Large-Scale Antenna Method And Apparatus Of Wireless Communication With Suppression Of Intercell Interference

• US 20130156021A1
• Filed: 12/19/2011
• Published: 06/20/2013
• Est. Priority Date: 12/19/2011
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Ashikhmin, Alexei, Marzetta, Thomas L.
• Granted Patent: US 8,774,146 B2
• Time in Patent Office: Days
• US Class Current: 370/338
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/2675 Pilot or known symbols
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/243 taking into account interferences

Abstract

Methods are provided for mitigating interference due to pilot contamination in a cellular network in which there is reuse of pilot signals. In embodiments, forward-link signals are precoded, using knowledge of slow-fading coefficients, to mitigate the interference. In embodiments, interference in reverse-link signals destined for a given base station is mitigated by linearly combining reverse-link signals destined for the given base station and for other base stations of the network, using knowledge of slow-fading coefficients.

Claims

1. A method performed by a base station in a cellular network in which the base station serves a population of same-cell terminals, the cellular network includes other base stations that serve respective populations of other-cell terminals, the terminals are allocated to two or more terminal groups, each terminal group is a reuse group for pilot signals transmitted by terminals, and each terminal within a given cell belongs to a respective terminal group;

the method comprising;

obtaining a message destined for each of one or more same-cell terminals;

further obtaining a message destined for each of one or more other-cell terminals belonging to each of two or more terminal groups;

linearly combining the messages destined for the same-cell and other-cell terminals of each terminal group, thereby to form a pilot contamination precoded message for each terminal group; and

transmitting the pilot contamination precoded messages synchronously with the other base stations.

2. The method of claim 1, further comprising performing beam-forming precoding on the pilot contamination precoded messages before transmitting them.

3. The method of claim 2, wherein the linearly combining step is performed using a set of slow-fading coefficients and the beam-forming precoding step is performed using a set of fast-fading coefficients.

4. The method of claim 3, wherein:

the transmitting step is performed using multiple antennas;

the fast-fading coefficients apply only to same-cell terminals;

the slow-fading coefficients apply to same-cell and to other-cell terminals; and

the fast-fading coefficients are updated more frequently than the slow-fading coefficients.

5. The method of claim 4, further comprising:

updating the fast-fading coefficients on a first schedule; and

updating the slow-fading coefficients on a second schedule that iterates more slowly than the first schedule.

6. The method of claim 5, wherein the slow-fading coefficients used for the linearly combining step do not discriminate among the multiple antennas used for the transmitting step.

7. The method of claim 1, wherein the transmitting step is performed using OFDM modulation.

8. A method performed by a base station in a cellular network in which the base station serves a population of same-cell terminals, the cellular network includes other base stations that serve respective populations of other-cell terminals, the terminals are allocated to two or more terminal groups, each terminal group is a reuse group for pilot signals transmitted by terminals, and each terminal within a given cell belongs to a respective terminal group;

the method comprising;

receiving a respective reverse-link signal from each of two or more terminal groups, wherein each said signal is a combination of reverse-link signals synchronously transmitted by a plurality of same-cell and other-cell terminals in the same terminal group;

obtaining from each of one or more other base stations a further reverse-link signal received by the other base station from each of the terminal groups; and

linearly combining selected received signals and obtained signals, thereby to recover reverse-link messages transmitted by same-cell terminals in each of two or more terminal groups.

9. The method of claim 8, wherein the receiving step is performed using OFDM demodulation and maximum-ratio combining.

10. The method of claim 8, wherein:

the receiving step is performed using multiple base station antennas;

the linearly combining step is performed using a set of slow-fading coefficients; and

the slow-fading coefficients apply to same-cell and to other-cell terminals.

11. The method of claim 10, wherein:

the receiving step is performed using maximum-ratio combining;

the maximum-ratio combining is performed using fast-fading coefficients;

the fast-fading coefficients apply only to same-cell terminals; and

the fast-fading coefficients are updated more frequently than the slow-fading coefficients.

