Reallocation of excess power for full channel-state information (CSI) multiple-input, multiple-output (MIMO) systems

• US 7,020,482 B2
• Filed: 01/23/2002
• Issued: 03/28/2006
• Est. Priority Date: 01/23/2002
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Medvedev, Irina, Ketchum, John W., Walton, Jay Rod
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): PEREZ, ANGELICA
• Application Number:
  US10/056,275
• Publication Number:
  US 20030139196A1
• Time in Patent Office: 1,525 Days
• Field of Search: 455/522, 455/127.1, 455/127.2, 455/103, 455/69, 455/450, 455/452.1, 455/452.2, 455/453
• US Class Current: 455/522
• CPC Class Codes: H04B 7/0443 utilizing "waterfilling" technique
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/267 taking into account the information rate
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 72/00 Local resource management

Abstract

Techniques to allocate the total transmit power to the transmission channels in a multi-channel communication system such that higher overall system spectral efficiency and/or other benefits may be achieved. The total transmit power may be initially allocated to the transmission channels based on a particular power allocation scheme (e.g., the water-filling scheme). The initial allocation may result in more power being allocated to some transmission channels than needed to achieve the required SNR (e.g., the SNR needed to achieve the maximum allowed data rate), which would then result in these transmission channels being operated in the saturation region. In such situations, the techniques reallocate the excess transmit power of transmission channels operated in the saturation region to other transmission channels operated below the saturation region. In this way, higher data rate may be achieved for the “poorer” transmission channels without sacrificing the performance of the “better” transmission channels.

Claims

1. A method for allocating transmit power to a plurality of transmission channels in a wireless communication system, comprising:

defining a set of one or more transmission channels to be allocated transmit power;

determining a total transmit power available to allocate to the transmission channels in the set;

allocating the total transmit power to the transmission channels in the set based on a particular allocation scheme;

identifying transmission channels in a saturation region resulting from the allocated transmit power;

reallocating each transmission channel in the saturation region with a revised amount of transmit power;

determining a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power; and

performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

2. The method of claim 1, wherein the total transmit power available for each iteration is allocated to the transmission channels in the set based on a water-filling allocation scheme.

3. The method of claim 1, wherein a transmission channel is deemed as being in the saturation region if it is allocated more transmit power than needed to achieve a particular maximum data rate.

4. The method of claim 3, wherein the revised amount of transmit power allocated to each transmission channel in the saturation region is a minimum amount needed to achieve the maximum data rate.

5. The method of claim 1, wherein a transmission channel is deemed as being in the saturation region if it is allocated more transmit power than needed to achieve a particular signal-to-noise ratio (SNR).

6. The method of claim 5, wherein a single SNR is used for all transmission channels in the set.

7. The method of claim 5, wherein each transmission channel is associated with a respective threshold SNR.

8. The method of claim 1, wherein the identifying includes

determining an effective signal-to-noise ratio (SNR) for each transmission channel in the set based in part on the transmit power allocated to the transmission channel,

comparing the effective SNR for each transmission channel in the set to a threshold SNR applicable to the transmission channel, and

declaring a transmission channel as being in the saturation region if its effective SNR is greater than the applicable threshold SNR.

9. The method of claim 8, wherein the threshold SNR corresponds to an SNR needed to achieve a particular maximum data rate.

10. The method of claim 1, wherein the wireless communication system is a multiple-input multiple-output (MIMO) communication system.

11. The method of claim 10, wherein the plurality of transmission channels correspond to a plurality of eigenmodes for a MIMO channel of the MIMO communication system.

12. The method of claim 1, wherein the wireless communication system is an orthogonal frequency division multiplexing (OFDM) communication system.

13. The method of claim 1, wherein the wireless communication system is a multiple-input multiple-output (MIMO) communication system that utilizes orthogonal frequency division multiplexing (OFDM).

14. A method for allocating transmit power to a plurality of spatial subchannels in a multiple-input multiple-output (MIMO) communication system, comprising:

defining a set of one or more spatial subchannels to be allocated transmit power;

determining a total transmit power available to allocate to the spatial subchannels in the set;

allocating the total transmit power to the spatial subchannels in the set based on a particular allocation scheme;

identifying spatial subchannels in a saturation region resulting from the allocated transmit power;

reallocating each spatial subchannel in the saturation region with a revised amount of transmit power;

determining a total excess transmit power for all spatial subchannels reallocated with revised amounts of transmit power; and

performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of spatial subchannels for a first iteration includes the plurality of spatial subchannels and for each subsequent iteration includes spatial subchannels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

15. The method of claim 14, wherein the total transmit power available for each iteration is allocated to the spatial subchannels in the set based on a water-filling allocation scheme.

