METHOD OF DOWNLINK SIGNAL TRANSPORT OVER BACKHAUL COMMUNICATIONS THROUGH DISTRIBUTED PROCESSING

• US 20120230691A1
• Filed: 03/11/2011
• Published: 09/13/2012
• Est. Priority Date: 03/11/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Hui, Dennis, Cheng, Jung-Fu, Guey, Jiann-Ching, Zangi, Kambiz, Wong, Shing-Wa
• Granted Patent: US 8,737,298 B2
• Time in Patent Office: Days
• US Class Current: 398/58
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0073 Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04W 92/12 between access points and access point controllers
• CPC Class Codes: H04W 92/20 between access points

Abstract

The amount of multi-antenna signals to be transmitted over the backhaul in a Coordinated MultiPoint (CoMP) system from the central processor (CP) to each base station is reduced. Embodiments of the present invention exploit characteristics of the underlying signal structure, and distribute some baseband processing functionalities—such as channel coding and the application of the multi-user precoding—from the CP to the remote base stations. Additionally, in some embodiments the non-precoded parts of multi-antenna signals are broadcast from the CP to all base stations in the CoMP system, to further reduce the burden on backhaul communications. In one embodiment, the backhaul network is a Gigabit-capable Passive Optical Network (GPON).

Claims

1. A method of distributing, from a Central Processor in a Coordinated Multipoint (CoMP) wireless communication system to a plurality of base stations, information to be transmitted to User Equipment (UE) in cells served by the base stations, comprising the steps of:

selecting a multi-user precoding matrix for each base station, each precoding matrix comprising precoding weights to be applied to symbols to be transmitted to UEs by a base station;

transmitting to each base station information about a precoding matrix selected for that base station;

computing the information bits to be transmitted to all UEs in the CoMP system; and

transmitting the set of information bits to all base stations in the CoMP system;

2. The method of claim 1 further comprising the step of computing a multi-user precoding matrix for each base station prior to selecting a multi-user precoding matrix for each base station.

3. The method of claim 2 further comprising

quantizing the selected precoding matrices;

and

wherein transmitting to each base station information about a precoding matrix selected for that base station comprises transmitting a quantized precoding matrix to each base station.

4. The method of claim 2 wherein the step of computing a multi-user precoding matrix for each base station comprises using a minimum mean square error linear precoding technique.

5. The method of claim 2 wherein the step of computing a multi-user precoding matrix for each base station comprises using a zero forcing linear precoding technique.

7. The method of claim 1 further comprising the steps of:

selecting a modulation and coding scheme (MCS) for each base station in the CoMP system; and

transmitting the MCS to each base station.

8. The method of claim 1 further comprising the steps of:

applying lossless compression to the information bits to be transmitted to all UEs in the CoMP system; and

wherein transmitting the set of information bits to all base stations in the CoMP system comprises transmitting compressed information bits to all base stations in the CoMP system.

9. The method of claim 1 wherein transmitting the set of information bits to all base stations in the CoMP system comprises broadcasting the information bits to all base stations in the CoMP system simultaneously.

10. The method of claim 9 wherein broadcasting the information bits to all base stations in the CoMP system simultaneously comprises broadcasting the information bits using a Gigabit-capable Passive Optical Network (GPON).

6. The method of claim wherein 1 transmitting to each base station information about a precoding matrix selected for that base station comprises transmitting to each base station an index into a precoding matrix codebook.

11. A method of transmitting signals to user equipment (UE) in a cell of a Coordinated Multipoint (CoMP) wireless communication system, comprising the steps of:

receiving, from a Central Processor (CP), information about a precoding matrix and the information bits to be transmitted to all UEs in the CoMP system;

applying a modulation and coding scheme (MCS) to the information bit to generate modulated symbols;

applying precoding weights from the precoding matrix to the modulated symbols to generate precoded symbols; and

transmitting the precoded symbols to UEs in the cell.

12. The method of claim 11 wherein the step of receiving, from a CP, information about a precoding matrix comprises receiving, from the CP, an index into a precoding matrix codebook;

and further comprising using the received index to retrieve a precoding matrix from the precoding matrix codebook.

13. The method of claim 11 wherein the step of receiving, from a CP, information about a precoding matrix comprises receiving, from the CP, a precoding matrix computed at the CP.

