The Impact of Antenna Diversity in Packet Data Systems with Scheduling

It has been observed through simulations of some specific scheduling algorithms that multi-user diversity gains in packet dats systems with channel-aware scheduling can be reduced in the presence of any form of link diversity, such as transmit diversity or wideband multipath diversity. We establish that asymptotically, in the limit of large number of transmit antennas and large number of users, the maximum throughout acheived by any optimal scheduling algorithm in the presence of tramsit diversity can be infinitely worse than that of a system with no diversity. We then present some bounds on the gap between the performance of systems with and without diversity for finite number of users. We also show that reveive antenna combining, on the other hand, is infinitely superior in the asymptotic limit. Our results are general and are independent of any particular schduling algorithm.