Cooperative relay system enabling simultaneous broadcast-unicast operation with efficient automatic repeat request functionality

• US 20090092073A1
• Filed: 10/09/2007
• Published: 04/09/2009
• Est. Priority Date: 10/09/2007
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Corporation
• Inventors: Doppler, Klaus, Hottinen, Ari
• Granted Patent: US 8,023,524 B2
• Time in Patent Office: Days
• US Class Current: 370/315
• 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 7/155 Ground-based stations H04B7/204 takes precedence

Abstract

A wireless node, such as a relay node, has different operating modes for unicast and broadcast/multicast subchannels. For unicast services the phase offsets of those relay nodes engaged in a cooperative transmission are optimized for the subchannels used for unicast services. Alternatively, when no feedback is available and an open loop MIMO or MIMO-type scheme is in use, retransmissions are performed in such a way that a destination (e.g., user terminal) receives effectively a distributed space-time block code. For the broadcast/multicast services time varying random phase offsets may be employed for the subchannels used for broadcast services. For reliable high data rate broadcast transmissions a cooperative retransmission scheme that effectively forms distributed space-time block codes may be used.

Claims

1. A method, comprising:

operating a plurality of wireless nodes to cooperatively transmit unicast data from a source to a destination; and

while cooperatively transmitting the unicast data, at least one of the plurality of wireless nodes responding to feedback signaling from the destination for causing transmissions from each of the plurality of wireless nodes to add constructively at the destination.

2. The method of claim 1, where responding comprises receiving at the at least one of the plurality of wireless nodes, from the destination, feedback signaling for each subchannel used to transmit the unicast data, the feedback signaling predetermined to cause transmissions from each of the plurality of wireless nodes to add constructively at the destination for each of the used subchannels.

3. The method of claim 1, where each of the plurality of wireless nodes is configurable to transmit the unicast data using one of n different phase offsets for each subchannel used to transmit the unicast data, where n is greater than one, where responding comprises receiving at the plurality of wireless nodes, from the destination, feedback signaling for indicating for each subchannel used to transmit the unicast data, which of the n different phase offsets provides the best reception for each of the used subchannels.

4. The method of claim 1, where the destination comprises one of a user terminal device or a relay node.

5. A method, comprising:

operating a plurality of wireless nodes to cooperatively transmit unicast data from a source to a destination; and

while cooperatively transmitting the unicast data, responding to a request for retransmission from the destination by at least one of the plurality of wireless nodes changing transmission symbols such that a cooperative retransmission results in the destination effectively receiving a distributed space-time block code, where the destination comprises one of a user terminal device or a relay node.

6. The method of claim 5, where each of the plurality of wireless nodes transmits to the destination using a single transmit antenna, where all of the data being transmitted is available at each of the wireless nodes involved in the cooperative retransmission, and where one wireless node changes its transmission symbols so that the combined transmission of a first transmission and at least one repeated transmission jointly form a signal that is amenable for improved decoding at the destination receiver.

7. The method of claim 6, where a first wireless node (R1) transmits during a first slot:

[x₁ x₃ . . . x_2N-1]^T,

where N specifies the number of symbols transmitted by a single wireless node during the slot, where a second wireless node (R2) transmits during the first slot;

[x₂ x₄ . . . x_2N]^T,

such that a two-antenna destination receiver is enabled to decouple the two transmit streams using a MIMO-compatible channel, and if a retransmission is requested, R1 and R2 respond by simultaneously transmitting during a second slot;

from R1;

[−

x₂* −

x₄* . . . −

x_2N*]^T,

from R2;

[x₁* x₃* . . . x_2N-1*]^T,

8. The method of claim 7, further comprising reversing an order of the symbols transmitted in the second slot,

for R1:

[−

x_2N* . . . −

x₄* −

x₂*]^T,

for R2;

[x_2N-1* . . . −

x₃* −

x_2N-1*]^T,

9. The method of claim 5, where each of the plurality of wireless nodes transmits to the destination using a single transmit antenna, where not all of the data being transmitted is available at each of the wireless nodes involved in the cooperative retransmission, where retransmission is accomplished to reduce interference between received symbols at the destination by performing retransmission from a first wireless node as in the original transmission and by performing retransmission from a second wireless node such that during a second slot the symbol signs are changed

[−

x₂−

x₄ . . . x_2N]^T,

10. The method of claim 9, further comprising signaling a relay-specific sign change pattern to the second wireless node.

