Method and architecture for wireless communication networks using cooperative relaying

• US 20040266339A1
• Filed: 05/28/2004
• Published: 12/30/2004
• Est. Priority Date: 05/28/2003
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Larsson, Peter
• Granted Patent: US 7,933,549 B2
• Time in Patent Office: Days
• US Class Current: 455/7
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/026 Co-operative diversity, e.g. using fixed or mobile stations as relays
• CPC Class Codes: H04B 7/15528 Control of operation parameters of a relay station to exploit the physical medium
• CPC Class Codes: H04B 7/15592 Adapting at the relay station communication parameters for supporting cooperative relaying, i.e. transmission of the same data via direct - and relayed path cooperative diversity H04B7/024
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 1/0021 in which the algorithm uses adaptive thresholds
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 2001/0097 Relays
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/20 Repeater circuits; Relay circuits
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0035 Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 52/40 during macro-diversity or soft handoff
• CPC Class Codes: H04W 52/46 in multi hop networks, e.g. wireless relay networks
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

The present invention relates to wireless networks using cooperative relaying which in a communication session involve more than one relay station. In the method according to the present invention, a transmitter 210′, a receiver 220′ and at least one relay station 215 are engaged in a communication session. The relay station 215 forwards signals from a first link between the transmitter 210′and the relay station 215 to a second link between the relay stations 215 and the receiver 220′. The relay station 215 forwards the signal with the use of a relative transmission parameter and optionally a common transmission parameter. The relative transmission parameter is determined locally in each relay station 215 and based on a characterization of a first link, or the second link or a combination of the first and second link.

Claims

1. A method of performing communication in a wireless communication network using cooperative relaying, wherein a transmitter, a receiver and at least one relay station are engaged in a communication session, and said at least one relay station forwards signals from a first link between the transmitter and the relay station to a second link between the relay stations and the receiver, wherein each at least one relay station forwards the signal with the use of a relative transmission parameter specific for each relay station, and said relative transmission parameter is determined locally in each relay station and at least partly based on a characterization of radio transmission conditions for that relay station.

2. The method according to claim 1, wherein each relative transmission parameter is based on a characterisation of a radio path of the first link.

3. The method according to claim 1, wherein each relative transmission parameter is based on a characterisation of a radio path of the second link.

4. The method according to claim 2, wherein the relative transmission parameter is based on a combination of the characterisation of a radio path of the first and second link.

5. The method according to claim 1, wherein each relay station in addition to the relative transmission parameter uses at least one common transmission parameter in the forwarding of the signal and the common transmission parameter is determined centralized and distributed to each relay station.

6. The method according to claim 5, wherein said at least one common transmission parameter is determined in the receiver and multicasted to each relay station.

7. The method according to claim 1, wherein the method is used for either phase control, power control or relay activation or any combination of phase control, power control, and relay activation.

8. The method according to claim 7, wherein the at least one common transmission parameter comprises a relay activation threshold, which is multicasted from the receiver to the relay stations and said relay activation threshold specifies conditions which the relay stations must fulfil in order to be active in the forwarding of the signal on the second link.

9. The method according to claim 8, wherein the relay condition comprises a parameter characterizing the first link, or the second link, or a combination of the first link and the second link.

10. The method according to claim 8, wherein the multicasted common parameter comprises a specification of which relay stations that should be activated or deactivated.

11. The method according to claim 7, wherein the method comprises the steps of:

characterizing the radio paths of the first and second link by the use of pilots;

determining in each relay station at least one relative transmission parameter at least partly based on one, or both, of the channel characterizations of each relay stations paths of the first and second link;

determining in the receiver at least one common transmission parameter;

broadcasting said common transmission parameter to the relay stations;

using in each relay station the relay station'"'"'s respective relative transmission parameter and the common transmission parameter in the forwarding of the signal on the second link.

12. The method according to claim 7, wherein the method comprises the steps of:

sending pilots on the k paths of link 1, from transmitter to relay stations, and on the k paths of link 2, from receiver to relay stations;

estimating in each relay station the k channel of link 1, h_1,k, and the k channel of 2, h_2,k;

determining in each relay station the relative transmission parameter or a set of relative transmission parameters, wherein the relative parameter is based on one, or both, of the channel estimates h_1,k, h_2,k characterizing each path;

determining in the receiver the common transmission parameter, or a set of common transmission parameters, based on the total communication quality experienced by the receiver;

broadcasting by the receiver the common transmission parameter(s) to the relay stations;

using in each relay station the relay station'"'"'s respective relative transmission parameter and the common transmission parameter(s) to adapt the subsequent transmissions on link 2.

13. The method according to claim 12, wherein the method further comprises the step of feedbacking control information from the receiver to the transmitter.

