Recent work has shown that in nearly line-of-sight (LOS) Multiple-Input Multiple-Output (MIMO) wireless communication systems, spacing antennas according to the symbol wavelength rather than the carrier wavelength improves multiuser performance. MIMO systems have a heavy reliance on a multipath rich environment, which may not always be present in close range ultra wideband conditions. By adding re ector elements to the antenna structure, this multipath rich environment can be induced. The performance of the users with respect to the arrangement of antennas and re ector elements is a non-linear function that a genetic algorithm (GA) seems applicable for exploiting both symbol-wavelength spacing and multipath inducing re ector elements. A GA optimization is used to determine the optimum characteristics for antennas and re ector elements. MIMO system models with four users, and three, four, and ve antennas are considered using a two-dimensional LOS channel with additive white noise. Subsequently, a GA optimization design and approach for solving this problem in three-dimensional space is presented. The addition of re ector elements to purposely increase multipath requires additional design considerations incorporating distributed processing, ray-tracing, and the determination of the channel impulse response.
This research was funded by an Alexander Graham Bell Canada Graduate Scholarship from the Natural Sciences and Engineering Research Council, by the Atlantic Innovation Fund from the Atlantic Canada Opportunities Agency, and by Bell Aliant, our industrial partner.