PER STREAM RATE CONTROL (PSRC) FOR IMPROVING SYSEM EFFICIENCY IN OFDM-MIMO COMMUNICATION SYSTEMS
A method and apparatus for separating a user-data stream into a plurality of sub-streams. The apparatus determines channel conditions for each of a plurality of sub-carriers. Next, a plurality of sub-carriers are modulated and encoded with the sub-stream data according to the selected modulation schemes and coding rates. The modulated sub-carriers are each allocated to one or more transmit antennas for transmission. The adaptive modulation and coding function, the sub-carrier allocation function, and the power control function are jointly controlled to optimize throughput, signal quality, and system efficiency.
1 . A wireless communications method comprising:
separating a user data stream into a plurality of data sub-streams;
determining channel conditions for each of a plurality of sub-carriers;
selecting a modulation scheme and coding rate for each sub-carrier;
modulating the sub carriers with the plurality of data sub-streams according to the selected modulation scheme and coding rate;
allocating each modulated sub-carrier to a transmit antenna; and
transmitting the data sub-streams.
2 . The method of claim 1 wherein each sub-carrier has a separate transmission power.
3 . The method of claim 2 wherein the separate transmission power of each sub-carrier is selectively adjusted prior to transmission.
4 . The method of claim 1 wherein determining channel conditions is based on feedback information provided by a receiver.
5 . The method of claim 1 wherein determining channel conditions is based on measuring predetermined quality metrics of received signals.
6 . The method of claim 1 wherein selecting a modulation scheme utilizes an adaptive modulation and coding technique based on channel conditions.
7 . The method of claim 1 wherein modulating the sub-carriers with the data sub-streams includes mapping a sub-stream to multiple sub-carriers.
8 . The method of claim 1 wherein allocating each modulated sub-carrier to a transmit antenna is based on increasing the sub-carrier transmit quality.
9 . The method of claim 1 wherein allocating each modulated sub carrier to a transmit antenna is based on a transmission quality and a throughput level.
10 . The method of claim 1 further comprising:
monitoring the modulation and coding rate, the sub carrier allocation, and power adjustment functions.
11 . A transmitter comprising:
a separation processor configured to separate a user data stream into a plurality of data sub-streams;
a channel analyzer configured to determine channel conditions for each of a plurality of sub-carriers;
a selector configured to select a modulation scheme and coding rate for each sub-carrier;
a modulator configured to modulate the sub carriers with the plurality of data sub-streams according to the selected modulation scheme and coding rate; and
an allocation processor configured to assign each modulated sub-carrier to an antenna for transmission.
12 . The transmitter of claim 11 , further comprising:
a power controller configured to adjust a transmit power of each of the modulated sub-carriers.
13 . The transmitter of claim 8 , further comprising:
a diversity processor configured to map sub-stream data to multiple sub-carriers based on channel condition information.
14 . The transmitter of claim 11 , wherein the channel analyzer is further configured to measure quality metrics of received signals to determine current channel conditions.
15 . The transmitter of claim 11 , wherein the channel analyzer is further configured to analyze feed back information to determine current channel conditions.
16 . The transmitter of claim 12 , further comprising a controller configured to control the selector, the allocation processor, and the power controller.