quelconque revendication précédente, dans lequel le récepteur (1510) est adapté pour recevoir un signal radio continu ayant une fréquence relativement élevée et un spectre de fréquence qui est symétrique autour d'une première fréquence et forme un signal intermédiaire ayant une fréquence relativement basse et un spectre de fréquence qui est symétrique autour d'un deuxième signal à partir du signal radio continu.
 
8. Récepteur de signaux (1500) selon la revendication 7, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer un ou plusieurs vecteurs candidats de fréquence porteuse par:

la détermination d'une variation maximale de fréquence de la deuxième fréquence en raison des effets Doppler ;

la définition d'un intervalle de fréquence Doppler autour de la deuxième fréquence, l'intervalle de fréquence Doppler ayant une limite en fréquence inférieure égale à la différence entre la deuxième fréquence et la variation de fréquence maximale et une limite en fréquence supérieure égale à la somme de la deuxième fréquence et la variation de fréquence maximale ;

la division de l'intervalle de fréquence Doppler en un nombre entier de pas de fréquence équidistants ; et

la définition d'un vecteur de fréquence candidat correspondant à chaque pas de fréquence.


 
9. Récepteur de signaux (1500) selon la revendication 8, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer un ou plusieurs vecteurs candidats de fréquence-phase de porteuse grâce à:

la détermination d'un nombre entier de positions de phases initiales pour l'un ou plusieurs vecteurs candidats de fréquence porteuse; et

la définition d'un vecteur candidat de fréquence-phase de porteuse pour chaque combinaison d'un vecteur candidat de fréquence porteuse et d'une position de phase initiale.


 
10. Récepteur de signaux (1500) selon la revendication 9, dans lequel l'unité de processeur numérique (1530) est adaptée pour ajouter au moins un élément à chaque segment d'un vecteur candidat de fréquence-phase de porteuse de sorte que chaque segment contient le même nombre d'échantillons comme un mot de données produit par l'unité d'interface (1520).
 
11. Récepteur de signaux (1500) selon l'une quelconque revendication précédente, dans lequel les vecteurs de code sont chacun représentatifs d'au moins une séquence de code spécifique de source de signal.
 
12. Récepteur de signaux (1500) selon la revendication 11, dans lequel l'au moins une séquence de code spécifique de source de signal est un bruit pseudo-aléatoire.
 
13. Récepteur de signaux (1500) selon l'une quelconque revendication précédente, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer un ou plusieurs candidats de débit de code représentatifs d'au moins une séquence de code spécifique de source de signal par :

la détermination d'une variation maximale d'un débit de code en raison des effets Doppler ;

la définition d'un intervalle de débit Doppler autour d'un débit de code central, l'intervalle de fréquence Doppler ayant une limite de débit de code inférieure égale à la différence entre le débit de code central et la variation maximale de débit de code et une limite de débit de code supérieure égale à la somme du débit de code central et la variation maximale de débit de code ;

la division de l'intervalle de débit Doppler en un nombre entier de pas de débit de code équidistants ; et

la définition d'un candidat de débit de code par rapport à chaque pas de débit de code.


 
14. Récepteur de signaux (1500) selon la revendication 13, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer un ou plusieurs candidats de débit de phase de code par ;
la détermination d'un nombre entier de positions de phase de code initiales possibles pour l'un ou plusieurs candidats de débit de code ;
la définition, pour chaque séquence de code spécifique de source de signal, d'un candidat de débit de phase de code pour chaque combinaison d'un candidat de débit de code et une position initiale de phase de code.
 
15. Récepteur de signaux (1500) selon la revendication 14, dans lequel l'unité d'interface (1520) est adaptée pour produire la séquence de valeurs d'échantillons par l'échantillonnage du signal électrique à un taux d'échantillonnage de base et l'unité de processeur numérique (1530) est adaptée pour échantillonner chaque candidat de débit de phase de code au taux d'échantillonnage de base, où un vecteur correspondant candidat de débit de phase de code est produit.
 
16. Récepteur de signaux (1500) selon la revendication 15, dans lequel l'unité de processeur numérique (1530) est adaptée pour générer un vecteur de code modifié à partir d'un vecteur candidat de débit de phase de code par :

le copiage d'un nombre d'éléments à partir de l'extrémité du vecteur candidat de débit de phase de code jusqu'au début du vecteur de code modifié ; et

le copiage d'un nombre d'éléments à partir du début du vecteur candidat de débit de phase jusqu'à l'extrémité du vecteur de code modifié.


