Relay station and method for enabling reliable digital communications between two nodes in a wireless relay based network

• US 8,125,938 B2
• Filed: 12/19/2003
• Issued: 02/28/2012
• Est. Priority Date: 12/19/2003
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Nystrom, Johan, Frenger, Pal
• Primary Examiner(s): Kincaid, Lester
• Assistant Examiner(s): Jama, Isaak R
• Application Number:
  US10/596,619
• Publication Number:
  US 20070116092A1
• Time in Patent Office: 2,993 Days
• Field of Search: 455/7, 455/15, 375/211, 370/315
• US Class Current: 370/315
• CPC Class Codes: H03M 13/3905 Maximum a posteriori probability [MAP] decoding or approximations thereof based on trellis or lattice decoding, e.g. forward-backward algorithm, log-MAP decoding, max-log-MAP decoding
• CPC Class Codes: H03M 13/45 Soft decoding, i.e. using symbol reliability information H03M13/41 takes precedence
• CPC Class Codes: H04B 7/155 Ground-based stations H04B7/204 takes precedence
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0045 Arrangements at the receiver end
• CPC Class Codes: H04L 1/0055 MAP-decoding
• CPC Class Codes: H04L 1/0082 fields explicitly indicating existence of error in data being transmitted, e.g. so that downstream stations can avoid decoding erroneous packet; relays
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 1/1845 Combining techniques, e.g. code combining
• CPC Class Codes: H04L 2001/0097 Relays
• CPC Class Codes: H04W 16/26 Cell enhancers or enhancement, e.g. for tunnels, building shadow

Abstract

A relay station (606, 806a, 806b, 906a, 906b, 1006 and 1106) and a method (700) are described herein that enables reliable digital communications to occur between two nodes in a wireless relay based network (600, 800, 900, 1000 and 1100). The wireless relay based network includes a first node (602, 802, 902, 1002 and 1102) that transmits information in coded/modulated digital communications to a second node (604, 804, 904, 1004 and 1104) via one or more relay stations. And, each relay station is capable of: (1) receiving (702) a coded/modulated digital communication from the first node; (2) computing (704) a plurality of reliability values for a plurality of information symbols or coded symbols in the received coded/modulated digital communication; and (3) transmitting (706) a coded/modulated digital communication that has the computed reliability values embedded therein to the second node.

Claims

1. A wireless relay based network, comprising:

a first node;

at least one relay station; and

a second node;

wherein said first node communicates with said second node via said at least one relay station, wherein each relay station is operative to;

receive a digital communication from said first node;

compute a plurality of reliability values for a plurality of symbols in the received digital communication, where each reliability value indicates how likely the corresponding symbol is a binary 0or a binary 1; and

,

transmit a digital communication which has a plurality of symbols that are same as the plurality of symbols in the received digital communication but also has the computed reliability values embedded therein to said second node.

2. The wireless relay based network of claim 1, wherein each relay station performs the computing operation using a maximum a posteriori (MAP) filter that computes reliability values for code symbols based on a code structure of the received digital communication.

3. The wireless relay based network of claim 2, wherein each MAP filter also filters the received digital communication and redistributes noise to unreliable parts in the transmitted digital communication.

4. The wireless relay based network of claim 1, wherein each relay station performs the computing operation using a soft output channel decoder that computes reliability values for information symbols based on a code structure of the received digital communication.

5. The wireless relay based network of claim 4, wherein said soft output channel decoder employs:

a maximum a posteriori (MAP) algorithm;

a soft output Viterbi algorithm (SOVA);

a Log-MAP algorithm;

or

a Max-LOG-MAP algorithm.

6. The wireless relay based network of claim 1, wherein the computed reliability values are embedded in the transmitted digital communication such that high reliability symbols are transmitted with higher power and low reliability symbols are transmitted with lower power to said second node.

7. The wireless relay based network of claim 1, wherein the computed reliability values are embedded in the transmitted digital communication in a manner where the reliability symbols are used to modulate an amplitude of the digital communication transmitted to said second node.

8. The wireless relay based network of claim 1, wherein the computed reliability values are embedded in the transmitted digital communication in a manner where the reliability symbols are used to modulate a phase of the digital communication transmitted to said second node.

9. The wireless relay based network of claim 1, wherein the computed reliability values are embedded in the transmitted digital communication in a manner where the reliability symbols are used to vary a bandwidth of the digital communication transmitted to said second node.

10. The wireless relay based network of claim 1, wherein the computed reliability values are embedded in the transmitted digital communication in a manner where the reliability symbols are used to vary a signal time occupation of the digital communication transmitted to said second node.

11. The wireless relay based network of claim 1, wherein the computed reliability values are embedded in the transmitted digital communication in a manner where the reliability symbols are used to vary a signal constellation size of the digital communication transmitted to said second node.

12. The wireless relay based network of claim 1, wherein said first node is:

a base station;

a mobile station;

or

a relay station.

13. The wireless relay based network of claim 1, wherein said second node is:

a base station;

a mobile station;

or

a relay station.

14. The wireless relay based network of claim 1, wherein each relay station is:

a base station;

a mobile station;

or

a stand alone relay station.

15. The wireless relay based network of claim 1, wherein said received digital communication is:

an uplink received digital communication;

a downlink received digital communication;

a base station peer-to-peer received digital communication;

or

a mobile station peer-to-peer received digital communication.

