MXPA97007231A - Antenna lobulo an - Google Patents

Abstract

The present invention relates to a method for broadcasting information in a cellular communication system comprising at least one base station with a training antenna and a plurality of mobile stations, comprising the steps of: pre-processing the information using a frequency shift, to generate orthogonal signals, to form the orthogonal signals by beam, so that the orthogonal signals are supplied to the elements of the formation antenna, to transmit the orthogonal signals, to receive the orthogonal signals in at least one of the mobile stations, and process signals to decipher orthogonal signal information

Description

"WIDE ANTENNA LOBE" FIELD OF THE INVENTION The present invention relates to transmitting information in a cellular communication system and, more particularly, to the creation of wide antenna lobes from the directional antennas to diffuse the common information tgh a wide coverage area.

BACKGROUND OF THE INVENTION Figure 1 illustrates ten cells C1-C10 in a typical cellular mobile radio communication system.

Normally, a cellular mobile radio system is deployed with more than ten cells. However, for purposes of simplification, the present invention can be explained using the simplified representation illustrated in Figure 1. For each cell C1-C10 there is a base station B1-B10 with the same reference number as the corresponding cell. Figure 1 illustrates the base stations as they are located in the vicinity of the cell center and having omnidirectional antennas. Figure 1 also illustrates nine mobile stations M1-M9 that are movable within a cell and from one cell to another. In a typical cellular radio communication system, there would normally be more than nine cellular mobile stations. In fact, there are typically many times the number of mobile stations that there are base stations. However, for the purposes of applying the present invention, the reduced number of mobile stations is sufficient. Also, in Figure 1 there is a mobile switching center MSC. The mobile switching center MSC illustrated in Figure 1 is connected to all ten base stations B1-B10 by keys. The mobile switching center MSC is also connected by cables with a fixed switching telephone network or a similar fixed network. All cables from the mobile switching center MSC to the base stations B1-B10 and the cables to the fixed network are not shown. In addition to the illustrated mobile switching center MSC, there are many additional mobile switching centers connected by cables to base stations other than those illustrated in Figure-1. Instead of cables, other means, for example, links can also be used. fixed radio to connect the base stations with the mobile switching centers. The MSC mobile switching center, the base stations and the mobile stations are all controlled by computer.

Current digital cellular systems employ base stations that separate mobile stations using orthogonality of time and frequency. The signals from a mobile station are propagated to a base station, where signals are received in a single or sometimes a plurality of antenna elements to obtain diversity effects. The processing of the receiving signal uses the orthogonality of time and frequency to separate the signals of different users. Sometimes, it is desirable to use a plurality of directional antennas or an array of antennas to communicate with the mobile stations. The use of directional antennas can reduce interference and increase coverage and number of users. The use of antenna arrays requires a certain type of beam formation. The beamforming can be implemented in a variety of ways such as digital beamforming, analog beamforming or by a beamforming matrix, such as the Butler matrix. Analog beamformers direct the beam by introducing a time delay independent of frequency, while digital beam formation usually involves a phase delay that is equivalent to the time delay at an operating frequency. Several beamformer systems are illustrated in Figures 2 and 3. A digital beamformer system usually has one receiver for each element, which down-converts the frequency into I and C channels (in phase and Quadrature) for an A-to-B converter. / D. Real-time beam formation is performed by multiplying these complex pairs of samples by appropriate weights in multiplier / accumulator integrated circuits. The output of the formation is formed using a complex signal from the channel n ^ n (Vn), a weighting coefficient (Wn), a direction phase shift (e), a correction factor (Cn). Corrections may be necessary due to several reasons. These reasons include errors in the position of the element, temperature effects and the difference in the compartment between those elements embedded in the formation and those near the edge. In this way, by configuring and directing the narrow antenna beams, a plurality of narrow beams can be used to simultaneously cover a large sector using the same array of antennas. The present invention can use an adaptive algorithm to select the most feasible functions for the antenna. The use of directional antennas, however, is sometimes complicated. For example, a base station must be capable of transmitting broadcast information to a mobile station with an arbitary position in the cell.