 
17. Récepteur de signaux (1500) selon la revendication 16, dans lequel le récepteur de signaux (1500) comprend une mémoire (1535), l'unité de processeur numérique (1530) étant adaptée pour stocker un ensemble de vecteurs de code modifiés correspondant à chaque séquence de code spécifique de source de signal dans la mémoire (1535), dans lequel :

chaque vecteur de code modifié comprend un nombre d'éléments représentatif d'une version échantillonnée d'au moins une séquence de code complet de la séquence correspondante de code spécifique de source de signal ; et

un vecteur correspondant de code modifié est défini pour chaque combinaison de candidat de débit de code et de position de phase de code.


 
18. Récepteur de signaux (1500) selon la revendication 1, dans lequel l'unité de processeur numérique (1530) est adaptée pour, lorsque le récepteur de signaux (1500) est en train de réaliser la phase d'acquisition initiale, établir un ensemble de paramètres préliminaires requis pour débuter le décodage de signaux reçus par le récepteur de signaux (1500) pendant la phase ultérieure de suivi.
 
19. Récepteur de signaux (1500) selon la revendication 18, dans lequel l'unité de processeur numérique (1530) est adaptée pour, lorsque le récepteur de signaux est en train de réaliser la phase d'acquisition initiale, identifier une séquence de code spécifique de source de signal qui a été utilisée pour former le signal reçu par le récepteur de signaux (1500).
 
20. Récepteur de signaux (1500) selon la revendication 18 ou 19, dans lequel l'unité de processeur numérique (1530) est adaptée pour, lorsque le récepteur de signaux (1500) est en train de réaliser la phase d'acquisition initiale, associer un ensemble de paramètres préliminaires à la séquence de code spécifique de source de signal, les paramètres préliminaires incluant :

un vecteur de code modifié ;

un vecteur candidat de fréquence porteuse ;

une position de phase initiale ;

une position de phase de code ; et

un index de code désignant une valeur d'échantillon de départ pour le vecteur de code modifié.


 
21. Récepteur de signaux (1500) selon l'une quelconque des revendications 1 ou 18 à 20, dans lequel le vecteur de code modifié comprend un nombre d'éléments du début copié à partir d'un nombre d'éléments d'extrémité d'un vecteur de code initial et un nombre d'éléments d'extrémité copié à partir d'un nombre d'éléments du début du vecteur de code initial, et dans lequel l'unité de processeur numérique (1530) est adaptée pour, lorsque le récepteur de signaux (1500) est en train de réaliser la phase ultérieure de suivi :

calculer un pointeur immédiat indiquant une position de début de séquence de code pour chaque vecteur de code modifié, le pointeur immédiat initial étant égal à l'index de code ; et

l'affectation, autour de chaque pointeur immédiat, d'au moins une paire de pointeurs en avance et en retard, où le pointeur en avance spécifie une valeur d'échantillon positionnée au moins un élément avant la position du pointeur immédiat et le pointeur de retard spécifie une valeur d'échantillon positionnée au moins un élément après la position du pointeur immédiat.


 
22. Récepteur de signaux (1500) selon l'une quelconque des revendications 1, ou 18 à 21, dans lequel l'unité de processeur numérique (1530) est adaptée pour, lorsque le récepteur de signaux (1500) est en train de réaliser la phase ultérieure de suivi, calculer un ensemble pertinent de vecteurs candidats de fréquence-phase de porteuse pour un mot de données reçu de l'unité d'interface et pour acquérir, pour chaque vecteur candidat de fréquence-phase de porteuse dans l'ensemble pertinent, une représentation en phase et une représentation en phase quadrature.
 
23. Récepteur de signaux (1500) selon la revendication 22, dans lequel le processeur numérique (1530) est adapté pour, lorsque le récepteur de signaux (1500) est en train de réaliser la phase ultérieure de suivi :

la multiplication de chaque mot de données avec la représentation en phase du vecteur candidat de fréquence-phase de porteuse dans l'ensemble pertinent pour produire un premier mot d'informations réduit à une fréquence intermédiaire, et

la multiplication de chaque mot de données avec la représentation de phase en quadrature du vecteur candidat de fréquence-phase de porteuse dans l'ensemble pertinent pour produire un deuxième mot d'informations réduit à une fréquence intermédiaire.


