Controlled superposition coding in multi-user communication systems

• US 8,553,595 B2
• Filed: 08/07/2008
• Issued: 10/08/2013
• Est. Priority Date: 02/19/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Laroia, Rajiv, Li, Junyi, Srinivasan, Murari
• Primary Examiner(s): Edouard, Patrick
• Assistant Examiner(s): PEREZ, JULIO R
• Application Number:
  US12/188,140
• Publication Number:
  US 20090296662A1
• Time in Patent Office: 1,888 Days
• Field of Search: 370/342, 370/345, 370/224, 370/335, 370310-315, 370/350, 455/509, 455/450, 455/513, 455/522, 455/427, 455/12.1, 455/13.3
• US Class Current: 370/310
• CPC Class Codes: H04L 1/1607 Details of the supervisory signal
• CPC Class Codes: H04L 1/1861 Physical mapping arrangements for ACK signaling see also H04L5/0053
• CPC Class Codes: H04L 27/2604 Multiresolution systems by means of multiresolution subcarriers H04L27/183, H04L27/3488
• CPC Class Codes: H04L 27/3488 Multiresolution systems
• CPC Class Codes: H04L 5/04 the signals being represented by different amplitudes or polarities, e.g. quadriplex
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/283 Power depending on the position of the mobile

Abstract

Methods of using superposition coding in a communications systems, e.g., a multi-user communications system. Superposition coding in accordance with the invention occurs in the case of an uplink by transmissions of different wireless terminals transmitting using the same communications resource, e.g., simultaneously transmitting using the same frequencies. The signals combine in the communications channel resulting in one transmission being superimposed on the other transmission. The device, e.g., base station, receiving the superimposed signals uses superposition decoding techniques to recover both signals. To obtain the benefit of the superposition, assignments of channel segments to multiple wireless terminals is controlled by the base station and/or transmission power levels are controlled by on or more wireless terminals sharing the same uplink communications resource, e.g., time slot, to make sure that the received signals from the different devices will have different received power levels making superposition decoding possible.

Claims

1. A method for superposition coding in a wireless communication system, the method comprising:

selecting two or more user terminals from a plurality of user terminals to be scheduled on a traffic segment, wherein the selected two or more user terminals differ in channel quality by at least one predefined amount;

transmitting, via the traffic segment, a composite traffic signal using superposition coding to the selected two or more user terminals; and

transmitting an assignment signal using superposition coding to the selected two or more user terminals, the assignment signal comprising a plurality of protected signals, each of the protected signals associated with one of the two or more user terminals, wherein a transmit power of each of the protected signals corresponds inversely to a signal strength of its associated user terminal of the selected two or more user terminals.

2. The method of claim 1 wherein the plurality of protected signals comprises a least protected signal corresponding to one of the selected two or more user terminals with a strongest signal strength.

3. The method of claim 2 wherein the plurality of protected signals comprises a most protected signal corresponding to one of the selected two or more user terminals with a weakest signal strength.

4. The method of claim 1 wherein the assignment signal conveys assignment information of the traffic segment including an identifier of at least one user terminal of the selected two or more user terminals which is assigned to utilize the traffic segment.

5. The method of claim 1 wherein selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment comprises:

maintaining a set of information indicating channel quality of the plurality of user terminals.

6. The method of claim 5 wherein selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment further comprises:

examining the set of information indicating channel quality of the plurality of user terminals to determine which of the plurality of user terminals differ in channel quality by the at least one predefined amount.

7. An apparatus for superposition coding in a wireless communication system, the apparatus comprising:

a scheduler module for selecting two or more user terminals from a plurality of user terminals within the wireless communication system to be scheduled on a traffic segment, wherein the selected two or more user terminals differ in channel quality by at least one predefined amount; and

a transmitter coupled to the scheduler module for performing the following;

a) transmitting, via the traffic segment, a composite traffic signal using superposition coding to the selected two or more user terminals; and

b) transmitting an assignment signal using superposition coding to the selected two or more user terminals, the assignment signal comprising a plurality of protected signals, each of the protected signals associated with one of the two or more user terminals, wherein a transmit power of each of the protected signals corresponds inversely to a signal strength of its associated user terminal of the selected two or more user terminals.

8. The apparatus of claim 7 wherein the plurality of protected signals comprises a least protected signal corresponding to one of the selected two or more user terminals with a strongest signal strength.

9. The apparatus of claim 8 wherein the plurality of protected signals comprises a most protected signal corresponding to one of the selected two or more user terminals with a weakest signal strength.

10. The apparatus of claim 7 wherein the assignment signal conveys assignment information of the traffic segment including an identifier of at least one user terminal of the selected two or more user terminals which is assigned to utilize the traffic segment.

11. The apparatus of claim 10 further comprising a memory unit coupled to the scheduler module for maintaining a set of information indicating channel quality of the plurality of user terminals.

12. The apparatus of claim 11 wherein the scheduler module is also for examining the set of information indicating channel quality of the plurality of user terminals to determine which of the plurality of user terminals differ in channel quality by the at least one predefined amount.