However, the cell can not be made too narrow since this will cause excessive deliveries and low open channel efficiency. Therefore, there is a desire for both highly directional antennas and wide-lobe antennas in a single cell. One option would be to use multiple antennas in the cell. However, the use of several individual antennas with associated hardware is expensive to install and organize. Another obvious solution for a person skilled in the art would be to transmit the common information or the same information in all the narrow antenna lobes used in the cell, as illustrated in Figure 4. The disadvantage with this solution is that the information of the lobes of different antenna can add up to zero, creating null or almost unwanted nulls in the combined antenna pattern 22. As illustrated in Figure 4, the data to be broadcast is transmitted in all three directional lobes 20. The signals are canceled in certain directions and in this way deep nulls appear in the combined antenna pattern 22. For example, two lobes with equal amplitude will sum to zero in a certain direction. As a result, a mobile station with all its scatter points in that direction may suffer from deep fading in signal strength as illustrated in Figure 5. Figure 5 illustrates that the mobile station 24 will suffer from very low received power that the mobile station 24 is placed in a null in the combined antenna pattern 22. Meanwhile, the signals received by the mobile station 26 will have an acceptable received power even when the mobile station is also placed in a null in the combined antenna pattern 22. In this case the signal is being reflected from a building 28 so that the intensity of the received signal is at an acceptable level. Therefore, there is a need for highly directional antennas in order to increase capacity and improve coverage. There is also a need for antennas with low directivity so that the information can be disseminated throughout the cell.

