System and method for multiple input multiple output wireless transmission
View Patent ↗Systems and methods for MIMO wireless transmission are provided. At the transmitter, a plurality of encoded packets are modulated, and the symbols are divided between several transmit antennas. The transmitter spreads some of the symbols of each packet using a respective subset of an available Walsh code space. A given transmit antenna then transmits part of each packet spread by the respective subset. In some implementations, this achieves the benefits of the PARC system, and at the same time achieves part of the benefits of the STTD system. Advantageously, only a single reverse link control channel is required if adaptive coding and modulation is to be performed.
1. A method of receiving a set of M signals using a receiver having M antennas, where M>=2, the method comprising: for each signal of the set of M signals:
Spreading each one of M subsets of modulation symbols, each of the M subsets of modulation symbols comprising at least two modulation symbols of the signal, by using a respective one of M disjoint orthogonal codes to generate a set of M corresponding spread signal components, each of the M corresponding spread signal components of the set of M corresponding spread signal components including a different one of the disjoint orthogonal codes; and for each antenna:
Generating a respective combined signal having one spread signal component of each signal by including the different one of the M disjoint orthogonal codes in each of the M corresponding spread signal components of the respective combined signal; and receiving the respective combined signal through the antenna.
2. A method according to claim 1 further comprising:
generating an average signal quality metric from the signals and transmitting the average signal quality metric back to the transmitter.
3. A receiver for receiving a set of M signals using M antennas, where M>=2, the receiver comprising: for each signal of the set of m signals:
A spreading function for spreading each one of M subsets of modulation symbols, each of the M subsets of modulation symbols comprising at least two modulation symbols of the respective signal, by using a respective one of M disjoint orthogonal codes to generate a set of M corresponding spread signal components, each of the M corresponding spread signal components of the set of M corresponding spread signal components including a different one of the M disjoint orthogonal codes;
Means for generating M combined signals, each of the M combined signals including one spread signal component of each signal, by including the different one of the M disjoint orthogonal codes in each of the M corresponding spread signal components of the M combined signals; and a respective antenna for receiving each of the M combined signals.
4. A receiver according to claim 3 further adapted to generate an average signal quality metric from the signals and transmit the average signal quality metric back to the transmitter.
5. A method of transmitting a set of M signals using a transmitter having M antennas, where M>—2, the method comprising:
for each signal of the set of M signals:
spreading each one of M subsets of modulation symbols, each of the M subsets of modulation symbols comprising at least two modulation symbols of the signal, by using a respective one of M disjoint orthogonal codes to generate a set of M corresponding spread signal components, each of the M corresponding spread signal components of the set of M corresponding spread signal components including a different one of the M disjoint orthogonal codes; and
for each antenna:
generating a respective combined signal having one spread signal component of each signal by including the different one of the M disjoint orthogonal codes in each of the M corresponding spread signal components of the respective combined signal; and
transmitting the respective combined signal through the antenna.
6. A method according to claim 5 wherein the M disjoint orthogonal codes are Walsh codes.
7. A method according to claim 5 wherein the modulation symbols of each signal are generated by:
encoding a raw information stream to generate corresponding encoded packets; and
modulating the corresponding encoded packets to generate the modulation symbols of the signal.
8. A method according to claim 7 further comprising, for each signal:
receiving respective channel quality information for the signal over a reverse link control channel, the respective channel quality information being generated by a receiver of the signal; and
adaptively controlling the steps of encoding the raw information stream and modulating the encoded packets as a function of the received respective channel quality information.
9. A method according to claim 8 wherein the respective channel quality information for the signal comprises an average carrier to interference ratio experienced across multiple antennas at a receiver of the signal.
10. A method according to claim 5 wherein the M signals of the set of M signals belong to at least one user, the method further comprising:
for each user, transmitting a respective forward link control channel identifying one or more of a number of slots, a transmission rate, a code rate/type and a modulation type.
11. A transmitter for transmitting a set of M signals using M antennas, where M>=2, the transmitter comprising:
for each signal of the set of M signals:
a spreading function for spreading each one of M subsets of modulation symbols, each of the M subsets of modulation symbols comprising at least two modulation symbols of the respective signal, by using a respective one of M disjoint orthogonal codes to generate a set of M corresponding spread signal components, each of the M corresponding spread signal components of the set of M corresponding spread signal components including a different one of the M disjoint orthogonal codes;
means for generating M combined signals, each of the M combined signals including one spread signal component of each signal, by including the different one of the M disjoint orthogonal codes in each of the M corresponding spread signal components of the M combined signals; and
a respective antenna for transmitting each of the M combined signals.
12. A transmitter according to claim 11 wherein the M disjoint orthogonal codes are Walsh codes.
13. A transmitter according to claim 11 further comprising, for each signal:
an encoder for encoding a raw information stream to generate corresponding encoded packets of the signal;
a modulator for modulating the corresponding encoded packets to generate the modulation symbols of the signal.
14. A transmitter according to claim 13 further comprising, for each signal:
an input for receiving respective channel quality information for the signal over a reverse link control channel, the respective channel quality information being generated by a receiver of the signal; and
an adaptive controller for adaptively controlling the encoder and the modulator as a function of the received respective channel quality information.
15. A transmitter according to claim 11 wherein the M combined signals belong to at least one user, the transmitter being further configured to transmit a respective forward link control channel for each user, each respective forward link control channel identifying one or more of a number of slots, a transmission rate, a code rate/type and a modulation type.