Method and device for space division multiplexing of radio signals transmitted in cellular radio communications

• US 6,240,098 B1
• Filed: 02/20/1998
• Issued: 05/29/2001
• Est. Priority Date: 08/22/1995
• Status: Expired due to Term

• Current Assignee: Thomson-CSF (Thales SA)
• Original Assignee: Thomson-CSF (Thales SA)
• Inventors: Thibault, Joel, Chevalier, Pascal, Monot, Jean-Jacques, Multedo, Gilbert, Pipon, Fran.cedilla.ois
• Primary Examiner(s): Chin, Wellington
• Assistant Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US09/011,477
• Time in Patent Office: 1,194 Days
• Field of Search: 370/312, 370/320, 370/321, 370/330, 370/337, 370/343, 370/347, 370/442, 370/478-480, 370/310, 370/431, 455/500, 455/501, 455/504, 455/506, 455/272, 455/63, 455/67.1, 455/132, 455/133, 455/134, 455/136, 455/440, 455/561, 455/562, 375/262, 375/229, 375/347, 375/346, 375/349, 375/350, 342/373, 342/383, 342/378
• US Class Current: 370/431
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A method and apparatus for spatial multiplexing and demultiplexing of radio signals. A multichannel transmitter and receiver is integrated in a base station and coupled to an antenna array. Using digital radio signals containing previously known or non-Gaussian sequences and arranged in frames, the spatial information about each mobile unit is estimated on the basis of the signal received by the receiver for the reception and transmission frequencies. This is done by known sequences or by blind source separation methods. The respective paths of each mobile unit with the power above a predetermined threshold is isolated by spatial filtering in the presence of multiple channel paths in order to provide spatial demultiplexing. Simultaneously, the intended signal is transmitted in the direction of the main path of each mobile unit while protecting each mobile unit from signals transmitted in the direction of other mobile units by spatial filtering with cancelling constraints in order to provide spatial multiplexing.

Claims

1. A method for space division multiplexing and demultiplexing of radio signals which are organized in frames and are transmitted in duplex between at least one base station and a plurality of mobile units communicating on a same frequency and time channel using a multipath receiver and transmitter integrated in the at least one base station and coupled to an antenna base, said method for non-gaussian radio signals comprising:

estimating spatial information relating to each mobile unit based on a radio signal received from a mobile unit in a single-transmission configuration by the multipath receiver, for reception and transmission frequencies using blind source separation methods, and based on the estimated spatial information;

isolating by spatial filtering, possibly in a presence of multiple routes in a channel, respective routes to each mobile unit whose power is greater than a predetermined threshold to perform space division demultiplexing; and

simultaneously transmitting in a direction of a main route of each mobile unit, a signal which is intended for the mobile unit, while protecting each mobile unit from signals transmitted to other mobile units by spatial filtering with cancelling constraints to perform the space division multiplexing.

2. The method according to claim 1, further comprising:

permuting, in each frame, the transmission and reception frequencies to acquire the spatial information on the transmission and reception frequencies when the transmission and reception frequencies are too far apart for the spatial information to be transposable from one to the other.

3. Then method according to claim 1, further comprising:

for optimizing an efficiency of the space division multiplexing and dermultiplexing, managing assignment of the channels in all frequency and time resources allocated to the at least one base station as a function of movements of the plurality of mobile units using a criterion of spatial correlation between the plurality of mobile units incorporating the spatial information acquired on the transmission and reception frequencies used alternately for the duplex transmission.

4. The method according to claim 1, wherein the spatial filtering, when transmitting a radio signal intended for a determined mobile unit, is adapted based on a synthetic correlation matrix for noise and interference source signal, established based on pairs of fictitious interference sources arranged spatially on either side of the determined mobile unit in a direction of which the at least one base station should not transmit the radio signal, so as to widen holes of a radiation diagram in a direction of the fictitious interference sources and to increase a tolerance with respect to aiming errors due to residual errors in setting transmission and reception paths.

5. The method according to claim 1, further comprising:

periodically applying a procedure for setting transmission and reception channels of each path formed by the antenna base and for pre-correcting a gain on transmission to limit the aiming errors in transmission.

