(19)
(11)EP 1 873 953 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
03.04.2013 Bulletin 2013/14

(21)Application number: 07111170.2

(22)Date of filing:  27.06.2007
(51)Int. Cl.: 
H04L 1/00  (2006.01)

(54)

Method of communication adapted to the transmission of data packets

Kommunikationsverfahren zur Übertragung von Datenpaketen

Procédé de communication adapté à la transmission de paquets de données


(84)Designated Contracting States:
DE FR GB

(30)Priority: 30.06.2006 FR 0652747

(43)Date of publication of application:
02.01.2008 Bulletin 2008/01

(73)Proprietor: Thomson Licensing
92130 Issy-les-Moulineaux (FR)

(72)Inventors:
  • Fontaine, Patrick
    92648, BOULOGNE CEDEX (FR)
  • Dore, Renaud
    92648, BOULOGNE CEDEX (FR)
  • Jeanne, Ludovic
    92648, BOULOGNE CEDEX (FR)

(74)Representative: Le Dantec, Claude 
Technicolor 1-5 rue Jeanne d'Arc
92130 Issy-les-Moulineaux
92130 Issy-les-Moulineaux (FR)


(56)References cited: : 
US-A1- 2003 031 275
US-A1- 2005 039 103
  
  • LI-CHUN WANG ET AL: "Cross-layer goodput analysis for rate adaptive IEEE 802.11a WLAN in the generalized Nakagami fading channel" COMMUNICATIONS, 2004 IEEE INTERNATIONAL CONFERENCE ON PARIS, FRANCE 20-24 JUNE 2004, PISCATAWAY, NJ, USA,IEEE, 20 June 2004 (2004-06-20), pages 2312-2316, XP010709679 ISBN: 0-7803-8533-0
  
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

1. Field of the invention



[0001] The present invention relates to the field of digital telecommunications and more precisely the transmission of packets at high-throughput on channels that are noisy and/or subject to interference.

2. Technological background



[0002] According to the state of the art, the transmission of data packets on a wireless link varies greatly in quality. In order to maximize the throughput of a communication, it is possible to implement link adaptation mechanisms.

[0003] , Thus, patent document US6643322 filed in the name of Aperto Networks, Inc. describes a communication system allowing the use of several types of modulations and therefore making it possible to choose a spectral efficiency (that is to say the number of useful bits transmitted per second and per hertz) on the basis of the correctly received or erroneous packets. Thus, if the number of consecutive packet acknowledgements exceeds a certain threshold, the modulation parameters are modified to allow an immediately higher spectral efficiency. If, conversely, the number of consecutive packets that are not acknowledged exceeds a certain limit, the modulation parameters are modified to allow an immediately lower spectral efficiency.

[0004] This technique presents the drawback of not being fully adapted to the quality of a communication channel that is noisy and/or subject to interference.

[0005] Document entitled "Cross-layer Goodput Analysis for Rate Adaptive IEEE 802.11 a WLAN in the Generalized Nakagami Fading Channel" written by Li-Chun Wang, Ya-Wen Lin and Wei-Cheng Liu, published on June 20, 2004 in Communications, 2004 IEEE International Conference on paris, France 20-24 June 2004, pages 2312-2316 describes a method for evaluating the goodput performance of an IEEE 802.11a wireless local area network from both the media access control layer and physical layer perspectives.

[0006] Patent document US2005/039103 published on February 17, 2005 describes a system to adjust the bit rate to the channel noise conditions to reduce the need for a cable system operator to monitor noise conditions on the line. Patent document US2003/0031275 published on February 13, 2003 describes a robust burst detection and acquisition method and system in a burst communication system.

3. Summary of the invention



[0007] The invention is aimed at alleviating these drawbacks of the prior art.

[0008] More particularly, the objective of the invention is to improve the performance of a communication system while remaining relatively simple to implement.

[0009] For this purpose, the invention proposes a method of communication adapted to the transmission of data packets that can be transmitted according to various physical modes according to claim 1.

[0010] Advantageously, at least some of the packets received are not intended for the apparatus that receives the packets and estimates the error rate on the basis of the packets.