COMPENDIUM OF THE INVENTION An object of one embodiment of the present invention is to provide a method and apparatus for providing common communication signals through a cell, using a base station with a training antenna. In accordance with one embodiment of the present invention, there is provided a method for broadcasting information in a cellular communication system comprising at least one base station or antenna array and a plurality of mobile stations. In this mode, the common information is pre-processed to create orthogonal signals. The orthogonal signals are then formed in a beam so that the orthogonal signals are supplied to the different elements in the training antenna. The orthogonal signals are transmitted and then received in at least one mobile station. The signals are then processed to the mobile station to decrypt the common information from the orthogonal signals. In accordance with another embodiment of the present invention, a cellular communication system for disseminating information has been disclosed, which contains at least one base station with an array of antennas and a plurality of mobile stations. Each base station contains a pre-processing means to pre-process the common information to create orthogonal signals. The beam-forming means then beam-forms the orthogonal signals so that the orthogonal signals can be supplied to the antenna elements of the array. The orthogonal signals are then transmitted by means of a transmitting medium. At least one mobile station, a receiving means receives the orthogonal signals and a processing means processes the signals to decipher the information of the orthogonal signal.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features and advantages of the invention will be readily apparent to a person skilled in the art of the following written description, used together with the drawings, in which: Figure 1 illustrates the basic project of a cellular communication system; Figure 2 illustrates an example of digital beamforming to create the directional beams; Figure 3 illustrates the beam formation in a radiofrequency to create directional beams; Figure 4 illustrates the nulls in an antenna pattern; Figure 5 illustrates a beamforming arrangement; Figure 6 illustrates a beamforming arrangement in accordance with one embodiment of the present invention, for pre-processing with digital beam formation; Figure 7 illustrates a beamforming arrangement for forming the beam to a frequency network in accordance with an embodiment of the present invention; Figure 8 illustrates an apparatus of a pseudo-omni site in accordance with an embodiment of the present invention; Figure 9 illustrates the possible form of coverage of a pseudo-omni site in accordance with an embodiment of the present invention; Figure 10 illustrates an antenna pattern from a pseudo-omni site in accordance with an embodiment of the present invention; and Figure 11 illustrates 20 antenna patterns of a pseudo-omni site in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXHIBITION The present invention is primarily intended for use in base stations and cellular communication systems, although it will be understood by those skilled in the art that this may also be used in other different communication applications. In accordance with one embodiment of the present invention, the common information to be disseminated through the cell is divided into parallel data streams one for each narrow lobe. This embodiment is illustrated in Figure 6. The diffusion data d (k) is divided into a plurality of parallel paths, where the number of parallel paths is equal to the number of directional antennas used. It should be noted that the present modality divides the diffusion data into three parallel paths, but is not limited to this. Each trajectory is then pre-processed using for example digital filters H (Z), H2 (Z), H3 (Z). Filters are used to create signals that are sufficiently orthogonal. The signals from the digital filters 40 are then fed to a beam forming means 42 that creates the three-way antenna beams. The signals are transmitted with a narrow antenna lobe and the information is combined in the air. In this embodiment, the filters are selected so that the signals can not add up to zero, which ensures that the combined antenna pattern 46 does not contain nulls. In other words, the signals from the different narrow lobes arrive at different times of time. As a result, the mobile station can not distinguish this situation from the situation where the interference between the symbols due to the multiple paths are received in the mobile station. Therefore, the equalizer of the mobile station can be used to analyze the arrival information in the same way that an equalizer is used to correct the received signal for interference between the symbols. In accordance with another embodiment of the present invention, analog filtering can also be used as illustrated in Figure 7. In this embodiment, the broadcast data is modulated and up-converted into radio frequency and then divided into three parallel paths. The broadcast data is then pre-processed to the radio frequency using, for example, a delay. As illustrated in Figure 7, the signals can be delayed by the delay means 52, where for example, the delay 1 is equal to zero seconds, the delay 2 is equal to Ts and the delay 3 is equal to zero seconds, where Ts is a symbol time. The delayed signals can then be accommodated in a Butler matrix 54 which forms the three individual antenna lobes in a known manner. The resultant combined antenna pattern 56 is also free of deep nulls, since the delayed signals are not canceled with respect to each other. In accordance with another embodiment of the present invention, the orthogonalization can be implemented as modulating each of the paths on a slightly different carrier frequency. The difference in frequency must be large enough to