Space-time processing for wireless systems with multiple transmit and receive antennas

• US 7,113,558 B2
• Filed: 05/11/2004
• Issued: 09/26/2006
• Est. Priority Date: 08/18/2000
• Status: Expired due to Term

• Current Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Lozano, Angel, Rashid-Farrokhi, Farrokh, Valenzuela, Reinaldo A
• Primary Examiner(s): TRAN, KHANH C
• Application Number:
  US10/842,857
• Publication Number:
  US 20040208258A1
• Time in Patent Office: 868 Days
• Field of Search: 375/259, 375/260, 375/267, 375/299, 375346-349, 375/358, 455/101, 455/132, 455134-135, 455/278.1, 455/296, 370/206, 370/208, 370/491
• US Class Current: 375/347
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/065 Variable contents, e.g. long-term or short-short
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0837 using pre-detection combining H04B7/0868 takes precedence

Abstract

Signals are developed for use in a wireless system with multiple transmit and multiple receive antennas so that even in the face of some correlation the most open-loop capacity that can be achieved using a substantially open-loop system with a channel of that level of correlation is obtained. In accordance with the principles of the invention, the signals transmitted from the various antennas are processed so as to improve their ability to convey the maximum amount of information. More specifically, the data to be transmitted is divided into M+1 substreams, where M is the number of transmit antennas. Each transmit antenna is supplied with a combination signal that is made up of a weighted version of a common one of the substreams and a weighted version of a respective one of the substreams that is supplied uniquely for that antenna, so that there are M transmit signals. A receiver having N antennas receives the M transmit signals as combined by the channel and reconstitutes the original data therefrom. This may be achieved using successive decoding techniques. Advantageously, the capacity, i.e., the rate of information that can be conveyed with an arbitrarily small probability of error when the instantaneous forward channel condition is unknown to the transmitter, is maximized.

Claims

1. A receiver for use in a MIMO system, comprising:

N receive antennas;

N radio frequency (RF) converters, each RF converter downconverting a signal it receives from a respective associated antenna to an analog baseband signal and converting said analog baseband signal to a digital representation;

an estimator, responsive to said digital representations, for determining an estimate of the average signal-to-interference-and-noise ratio (SINR) for a forward channel being received by said receiver;

an estimator for determining an estimate of a correlation among the channel components for a forward channel being received by said receiver; and

a weight calculator for calculating at least one weight for use by a transmitter of said forward channel to transmit data substreams to said receiver as a function of said estimates of SINR end correlation among the channel components, said at least one weight being determined in said weight calculator by solving at least one equation of the set consisting of

$\begin{array}{c}{\mathrm{\alpha <br><br>}}_1=\sqrt{\frac{P_T}{M}-{\mathrm{\alpha <br><br>}}_2^2}\\ {\mathrm{\alpha <br><br>}}_2=\sqrt{\frac{P_T<br><br>\mathrm{\eta <br><br>}}{\mathrm{\rho <br><br>}<br><br><br><br>N<br><br>\left(1-\mathrm{\eta <br><br>}\right)<br><br>\left(M<br><br><br><br>\mathrm{\eta <br><br>}+1-\mathrm{\eta <br><br>}\right)}}\end{array}$

where

α

₁ and α

₂ are said first and second weights, respectively,

P_T is the total available transmit power

ρ

is an estimate of the average signal-to-interference-and-noise ratio (SINR), and

η

is the correlation among the channel components,

M is the number of transmit antennas, and

N is the number of receiver antennas.