[0011] Thus, the terminal can have a very good estimate of the transmission channel for the set of physical modes considered.

[0012] According to advantageous characteristics, the physical mode comprises the modulation and/or the rate of an error correcting code and/or the type of an error correcting code.

[0013] According to a particular characteristic, the estimation of the error rate comprises an error detection code verification step.

[0014] According to an advantageous characteristic, the method comprises a step of transmitting a cue representative of the packet error rate for each physical mode, the cue representative of the rate being transmitted to a station that is able to send radio bursts intended for the terminal.

[0015] Advantageously, the method comprises a step for determining statistical data regarding error rates for packets received on the basis of the estimation of the packet error rate and of at least one parameter associated with a physical mode.

[0016] According to a particular characteristic, the method comprises a step of transmitting cues representative of the statistical data, the cue representative of the statistical data being transmitted to a station that is able to send radio bursts intended for the terminal.

[0017] According to a particular characteristic, the method comprises a step of estimating a signal-to-noise ratio on the basis of the estimation of the packet error rate and of at least one parameter associated with a physical mode.

[0018] According to another characteristic, the method comprises a step of transmitting data representative of a signal-to-noise ratio for at least some of the physical modes of the set, these data being transmitted to a station that is able to send radio bursts for the terminal.

[0019] According to a particular embodiment, the transmission of data packets is performed in accordance with a protocol of the IEEE 802.16 type.

[0020] According to an advantageous characteristic, the method comprises a step of transmitting a physical mode modification request for the transmission of data packets.

4. List of figures



[0021] The invention will be better understood, and other features and advantages will appear on reading the description which follows, the description referring to the appended drawings among which:
  • Figure 1 represents a communication network according to a particular embodiment of the invention;
  • Figure 2 schematically illustrates an apparatus of the communication network of Figure 1, according to a particular embodiment of the invention;
  • Figures 3 to 4 present a method respectively of reception and of transmission implemented in elements of the network of Figure 1; and
  • Figure 5 illustrates a downlink sub-frame transmitted in the network of Figure 1.

5. Detailed description of the invention



[0022] According to the prior art, the link adaptation is performed as a function of data received by a local communication node. According to the invention, conversely, the local communication node uses MAC level packets ("Medium Access Channel", which corresponds to level II of the ISO communication layers of the OSI and is located immediately above the physical layer) which are not intended for it so as to obtain complementary cues regarding the quality of the link that may be associated with several types of communication parameters. Thus, the local node can benefit from relatively rich statistics which correspond to recent and numerous measurements, even when the local node receives little data. Furthermore, the local can a prediction of the quality on various physical modes used for communications to other nodes. In this way, the stations (or nodes) are no longer aware only of the quality of the link on the physical mode that they use but also on other physical modes used.

[0023] Figure 1 presents a communication network 1 according to a particular embodiment of the invention. The network 1 comprises a base station 10 and subscriber stations (or SS) 11 to 13 which correspond to terminals. The base station 10 transmits downlink sub-frames the SSs 11 to 13. It receives uplink sub-frames from the SSs 11 to 13. The exchanges are done in accordance with an IEEE 802.16 (or WiMax®) protocol.

[0024] Figure 5 illustrates a downlink sub-frame 5 transmitted the BS 10 and comprising:
  • a preamble 50;
  • a header 51 which describes the start of the sub-frame 5;
  • a burst 52 transmitted which describes the remainder of the sub-frame 5;
  • a succession of bursts 53 to 55 intended respectively for the SSs 11 to 13.
According to the IEEE802.16 standard, there is provision for several physical modes (that is to say association of a modulation (on OFDM or "Orthogonal Frequency Division Multiplexing") and of an error correcting code (or FEC = "Forward Error Correction") making it possible to choose a spectral efficiency (that is to say the number of useful bits transmitted per second and per hertz). Thus, the bursts 53 to 55 are ordered by physical mode from the most robust to the least robust. The header 51 is, for example, modulated in accordance with a BPSK modulation (or "Binary Phase Shift Keying" or two-phase modulation) with a corrector code with a rate 1/2, the corresponding physical mode being denoted BPSK1/2. The burst 52 (respectively 53) is, for example, modulated in accordance with a QPSK modulation (or "Quaternary Phase Shift Keying" or four-phase modulation) with a corrector code with a rate ¾ (respectively ½), the corresponding physical mode being denoted QPSK3/4 (respectively QPSK1/2). The burst 54 (respectively 55) is, for example, modulated in accordance with a QAM modulation (or "Quadrature Amplitude Modulation" or sixteen-state, respectively sixty-four state, phase quadrature amplitude modulation) with a corrector code with a rate ¾ (respectively ½), the corresponding physical mode being denoted 16QAM3/4 (respectively 64QAM1/2).