11. The method of claim 9, where a symbol sign change pattern is obtained from an orthogonal, unitary matrix by multiplying an n th retransmission with a (k, n) th element of said orthogonal, unitary matrix.

12. The method of claim 5, where each of the plurality of wireless nodes transmits to the destination using a plurality of transmit antennas, where all of the data being transmitted is available at each of the wireless nodes involved in the cooperative retransmission, where retransmission is accomplished by making the first transmission from a first antenna and a second is taken from columns 1,2 and 3,4 of the matrix:

X[t₁]=[X_A X_B].

13. The method of claim 12, further comprising, responsive to a retransmission request from the destination, performing the retransmission using matrix:

X[t₂]=[X_A −

X_B].

14. The method of claim 13, responsive to another retransmission being requested, performing the another retransmission during two time epochs using permuted antenna indices with a modulation matrix:

$X=\left[\begin{array}{cc}{X}_A& X_B\\ X_A& -X_B\\ X_B& X_A\\ X_B& -X_A\end{array}\right],$

15. A method, comprising:

operating a plurality of wireless nodes to cooperatively transmit at least one of broadcast and multicast data through first subchannels, and to also cooperatively transmit unicast data through at least one second subchannel, from a source to a plurality of destinations; and

while cooperatively transmitting the at least one of broadcast and multicast data and the unicast data, controlling transmission through the first subchannels differently than through the at least one second subchannel wireless node.

16. The method of claim 15, where each of the plurality of wireless nodes uses time varying phase offsets to induce temporal variations in an effective channel seen at each of the plurality of destinations, where the phase offsets create a temporal variation within a forward error correction code length, while still enabling each destination to estimate and track the effective channel.

17. The method of claim 15, where at least one of the plurality of destinations comprises one of a user terminal device or a relay node.

18. A method, comprising:

operating a plurality of wireless nodes to cooperatively transmit at least one of broadcast and multicast data from a source to a plurality of destinations; and

while cooperatively transmitting the at least one of broadcast and multicast data, responding to a request for retransmission from one of the destinations by at least one of the plurality of wireless nodes changing transmission symbols such that a cooperative retransmission results in the destination effectively receiving a distributed space-time block code, where at least one of the plurality of destinations comprises one of a user terminal device or a relay node.

19. The method of claim 18, where responding occurs after a delay period sufficient to allow the plurality of cooperating wireless nodes to signal to one another if a retransmission is necessary.

20. The method of claim 18, further comprising sending acknowledgement/negative acknowledgement signaling over a control channel between destinations and the plurality of wireless nodes, and sending an indication from the plurality of wireless nodes and the destinations of whether the transmitted data is new data or a retransmission of data previously sent.

21. The method of claim 18, where cooperatively transmitting the at least one of broadcast and multicast data occurs through certain subchannels, and where other subchannels are simultaneously used for cooperatively transmitting unicast data that are controlled differently than the certain subchannels.

22. An apparatus, comprising a wireless receiver, a wireless transmitter, and a transmission control unit configurable to cooperatively transmit at least one of broadcast and multicast data through first subchannels to a plurality of destination nodes, and to simultaneously cooperatively transmit unicast data through second subchannels to at least one destination node, where the first subchannels and the second subchannels are controlled differently.

23. The apparatus as in claim 22, where said transmission control unit responds to feedback from the at least one destination node to change how the second subchannels are controlled to cause a received transmission at the at least one destination node to add constructively with a received transmission from another apparatus, where the another apparatus is one of a relay node or a base station, and

where said transmit control unit responds to a request for a retransmission from a destination node to change transmission symbols such that a cooperative retransmission results in the destination node effectively receiving a distributed space-time block code.

24. The apparatus of claim 23, where all of the data being transmitted is available at the apparatus and at another apparatus that cooperates in the transmission to the at least one destination node, and where the transmission symbols are changed so that the combined transmission of a first transmission and at least one repeated transmission jointly form a signal that is amenable for improved decoding at the destination node, and where retransmission is accomplished to reduce interference between received symbols at the destination node by performing retransmission from the apparatus as in the original transmission, and by performing retransmission from the another apparatus such that during a second slot symbol signs are changed.

25. The apparatus as in claim 22, where said transmit control unit when transmitting on the first subchannels applies a time varying phase offset, in cooperation with another apparatus that is transmitting the at least one of broadcast and multicast data, that is intended to induce temporal variations in an effective channel received by each of the plurality of destination nodes.