A tagging-based medium access scheme for wireless data applications in CDMA/TDM networks

In this paper, a packet scheduling scheme based on real-time channel conditions and avoidance of dominant inter-cell interferers is proposed and studied. This scheme is implemented by the distribution of tags by receivers among transmitters. We focus on reverse links of a CDMA/TDM system where for every slot, each base station issues M(/spl ges/1) tags to M mobile users (MU) based on the ranked reverse link gains. The number of tags thus issued depends on the expected traffic, the number of cells and the propagation conditions in the network. Two types of tags can be issued: eg, hard and soft tags. A MU will transmit only if it receives a tag from its home base station (BS) and no hard tag from any other BS. Hence, in our scheme, MU that not only have stronger channel pins to their respective home BS but also cause relatively lower inter-cell interference are scheduled for transmissions. This scheme is hence a cooperative approach whereby good-neighbor behaviour is exhibited. Soft-tagging offers flexibility in allowing MU that cause moderate inter-cell interference to transmit under certain conditions such as longer starved time. Simulation results in shadow and a Rayleigh failing environment are presented to show that our scheme outperforms the conventional scheme by 30% in transmit bit energy when M = 10 in a 9-cell network with 100 MU uniformly distributed.