Diversity transmission modes for MIMO OFDM communication systems
Techniques for transmitting data using a number of diversity transmission modes to improve reliability. At a transmitter, for each of one or more data streams, a particular diversity transmission mode is selected for use from among a number of possible transmission modes. These transmission modes may include a frequency diversity transmission mode, a Walsh diversity transmission mode, a space time transmit diversity (STTD) transmission mode, and a Walsh-STTD transmission mode. Each diversity transmission mode redundantly transmits data over time, frequency, space, or a combination thereof. Each data stream is coded and modulated to provide modulation symbols, which are further processed based on the selected diversity transmission mode to provide transmit symbols. For OFDM, the transmit symbols for all data streams are further OFDM modulated to provide a stream of transmission symbols for each transmit antenna used for data transmission.
1. A method for processing data for transmission in a multiple-input multiple-output (MIMO) communication system that utilizes orthogonal frequency division multiplexing (OFDM), comprising:
selecting a particular diversity transmission mode from among a plurality of possible transmission modes to use for each of one or more data streams, wherein each selected diversity transmission mode redundantly transmits data over time, frequency, space, or a combination thereof by using frequency diversity, Walsh transmit diversity, space time transmit diversity (STTD), or any combination and further wherein the selecting is done based in part upon at least one specific data stream channel being transmitted;
coding and modulating each data stream based on coding and modulation schemes selected for the data stream to provide modulation symbols, wherein the coding and modulating is done based in part upon the at least one specific data stream channel being transmitted; and
processing the modulation symbols for each data stream based on the selected diversity transmission mode to provide transmit symbols for transmission over a plurality of transmit antennas.
2. The method of claim 1 , wherein the plurality of possible transmission modes includes a frequency diversity transmission mode, a Walsh diversity transmission mode, and a STTD transmission mode.
3. The method of claim 2 , wherein the plurality of possible transmission modes further includes a Walsh-STTD transmission mode.