Opportunistic scheduling for wireless systems with multiple interfaces and multiple constraints

We consider a scheduling problem for packet based systems with time-varying channel conditions. Designing schedul-ing mechanisms that take advantage of time-varying channel conditions, which are different for different users, is neces-sary to improve system performance; however this has to be done in a way that provides some level of fairness among the users. Such scheduling mechanisms are termed as oppor-tunistic. We generalize the opportunistic scheduling mech-anisms in the literature on two fronts. First, we formulate and solve an opportunistic scheduling problem with multi-ple general long term QoS constraints and a general system objective function. We call the solution of this opportunis-tic scheduling problem as a generalized water filling solution. Then, we generalize this problem to include multiple inter-face systems in which several users can be served simulta-neously. Apart from the long term QoS constraints speci-fied by each user, multiple interface systems are constrained with other physical limitations imposed by the system struc-ture. Our main contribution is to show that the structure of the optimal opportunistic scheduling policy is carried over to the problem with general constraints and multiple inter-faces. We also study the stability of the multiple interface systems and propose a throughput optimal scheduling rule for such systems