6. A device for implementing a method for space division multiplexing and demultiplexing of radio signals which are organized in frames and are transmitted in duplex between at least one base station and a plurality of mobile units communicating on a same frequency and time channel using a multipath receiver and transmitter integrated in the base station and coupled to an antenna base, in which the method for non-gaussian radio signals includes estimating spatial information relating to each mobile unit based on a radio signal received from a mobile unit in a single-transmission configuration by the multipath receiver, for reception and transmission frequencies using blind source separation methods, and based on the estimated spatial information isolating by spatial filtering, possibly in a presence of multiple routes in a channel, respective routes to each mobile unit whose power is greater than a predetermined threshold to perform space division demultiplexing, and simultaneously transmitting in a direction of a main route of each mobile unit, a signal which is intended for the mobile unit, while protecting each mobile unit from signals transmitted to other mobile units by spatial filtering with cancelling constraints to allow the space division multiplexing, said device comprising:

switching and setting mechanisms coupled to said antenna base;

said multipath receiver including a frequency transposition mechanism an amplification mechanism and a analogue/digital conversion mechanism, coupled to an output of the switching and setting mechanisms;

a space division demultiplexer coupled to an output of the multipath receiver and including a predetermined number of spatial filters, each spatial filter forming one spatial channel;

a predetermined number of demodulators equal to a number of spatial channels determined per frequency and time channel coupled to an output of the demultiplexer, and configured to supply the at least one base station with data transmitted by the plurality of mobile units;

a predetermined number of modulators equal to a number of the demodulators, respectively receiving data received from the at least one base station and to be transmitted by the at least one antenna base to the plurality of mobile units;

a space division multiplexer coupled to an output of the modulators and including a predetermined number of spatial filters equal to a number of the modulators;

a multipath transmitter including an analog/digital conversion mechanism, a frequency transposition mechanism and an amplification mechanism coupled to an output of the space division multiplexer; and

an SDMA digital processing module including an SDMA controller and an SDMA estimator configured to estimate direction vectors of routes relating to the plurality of mobile units based on the signal received from the mobile unit in single-transmission configuration, the plurality mobile units communicating with the at least one base station, and configured to update weightings of the spatial filters on transmission and reception, to manage the transmission and reception frequencies, and to control the switching and setting mechanisms.

7. The device according to claim 6, wherein the setting mechanism includes for each respective path a transmission system and a reception system formed by each antenna included in the antenna base;

a filter configured to equalize the transmission signal and being coupled to an input of the transmission system;

a filter configured to equalize the reception signal and being coupled to an output of the reception system;

a switch at the input and output of the reception system, a switch at the input of the transmission system and a two-way switch at the output of the transmission system, and configured to change to various operating modes including at least one of reception setting, transmission setting, and transmission/reception;

a coupler arranged between the antenna and the two-way switch, and configured to sample a part of the transmission signal and to inject the part of the transmission signal at the input of the reception system via the input switch of the reception system;

a setting analyzer configured to analyze various setting signals arriving on the input and output switches, respectively, of the transmission and reception systems, and to adapt the equalizing filters of the transmission and reception systems.

8. The device according to claim 7, further comprising:

a filter configured to pre-correct the transmission system arranged between an equalizing filter of the transmission system and the reception system.

9. The device according to claim 6, further comprising:

a frequency permutation controller coupled respectively to the multipath receiver and transmitter, and to the switching and setting mechanisms and configured to permute the transmission and reception frequencies on a same frequency channel.

10. A method for space division multiplexing and demultiplexing of digital radio signals organized in frames, including sequences which are known a priori and are transmitted in duplex between at least one base station and a plurality of mobile units communicating on a same frequency and time channel using a multipath receiver and transmitter integrated in the at least one base station and coupled to an antenna base, said method comprising:

estimating spatial information relating to each mobile unit based on a radio signal received from a mobile unit in a single-transmission configuration by the multipath receiver, for reception and transmission frequencies using filtering methods while utilizing the a priori known sequences, and based on the estimated spatial information;

isolating, possibly in a presence of multiple routes in a channel, respective routes to each mobile unit whose power is greater than a predetermined threshold, and demodulating the received signal of each of the plurality of mobile units in contact with the at least one base station to perform the space division demultiplexing; and

simultaneously transmitting in a direction of a main route of each mobile unit, a signal which is intended for the mobile unit, while protecting each mobile unit from signals transmitted to other mobile units by spatial filtering with cancelling constraints to perform the space division multiplexing.

11. The method according to claim 10, further comprising:

isolating the main routes by spatial filtering.

12. The method according to claim 11, wherein the spatial filtering is implemented by an ASF structure associated with a decision and equalization component.

13. The method according to claim 10, further comprising:

isolating the main routes by spatio-temporal filtering.

14. The method according to claim 13, wherein the spatio-temporal filtering is implemented by an STAF-TWN structure associated with a decision and equalization component.

15. The method according to claim 12, wherein the decision and equalization component is implemented by a DFE.

16. The method according to claim 12, wherein the decision and equalization component is implemented by a Viterbi algorithm.

17. The method according to claim 13, wherein the spatio-temporal filtering is implemented by an STAF-TWN structure.

18. The method according to claim 10, wherein the spatial information is estimated based on a value taken by a multipath detection function of the a priori known sequence, at an optimum synchronization time corresponding to a arrival time of a most powerful route.