[0025] Each burst 53 to 55 groups together several PDUs ("Protocol Data Unit") of MAC level (or MAC PDUs). Thus, burst 53 groups together several MAC PDUs 530,.. , 53n,.... Each MAC PDU comprises a header 53n1, useful data 53n2 (or "payload data") and a CRC 53n3 ("Cyclic Redundancy Check"). The CRC makes it possible to check whether the packet is in error. The MAC PDUS themselves comprise useful data to be transmitted and associated with MSDUs ("MAC Service Data Unit").

[0026] According to the IEEE802.16 standard in its 2004 or 2005 version, the modulation is determined as a function of a ratio C/(N+I) where C represents the power of the useful signal received, N the noise level and I the interference level. The measurement of the ratio C/(N+I) is made on receipt of a burst intended for the terminal which performs this measurement.

[0027] According to the invention, the measurement of the ratio C/(N+I) is also made on receipt of a burst intended for the terminal which performs this measurement and on receipt of bursts intended for the other terminals.

[0028] Figure 2 schematically illustrates an apparatus 2 corresponding to one of the terminals 11 to 13.

[0029] The apparatus 2 comprises, linked together by an address and data bus 24, also transporting a clock signal:
  • a microprocessor 21 (or CPU);
  • a nonvolatile memory of ROM type ("Read Only Memory") 22;
  • a random access memory or RAM ("Random Access Memory") 23;
  • a module 25 for transmitting a signal on the wireless link; and
  • a module 26 for receiving a signal on the wireless link.


[0030] Moreover, each of the elements 21 to 27 is well known to the person skilled in the art. These common elements are not described here.

[0031] It is observed that the word "register" used in the description designates in each of the memories mentioned, both a memory area of small capacity (a few binary data items) and also a memory area of large capacity (making it possible to store an entire program or all or part of the data representative of an audio/video service received).

[0032] The ROM memory 22 comprises in particular:
  • a program "prog" 220;
  • preprogrammed physical modes 221; and
  • threshold values 222.


[0033] The algorithms implementing the steps of the method described hereafter are stored in the ROM memory 22 associated with the apparatus 2 implementing these steps. On power-up, the microprocessor 21 loads and executes the instructions of these algorithms.

[0034] The random access memory 23 comprises in particular:
  • in a register 230, the program for operating the microprocessor 21 loaded on power-up of the apparatus 23;
  • a cue representative of physical mode and in particular of the modulation in a register 231 of the rate or type of error correcting code in a register 232;
  • an estimated value of C/(N+I) in a register 233
  • results of reception quality measurements in a register 234;
  • data received or to be transmitted in a register 235.


[0035] Figure 3 schematically illustrates a downlink sub-frame reception algorithm, implemented in the apparatus 2.

[0036] In the course of a first step 30, the apparatus 2 initializes its various components and variables.

[0037] Then, in the course of a step 31, the apparatus 2 receives the start of a downlink sub-frame 5 and decodes the preamble 50 and the header 51. In the course of this step, the apparatus 2 initializes a variable corresponding to a rank of current burst (rank 0 corresponding to burst 52). The header 51 comprises a descriptor of the first four bursts while the first burst 52 comprises a descriptor of the subsequent bursts. Thus, the apparatus 2 extracts from the header 51, the cues representative of the modulation and coding (physical mode) of the first four bursts as well as their length, and stores them.

[0038] Thereafter, in the course of a step 32, the apparatus 2 receives a burst of rank corresponding to the current burst.

