System and method for antenna diversity using equal power joint maximal ratio combining

• US 20080014977A1
• Filed: 07/16/2007
• Published: 01/17/2008
• Est. Priority Date: 03/01/2002
• Status: Active Grant

• Current Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Original Assignee: IPR Licensing Incorporated (InterDigital, Inc.)
• Inventors: Sugar, Gary, Vaidyanathan, Chandra
• Granted Patent: US 7,881,674 B2
• Time in Patent Office: Days
• US Class Current: 455/517
• CPC Class Codes: H01Q 3/28 varying the amplitude
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H03G 3/3089 Control of digital or coded signals
• CPC Class Codes: H04B 1/0483 Transmitters with multiple parallel paths
• CPC Class Codes: H04B 7/0465 taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04B 7/0837 using pre-detection combining H04B7/0868 takes precedence
• CPC Class Codes: H04B 7/0845 per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch rake receivers as such H04B1/7115
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04L 1/06 using space diversity
• CPC Class Codes: H04L 2025/03445 Time domain
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

An equal gain composite beamforming technique which constrains that the power of the signal output by each antenna is the same, and is equal to the total power of the transmit signal divided by the number N of transmit antennas from which the signal is to be transmitted. By reducing output power requirements for each power amplifier, the silicon area of the power amplifiers are reduced by as much as N times (where N is equal to the number of transmit antennas) relative to a non-equal gain CBF.

Claims

1. A wireless communication system having a first communication device and a second communication device, comprising:

at the first communication device;

a plurality of N antennas;

a first baseband processor configured to determine a receive weight vector of a plurality of complex receive antenna weights for the plurality of antennas of the first communication device;

compute a transmit weight vector by computing a conjugate of the receive weight vector, the transmit weight vector comprising a complex transmit antenna weight for each of plurality of antennas of the first communication device, wherein each complex transmit antenna weight has a magnitude and a phase whose values may vary with frequency across a bandwidth of the baseband signal, thereby generating a plurality of transmit signals each of which is weighted across the bandwidth of the baseband signal to be transmitted from corresponding ones of the plurality of antennas to the first communication device, wherein the magnitude of the complex transmit antenna weight associated with each antenna is such that the power to be output at each antenna is the same and is equal to the total power to be output by all of the N antennas divided by the number of antennas and such that the sum of the power at each corresponding frequency across the plurality of transmit signals is equal to a constant; and

apply the transmit weight vector to a baseband signal for transmission via the plurality of N antennas of the first communication device to the second communication device; and

at the second communication device;

a plurality of M antennas;

a second baseband processor configured to determine a receive weight vector comprising a plurality of complex receive antenna weights for the plurality of antennas of the second communication device;

compute a transmit weight vector by computing a conjugate of the receive weight vector, the transmit weight vector comprising a complex transmit antenna weight for each of plurality of antennas of the second communication device, wherein each complex transmit antenna weight has a magnitude and a phase whose values may vary with frequency across a bandwidth of the baseband signal, thereby generating a plurality of transmit signals each of which is weighted across the bandwidth of the baseband signal to be transmitted from corresponding ones of the plurality of antennas to the second communication device, wherein the magnitude of the complex transmit antenna weight associated with each antenna is such that the power to be output at each antenna is the same and is equal to the total power to be output by all of the M antennas divided by the number of antennas and such that the sum of the power at each corresponding frequency across the plurality of transmit signals is equal to a constant; and

apply the transmit weight vector to a baseband signal for transmission via the plurality of M antennas of the second communication device to the first communication device;

wherein the first communication device repeats the steps of determining and computing each time signals are received from the second communication device to update the transmit weight vector for transmitting to the second communication device, and the second communication device repeats the steps of determining and computing each time signals are received from the first communication device to update the transmit weight vector for transmitting to the first communication device.

2. The system of claim 1, wherein the bandwidth of the baseband signal processed by each of the first and second communication devices comprises K plurality of frequency sub-bands, and the magnitude of the complex transmit antenna weights associated with each of the plurality of antennas of the respective communication device is such that the power to be output by each antenna is the same and is equal to 1/(KN) of the total power to be output for all of the K frequency sub-bands of the first communication device, and equal to 1/(KM) of the total power to be output for all of the K frequency sub-bands of the second communication device.

3. The system of claim 1, wherein the receive weight vector, the transmit weight vector and the baseband signal of the first and second communication devices are applied to each of K frequency sub-bands of the baseband signal that correspond to sub-carriers of a multi-carrier baseband signal or synthesized frequency sub-bands of a single carrier baseband signal.

4. The system of claim 2, further comprising a first baseband memory in the first communication device configured to store, for each of the N antennas, complex transmit antenna weights for a subset of the K frequency sub-bands or sub-carriers;

and a second baseband memory in the second communication device configured to store, for each of the M antennas, complex transmit antenna weights for a subset of the K frequency sub-bands or sub-carriers.

5. The system of claim 4, wherein the first baseband processor and the second baseband processor retrieve the stored subset of complex transmit antenna N and M weights and generate therefrom the complete set of antenna weights for all of the K frequency sub-bands or sub-carriers using interpolation techniques.