Dynamic slot allocation (DSA) in indoor SDMA/TDMA using a smart antenna basestation

In this paper, we introduce and study the use of dynamic slot allocation (D SA) in packet-switched space-division-multiple-access (SDMA) systems. In co ntentional SDR-W, a smart antenna is used at the basestation to simultaneou sly communicate with multiple stations on the same frequency channel. When dynamic slot allocation is added, the basestation uses uplink channel measu rements to intelligently construct future SDMA/TDMA frames, It is shown tha t under a simple minimum signal-to-interference-plus-noise ratio (SMR) cons traint, the problem of performing optimal dynamic slot allocation is NP-com plete. Heuristic slot allocation algorithms are introduced which are capabl e of greatly increasing SDMA/TDMA frame capacity compared with a random all ocation of stations. The paper uses both theoretical results and measured d ata from an experimental testbed to characterize the performance of dynamic slot allocation. The experimental system operates at a carrier frequency o f 1.86 GHz and uses an eight-element circular antenna array. It is demonstr ated that significant increases in system capacity are possible using DSA i n the indoor situations that were tested. Dynamic slot allocation requires the channel to be essentially constant from the time that channel measureme nts are made until the SDMA/TDMA frame is transmitted, We also present chan nel measurements which show the effects of channel time coherence in the pr esence of indoor pedestrian movement. This and other results we have taken suggest that dynamic slot allocation is possible at the frequency considere d, provided turnaround times are in the low-to-mid tens of milliseconds.