14. The method of claim 11 further comprising the step of receiving, from the CP, the MCS to apply to the information bits.

15. The method of claim 11 wherein the step of receiving, from a CP, the information bits to be transmitted to all UEs in the CoMP system comprises receiving compressed information bits, and further comprising decompressing the compressed information bits prior to applying the MCS.

16. A Central Processor (CP) in a Coordinated Multipoint (CoMP) wireless communication system, comprising:

a backhaul network interface operative to communicatively couple the CP to a plurality of base stations in the CoMP system; and

a controller operative to

select a multi-user precoding matrix for each base station, each precoding matrix comprising precoding weights to be applied to symbols to be transmitted to user equipment (UE) by a base station;

transmit to each base station, via the backhaul network interface, information about a precoding matrix selected for that base station;

compute the information bits to be transmitted to all UEs in the CoMP system; and

transmit the set of information bits to all base stations in the CoMP system, via the backhaul network interface.

17. The CP of claim 16 wherein the controller is further operative to compute a multi-user precoding matrix for each base station prior to selecting a multi-user precoding matrix for each base station.

18. The CP of claim 17 wherein the controller is further operative to

quantize the selected precoding matrices;

and

wherein the controller is operative to transmit to each base station information about a precoding matrix selected for that base station by transmitting a quantized precoding matrix to each base station, via the backhaul network interface.

19. The CP of claim 17 wherein the controller is operative to compute a multi-user precoding matrix for each base station by using a minimum mean square error linear precoding technique.

20. The CP of claim 17 wherein the controller is operative to compute a multi-user precoding matrix for each base station by using a zero forcing linear precoding technique.

21. The CP of claim 16 wherein the controller is operative to transmit to each base station information about a precoding matrix selected for that base station by transmitting, via the backhaul network interface, to each base station, an index into a precoding matrix codebook.

22. The CP of claim 16 wherein the controller is further operative to

select a modulation and coding scheme (MCS) for each base station in the CoMP system;

and

transmit the MCS to each base station via the backhaul network interface.

23. The CP of claim 16 wherein the controller is further operative to

apply lossless compression to the information bits to be transmitted to all UEs in the CoMP system;

and

wherein the controller is operative to transmit the set of information bits to all base stations in the CoMP system by transmitting compressed information bits to all base stations in the CoMP system, via the backhaul network interface.

24. The CP of claim 16 wherein the controller is operative to transmit the set of information bits to all base stations in the CoMP system by broadcasting the information bits to all base stations in the CoMP system simultaneously, via the backhaul network interface.

25. The CP of claim 16 wherein the backhaul network interface comprises a Gigabit-capable Passive Optical Network (GPON) interface.

26. A base station operative to provide communication services to user equipment (UE) in a cell of a Coordinated Multipoint (CoMP) wireless communication system, comprising:

a backhaul network interface operative to communicatively couple the base station to a Central Processor (CP) of the CoMP system;

a transmitter operative to transmit precoded symbols to UEs in the cell; and

a controller operative to

receive, from a CP via the backhaul network interface, information about a precoding matrix and the information bits to be transmitted to all UEs in the CoMP system;

apply a modulation and coding scheme (MCS) to the information bit to generate modulated symbols;

apply precoding weights from the precoding matrix to the modulated symbols to generate precoded symbols; and

transmit, via the transmitter, the precoded symbols to UEs in the cell.

27. The base station of claim 26 wherein the controller is operative to receive, from a CP via the backhaul network interface, information about a precoding matrix by receiving, from the CP via the backhaul network interface, an index into a precoding matrix codebook;

and wherein the controller is further operative to use the received index to retrieve a precoding matrix from the precoding matrix codebook.

28. The base station of claim 26 wherein the controller is operative to receive, from a CP via the backhaul network interface, information about a precoding matrix by receiving, from the CP via the backhaul network interface, a precoding matrix computed at the CP.

29. The base station of claim 26 wherein the controller is further operative to receive, from the CP via the backhaul network interface, the MCS to apply to the information bits.

30. The base station of claim 26 wherein the controller is operative to receive, from a CP via the backhaul network interface, the information bits to be transmitted to all UEs in the CoMP system by receiving compressed information bits, and further wherein the controller is further operative to decompress the compressed information bits prior to applying the MCS.