create fading, but so slow that it can not create problems for the demodulator. In accordance with another embodiment of the present invention, the pseudo-omni sites are described. The advantage with the pseudo-omni sites is their large area of coverage per site that results in low implementation costs in rural areas. In this embodiment of the present invention, multireceptor radio base stations are used to construct the pseudo-omni sites, however, the present invention is not limited to this. Figure 8 illustrates a hardware configuration of a pseudo-omni site in accordance with an embodiment of the present invention. As illustrated in Figure 8, at least one transceiver 80 is connected through a coupler 82 with an array 84 of receiver antennas and an array 86 of transmit antennas. In accordance with one embodiment of the present invention, the array of receiving antennas consists of four dual polarized sector antennas which are mounted in equally spaced locations around a mast. The arrangement of transmitting antennas comprises four active sector antennas in which each sector antenna is fed with the same low power input. The bearer / noise uplink operation of this system will now be described. The multi-receiver equalizer can use diversity combination to select and combine the appropriate received signal from all four sector antennas. An additional diversity gain is possible for existing spatial diversity arrangements for the mobile stations received in more than one sector antenna, i.e. in more than two diversity branches. This gain in diversity typically depends on the quotient between the separation between the sector antennas and the cell scale. According to one embodiment of the present invention, the sector antennas are mounted on a relatively thin mast so that the separation is small, typically one to two meters and the cells are relatively large, typically 10 to 20 kilometers. The antenna gain in the pseudo-omni sites could be from 19 to 20 decibels according to an isotropic antenna, which is a considerable increase in relation to the existing omni-antennas that have a gain of 11 to 12 decibels in relation to the isotropic antenna. An example of the possible coverage configuration of the pseudo-omni site is illustrated in Figure 9 and assumes a path loss of the sector antenna? 2.5 and cos ^ (a). In this embodiment, the sector antennas are directed in the direction of ± 45, + 135 degrees, but the present invention is not limited thereto. The antenna is assumed to provide a loss of six decibels in the gain of the antenna 45 degrees from the wide side. However, this is partly compensated by a noise diversity gain of three decibels in the equalizer at these points, thus resulting in a total of a loss of three decibels in C / N operation. Finally, the loss of three decibels in the operation is prepared on a map until a reduction in coverage using the assumption of trajectory loss that is illustrated by line 90 in Figure 9. An assumption of additional diversity between the sectors would make the coverage area outside of more circular configuration. Carrier / noise downlink operation will now be described. According to one embodiment of the present invention, four transmit antennas are used to distribute the downlink in a pseudo-omni pattern with the aim of protecting the area shown in Figure 9. Directly to feed the sector antennas will cause null deep in the antenna diagram, as illustrated by the dashed line in Figure 10, which shows an example of nulls that is calculated with sector antennas eos4 (a), 1900 MHz and antenna separation of one meter. The two sector antennas will interfere in half between their orientation directions. Furthermore, the null problem can not be solved by simply introducing a variable phase error in relative time between the antennas or by not coherently feeding the antennas as illustrated in Figure 11. Figure 11 illustrates 20 antenna patterns of a pseudo-omni site generated with four sector antennas around the mast showing that the nulls, even when they have moved, they are still present. The nulls in the total antenna pattern can be avoided using any of the frequency or time orthogonalization means mentioned above. In accordance with one embodiment of the present invention, the problem with nulls in the combined signals is overcome by using transmit antennas with different polarizations to create orthogonal signals. Using orthogonal polarization so that the E field from the antennas oriented in the 45 ° and -135 ° directions is orthogonal to the E field from the antennas oriented in the -45 ° and 135 ° directions, the nulls are removed from the pattern field antenna E total, that is, | EV + En | 2 >; or. The operation of the present invention depends on the environment. For example, suppose the cross polarization discrimination is close to one and is symmetric in the sense that the vertical and horizontal polarizations have approximately the same properties. It is evident then that the operation on the wide side is not altered, that is, it is approximated to the solid line in Figure 10. The mobiles in between the sector antennas will be two antennas with independent fading due to the orthogonal polarization and the signals from the antennas will add up to a new Rayleigh fading channel. In this way, the operation in the middle between the antennas will approach the continuous line illustrated in Figure 10. It will be appreciated by those skilled in the art that the present invention can be encompassed in other specific forms without deviating from the spirit and character central of it. The modalities disclosed herein are therefore considered in all respects as being illustrative and not restrictive. The scope of the invention is indicated by the appended claims instead of the foregoing description, all changes that fall within the meaning and scale of equivalence thereof are of course covered herein.