[0039] Then, in the course of a step 33, the apparatus 2 demodulates and decodes the burst depending on its physical mode. If it is the first burst 52, the apparatus 2 extracts therefrom the cues representative of the physical mode of the bursts according to the fourth burst as well as their length, and stores them. The apparatus 2 stores, in the register 234, the result of a measurement of quality of reception of the burst received associated with the CRC after decoding (number of MAC PDUs received properly, that is to say correct CRC after FEC decoding and/or number of MAC PDUs received badly, that is to say false CRC after FEC decoding), while associating it with the physical parameters of the current burst (as stored during reception of the header 51 and the first burst 52). This step 32 is performed even if the current burst is not intended the apparatus 2. This implementation is relatively simple and it possible to have very complete measurement data. In the course of step 33, number of PDUs received properly and/or received badly (and possibly the total number of PDUs received) is stored as a function of the physical parameters for each frame, so as to have to keep the age of the measurements. Thus, for example, the apparatus 2 increments a counter of properly received PDUs and/or a counter of badly received PDUS, each counter being associated with a (modulation, FEC) pair (FEC representing here a rate and/or a type of FEC) and with a measurement time-stamp. Advantageously, a sliding time window is employed to store the measurements; thus, the most recent measurements overwrite the oldest measurements (thereby making it possible to have up-to-date (and not obsolete) measurements and to limit the necessary memory size). According to a variant, the counters corresponding to a time-stamp older than a predetermined time-stamp (for example 100 ms or a few hundred milliseconds to several seconds depending on the speed of fluctuation of the channel) are erased. According to another variant, the counters are associated with numbers of properly received PDUs and/or with numbers of badly received PDUs (without being associated with a time-stamp). Advantageously, according to this variant, the counters are set to zero periodically (for example every 200 ms) so as to avoid having obsolete measurements.

[0040] According to a variant, measurements are performed only on the bursts corresponding to a subset of the available physical parameters, certain physical parameters not necessarily being implemented by the apparatus 2 (for example if the throughput offered by a given modulation/FEC rate is too high or too low for an application implemented in the apparatus 2).

[0041] According to the embodiment described previously, if the MAC header of a PDU at the start of a burst is badly received, the terminal does not decode the remainder of the burst and goes to the next burst. According to a variant, if the MAC header of a MAC PDU at the start of a burst is badly received, the terminal implements a technique of decoding the remainder of the burst by resynchronizing itself in an arbitrary manner (for example according to the technique described in the French patent application registered under the reference 0650841 but not published to date and which envisages a resynchronization to error check fields of the HCS ("Header Check Sum") or CRC type; according to the technique described in this document, when packet level synchronization is lost in a MAC PDU, resynchronization is effected by searching for known data in the burst and/or by checking whether, in a sliding window of length corresponding to a MAC PDU length, data received satisfies a CRC or HCS condition).

[0042] Then, in the course of a test 34, the apparatus 2 checks whether at least one MAC PDU of the current burst is intended for the apparatus 2.

[0043] In the affirmative, in the course of a step 35, the apparatus 2 transmits the decoded MAC PDUs, arising from the current burst and intended for the apparatus 2, to an application or stores them in the register 235.

[0044] In the negative or after step 35, in the course of a test 36, the apparatus 2 checks whether the current burst is the last burst of the sub-frame 5.

[0045] In the negative, in the course of a step 39, the apparatus 2 points to the next burst which becomes a new current burst and step 32 is repeated.

[0046] In the affirmative, in the course of a step 36, the apparatus 2 calculates statistics based on the measurements recorded in the course of step 33.

[0047] Thereafter, in the course of a step 37, the apparatus calculates for each (modulation, FEC) pair a packet error rate or PER by taking into account all the counters associated with this pair and updated during step 33.

[0048] Then, in the course of a step 38, the apparatus 2 determines a (modulation, FEC) pair whose (calculated during step 37) is less than a PER threshold (for example requested by an application or determined by during the initialization step 30). When several (modulation, FEC) pairs have a required PER, the pair ensuring the highest throughput is advantageously chosen. When no pair the required PER, the most robust pair is chosen.

