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

• US 20060116155A1
• Filed: 01/11/2006
• Published: 06/01/2006
• Est. Priority Date: 01/23/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Medvedev, Irina, Ketchum, John W., Walton, Jay Rod
• Granted Patent: US 8,078,211 B2
• Time in Patent Office: Days
• 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:

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

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

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

determining an excess spectral efficiency based in part on the transmit power allocated to the transmission channels; and

reallocating one or more transmission channels with reduced amounts of transmit power to reduce the excess spectral efficiency.

2. The method of claim 1, further comprising:

reducing the transmit power allocated to each transmission channel to achieve a preferred operating point.

3. The method of claim 1, further comprising:

determining incremental changes in spectral efficiency for a plurality of transmit power reductions for the transmission channels; and

selecting a largest transmit power reduction associated with an incremental spectral efficiency change that is less than or equal to the excess spectral efficiency.

4. The method of claim 1, further comprising:

determining a backed-off transmit power; and

allocating the backed-off transmit power to the transmission channels in the set.

5. The method of claim 1, further comprising:

performing the determining the backed-off transmit power and the allocating the backed-off transmit power one or more times until the excess spectral efficiency is within a particular threshold.

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

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

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

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

means for determining an excess spectral efficiency based in part on the transmit power allocated to the transmission channels; and

means for reallocating one or more transmission channels with reduced amounts of transmit power to reduce the excess spectral efficiency.

7. 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.

8. The transmitter unit of claim 7, 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.

9. The transmitter unit of claim 7, further comprising:

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

10. A base station comprising the transmitter unit of claim 7.

11. 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 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

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, and allocating total remaining transmit power to transmission channels not in the saturation region.

12. The receiver unit of claim 11, wherein the RX MIMO processor is further operative to pre-condition the plurality of received symbol streams to diagonalize the plurality of transmission channels.

13. The receiver unit of claim 11, further comprising:

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

14. 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, and allocating total remaining transmit power to transmission channels not in the saturation region.