12. The method of claim 11, wherein the slow-fading coefficients used for the linearly combining step do not discriminate among the multiple base station antennas used for the receiving step.

13. Base station apparatus adapted to serve a population of same-cell terminals within a cellular network that also includes other base stations that serve respective populations of other-cell terminals, comprising:

a module adapted for obtaining messages destined for a plurality of same-cell terminals and for a plurality of other-cell terminals;

a module adapted to form a plurality of pilot contamination precoded messages from said messages, wherein each said precoded message pertains to a respective terminal group, each terminal group is a reuse group for pilot signals transmitted by terminals, each terminal within a given cell belongs to a respective terminal group, and each pilot contamination precoded message is a linear combination of the messages destined for the same-cell and other-cell terminals of a respective terminal group; and

a module adapted for transmitting the pilot contamination precoded messages synchronously with the other base stations.

14. The base station apparatus of claim 13, wherein the transmitting module comprises an OFDM transmitter.

15. The base station apparatus of claim 13, further comprising a beam-forming precoder configurable to operate on the pilot contamination precoded messages before they are transmitted.

16. The base station apparatus of claim 15, wherein:

the base station apparatus further comprises a module adapted to measure and to update a set of slow-fading coefficients and a set of fast-fading coefficients;

the precoded message-forming module is configured to form the linear combinations using the slow-fading coefficients;

the beam-forming precoder is configured to further precode the pilot contamination precoded messages using the fast-fading coefficients.

17. The base station apparatus of claim 16, wherein:

the base station apparatus further comprises two or more antennas;

the fast-fading coefficients apply only to same-cell terminals;

the slow-fading coefficients apply to same-cell and to other-cell terminals; and

the base station apparatus is configured to update the fast-fading coefficients more frequently than the slow-fading coefficients.

18. Base station apparatus adapted to serve a population of same-cell terminals within a cellular network that also includes other base stations that serve respective populations of other-cell terminals, comprising:

a module adapted for receiving a respective reverse-link signal from each of a plurality of terminal groups, wherein each terminal group is a reuse group for pilot signals transmitted by terminals, each terminal within a given cell belongs to a respective terminal group, and each said signal is a combination of reverse-link signals synchronously transmitted by a plurality of same-cell and other-cell terminals in the same terminal group;

a module adapted for obtaining from each of a plurality of other base stations a further reverse-link signal received by the other base station from each of the terminal groups; and

a module adapted for linearly combining selected received signals and obtained signals, thereby to recover reverse-link messages transmitted by same-cell terminals in each of two or more terminal groups.

19. The base station apparatus of claim 18, wherein the receiving module comprises a maximum ratio combiner.

20. The base station apparatus of claim 19, wherein:

the base station apparatus comprises two or more antennas;

the linearly combining module is configurable to form the linear combinations using a set of slow-fading coefficients;

the receiving module comprises a maximum ratio combiner;

the maximum ratio combiner is configured to perform maximum ratio combining using a set of fast-fading coefficients;

the slow-fading coefficients apply to same-cell and to other-cell terminals; and

the fast-fading coefficients apply only to same-cell terminals.

21. The base station apparatus of claim 20, wherein:

the base station apparatus further comprises a module configured to measure and to update the slow-fading coefficients and the fast-fading coefficients; and

said module is configured to update the fast-fading coefficients more frequently than the slow-fading coefficients.

22. The base station apparatus of claim 18, wherein the receiving module further comprises an OFDM demodulator.

23. A base station adapted for operation in a cellular network in which reverse-link pilot signals are reused by mobile terminals transmitting synchronously from different, mutually interfering cells, comprising a module adapted to precode forward-link signals to mitigate inter-cell interference due to pilot contamination arising from reuse of pilot signals.

24. The base station of claim 23, further comprising a module adapted to linearly combine signals received on the reverse link by said base station with signals received on the reverse link by other base stations of said cellular network, thereby to mitigate interference in said reverse-link signals due to said pilot contamination.