Abstract
A novel structure for multiple antenna transmissions utilizing space-time dispersion is proposed, where the original data stream is divided into substreams which are modulated onto all available transmit antennas using stream-specific transmit signature sequences. In order to achieve this, the transmit antennas are partitioned into groups of antennas, called partitions. The signals from the data streams are independently interleaved by partition over the entire transmission frame. The interleaved partitions are then added over all substreams prior to transmission over the MIMO channel. At the receiver, a low-complexity iterative detector adapted from recent CDMA multiuser detection research is used. It is shown that with careful substream power assignments this transmission methodology can efficiently utilize the capacity of rank-deficient channels as it can approach the capacity limits of the multiple antenna channel closely over the entire range of available signal-to-noise ratios and system sizes. This transmission methodology and receiver structure are then applied to multiuser MIMO systems where several multiple antenna terminals communicate concurrently to a joint receiver. It is shown that different received power levels from the different MIMO terminals can be beneficial and that higher spectral efficiencies can be achieved than in the single-terminal case.
Highlights
Emerging wireless networks are likely to incorporate multiple-input multiple-output (MIMO) antenna systems in order to meet requirements for high transmission capacities and link availability. Since their introduction by Foschini [1], and the prototyping of Bell Lab’s BLAST project [2], research into MIMO transmission has exploded, and a large body of work has been published in recent years
Various low-complexity receivers based on linear matrix methods such as the zero-forcing (ZF) and the minimum mean-square error (MMSE) receivers have received much attention
If the MIMO channel rank is limited by the number of transmit antennas, Nt, and if there are more than about twice as many uncorrelated receive antennas, Nr, it can be shown that linear methods perform very well, and come close to the capacity of the channel as long as Nt Nr/2 [4]
Summary
Emerging wireless networks are likely to incorporate multiple-input multiple-output (MIMO) antenna systems in order to meet requirements for high transmission capacities and link availability. If the MIMO channel rank is limited by the number of transmit antennas, Nt, and if there are more than about twice as many uncorrelated receive antennas, Nr, it can be shown that linear methods perform very well, and come close to the capacity of the channel as long as Nt Nr/2 [4] This typically requires significantly more receive antennas than transmit antennas and may not be practical for downlink transmissions to mobile terminals, or where multiple MIMO terminals communicate concurrently to a central receiver. It is shown how higher-order modulations can be accommodated to increase spectral efficiency as signal-to-noise ratio becomes available.
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More From: EURASIP Journal on Wireless Communications and Networking
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