An adaptive downlink spread spectrum OFDM packet data system with two-dimensional radio resource allocation: performance in low-mobility cellular environments

In multipath mobile radio channels, fading is both frequency selective and time varying The SS-OFDM-F/TA system allocates time and frequency resources adaptively to provide high bit rate services on the downlink to low-mobility users. Multiuser diversity is employed in this system so that users receive data packets only when conditions are favorable. It is shown that fast best sector selection (1 Hz) provides significant throughput gains in severely shadowed environments. Further, asynchronous retransmission of packets increases the data throughput of the system in comparison to synchronous m-transmissions with only a small increase in packet delay. In a highly frequency selective channel, the allocation of single sub-bands is compared with the allocation of groups of narrower disjoint sub-bands.