OFDMA/TDD packet transmission system with an adaptive subcarrier selection scheme for asymmetric wireless communication services

This paper proposes an orthogonal frequency division multiple access/time division duplex (OFDMA/TDD) packet transmission system with an adaptive subcarrier selection scheme to support high speed and flexible bit rate transmission in wireless local area networks (LANs) and home link. In the proposed scheme, the spectral resource ratio between the uplink and downlink is adaptively controlled by changing the frame format, coding rate and transmit power in the OFDMA/TDD system, according to the uplink traffic load estimated by the ratio of used to unused subcarriers at the base station. For suppression of inter-subchannel interference, packet-switching based transmission is employed in the uplink. Moreover, to enhance frequency selective fading immunity, a channel monitoring-assisted adaptive subcarrier selection scheme is employed. Computer simulation confirms that the proposed system is effective in achieving a low message delay system even under dynamically varying traffic conditions