MIMO detection and capacity

Wireless transmissions are very popular nowadays for a wide variety of applications. Because of the demand of high data rate from multimedia services, Multiple-Input Multiple-Output (MIMO) technologies are considered in many standards, to enhance the data rate and the link robustness. MIMO systems boost the link capacity in proportion to the number of transmitting or receiving antennas, when spatial diversity is available. At this purpose they are often combined with OFDM modulation, which ensures that flat channels are experienced by different tones within an OFDM symbol.
To increase the spectral efficiency of the link, the transmitting antennas can be used in layered mode, i.e. each antenna transmits a different symbol in the same bandwidth at the same time. To solve the spatial inter-symbol interference, the binary information stream can be encoded and interleaved over different tones and antennas, thus transmitting a space-frequency Bit Interleaved Coded Modulation. An ideal receiver should consider the likelihood of the received vectors for each possible codeword, jointly performing detection and decoding. This has prohibitive complexity, except for simple space-time codes. In the last years we have investigated suboptimal limited complexity strategies, trying to approach the ideal receiver performance.
Detection and decoding can be decoupled, and Soft-Input Soft-Output (SISO) detectors can be used in conjunction with SISO decoders in iterative schemes, to approximate the ideal receiver through disjoint stages, according to the turbo principle. This is the object of our research on MIMO detection in the last years.

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Last Update:
Wed, March 9, 2011