16. The wireless relay based network of claim 1, wherein said transmitted digital communication is:

an uplink transmitted digital communication;

a downlink transmitted digital communication;

a base station peer-to-peer transmitted digital communication;

or

a mobile station peer-to-peer transmitted digital communication.

17. The wireless relay based network of claim 1, wherein when multiple relay stations each transmit the digital communication then said second node combines the transmitted digital communications.

18. The wireless relay based network of claim 1, wherein when one relay station transmits multiple digital communications at different times then said second node combines the transmitted digital communications.

19. The wireless relay based network of claim 1, wherein when one relay station knows a channel response of a link between that relay station and said second node then that relay station is able to construct a transmitted digital communication which is coherently combined at said second node with a similar transmitted digital communication received from another relay station.

20. The wireless relay based network of claim 1, wherein said at least one relay station by computing the plurality of reliability values for a plurality of symbols in the received digital communication and transmitting the digital communication which has the plurality of symbols that are the same as the plurality of symbols in the received digital communication but also has the computed reliability values embedded therein to the second node avoids having to make hard decisions on the plurality of symbols in the received digital communication, and wherein the second node makes hard decisions on the plurality of symbols in the received digital communication by taking into account the reliability values for the plurality of symbols in the received digital communication.

21. A method for enabling a relay station to provide reliable digital communications between a first node and a second node, said method comprising the steps of:

receiving, at said relay station, a digital communication from said first node;

computing, at said relay station, a plurality of reliability values for a plurality of symbols in the received digital communication, where each reliability value indicates how likely the corresponding symbol is a binary 0 or a binary 1; and

,

transmitting, at said relay station, a digital communication which has a plurality of symbols that are same as the plurality of symbols in the received digital communication but also has the computed reliability values embedded therein to said second node.

31. The method of claim 21, wherein said relay station by computing the plurality of reliability value for a plurality of symbols in the received digital communication and transmitting the digital communication which has the plurality of symbols that are the same as the plurality of symbols in the received digital communication but also has the computed reliability values embedded therein to the second node avoids having to make hard decisions on the plurality of symbols in the received digital communication, and wherein the second node makes hard decisions on the plurality of symbols in the received digital communication by taking into account the reliability values for the plurality of symbols in the received digital communication.

32. The method of claim 21, wherein said computing step if performed a maximum a posteriori (MAP) filter that computes reliability values for code symbols based on a code structure of the received digital communication.

33. The method of claim 21, wherein said computing step if performed a soft output channel decoder that computes reliability values for information symbols based on a code structure of the received digital communication.

34. The method of claim 21, wherein the computed reliability values are explicitly embedded in the digital communication transmitted to said second node.

35. The method of claim 21, wherein the computed reliability values are implicitly embedded in the digital communication transmitted to said second node.

22. A relay station operative to provide communications between a first node and a second node, said relay station operative to:

receive a coded/modulated digital communication from said first node;

compute a plurality of reliability values for a plurality of symbols in the received coded/modulated digital communication, where each reliability value indicates how likely the corresponding symbol is a binary 0 or a binary 1; and

transmit a coded/modulated digital communication which has a plurality of symbols that are same as the plurality of symbols in the received coded/modulated digital communication but also has the computed reliability values embedded therein to said second node.

23. The relay station of claim 22, further comprising a maximum a posteriori (MAP) filter that computes reliability values for code symbols based on a code structure of the received coded/modulated digital communication.

24. The relay station of claim 22, further comprising a soft output channel decoder that computes reliability values for information symbols based on a code structure of the received coded/modulated digital communication.

25. The relay station of claim 22, wherein the computed reliability values are explicitly embedded in the coded/modulated digital communication transmitted to said second node.

26. The relay station of claim 22, wherein the computed reliability values are implicitly embedded in the coded/modulated digital communication transmitted to said second node.

27. The relay station of claim 22, wherein said relay station is used in a wireless multi-hop network.

28. The relay station of claim 22, wherein a link between said relay station and said first node has a smaller bandwidth than a link between said relay station and said second node.

29. The relay station of claim 22, wherein each relay station is:

a base station;

a mobile station;

or,

a stand alone relay station.

30. The relay station of claim 22, wherein said relay station by computing the plurality of reliability value for a plurality of symbols in the received coded/modulated digital communication and transmitting the coded/modulated digital communication which has the plurality of symbols that are the same as the plurality of symbols in the received coded/modulated digital communication but also has the computed reliability values embedded therein to the second node avoids having to make hard decisions on the plurality of symbols in the received coded/modulated digital communication, and wherein the second node makes hard decisions on the plurality of symbols in the received coded/Modulated digital communication by taking into account the reliability values for the plurality of symbols in the received coded/modulated digital communication.

36. A wireless relay based network, comprising:

a first node;

at least one relay station; and

a second node;

wherein said first node communicates with said second node via said at least one relay station, wherein each relay station is operative to;

receive a digital communication from said first node;

compute a plurality of reliability values for a plurality of symbols in the received digital communication; and

,

transmit a digital communication that has the computed reliability values embedded therein to said second node, wherein when one relay station knows a channel response of a link between that relay station and said second node then that relay station is able to construct a transmitted digital communication which is coherently combined at said second node with a similar transmitted digital communication received from another relay station.