Claims (29)

R E I V I N D I C A C I O N E S:

1. A method for broadcasting information in a cellular communication system comprising at least one base station with a training antenna and a plurality of mobile stations, comprising the steps of: re-processing the information to create orthogonal signals; forming the orthogonal signals in a beam so that the orthogonal signals are sied to the antenna elements of the array; transmit the orthogonal signals; receive the orthogonal signals in at least one of the mobile stations; and process the signals to decipher the information from the orthogonal signals.

A method for disseminating the information according to claim 1, wherein the information is pre-processed individually for each beam so that the deep nulls in a combined antenna pattern are avoided.

3. A method for disseminating the information according to claim 1, wherein the pre-processing step uses digital filtering in the baseband.

4. A method for disseminating the information according to claim 1, wherein the pre-processing step uses analog filtering at a radio frequency or at the intermediate frequency.

5. A method for disseminating the information according to claim 1, wherein the pre-processing step uses frequency offset to generate the orthogonal signals.

6. A method for disseminating the information according to claim 1, wherein the pre-processing step uses dual polarized antennas to generate orthogonal signals.

A cellular communication system for broadcasting the information comprising at least one base station with a formation antenna and a plurality of mobile stations comprising: a means for pre-processing the information in order to create orthogonal signals; a beam-forming means for beam-forming orthogonal signals; a transmitting means for transmitting the orthogonal signals in a training antenna; a receiving means in a mobile station for receiving the orthogonal signals; and a processing means for processing the signals to decipher the information from the orthogonal signals.

A cellular communication system according to claim 7, wherein the information is pre-processed individually for each base station so as to avoid deep nulls in a combined antenna pattern.

9. A cellular communication system according to claim 7, wherein the pre-processing means uses digital filtering in the baseband.

10. A cellular communication system according to claim 7, wherein the pre-processing means uses analog filtering at a radiofrequency or at any intermediate frequency.

11. A cellular communication system according to claim 7, wherein the pre-processing means uses dual polarized antennas to generate the orthogonal signals.

12. A cellular communication system according to claim 7, wherein the pre-processing means uses frequency offset to generate the orthogonal signals.

13. A cellular communication system for broadcasting information comprising at least one base station and a plurality of mobile stations comprising: means for duplicating and processing the information in a plurality of identical parallel signals; means for orthogonalizing the identical parallel signals; a transmitting means for transmitting each signal using a directional antenna; a receiving means in the mobile stations to receive the signals from the directional antennas; and a means to combine the energy of each of the received signals to restore the information.

14. A cellular communication system according to claim 13, wherein the number of identical parallel signals is equal to the number of directional antennas.

15. A cellular communication system according to claim 13, wherein the digital filters are used to orthogonalize the parallel signals.

16. A cellular communication system according to claim 15, wherein the digital filters are selected such that the transmitted signals do not add up to zero when combined.

17. A cellular communication system according to claim 13, wherein the parallel signals are orthogonalized by modulating the parallel signals with slightly different carrier frequencies.

18. A cellular communication system according to claim 13, wherein the double-polarized antennas are used to generate orthogonal signals.

19. A cellular communication system according to claim 13, wherein the orthogonalization means uses analog filtering at a radiofrequency or at any intermediate frequency.

20. A cellular communication system for disseminating the information comprising: at least one base station wherein each base station uses a plurality of antennas to cover or cover an assigned area; a processing means in each base station for processing the information to be broadcast so that the signals of the plurality of antennas used by the base station do not cancel each other when they are transmitted; and a transmitting means in each base station to transmit the signals.

21. A cellular communication system according to claim 20, further comprising: a plurality of mobile stations wherein each mobile station uses a receiver / demodulator to process the signals received from the base station, in order to extract the information Orthogonalized

22. A pseudo-omni site for use in a cellular communication system for transmitting signals and for receiving signals from a plurality of mobile stations, comprising: a plurality of transceiver means for processing the information; an arrangement of receiving antennas to receive the signals; an arrangement of transmitting antennas to transmit signals in a pseudo-omni antenna pattern; a coupling means for connecting the plurality of transceivers with the receiving and transmitting antenna arrangements; a means for combining by diversity the signals received from the receiving antenna array; means for orthogonalizing signals to be transmitted to the mobile stations in order to prevent nulls from occurring in the antenna pattern.

23. A pseudo-omni site according to claim 22, wherein the digital filters are used to orthogonalize the signals to be transmitted.

24. A pseudo-omni site according to claim 23, wherein the digital filters are selected such that the transmitted signals do not add up to zero when combined.

25. A pseudo-omini site according to claim 22, wherein the signals to be transmitted are orthogonalized by modulating the parallel signals with slightly different carrier frequencies.

26. A pseudo-omni site according to claim 22, wherein the array of receiving antennas consists of four dual polarized sector antennas that are mounted around a mast.

27. A pseudo-omni site according to claim 26, wherein the double polarized antennas are equally spaced around the mast.

28. A pseudo-omni site according to claim 22, wherein the arrangement of transmitting antennas comprises four active sector antennas.

29. A pseudo-omni site according to claim 22, wherein the orthogonalization means uses analog filtering at a radio frequency or any intermediate frequency.