[0049] According to the IEEE 802.16 standard, for each pair of physical parameters, a high threshold and a low threshold of ratio C/N+l is defined. When the ratio C/N+I measured for the current physical parameters is outside the permitted range, a message containing the value of C/N+I is transmitted to the base station so as to change physical parameters. According to the invention, a ratio C/N+I depending on the desired (modulation, FEC) pair is transmited.

[0050] Thereafter, in the course of a step 310, the apparatus 2 deduces from the measurements performed, a ratio C/(N+I) representative of the quality of the link by converting the statistics into a value of C/(N+I) compatible with the IEEE 802.16 standard. Thus, with each possible (modulation, FEC) pair, the apparatus 2 matches a value C/N+l lying between the low and high thresholds defined for these physical parameters. By way of illustration, if a 16QAM1/2 modulation is desired and if the low and high thresholds are respectively -78dBm and -73dBm, to impose these physical parameters, the apparatus 2 transmits a message with, for example, C/N+l equal to -75dBm (this value not being in the ranges authorized for the other modulations).

[0051] Then, the apparatus 2 transmits this value C/(N+I) to the base station 10 by transmitting a message of the type RNG-REQ ("Ranging Request") or DBPC-REQ ("Downlink Burst Profile Change request") during the maintenance intervals provided for this purpose according to the IEEE802.16 standard (the transmission of a data item of the type C/N+I making it possible to preserve compatibility with the IEEE802.16 standard). The base station 1 acknowledges a new burst profile. According to the IEEE802.16 standard, a profile is determined by a (modulation, FEC) pair and associated low and high thresholds C/N+I.

[0052] According to a variant embodiment (for example for a communication that is not compatible with the 2004 or 2005 version of lEEE802.16 or a communication according to a proprietary protocol), step 310 is replaced with a step of transmitting a message (from the terminal to the base station) comprising the desired physical parameters or the PER (for each pair) or the statistics. If the terminal transmits the statistics or the PER for each pair, the base station determines the optimum physical parameters (possibly taking account of the constraints associated with the global network (in particular available bandwidth)).

[0053] Then, step 31 is repeated.

[0054] According to the IEEE802.16 standard (in its 2004 or 2005 version), a terminal transmits a value of C/(N+I) as a function of physical measurements performed on a burst intended for the terminal which performs the measurement. On the other hand, according to the invention, a terminal transmits a value of C/(N+I) deduced, in particular, from calculated statistics deduced from for and decoding bursts intended for other terminals.

[0055] Furthermore, according to the state of the art, the quality of reception is measured at a relatively low physical level, which does not make it possible to distinguish a disturbance related to an interferer or to a propagation channel poorly adapted to the system (for example very frequency-selective channel) (in this case, increasing the robustness of the physical mode does nothing to change the quality of reception). According to the invention, account is taken of the measurement of quality of reception at the higher level. Thus, two distinct measurements of C/N+I at the physical level before FEC decoding that give one and the same result may correspond to a very different quality of link. In a dual manner, two distinct measurements of C/N+I at the physical level before FEC decoding that give a very different result may correspond to a similar quality of link with much the same PER. A determination of the quality of the link based on the PER at the MAC level enables better adjustment of the physical parameters since it takes into account the real decoding performance. Moreover, the invention makes it possible to go down or up by several robustness levels in the physical parameters. Thus, it is possible to go from an OFDM-based modulation of the type 64QAM1/2 to QPSK3/4 (or vice versa) without going through an intermediate 16QAM1/2 modulation.

[0056] Figure 4 schematically illustrates a downlink sub-frame transmission algorithm, implemented in the base station 10.

[0057] In the course of a first step 40, the base station 10 initializes its various components and variables. In the course of this step, physical mode parameters are defined by default.

[0058] Then, in the course of a step 41, the base station 10 receives an uplink frame from a terminal with a ratio value C/(N+I). This ratio can be calculated in accordance with procedures known per se or be estimated in accordance with the invention, as presented previously. The base station 10 deduces corresponding physical mode parameters therefrom (based only on the mode corresponding to the ratio C/N+I transmitted by the terminal). These parameters are, for example, stored in a table and their values are determined as a function of a predetermined interval C/(N+I) to which the value C/(N+I) received belongs. According to a variant, the base station also takes into account the ratios of all or some of the other terminals so as to allocate each one a mode that makes it possible to optimize the global bandwidth.

