The invention is related to wireless communication systems, and, in particular, to digital cellular teleommunications networks, specifically referring to an antenna system architecture that is intelligent modular and compatible, that is pluggable to any Node B or Base Station as the antenna can be shared by several operators, so that the different base stations of the latter can connect to said antenna. In addition, the compatibility implies that the antenna system architecture can be plugged to the radiofrequency (RF) interface (Fig 1a), b) & c))used together with the rest of the base station's equipment, regardless of the manufacturer, which means that it is not necessary to change or modify the base station when you wish to replace the conventional antenna with the antenna that is the object of the invention.
The use of intelligent antennas is a very promising solution for cellular communications systems, since they allow for a substantial increase in the system's capacity. However, these antennas are integrated in the base station and they do not allow either a total modularization, in other words, increasing the number of channels in service as demand for them grows by inserting new modules, or the installation of the intelligent antenna independently from the rest of the base station. As a result, operators of a cellular system network have to predict the number of channels they are going to provide service to and if they are going to include an intelligent antenna or not, since if they decide after the installation to include this type of antenna, they would be forced to replace the entire base station by another with an antenna with these features and with the appropriate number of channels.
Another serious drawback is that this network infrastructure cannot be shared by several operators. They each have to install their own intelligent antenna, and the result of this fact is a large urban and environmental impact.
Another problem they have is that they can only support one standard of cellular communications, and an intelligent antenna cannot be shared by operators of different systems, such as the Global System for Mobile Communications (GSM) standard, the Universal Mobile Telecommunications System (UMTS) standard, the Multichannel Multipoint Distribution System (MMDS) standard, the Local Multipoint Distribution Service (LMDS) standard, and others.
The prior art, as described in documents (D1): "P.B. KENINGTON: Emerging technologies for software radio. ELECTRONICS & COMMUNICATIONS ENGINEERING JOURNEL, vol. 11, no.2, April 1999 (1999-04), pages 69 - 83."; and (D2): "USB-6,317,586 B1 (HAARDT MARTIN), 13 November 2001 (200111-13)", discloses in the first case (D1), software radio architectures for receiver and transmitters applicable for handportable terminals and also for Base Stations, and in the second case (D2), wireless data transmission methods applicable for Base Stations. Clearly, in both this two cases is, as stated, applicable the prior art for the base stations, and therefore can not be applied to an intelligent modular compatiblentenna system equipment, object of this invention. Moreover, the object of the present invention, though some ideas from the described prior art are used, is to provide this intelligent modular compatible antenna system achieved by demodulating, shaping he beam with the diagram adaptation criterion selected and modulating again, and the process is the same in both transmission and reception (DEREM concept), which is a standalone equipment not to be included internally to the Base Station or Node B.
The problems described above are solved by using this invention. It consists of the definition of a modular intelligent antenna system architecture that is compatible, that is pluggable to the RF interface of any Node B or Base Station,with the rest of the base station.
The intelligence refers to the possibility of the antenna having a variable radiation diagram, being capable of generating or selecting directive beams focussed on the required user.
It is modular in that it enables a gradual growth of the channels served and of the frequency bands used when demand increases, by including new radio frequency modules. It is modular in that it allows this intelligent antenna to be used by an increasing number of new operators. Moreover, it is independent and compatible with the rest of the base station, since the operator can set up one base station using a conventional sectoral antenna first (without an intelligent antenna) and then, when an increase in capacity is required, it can be replaced by the intelligent antenna that is the object of this invention. The modularization concept is based on the use of combiners (in transmission) and dividers (in reception) before and after each channel's transmission and reception. The transmission and reception are separated by duplexers. Adding new channels or using new bands can be carried out by adding new radio frequency modules in both transmission and reception.
Furthermore, it can allow the antenna to be shared by several operators, so that their different base stations connect to it. The radio software techniques also allow the shared use of the intelligent antenna by different communication standards, such as GSM, UMTS, MMDS, LMDS and others, including the processing modules required.
The compatibility refers to the possibility of using this antenna together with the rest of the base station's equipment, regardless of the manufacturer, making it possible to use it with base stations that are not prepared expressly to use the same. In other words, it is not necessary to change the base station when you wish to replace the conventional antenna by the antenna that is the object of this invention, enables direct connection into the radiofrequency interface, both at the transmitter power amplifier output as at the receiver low noise amplifier input with the Node B or Base Station without performing any change or modification in its hardware or software. That is the multistandard intelligent modular compatible antenna system allows the direct substitution of the connventional antennas from the Node B or Base Station by means of disconnecting its coaxial connectors of the later, and connecting instead the ones from the antenna object of this invention. This property is achieved by demodulating, shaping the beam with the diagram adaptation criterion selected and modulating again, and the process is the same in both transmission and reception (DEREM concept). In this way, the quality of the signal is improved with a processing that is transparent to the rest of the base station's equipment (e.g., Node B in UMTS terminology).
