On the performance of a two-user MIMO downlink system in heavy traffic
S. Bhardwaj, R. J. Williams, and A. S. Acampora
A MIMO downlink system in which data is transmitted to two users over a common wireless channel is considered. The channel is assumed to be fixed for all transmissions over the period of interest and the ratio of anticipated average arrival rates for the two users, also known as the relative traffic rate, is the system design parameter. A packet-based traffic model is considered where data for each user is queued at the transmit end. A queueing analogue for this system leads to a coupled queueing system for which a simple policy is known to be throughput-optimal under Markovian assumptions. Since an exact expression for the performance is not available, as a measure of performance (in heavy traffic), a diffusion approximation is established. This diffusion process is a two-dimensional semimartingale reflecting Brownian motion living in the positive quadrant of two-dimensional space.
For a copy of a preprint for personal, scientific, non commercial use, click here for pdf.
This paper appears in IEEE Transactions on Information Theory, Vol. 53 (2007), 1851-1859.
Last updated: April 27, 2007