 
24. Récepteur de signaux (1500) selon la revendication 23, dans lequel l'unité de processeur numérique (1530) est adaptée pour, lorsque le récepteur de signaux (1500) est en train de réaliser la phase ultérieure de suivi :

la multiplication du premier mot d'informations réduit à une fréquence intermédiaire avec un vecteur de code modifié débutant à une position indiquée par le pointeur immédiat pour produire une première chaîne de symboles désétalés immédiats,

la multiplication du premier mot d'informations réduit à une fréquence intermédiaire avec un vecteur de code modifié débutant à une position indiquée par un pointeur en avance pour produire une première chaîne de symboles désétalés en avance,

la multiplication du premier mot d'informations réduit à une fréquence intermédiaire avec un vecteur de code modifié débutant à une position indiquée par un pointeur en retard pour produire une première chaîne de symboles désétalés en retard,
la multiplication du deuxième mot d'informations réduit à une fréquence intermédiaire avec un vecteur de code modifié débutant à une position indiquée par le pointeur immédiat pour produire une deuxième chaîne de symboles désétalés immédiats,

la multiplication du deuxième mot d'informations réduit à une fréquence intermédiaire avec un vecteur de code modifié débutant à une position indiquée par le pointeur en avance pour produire une deuxième chaîne de symboles désétalés en avance, et

la multiplication du deuxième mot d'informations réduit à une fréquence intermédiaire avec un vecteur de code modifié débutant à une position indiquée par le pointeur en retard pour produire une deuxième chaîne de symboles désétalés en retard.


 
25. Récepteur de signaux (1500) selon la revendication 24, dans lequel l'unité de processeur numérique (1530) est adaptée pour obtenir, pour chaque chaîne de symboles désétalés, un mot de données résultant.
 
26. Récepteur de signaux (1500) selon la revendication 25, dans lequel l'unité de processeur numérique (1530) est adaptée pour obtenir les mots de données résultants en recherchant une valeur respective produite à l'avance dans une table.
 
27. Récepteur de signaux (1500) selon l'une quelconque des revendications 22 à 25, dans lequel l'unité de processeur numérique (1530) est adaptée pour réaliser la multiplication entre le mot de données et la représentation en phase du vecteur candidat de fréquence-phase de porteuse respectif entre le mot de données et la représentation de phase en quadrature du vecteur candidat de fréquence-phase de porteuse aux moyens d'au moins une parmi une opération SIMD et une opération XOR.
 
28. Récepteur de signaux (1500) selon l'une quelconque des revendications 22 à 27, dans lequel l'unité de processeur numérique (1530) est adaptée pour réaliser la multiplication entre les mots d'information réduits à la fréquence intermédiaire et les vecteurs de code modifiés aux moyens d'au moins une opération SIMD ou une opération XOR.
 
29. Récepteur de signaux (1500) selon l'une quelconque des revendications 22 à 28, dans lequel l'unité de processeur numérique (1530) est adaptée pour réaliser la multiplication entre les mots d'information réduit à la fréquence intermédiaire et les vecteurs de code modifiés aux moyens d'au moins une parmi une opération SIMD et an opération XOR.
 
30. Récepteur de signaux (1500) selon l'une quelconque des revendications 18 à 29, dans lequel l'unité de processeur numérique (1530) est adaptée pour propager, en relation avec l'accomplissement du traitement d'un mot de données actuel et l'initiation du traitement d'un mot de données suivant :

un pointeur indiquant une première valeur d'échantillon du mot de données suivant,

une groupe de paramètres décrivant l'ensemble pertinent de vecteurs candidats de fréquence-phase de porteuse,

l'ensemble pertinent de vecteurs de code, et

les pointeurs immédiat, en avance et en retard.


 
31. Programme informatique directement chargeable dans la mémoire interne (1535) d'un récepteur de signaux (1500), caractérisé en ce que
le programme informatique comprend un logiciel adapté pour contrôler le récepteur de signaux (1500) pour fonctionner comme un récepteur de signaux (1500) selon l'une quelconque des revendications 1 à
 
32. Procédé pour la réception et le décodage de signaux à étalement de spectre via un processus à deux étapes comprenant une phase d'acquisition initiale et une phase ultérieure de suivi, le procédé comprenant :

la réception (1610) d'un signal continu ;

la formation (1630) d'une pluralité de mots de données par l'échantillonnage du signal continu pour produire une séquence de valeurs d'échantillons, chaque mot de données comprenant une pluralité de valeurs d'échantillons quantifiées successives ; le procédé caractérisé par :

la génération (1600) de multiples vecteurs candidats de fréquence-phase de porteuse et de vecteurs de code, chaque vecteur étant généré pour être sous un format compatible avec les mots de données ou des vecteurs dérivés des mots de données de sorte qu'une opération de corrélation peut être réalisée par étapes incluant la multiplication de multiples échantillons en parallèle ; et

la réalisation (1640), pendant la phase de suivi, d'une opération de corrélation en multipliant chacune de la pluralité de mots de données avec un vecteur candidat de fréquence-phase de porteuse pour décoder le mot de données et en multipliant un vecteur dérivé du mot de données décodé avec un vecteur de code, le vecteur candidat de fréquence-phase de porteuse et le vecteur de code faisant partie d'un des multiples vecteurs générés, l'opération de corrélation incluant la multiplication en parallèle de multiples échantillons.


 




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REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description




Non-patent literature cited in the description