13. The apparatus of claim 7 wherein the apparatus is a base station within the wireless communication system.

14. An apparatus comprising a processor and a memory, the memory containing program code executable by the processor for performing the following:

selecting two or more user terminals from a plurality of user terminals to be scheduled on a traffic segment, wherein the selected two or more user terminals differ in channel quality by at least one predefined amount;

transmitting, via the traffic segment, a composite traffic signal using superposition coding to the selected two or more user terminals; and

transmitting an assignment signal using superposition coding to the selected two or more user terminals, the assignment signal comprising a plurality of protected signals, each of the protected signals associated with one of the two or more user terminals, wherein a transmit power of each of the protected signals corresponds inversely to a signal strength of its associated user terminal of the selected two or more user terminals.

15. The apparatus of claim 14 wherein the plurality of protected signals comprises a least protected signal corresponding to one of the selected two or more user terminals with a strongest signal strength.

16. The apparatus of claim 15 wherein the plurality of protected signals comprises a most protected signal corresponding to one of the selected two or more user terminals with a weakest signal strength.

17. The apparatus of claim 14 wherein the assignment signal conveys assignment information of the traffic segment including an identifier of at least one user terminal of the selected two or more user terminals which is assigned to utilize the traffic segment.

18. The apparatus of claim 14 wherein selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment comprises:

maintaining a set of information indicating channel quality of the plurality of user terminals.

19. The apparatus of claim 18 wherein selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment further comprises:

examining the set of information indicating channel quality of the plurality of user terminals to determine which of the plurality of user terminals differ in channel quality by the at least one predefined amount.

20. An apparatus for superposition coding in a wireless communication system, the apparatus comprising:

means for selecting two or more user terminals from a plurality of user terminals to be scheduled on a traffic segment, wherein the selected two or more user terminals differ in channel quality by at least one predefined amount;

means for transmitting, via the traffic segment, a composite traffic signal using superposition coding to the selected two or more user terminals; and

means for transmitting an assignment signal using superposition coding to the selected two or more user terminals, the assignment signal comprising a plurality of protected signals, each of the protected signals associated with one of the two or more user terminals, wherein a transmit power of each of the protected signals corresponds inversely to a signal strength of its associated user terminal of the selected two or more user terminals.

21. The apparatus of claim 20 wherein the plurality of protected signals comprises a least protected signal corresponding to one of the selected two or more user terminals with a strongest signal strength.

22. The apparatus of claim 21 wherein the plurality of protected signals comprises a most protected signal corresponding to one of the selected two or more user terminals with a weakest signal strength.

23. The apparatus of claim 20 wherein the assignment signal conveys assignment information of the traffic segment including an identifier of at least one user terminal of the selected two or more user terminals which is assigned to utilize the traffic segment.

24. The apparatus of claim 20 wherein the means for selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment comprises:

means for maintaining a set of information indicating channel quality of the plurality of user terminals.

25. The apparatus of claim 24 wherein the means for selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment further comprises:

means for examining the set of information indicating channel quality of the plurality of user terminals to determine which of the plurality of user terminals differ in channel quality by the at least one predefined amount.

26. The apparatus of claim 25 wherein the apparatus is a base station within the wireless communication system.

27. A non-transitory computer-readable medium having instructions stored thereon, which when executed by at least one processor causes the at least one processor to:

select two or more user terminals from a plurality of user terminals to be scheduled on a traffic segment, wherein the selected two or more user terminals differ in channel quality by at least one predefined amount;

transmit, via the traffic segment, a composite traffic signal using superposition coding to the selected two or more user terminals; and

transmit an assignment signal using superposition coding to the selected two or more user terminals, the assignment signal comprising a plurality of protected signals, each of the protected signals associated with one of the two or more user terminals, wherein a transmit power of each of the protected signals corresponds inversely to a signal strength of its associated user terminal of the selected two or more user terminals.

28. The non-transitory computer-readable medium of claim 27 wherein the plurality of protected signals comprises a least protected signal corresponding to one of the selected two or more user terminals with a strongest signal strength.

29. The non-transitory computer-readable medium of claim 28 wherein the plurality of protected signals comprises a most protected signal corresponding to one of the selected two or more user terminals with a weakest signal strength.

30. The non-transitory computer-readable medium of claim 27 wherein the assignment signal conveys assignment information of the traffic segment including an identifier of at least one user terminal of the selected two or more user terminals which is assigned to utilize the traffic segment.

31. The non-transitory computer-readable medium of claim 27 wherein selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment comprises:

maintaining a set of information indicating channel quality of the plurality of user terminals.

32. The non-transitory computer-readable medium of claim 31 wherein selecting two or more user terminals from the plurality of user terminals to be scheduled on the traffic segment further comprises:

examining the set of information indicating channel quality of the plurality of user terminals to determine which of the plurality of user terminals differ in channel quality by the at least one predefined amount.