19. The method according to claim 10, further comprising:

permuting, in each frame, the transmission and reception frequencies to acquire the spatial information on the transmission and reception frequencies when the transmission and reception frequencies are too far apart for the spatial information to the transposable from one to the other.

20. The method according to claim 10, further comprising:

for optimizing an efficiency of the space division multiplexing and demultiplexing, managing assignment of the channels in all frequency and time resources allocated to the at least one base station as a function of movements of the plurality of mobile units using a criterion of spatial correlation between the plurality of mobile units incorporating the spatial information acquired on the transmission and reception frequencies used alternately for the duplex transmission.

21. The method according to claim 10, wherein the spatial filtering, when transmitting a radio signal intended for a determined mobile unit, is adapted based on a synthetic correlation matrix for a noise and interference source signal, established based on pairs of fictitious interference sources arranged spatially on either side of the determined mobile unit in a direction of which the at least one base station should not transmit the radio signal, so as to widen holes of a radiation diagram in a direction of the fictitious interference sources and to increase a tolerance with respect to aiming errors due to residual errors in setting transmission and reception channels.

22. The method according to claim 10, further comprising:

periodically applying a procedure of setting and of pre-correction of amplification on transmission to limit the aiming errors in transmission.

23. A device for implementing a method for space division multiplexing and demultiplexing of digital radio signals organized in frames, including sequences which are known a priori and are transmitted in duplex between at least one base station and a plurality of mobile units communicating on a same frequency and time channel using a multipath receiver and transmitter integrated in the at least one base station and coupled to an antenna base, in which the method includes estimating spatial information relating to each mobile unit based on a radio signal received from a mobile unit in a single-transmission configuration by the multipath receiver, for reception and transmission frequencies using filtering methods while utilizing the a priori known sequences, and based on the estimated spatial information isolating, possibly in a presence of multiple routes in a channel, respective routes to each mobile unit whose power is greater than a predetermined threshold, and demodulating the received signal of each of the plurality of mobile units in contact with the at least one base station to perform the space division demultiplexing:

and simultaneously transmitting in a direction of a main route of each mobile unit, a signal which is intended for the mobile unit, while protecting each mobile unit from signals transmitted to other mobile units by spatial filtering with cancelling constraints to perform the space division multiplexing, said device comprising;

switching and setting mechanisms coupled to said antenna base;

said multipath receiver including a frequency transposition mechanism, an amplification mechanism and an analogue/digital conversion mechanism coupled to an output of the switching and setting mechanisms;

a space division demultiplexer coupled to an output of the multipath receiver and including a pedetermined number of spatial or spatio-temporal filters, each spatial or spatio-temporal filter forming one spatial or spatio-temporal channel;

a predetermined number of demodulators equal to a number of spatial channels determined per frequency and time channel coupled to an output of the demultiplexer, and configured to supply the at least one base station with data transmitted by the pluralit of mobile units;

a predetermined number of modulators equal to a number of the demodulators, respectively receiving data to be transmitted by the antenna base to the plurality of mobile units;

a space division multiplexer coupled to an output of the modulators and including a predetermined number of spatial filters equal to a number of the modulators;

a multipath transmitter including a digital/analog mechanism, a frequency transposition mechanism and an amplification mechanism coupled to an output of the space division multiplexer; and

an SDMA digital processing module including an SDMA controller and an SDMA estimator configured to estimate direction vectors of routes relating to the plurality of mobile units based on the signal received from the mobile unit in single-transmission configuration, the pluralit of mobile units communicating with the at least one base station, and configured to update weightings of the spatial filters on transmission and spatial or spatio-temporal filters on reception, to manage the transmission and reception frequencies, and to control the switching and setting mechanisms.

24. The device according to claim 23, wherein the setting mechanism includes, for each respective, path a transmission system and a reception system formed by each antenna included in the antenna base;

a filter configured to equalize the transmission signal and being coupled to an input of the transmission system;

a filter configured to equalize the reception signal and being coupled to an output of the reception system;

a switch at the input and output of the reception system, a switch at the input of the transmission system and a two-way switch at the output of the transmission system, and configured to change to various operating modes including at least one of reception setting, transmission setting, and transmission/reception;

a coupler arranged between the antenna and the two-way switch, and configured to sample a part of the transmission signal and to inject the part of the transmission signal to the input of the reception system via the input switch of the reception system;

a setting analyzer mechanism configured to analyze various setting signals arriving on the input and output switches, respectively, of the transmission and reception systems, and to adapt the equalizing filters of the transmission and reception systems.

25. The device according to claim 24, further composing:

a filter configured to pre-correct the transmission system arranged between an equalizing filter of the transmission system and the reception system.

26. The device according to claim 23, further comprising:

a frequency permutation controller coupled respectively to the multipath receiver and transmitter, and to the switching and setting mechanisms and configured to permute the transmission and reception frequencies on a same frequency channel.