System and method for distributed input-distributed output wireless communications

• US 8,160,121 B2
• Filed: 06/20/2008
• Issued: 04/17/2012
• Est. Priority Date: 08/20/2007
• Status: Active Grant

• Current Assignee: Rearden, LLC
• Original Assignee: Rearden, LLC
• Inventors: Forenza, Antonio, Heath, Robert W. Jr., Perlman, Stephen G.
• Primary Examiner(s): Ha, Dac V
• Application Number:
  US12/143,503
• Publication Number:
  US 20090067402A1
• Time in Patent Office: 1,397 Days
• Field of Search: 375/140, 375/141, 375/146, 375/219, 375/220, 375/222, 375/261, 375/267, 375/285, 375/296, 375/298, 375/299, 455/501, 455/67.13, 455/69, 455/561, 455/103, 455/114.2, 455/114.3, 455/126, 370/278, 370/282, 370/286, 370/464, 370/465
• US Class Current: 375/141
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0684 using different training sequences per antenna
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/007 Unequal error protection for format H04L1/0078; for codes per se H03M13/35
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/0377 during the reception of training signals
• CPC Class Codes: H04L 2025/03802 Signalling on the reverse channel
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

A system and method are described for dynamically adapting the communication characteristics of a multiple antenna system (MAS) with multi-user (MU) transmissions (“MU-MAS”). For example, a method according to one embodiment of the invention comprises: transmitting a training signal from each antenna of a base station to each of a plurality of wireless client devices, each of the client devices analyzing each training signal to generate channel characterization data, and receiving the channel characterization data at the base station; computing a plurality of MU-MAS precoder weights based on the channel characterization data, the combined MU-MAS precoder weights comprising a MU-MAS channel matrix; determining instantaneous or statistical channel quality (“link quality metric”) for the wireless client devices using mutual information of MU-MAS links or singular values of the MU-MAS composite channel matrix; determining a subset of users and a MU-MAS transmission mode based on the link quality metric; precoding data using the MU-MAS precoder weights to generate precoded data signals for each antenna of the base station; and transmitting the precoded data signals through each antenna of the base station to each respective client device within the selected subset.

Claims

1. A method for dynamically adapting the communication characteristics of a multiple antenna system (MAS) with multi-user (MU) transmissions (“

MU-MAS”

);

transmitting a training signal from each antenna of a base station to each of a plurality of wireless client devices, each of the client devices analyzing each training signal to generate channel characterization data, and receiving the channel characterization data at the base station;

computing a plurality of MU-MAS precoder weights based on the channel characterization data, the combined MU-MAS precoder weights comprising a MU-MAS channel matrix;

determining instantaneous or statistical channel quality (“

link quality metric”

) for the wireless client devices using mutual information of MU-MAS links or singular values of the MU-MAS composite channel matrix;

determining a subset of users and a MU-MAS transmission mode based on the link quality metric;

precoding data using the MU-MAS precoder weights to generate precoded data signals for each antenna of the base station; and

transmitting the precoded data signals through each antenna of the base station to each respective client device within the selected subset.

2. The method as in claim 1 wherein the multiple antenna system is a TDD system, the method further comprising:

transmitting a training signal from each antenna of the users to each of a plurality of antennas at the base station, the base station analyzing each training signal to generate channel characterization data.

3. The method as in claim 1 further comprising:

defining different link-quality regions for two or more different MU-MAS modes based on the instantaneous channel quality metrics.

4. The method as in claim 1 wherein the MU-MAS transmission modes includes different combinations of antenna selection/diversity or multiplexing, modulation/coding schemes (MCSs) and array configurations/geometries.

5. The method as in claim 1 wherein the link quality metric is estimated in the time, frequency and/or space domains.

6. The method as in claim 1 wherein the link quality metric includes the signal to noise ratio (SNR) of the signals received at the client devices.

7. The method of claim 1 wherein the MU-MAS system is a distributed-input distributed-output (DIDO) communication system and wherein the MU-MAS transmission mode is a DIDO transmission mode based on the link quality metric and wherein the MU-MAS precoder weights are DIDO precoder weights.

8. A system for dynamically adapting the communication characteristics of a MU-MAS communication system comprising:

one or more coding modulation units to encode and modulate information bits for each of a plurality of wireless client devices to produce encoded and modulated information bits;

one or more mapping units to map the encoded and modulated information bits to complex symbols; and

a MU-MAS configurator unit to determine a subset of users and a MU-MAS transmission mode based on channel characterization data obtained through feedback from the wireless client devices and to responsively control the coding modulation units and mapping units;

a MU-MAS precoding unit operating under control of the MU-MAS configurator unit to compute precoding weights for precoding data signals prior to transmission to the client devices;

wherein the MU-MAS configurator unit determines instantaneous or statistical channel quality (“

link quality metric”

) for the wireless client devices using mutual information of MU-MAS links or singular values of the MU-MAS channel matrix.

9. The system as in claim 8 wherein the MU-MAS configurator unit determines a subset of users and a MU-MAS transmission mode based on channel characterization data estimated at the base station by processing training signals from the client devices and exploiting channel reciprocity.

10. The system as in claim 8 further comprising:

one or more orthogonal frequency division multiplexing (OFDM) units to receive the precoded signals from the precoding unit and to modulate the precoded signals according to an OFDM standard.

11. The system as in claim 10 wherein the OFDM standard comprises computing an inverse fast Fourier transform (IFFT) and adding a cyclic prefix.

12. The system as in claim 10 further comprising one or more D/A units to perform digital to analog (D/A) conversion on the output of the OFDM units to generate an analog baseband signal;

and

one or more radio frequency (RF) units to upconvert the baseband signal to radio frequency and transmit the signals using a corresponding one or more transmit antennas.

13. The system as in claim 8 wherein the MU-MAS precoding unit is implemented as a minimum mean square error (MMSE), a weighted MMSE, a zero-forcing (ZF) or a block diagonalization (BD) precoder.

14. The system as in claim 8 wherein the MU-MAS system is a DIDO system and wherein the MU-MAS configurator unit is a DIDO configurator unit to determine a subset of users and a DIDO transmission mode based on channel characterization data obtained through feedback from the wireless client devices and to responsively control the coding modulation units and mapping units.

15. The system as in claim 14 wherein the MU-MAS configurator unit is a DIDO configurator unit to determine a subset of users and a DIDO transmission mode based on channel characterization data estimated at the base station by processing training signals from the client devices and exploiting channel reciprocity.