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The problem of medium access control(MAC) in wireless single-input multiple-output-orthogonal frequency division multiplexing(SIMO-OFDM) systems is addressed. Traditional random access protocols have low overheads and inferior performance. Centralized methods have superior performance and high overheads. To achieve the tradeoff between overhead and performance,we propose a channelaware uplink transmission(CaUT) scheme for SIMO-OFDM systems. In CaUT,users transmit requestto-send(RTS) at some subcarriers whose channel gains are above a predetermined threshold. Using the channel state information provided by RTS,access point performs user selection with receive beamforming to decide which users can access and then broadcasts the selection results via clear-to-send(CTS) to users. We present a distributed power control scheme by using a simple fixed modulation mode. We optimize the modulation order and channel gain thresholds to maximize the separable packets subject to the bit-error-rate(BER) and temporal fairness requirements and the individual average transmit power constraints. The performance of CaUT scheme is analyzed analytically and evaluated by simulations. Simulation results show that CaUT can achieve more significant throughput performance than traditional random access protocols.
The problem of medium access control (MAC) in wireless single-input multiple-output-orthogonal frequency division multiplexing (SIMO-OFDM) systems is addressed. Traditional random access protocols have low overheads and inferior performance. Centralized methods have superior performance and high overheads To achieve the tradeoff between overhead and performance, we propose a channelaware uplink transmission (CaUT) scheme for SIMO-OFDM systems. In CaUT, users transmit requestto-send (RTS) at some subcarriers whose channel gains are above a predetermined threshold. the channel state information provided by RTS, access point performs user selection with receive beamforming to decide which users can access and then broadcasts the selection results via clear-to-send (CTS) to users. We present a distributed power control scheme by using a simple fixed modulation mode. We optimize the modulation order and channel gain thresholds to maximize the separable packets subject to the bit-error-rate (B ER) and temporal fairness requirements and the individual average transmit power constraints. The performance of CaUT scheme is analyzed analytically and evaluated by simulations. Simulation results show that CaUT can achieve more significant throughput performance than traditional random access protocols.