16. A method for allocating transmit power to a plurality of transmission channels in a wireless communication system, comprising:

identifying a first set of transmission channels to be allocated transmit power;

determining a total transmit power available to allocate to the transmission channels in the first set;

allocating the total transmit power to the transmission channels in the first set based on a particular allocation scheme;

identifying a second set of one or more transmission channels allocated excessive transmit power for preferred operating points;

allocating each transmission channel in the second set with a revised amount of transmit power to achieve the preferred operating point;

determining a total excess power for all transmission channels in the second set;

identifying a third set of one or more transmission channels capable of supporting higher preferred operating points; and

reallocating the total excess power to the one or more transmission channels in the third set.

17. The method of 16, wherein each preferred operating point is associated with a signal-to-noise ratio (SNR) needed to support a particular discrete data rate.

18. The method of 16, further comprising:

evaluating a plurality of possible reallocations of the total excess power to the one or more transmission channels in the third set.

19. The method of 18, further comprising:

selecting a reallocation associated with a highest gain in throughput.

20. The method of 16, wherein the total excess power is reallocated, one channel at a time, to the one or more transmission channels in the third set.

21. The method of 16, wherein each transmission channel is reallocated sufficient transmit power to achieve a next higher preferred operating point.

22. The method of 16, wherein the reallocating includes

determining an amount of transmit power needed for each transmission channel in the third set to achieve a next higher preferred operating point, and

reallocating the total excess power to the transmission channel associated with a highest gain in throughput.

23. The method of 16, wherein the total transmit power is allocated to the transmission channels in the first set based on a water-filling scheme.

24. The method of 16, wherein the plurality of transmission channels correspond to spatial subchannels in a MIMO system.

25. The method of 16, wherein the plurality of transmission channels correspond to frequency subchannels in an OFDM system.

26. The method of 16, wherein the plurality of transmission channels correspond to frequency subchannels of spatial subchannels in a MIMO-OFDM system.

27. A memory communicatively coupled to a digital signal processing device (DSPD) capable of interpreting digital information to:

define a set of one or more transmission channels to be allocated transmit power;

determine a total transmit power available to allocate to the transmission channels in the set;

allocate the total transmit power to the transmission channels in the set based on a particular allocation scheme;

identify transmission channels in a saturation region resulting from the allocated transmit power;

reallocate each transmission channel in the saturation region with a revised amount of transmit power;

determine a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power; and

perform the define, determine, allocate, identify, and reallocate for one or more iterations, wherein the set of transmission channels for a first iteration includes a plurality of transmission channels in a wireless communication system and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

28. A computer program product for allocating transmit power to a plurality of transmission channels in a wireless communication system, comprising:

code for defining a set of one or more transmission channels to be allocated transmit power;

code for determining a total transmit power available to allocate to the transmission channels in the set;

code for allocating the total transmit power to the transmission channels in the set based on a particular allocation scheme;

code for identifying transmission channels in a saturation region resulting from the allocated transmit power;

code for reallocating each transmission channel in the saturation region with a revised amount of transmit power;

code for determining a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power;

code for performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration; and

a computer-usable medium for storing the codes.

29. An apparatus in a wireless communication system, comprising:

means for defining a set of one or more transmission channels to be allocated transmit power;

means for determining a total transmit power available to allocate to the transmission channels in the set;

means for allocating the total transmit power to the transmission channels in the set based on a particular allocation scheme;

means for identifying transmission channels in a saturation region resulting from the allocated transmit power;

means for reallocating each transmission channel in the saturation region with a revised amount of transmit power;

means for determining a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power; and

means for performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

30. A controller in a wireless communication system, comprising:

means for defining a set of one or more transmission channels to be allocated transmit power;

means for determining a total transmit power available to allocate to the transmission channels in the set;

means for allocating the total transmit power to the transmission channels in the set based on a particular allocation scheme;

means for identifying transmission channels in a saturation region resulting from the allocated transmit power;

means for reallocating each transmission channel in the saturation region with a revised amount of transmit power;

means for determining a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power; and

means for performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

31. The controller of claim 30, further comprising:

means for determining an effective signal-to-noise ratio (SNR) for each transmission channel in the set based in part on the transmit power allocated to the transmission channel;

means for comparing the effective SNR for each transmission channel in the set to a threshold SNR applicable to the transmission channel; and

means for declaring a transmission channel as being in the saturation region if its effective SNR is greater than the applicable threshold SNR.