With regard to the architecture of the compatible modular intelligent antenna for cellular communications in multioperator multistandard environments, in accordance with the object of the invention, it is basically formed of: an antenna subsystem that includes the set of radiating elements, duplexers, low-noise amplifiers in reception, combining networks in transmission and dividing networks in reception, and passive control elements of the antenna diagram; an RF/IF subsystem, which includes all the analogical components associated with the transmitter and the receiver, amplifiers, frequency converters, filters, power amplifiers and A/D and D/A converters; a radio software subsystem, which includes all the channel separation processes, modulation, demodulation, filtering, coding and decoding, associated with the digital transmission and reception processes; an adaptive algorithm subsystem, which includes the digital processes associated with the signal control of the whole of the antenna, in both reception and transmission. This subsystem is very related to the previous one.
These and other features, which will be explained throughout this specification, will enable a configurable and very flexible system to be obtained, which is adaptable to every user's requirements. In this way, it can be used in the following configurations:
In order to complement the description that is going to be made below and so that the invention's characteristics can be better understood, this specification is accompanied by a set of plans, as an integral par t of the same, in which the following has been represented by way of example and non-limiting.
Before going onto describing the antenna that is the object of this invention, the diagram represented in figure 1 has to be described, which corresponds to a conventional base station, including a system (1) of conventional antennas (not intelligent), a link (2), by which the signal is taken from the antenna to the equipment (3) of the base station (for example, Node B in UMTS terminology). Finally, the conventional base station mentiodeis joined by a link (4) to the rest of the network (5).
However, in the same coverage area, normally in different sites, said typical base station structure would have to be repeated as many times as there are different systems and operators. For exampl if you wish to cover a specific area using three GSM operators, another three UMTS operators and another three MMDS operators, you would need nine different radiating structure systems. This fact causes a great urban and environmental impact.
Solving this problem is the reason why the the multistandard compatible, that is pluggable to the RF interface of any Node B or Base Station, modular intelligent antennasystem for cellular communications in a multioperator, multistandard environment, the object of this invention, has been devised, with the block (6) corresponding to the general diagram of the system shown in figure 2, with reference (7) as the antenna array, which is connected to a diplexer (8), which separates the signal into the different bands used (9), with block (10) corresponding to the UMTS module, block (11) to the GSM-1800 module, with (12) as the module corresponding to the nth standard. Every one of these modules has a similar structure: an RF block (13), a radio software block (14) and a beam shaping block (15). The output signals of modules (10), (11) and (12) go to the rest of the equipment (16) of every one of the base stations of the different operators of the different standards (Node B of UMTS, BTS of GSM, etc.).
As can be seen from this figure 2, the architecture presented allows the same for a multistandard compatible that is pluggable to the RF interface of any Node B or Base Station, modular intelligent antenna system to be shared by different operators that have different standards, so the architecture's modularity allows the number of operators to increase and for them to be able to support the different communications standards thanks to the flexibility provided by the radio software. Besides, given a certain standard, the compatibility concept is achieved by demodulating, shaping the beam with the criterion of adapting the diagram selected and then modulating again (DEREM concept).
Figure 3 shows the modular architecture of the a multistandard compatible, that is pluggable to the RF interface of any Node B or Base Station, intelligent antenna systemparticularised to support different operators in a certain standard, in which you can see a set of antennas (17) for every one of the orthogonal polarisations established in blocks (18) and (19), so that each antenna (17) is attacked by a duplexer/combiner/divider (20) which manages t separate the channels. The process for every one of them is as follows: radio frequency (RF) conversion to intermediate frequency (IF) by the converters (21); analog/digital (A/D) conversion by an analog/digital and digital/analog conversion block (22); digital demodulation by a digital transmitter/receiver block (23), and an optimum combination of the signals from the different antennas, in accordance with the shaping criterion for every channel, by a beam shaper (24). After this, the process for every channel is similar, in other words a digital modulation (23), a digital/analog conversion (22) and a conversion from intermediate frequency to radio frequency (21). Next, the channels are combined by means of a duplexer/combiner/divider (20) to be able to provide the nodes (25) of the different operators with service. The transmission process would be analogue to the reception process, which is the one that has been explained, but the signals would flow in the opposite direction, in other words from the nods of the different operators (25) to the antennas (17), in other words, the signal of a specific node would be divided into its different channels (20), with the process for every channel as follows: RF/IF conversion (21), A/D conversion (22), digital demodulation (23), beam shaping (24), digital remodulation (23), D/A conversion (22), IF/RF conversion (21). Then the channels (20) combine and they are transferred to the antennas (17).