14. The method according to claim 12, wherein the step of using the relay station'"'"'s respective relative transmission parameter and the common transmission parameter(s) to adapt the subsequent transmissions on link 2, comprises to, on the reception of signal y_k, transmit the signal:

15. The method according to claim 12, wherein the steps of determining, broadcasting and using the common transmission parameter represent a first control loop and the step of feedbacking to the transmitter represent a second control loop from the receiver to the relay stations and the transmitter, respectively.

16. The method according to claim 15, wherein the first control loop further comprises the substeps of:

the receiver measuring at time n, the quality of the received signal C_r, the relay induced noise N_r, and the internal noise in the receiver N_i;

the receiver determines based on the previous measurement, and a desired SNR-target Γ

₀, an update of at least one of the normalization factor Φ

⁽ⁿ⁺¹⁾ and the aggregate relay power P⁽ⁿ⁺¹⁾_RS;

the receiver distribute the updates, P⁽ⁿ⁺¹⁾_RS and Φ

⁽ⁿ⁺¹⁾ to all relays through a multicast control message.

17. The method according to claim 15, wherein the second control loop further comprises the substep of the receiver updating the transmitter power P⁽ⁿ⁺¹⁾_BS.

18. A system adapted for communication in a wireless communication network using cooperative relaying, the system comprises a transmitter, a receiver and at least one relay station, wherein the relay station is adapted to forward signals from a first link between the transmitter and the relay station to a second link between the relay stations and the receiver, said system has a logical architecture wherein:

at least one relay station has means for performing channel characterization and means for determining relative transmission parameters based on channel characterization and means for adapting the forwarding based on a common transmission parameter and a relative transmission parameter;

the receiver has means for determining a common transmission parameter and means for distributing the common transmission parameter to the relay stations; and

the logical architecture comprises a first control loop between the receiver and the relay stations adapted to feedback the common parameter from receiver to the relay stations.

19. The system according to claim 18, further comprising a second control loop between the receiver and the transmitter adapted to feedback the transmission parameters from receiver to the transmitter.

20. The system according to claim 18, wherein each relay station is adapted to perform the channel characterization on its radio path of the first link.

21. The system according to claim 18, wherein each relay station is adapted to perform the channel characterization on its radio path of the second link.

22. The system according to claim 20, wherein each relay station is adapted to base the determination of the relative transmission parameter on a combination of the characterisation of a radio path of the first and second link

23. The system according to claim 18, wherein the system is adapted to utilize the relative transmission parameter and the common transmission parameter for either phase control, power control or relay activation or any combination of phase control, power control, and relay activation.

29. A control message structure adapted for the control signalling in the first control loop according to claim 18, wherein the control message comprises at least one of, or a selection of the fields:

a relay concept field specifying the type of relay concept;

a power control field giving the common transmission parameters used by the relay stations to determine a suitable power for the forwarding on the second link;

a relay activation control field specifying the relay activation threshold and/or specifying relay stations to be activated/deactivated;

a phase control field giving the common transmission parameters used by the relay stations to phase align the signals to be forwarded on the second link.

24. A relay station adapted for use in a wireless communication network using cooperative relaying, wherein the relay station is adapted to forward signals from a first link between a transmitter and a relay station to a second link between the relay stations and the receiver, wherein the relay station has means for performing channel characterization and means for determining relative transmission parameters based on channel characterization and means for adapting the forwarding at least partly based on the relative transmission parameter.

25. The relay station according to claim 24, wherein the adapting and forwarding means also are adapted for using a common transmission parameter in the forwarding of the signal to the second link, wherein said common transmission parameter has been distributed to the relay station.

26. The relay station according to claim 24, further comprising means for activating/deactivating the relay station and the activating/deactivating means are responsive to the relative transmission parameter and/or the common transmission parameter.

27. A basestation adapted for use in a wireless communication network using cooperative relaying, wherein the basestation comprises a receiver, and the network comprises at least one relay station which is adapted to forward signals from a first link between a transmitter and a relay station to a second link between the relay stations and the receiver, wherein the receiver of the base station, has means for determining a common transmission parameter and means for distributing the common transmission parameter to the relay stations, and wherein the common transmission parameter is at least partly based on a measure of the total communication quality between the transmitter and the receiver of the basestation.

28. A mobile station adapted for use in a wireless communication network using cooperative relaying, wherein the mobile station comprises a receiver, and the network comprises at least one relay station which is adapted to forward signals from a first link between a transmitter and a relay station to a second link between the relay stations and the receiver, wherein the receiver has means for determining a common transmission parameter and means for distributing the common transmission parameter to the relay stations, and wherein the common transmission parameter is at least partly based on a measure of the total communication quality between the transmitter and the receiver of the mobile station.