US 7,606,319 B2 · Method and detector for a novel channel quality indicator for space-time encoded MIMO spread spectrum systems in frequency selective channels

Abstract

In a JE, spread spectrum communication MIMO system where a demultiplexed packet is transmitted over multiple streams, two versions of a single CQI are disclosed: generalized SNR or constrained mutual information CMI between the transmitted and received chip vectors. In the receiver, the CMI is constrained so that filtering is suboptimal. The filter bank is preferably LMMSE or MVDR filters that convert the multi-path channel into a single path channel so that joint sequence detection is unnecessary. Detection is by a per-Walsh code architecture, wherein a plurality of Walsh-code specific detectors in parallel detect bits or symbols from the single-channel chips after downconverting chip to symbols. Link to system mapping is realizable using the disclosed CQI for a JE MIMO system in that the CQI or related information is returned to the transmitter, which adapts coding rate and/or modulation for the channel as represented by the CQI.

Claims34

Dependent claims

A method comprising:

receiving a jointly encoded signal over a multi-path channel by N receive antennas, wherein N is an integer greater than one;
estimating a transmitted chip vector within a chip interval for the jointly encoded signal;
for each of the N receive antennas, sampling the received signal to resolve an antenna-wise received chip vector for each of the N receive antennas;
filtering a block of antenna-wise received chip vectors, the block comprising each of the N antenna-wise chip vectors, using a channel quality indicator that maximizes constrained mutual information between the estimated transmitted chip vector and the block of antenna-wise received chip vectors;
downconverting the filtered block to one of bits and symbols;
detecting in parallel, for each spreading code by which the jointly encoded signal is spread, the downconverted bits or symbols,
wherein the channel quality indicator describes the entire multi-path channel over which the signal was received by the N antennas and wherein the channel quality indicator comprises a generalized signal to noise ratio that represents all channel uses of the multiple input/multiple output multi-path channel over which the jointly encoded signal was received.

4 more elements

A method comprising:

receiving a jointly encoded, spread spectrum signal from a multi-path channel over at least two receive antennas in a chip interval;
estimating a transmitted chip vector for the signal;
sampling the signal to achieve a chip-wise signal vector from each receive antenna;
storing the chip-wise signal vectors as a block;
estimating the multi-path channel by determining mutual information between the block of chip-wise signal vectors and the estimated transmitted chip vector, wherein the estimated multi-path channel describes the entire multi-path channel over which the signal was received by the N antennas and wherein the estimated multi-path channel comprises a generalized signal to noise ratio that represents all channel uses of the multiple input/multiple output multi-path channel over which the jointly encoded signal was received;
using the estimate of the multi-path channel, filtering the block of chip-wise signal vectors to restore orthogonality to spreading codes used to spread the signal;
down-converting, descrambling and despreading the filtered block of chip-wise signal vectors to yield parallel outputs of symbol-level signal vectors, each parallel output corresponding to a spreading code;
and
for each of the parallel outputs, spatially detecting one of bits or symbols using one spreading code.

6 more elements

A method comprising:

in a first transceiver,
jointly encoding a first signal to be transmitted at a first coding rate,
modulating the first signal to be transmitted with a first modulation, and
transmitting the jointly encoded and modulated first signal over a spread spectrum multi-path wireless channel by at least one transmit antenna;
in a second transceiver,
receiving the jointly encoded and modulated first signal by at least two receive antennas over the multi-path channel;
converting the multi-path channel over which the first signal was received to an effective single-path channel;
determining a single channel quality indicator that characterizes the effective single-path channel by constraining mutual information between an estimate of a transmitted chip and a block of antenna-wise received chip vectors;
from the effective single-path channel, detecting in parallel one of bits and symbols, each parallel detection being according to one spreading code by which the first signal is spread over the spectrum;
and
transmitting to the first transceiver a feedback based on the channel quality indicator,
wherein the channel quality indicator describes the entire multi-path channel over which the signal was received by the N antennas and wherein the channel quality indicator comprises a generalized signal to noise ratio that represents all channel uses of the multiple input/multiple output multi-path channel over which the jointly encoded signal was received;
and
in the first transceiver,
receiving the feedback;
jointly encoding a second signal to be transmitted,
modulating the second signal to be transmitted, and
transmitting the jointly encoded and modulated second signal over a spread spectrum multi-path wireless channel by the at least one transmit antenna,
wherein, in response to the feedback, the second signal is at least one of encoded at a second coding rate and modulated with a second modulation.

16 more elements

A receiver comprising:

at least two receive antennas;
a filter bank of linear filters having a first input coupled to an output of each receive antenna and a second input, said filter bank for equalizing signal vectors received over sub-channels of a multipath channel into signal vectors of a single channel by constraining mutual information between an estimate of a transmitted chip and a block of antenna-wise received chip vectors;
a channel estimator having an input coupled to an output of each receive antenna and an output coupled to the second input of the filter bank, wherein channel estimator is configured to estimate the multi-path channel which describes the entire multi-path channel over which the signal was received by the at least two receive antennas and wherein the estimated multi-path channel comprises a generalized signal to noise ratio that represents all channel uses of the multi-path channel over which the jointly encoded signal was received;
a plurality of joint detectors in parallel with one another, each joint detector having an input coupled to an output of the filter bank and an output coupled to a decoder, each joint detector for detecting one of bits or symbols according to one spreading code;
a chip-to-symbol down-converter, a de-scrambler, and a de-spreader, each disposed between the filter bank and the plurality of joint detectors.

2 more elements

An apparatus comprising:

a processing unit configured to compute a channel quality indicator of a channel comprising multiple streams;
and
a transmitter configured to transmit the channel quality indicator,
where the channel quality indicator averages constrained mutual information between an estimated transmitted chip vector within a chip interval for a jointly encoded signal received over a multi-path channel by N receive antennas, wherein N is an integer greater than one and a filtered block of antenna-wise received chip vectors comprising each of the N antenna-wise chip vectors,
wherein the channel quality indicator describes the entire multi-path channel over which the signal was received by the N antennas and wherein the channel quality indicator comprises a generalized signal to noise ratio that represents all channel uses of the multiple input/multiple output multi-path channel over which the jointly encoded signal was received.

2 more elements

An apparatus comprising:

a receiver configured to receive a channel quality indicator of a channel comprising multiple streams;
and
a processing unit configured to adjust, on the bases of the channel quality indicator, a transmission of the multiple streams on the channel,
where the channel quality indicator averages constrained mutual information between an estimated transmitted chip vector within a chip interval for a jointly encoded signal received over a multi-path channel by N receive antennas, wherein N is an integer greater than one and a filtered block of antenna-wise received chip vectors comprising each of the N antenna-wise chip vectors,
wherein the channel quality indicator describes the entire multi-path channel over which the signal was received by the N antennas and wherein the channel quality indicator comprises a generalized signal to noise ratio that represents all channel uses of the multiple input/multiple output multi-path channel over which the jointly encoded signal was received.

2 more elements

Dependencies are inferred from the claim text.

Method and detector for a novel channel quality indicator for space-time encoded MIMO spread spectrum systems in frequency selective channels

Life of this patent

Method and detector for a novel channel quality indicator for space-time encoded MIMO spread spectrum systems in frequency selective channels

Life of this patent

Abstract

Claims34