[0059] According to a variant of step 41, the base station 10 receives an uplink frame from a terminal a message comprising the desired physical parameters or the PER (for each pair) or the statistics. The base station then fixes the physical mode for the corresponding terminal as a function of these data (possibly taking into account the data of C/N+I, PER, statistics and/or particular physical mode request transmitted by the other terminals). When the base station receives an uplink frame comprising statistics, it calculates a packet error rate for each (modulation, FEC) pair. When the base station receives an uplink frame comprising the PER or has calculated a PER, it determines a (modulation, FEC) pair whose PER is less than a determined PER threshold (for example by parametrization on the basis or otherwise of the type of terminal).

[0060] Thereafter, in the course of a step 42, the MAC layer of the base station receives from a higher layer, a request to transmit data to a terminal.

[0061] Then, in the course of a step 43, the base station 10 constructs one or more bursts containing the data to be transmitted as a function of the physical mode parameters associated with the destination terminals. The burst or bursts are then inserted into downlink sub-frames so as to be transmitted to their destination and allow other terminals to make measurements of quality of transmission as a function of the corresponding physical mode parameters. Step 41 is thereafter repeated.

[0062] Of course, the invention is not limited to the embodiments described above.

[0063] In particular, neither is the invention limited to the transmission of data in accordance with a wireless communication standard (for example IEEE802.16) but relates also to all transmissions on any medium, and in particular on noisy wire-based channels or on a recording channel. The invention applies not only to centralized networks with a master station or base station but also to networks where a terminal can receive data bursts originating from several stations with several physical modes. According to this configuration, the terminal receives the packets sent by all or some of the stations, including the bursts which are not intended for it and estimates the packet error rate for all or some of physical modes as a function of each sending station.

[0064] The invention is compatible with numerous applications. It makes it possible in particular to undertake video coding or SVC ("Scalable Video Coding" (such a possibility In in the MPEG4 video standard); according to an SVB, it is possible to undertake high-definition video if the throughput is good (that is to say if the spectral efficiency is high, this corresponding to a high-rate modulation (for example 64QAM) and a low FEC rate) and single-definition if the throughput is lower (for example 8PSK).

[0065] According to certain embodiments, the invention also makes it possible to enhance the reliability of the link.

[0066] The invention uses error detection at packet level advantageously at MAC level or in the higher layers which can be based on any error detection procedure. According to a variant, packet error detection can also be based on the verification of an FEC (for example the number of false bytes detected by a Reed-Solomon decoder or metric given by a Viterbi decoder).

[0067] The application of the invention to transmissions of data modulated in accordance with a modulation based on OFDM is particularly advantageous, since the data are transmitted along a broadband channel which may be very frequency-selective. Nevertheless, the invention also applies to modulations of the spread spectrum or narrowband type.

[0068] According to various implementations of the invention, the type of modulation (for example PSQK, QPSK, 8PSK, 16QAM, 32QAM, 64QAM associated or otherwise with an OFDM modulation) and/or the rate of the error correcting code considered (for example ½ or ¾) and/or the type of error correcting coding (Reed-Solomon, Convolutional code or turbo-code, for example) are considered among the physical parameters for which the error rate is estimated.


Claims

1. Method of communication adapted to the transmission of data packets (530, 53n), that can be transmitted according to various physical modes, the method comprising the step of:

- reception of packets (32), each packet being sent in at least one radio burst (52 to 55) associated with a physical mode chosen from a set of at least two physical modes;
the method being characterized in that it further comprises the step of:

- estimation of the packet error rate (33) based on a count of properly received packets and on a count of badly received packets for each physical mode of the said set.


 
2. Method according to Claim 1, characterized in that at least some of the packets received are not intended for the apparatus that receives the said packets and estimates the error rate on the basis of the said packets.
 
3. Method according to either of Claims 1 and 2, characterized in that the said physical mode comprises the modulation.
 
4. Method according to any one of Claims 1 to 3, characterized in that the said physical mode comprises the rate or the type of an error correcting code.
 
