MIMO communications in ad hoc networks

We consider MIMO (multiple-input multiple output) communications in an ad hoc network with K simultaneous communicating transceiver pairs. In particular, we compare channelized MIMO transmission and the MIMO interference transmission using the inherent multiplexing gain of multiple transmit/receive antennas. The relative performance in terms of their limiting spectral efficiencies largely hinges on the power constraint used in the system. In particular, for a MIMO network with per-user power constraint, we show that the channelized transmission has unbounded limiting spectral efficiencies while the interference transmission is inherently limited by the degrees of freedom of the system, namely the transceiver antenna numbers. On the other hand, with a total power constraint, both transmission schemes have saturating asymptotic spectral efficiencies as the number of users increases. For MIMO interference transmission, we also point out the importance of channel state information (CSI) at the transmitter. In particular, we show that with finite transmitter-receiver pairs, better throughput may result with stronger CSI assumption at the transmitter