The area marked with the reference (26) in figure 3, does not break the modularity, since it can be implemented by radio software techniques, and it is therefore a software that can be updated, respecting all the hardware.
Figure 4 shows the corresponding elements of the RF system, which are as follows:
Figure 5 shows the diagram of the hardware required for the digital receiver, which has to be accompanied by the digital process signal. Shown in said figure are the A/D converter (37), the numeric oscillator (38) of fo frequency (39). The output signal of said oscillator and its 90° phase shift by block (40), multiply the digital signal, which after being decimated by the block (41), gives rise to inphase (42) and quadrature (43) signals.
Figure 6 shows the configuration for the beam shaping subsystem using the case of the uplink for the UMTS standard as an example. The adaptive process subsystem is responsible for updating the array factor, using the synchronisation pilot reference signal for the shaping, which is sent via the Dedicated Physical Control Channel (DPCCH) for every one of the users. The elements this figure has are:
Below is a detailed explanation of the a multistandard compatible, that is pluggable to the RF interface of any Node B or Base Station, modular intelligent antenna system described, but applied to use with the UMTS standard:
An adaptive array is going to be used as the intelligent antenna. There are four subsystems in this antenna, which are closely connected, even in some cases with regard to hardware. Figure 3 shows the diagram of the system blocks. Four subsystems can be identified in it:
The antenna subsystem for the UMTS adaptive array application is formed of a group of vertical linear arrays formed by coincident or alternated dual-polarised antennas. In principle, the base stations are formed of three sectors, so every one of the flat groups would replace one of those with a 120° coverage. The base element of every group will be a vertical panel of dual linear polarisation (±45° or V/H) with vertical beam widths of around 7.5° and beam widths in the hor izontal plane of 65° or 90°. For the case of a 65° beam width, the typical gain is 17 dBi.
The RF subsystem is the one that appears separated in more detail in the diagram in figure 4, although it is understood that it would all go in the same module. The components of the same are the ones mentioned in the description of the drawings.
The IF is chosen high to allow a better elimination of the image band, avoiding possible interferences. The digital conversion is carried out in IF, avoiding filtering and analog phase noise.
The radio software subsystem is formed of an A/D converter with a high capacity (e.g. 75 MHz, 12/14 bits) followed by a digital I/Q converter controlled by an NCO, such as the one shown in figure 5, in which phase noise is not created and the features are improved. The sampling is carried out at the required frequency (fs) depending on the value of the IF to fulfil the Nyquist theorem. The NCO generates sine and cosine signals corresponding to the fs frequency selected from the A/D converter. The frequency change only consists of writing a numeric value in the register. The signal generated does not modify its frequency, so no phase noise is introduced. Next, to decrease the sampling frequency to the frequency required for the signal's bandwidth, the M rate decimator is introduced. In our case, M should equal 16 (IF=70 MHz, fs=80 MHz and Bandwidth = 5 MHz). Next, the signal process cards would be sited, where the processes of spreading/unspreading would be carried out by software in order to separate every one of the channel codes, and spreading/unspreading in order to regenerate the CDMA signal again (FDD mode). Moreover, the signals separated by code multiply by the array factor weights [w] for the beam shaping for every one of the channels.
The adaptive process subsystem is responsible for calculating those weights, using the synchronisation pilot reference signal for the shaping, which is sent by the dedicated physical control channel for every one of the users. The shaping algorithm proposed here is a temporary reference one. A configuration example of this shaper for the uplink is the content in figure 6. It does not include the RAKE (receiver structure that behaves as a filter adapted to the multipath signal received, so that its detrimental effect can be combated), so the system is simplified by making the intelligent antenna, which is only directed towards the main path, responsible for the elimination.
The implementation of the downlink is carried out in the same way, bearing in mind that the channels are modulated simultaneously, partly real and partly imaginary.
A first version of this intelligent antenna has been planned for use with the UMTS standard. This implementation is modular, since it allows the number of channels used to be increased. Modularity makes it possible to provide different operators with service, and this fact means that this network infrastructure can be shared. This results in a better use of the infrastructures, as well as less visual and environmental impact. On the other hand, the system implemented enables it to be used together with any system of base stations, in other words, the system is compatible with any manufacturer of B Nodes.