5. Method according to any one of Claims 1 to 4, characterized in that the estimation of the error rate comprises an error detection code verification step.
 
6. Method according to Claim 5, characterized in that it comprises a step of transmitting a cue representative of the said packet error rate for at least some of the physical modes of the said set, the said cue representative of the said rate being transmitted to a station that is able to send radio bursts to the said terminal.
 
7. Method according to any one of Claims 1 to 6, characterized in that it comprises a step (37) of determining statistical data regarding error rates for packets received on the basis of the said estimation of the said packet error rate and of at least one parameter associated with a physical mode.
 
8. Method according to Claim 7, characterized in that it comprises a step of transmitting cues representative of the said statistical data, the said cues representative of the said statistical data being transmitted to a station that is able to send radio bursts to the terminal implementing the method.
 
9. Method according to any one of Claims 1 to 8, characterized in that it comprises a step (310) of estimating a signal-to-noise ratio on the basis of the said estimation of the said packet error rate and of at least one parameter associated with a physical mode.
 
10. Method according to Claim 9, characterized in that it comprises a step (310) of transmitting data representative of a signal-to-noise ratio for at least some of the physical modes of the said set, the data representative of a signal-to-noise ratio being transmitted to a station that is able to send radio bursts to the said terminal.
 
11. Method according to any one of Claims 1 to 10, characterized in that the said transmission of data packets is performed in accordance with a protocol of the IEEE 802.16 type.
 
12. Method according to any one of Claims 1 to 11, characterized in that it comprises a step of transmitting a physical mode modification request for the transmission of data packets.
 


Ansprüche

1. Verfahren für die Kommunikation, das für die Übertragung von Datenpaketen (530, 53n) ausgelegt ist, die in Übereinstimmung mit verschiedenen physikalischen Betriebsarten übertragen werden können, wobei das Verfahren den folgenden Schritt umfasst;

- Empfangen von Paketen (32), wobei jedes Paket in mindestens einem Funkbündel (52 bis 55), das einer physikalischen Betriebsart zugeordnet ist, die aus einer Menge mindestens zweier physikalischer Betriebsarten gewählt wird, gesendet wird;
wobei das Verfahren dadurch gekennzeichnet ist, dass es ferner den folgenden Schritt umfasst:

- Schätzen der Paketfehlerrate (33) auf der Grundlage eines Zählwerts ordnungsgemäß empfangener Pakete und eines Zählwerts schlecht empfangener Pakete für jede physikalische Betriebsart der Menge.


 
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass mindestens einige der empfangenen Pakete nicht für die Vorrichtung, die die Pakete empfängt und auf der Grundlage der Pakete die Fehlerrate schätzt, bestimmt sind.
 
3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die physikalische Betriebsart die Modulation umfasst.
 
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die physikalische Betriebsart die Rate oder den Typ eines Fehlerkorrekturcodes umfasst.
 
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Schätzung der Fehlerrate einen Fehlerkorrekturcode-Verifizierungsschritt umfasst.
 
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass es einen Schritt des Übertragens eines Achtungssignals, das die Paketfehlerrate für mindestens einige der physikalischen Betriebsarten der Menge repräsentiert, umfasst, wobei das Achtungssignal, das die Rate repräsentiert, an eine Station übertragen wird, die Funkbündel an das Endgerät senden kann.
 
7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch gekennzeichnet, dass es einen Schritt (37) des Bestimmens statistischer Daten hinsichtlich der Fehlerraten für empfangene Pakete auf der Grundlage der Schätzung der Paketfehlerrate und mindestens eines einer physikalischen Betriebsart zugeordneten Parameters umfasst.
 
8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass es einen Schritt des Übertragens von Achtungssignalen, die die statistischen Daten repräsentieren, umfasst, wobei die Achtungssignale, die die statistischen Daten repräsentieren, an eine Station übertragen werden, die Funkbündel an das Endgerät senden kann, das das Verfahren implementiert.
 
9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass es einen Schritt (310) des Schätzens eines Signal/Rausch-Verhältnisses auf der Grundlage der Schätzung der Paketfehlerrate und mindestens eines einer physikalischen Betriebsart zugeordneten Parameters umfasst.
 
