Lucent Technologies Inc.

Farrokh Rashid-Farrokhi

Reinaldo A Valenzuela

Angel Lozano

Gerard Joseph Foschini

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.

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

In a MIMO system the signals transmitted from the various antennas are processed so as to improve the ability of the receiver to extract them from the received signal even in the face of some correlation. More specifically the number of bit streams that is transmitted simultaneously is adjusted, e.g., reduced, depending on the level of correlation, while multiple versions of each bit stream, variously weighted, are transmitted simultaneously. The variously weighted versions are combined to produced one combined weighted signal. The receiver processes the received signals in the same manner as it would have had all the signals reaching the receive antennas been uncorrelated. The weight vectors may be determined by the forward channel transmitter using the channel properties of the forward link which are made known to the transmitter of the forward link by being transmitted from the receiver of the forward link by the transmitter of the reverse link or the weight vectors may be determined by the forward channel transmitter using the channel properties of the forward link and the determined weight vectors are made known to the transmitter of the forward link by being transmitted from the receiver of the forward link by the transmitter of the reverse link. The channel properties used to determine the weight vectors may include the channel response from the transmitter to the receiver and the covariance matrix of noise and interference measured at the receiver.

Space-time processing for multiple-input, multiple-output, wireless systems

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&plus;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.

The signal to interference and noise ratio (SINR) of wireless systems can be improved, if not optimized, by determining operating parameters used by the base station to substantially simultaneously control the transmit beam patterns that are each formed to establish a communication channel between a base station and a respective one of the wireless terminals as a function of received channel information from at least two of the wireless terminals. In an exemplary embodiment of the invention, the weight vectors and the power allocation employed by a base station are determined by the base station using information supplied by at least each of the wireless terminals served by the base station, and potentially from wireless terminals served by other base stations, e.g., in neighboring cells to the cell served by the base station, the information from the other cells being supplied via the neighboring cell base stations using inter-base-station communication, e.g., a wire line connection.

Space-time diversity for wireless systems

The performance of a CDMA receiver employing multiple antennas can be improved, in accordance with the principles of the invention, by directly combining together appropriately weighted signals from the rake receiver fingers that are being supplied by at least two different antennas, i.e., they are in two different receiver modules each of which is what would have been called in the prior art a rake receiver module but without the associated summer, to develop an output with at least as good, and more likely an improved, signal to interference and noise ratio (SINR), as compared to the prior art rake receiver architecture. By doing so the functionality of the beamforming coefficients and the rake multiplier vectors is joined, and it is possible to optimize the rake receiver performance. In other words, because of the inventive architecture, the optimization of the weights for the rake multiplier and the beam forming may be performed jointly to yield a single rake combining weight vector which optimally weights the output of each rake finger. A training sequence which is used to determine the rake combining weight vector may be received as a low bit-rate signal carried on the CDMA pilot signal.

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Fremont, CA, United States of America

Farrokh Rashid-Farrokhi