Considerations on adaptive techniques for time-division multiplexing radio systems

This paper addresses the problem of providing a fair comparison among the performance of the different techniques that adapt the transmission parameters, such as the modulation, power, and bit rate, to the channel characteristics. A coordinated time-division multiplexing (TDM) scheme is adopted. Both an isolated cell scenario and a cellular system scenario are taken into consideration. In the single-cell case, closed-form expressions of the optimum power and modulation adaptation law are found. It is shown that the examined techniques offer a similar performance in most cases, although modulation adaptation is somewhat superior to power control in the cellular case. It is made clear that the improvement obtained by adopting an adaptive technique should not be evaluated without specifying the acceptable consequences on service distribution because it is the service distribution that determines the achievable gain ultimately. Previously, a new wireless access system, called Infostations, has been proposed which provides isolated pockets of high-bandwidth connectivity for future data and messaging services. Although the main considerations hold in general, they are particularly useful for defining a time multiplexing scheme for Infostations.