32. A base station comprising the controller of claim 30.

33. A controller in a wireless communication system, comprising:

means for identifying a first set of transmission channels to be allocated transmit power;

means for determining a total transmit power available to allocate to the transmission channels in the first set;

means for allocating the total transmit power to the transmission channels in the first set based on a particular allocation scheme;

means for identifying a second set of one or more transmission channels allocated excessive transmit power for preferred operating points;

means for allocating each transmission channel in the second set with a revised amount of transmit power to achieve the preferred operating point;

means for determining a total excess power for all transmission channels in the second set;

means for identifying a third set of one or more transmission channels capable of supporting higher preferred operating points; and

means for reallocating the total excess power to the one or more transmission channels in the third set.

34. A transmitter unit in a wireless communication system, comprising:

a transmit (TX) data processor operative to code data for a plurality of transmission channels based on one or more coding and modulation schemes to provide a plurality of streams of symbols;

a plurality of transmitters operative to process the plurality of symbol streams to provide a plurality of modulated signals suitable for transmission over a communication channel; and

a controller operative to allocate transmit power to the plurality of transmission channels by

defining a set of one or more transmission channels to be allocated transmit power,

determining a total transmit power available to allocate to the transmission channels in the set,

allocating the total transmit power to the transmission channels in the set based on a particular allocation scheme,

identifying transmission channels in a saturation region resulting from the allocated transmit power,

reallocating each transmission channel in the saturation region with a revised amount of transmit power,

determining a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power, and

performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

35. The transmitter unit of claim 34, wherein the TX data processor is further operative to scale each modulation symbol with a particular weight determined based on the transmit power allocated to the transmission channel used for the modulation symbol.

36. The transmitter unit of claim 34, further comprising:

a MIMO processor operative to pre-condition the plurality of symbol streams to diagonalize the plurality of transmission channels.

37. A base station comprising the transmitter unit of claim 34.

38. A receiver unit in a wireless communication system, comprising:

a receive (RX) MIMO processor operative to receive and process a plurality of streams of samples to provide a plurality of steams of received symbols, and to derive channel state information (CSI) for a plurality of transmission channels used for the plurality of received symbol streams; and

a RX data processor operative to process the plurality of received symbol streams in accordance with one or more demodulation and decoding schemes to provide decoded data, and

wherein transmit power for the plurality of transmission channels is allocated based in part on the CSI by allocating a total available transmit power to the plurality of transmission channels based on a particular allocation scheme, reallocating each transmission channel in a saturation region with a revised amount of transmit power, determining a total excess transmit power for all transmission channels reallocated wit revised amounts of transmit power; and

performing the defining, determining, allocating, identifying, and reallocating for one or mare iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.

39. The receiver unit of claim 38, wherein the RX MIMO processor is further operative to pre-condition the plurality of received symbol streams to diagonalize the plurality of transmission channels.

40. The receiver unit of claim 38, further comprising:

a TX data processor operative to process the CSI for transmission back to a transmitter unit.

41. A receiver apparatus in a wireless communication system, comprising:

means for processing a plurality of streams of samples to provide a plurality of streams of received symbols, and to derive channel state information (CSI) for a plurality of transmission channels used for the plurality of received symbol streams; and

means for processing the plurality of received symbol streams in accordance with one or more demodulation and decoding schemes to provide decoded data, and

wherein transmit power for the plurality of transmission channels is allocated based in part on the CSI by allocating a total available transmit power to the plurality of transmission channels based on a particular allocation scheme, reallocating each transmission channel in a saturation region with a revised amount of transmit power, determining a total excess transmit power for all transmission channels reallocated with revised amounts of transmit power; and

performing the defining, determining, allocating, identifying, and reallocating for one or more iterations, wherein the set of transmission channels for a first iteration includes the plurality of transmission channels and for each subsequent iteration includes transmission channels not in the saturation region, and wherein the total transmit power available for each subsequent iteration includes the total excess transmit power determined in a current iteration.