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass es einen Schritt (310) des Übertragens von Daten, die ein Signal/Rausch-Verhältnis repräsentieren, für mindestens einige der physikalischen Betriebsarten der Menge umfasst, wobei die Daten, die ein Signal/Rausch-Verhältnis repräsentieren, an eine Station übertragen werden, die Funkbündel an das Endgerät senden kann.
 
11. Verfahren nach einem der Ansprüche 1 bis 10, dadurch gekennzeichnet, dass die Übertragung von Datenpaketen in Übereinstimmung mit einem Protokoll des Typs IEEE 802.16 ausgeführt wird.
 
12. Verfahren nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, dass es einen Schritt des Übertragens einer Anforderung für die Änderung der physikalischen Betriebsart für die Übertragung von Datenpaketen umfasst.
 


Revendications

1. Procédé de communication adapté à la transmission de paquets de données (530, 53n), pouvant être transmis selon divers modes physiques, la procédé comprenant l'étape de :

- réception de paquets (32), chaque paquet étant transmis en au moins une rafale radio (32 à 55) associée à un mode physique choisi dans un ensemble d'au moins deux modes physiques ;
le procédé étant caractérisé en ce qu'il comprend en outre l'étape suivante :

- estimation du taux d'erreur du paquet (33) basée sur le nombre de paquets reçus correctement et sur le nombre de paquets reçus incorrectement pour chaque mode physique dudit ensemble.


 
2. Procédé selon la revendication 1, caractérisé en ce qu'au moins quelques uns des paquets reçus ne sont pas destinés à l'appareil qui reçoit lesdits paquets et qui estime le taux d'erreur en fonction desdits paquets.
 
3. Procédé selon l'une quelconque des revendications 1 et 2, caractérisé en ce que ledit mode physique comprend la modulation.
 
4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que ledit mode physique comprend le taux ou le type d'un code de correction d'erreur.
 
5. Procédé selon l'une quelconque des revendications 1 à 4, caractérisé en ce que l'estimation du taux d'erreur comprend une étape de vérification du code de détection d'erreur.
 
6. Procédé selon la revendication 5, caractérisé en ce qu'il comprend une étape de transmission d'un indice représentatif dudit taux d'erreur de paquet pour au moins quelques uns des modes physiques dudit ensemble, ledit indice représentatif dudit taux étant transmis à une station qui peut transmettre des rafales radio vers ledit terminal.
 
7. Procédé selon l'une quelconque des revendications 1 à 6, caractérisé en ce qu'il comprend une étape (37) de détermination de données statistiques concernant les taux d'erreur pour des paquets reçus basés sur ladite estimation dudit taux d'erreur de paquets et d'au moins un paramètre associé à un mode physique.
 
8. Procédé selon la revendication 7, caractérisé en ce qu'il comprend une étape de transmission d'indices représentatifs desdites données statistiques, lesdits indices représentatifs desdites données statistiques étant transmis à une station qui peut transmettre des rafales radio vers le terminal qui met en oeuvre le procédé.
 
9. Procédé selon l'une quelconque des revendications 1 à 8, caractérisé en ce qu'il comprend une étape (310) d'estimation d'un ratio signal/ bruit basée sur ladite estimation dudit taux d'erreur de paquets et d'au moins un paramètre associé à un mode physique.
 
10. Procédé selon la revendication 9, caractérisé en ce qu'il comprend une étape (310) de transmission de données représentatives d'un ratio signal/ bruit pour au moins quelques uns des modes physiques dudit ensemble, les données représentatives d'un ratio signal/ bruit étant étant transmises à une station qui peut transmettre des rafales radio vers ledit terminal
 
11. Procédé selon l'une quelconque des revendications 1 à 10, caractérisé en ce que ladite transmission des paquets de données est effectuée selon un protocole de type IEEE 802.16.
 
12. Procédé selon l'une quelconque des revendications 1 à 11, caractérisé en ce qu'il comprend une étape de transmission d'une demande de modification de mode physique pour la transmission de paquets de données.
 




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REFERENCES CITED IN THE DESCRIPTION



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Patent documents cited in the description




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