N.H. Dawod, R. Hafez, and I. Marsland (Canada)
MIMO, OFDM, SDMA, TDMA
We compare the performance of an improved downlink SDMA based MIMO-OFDM system with that of a traditional TDMA based MIMO-OFDM system. The SDMA system is based on null steering that spatially multiplexes to each user several data symbols in each channel use that is even if the users' channel matrices seen by several OFDM tones are cross-correlated. In the SDMA system, several basestation multi-antenna arrays are distributed in a given area. Each array is communicating with the basestation via optical fiber links. All signal processing is performed at the basestation. Multi-antenna users are spatially separated such that in each tone of the OFDM symbol only a certain number of users (out of the total number of users) are selected. The selection is based on an algorithm that reduces the pair wise intra-user correlations. The channel matrix of each user is assumed correlated and Ricean distributed. The improved SDMA system shows significant improvement in channel capacity compared to the TDMA based system.
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