Switched Opportunistic Packet Scheduling for High Speed Packet Access MIMO Systems

Abstract

In this paper, we propose an algorithm for scheduling users in wireless MIMO systems. The scheduler in the base station defines a utility function for each user that depends on the user transmissible rates and the user QoS criteria. For each channel scheduling epoch, the scheduler has to resolve the maximization of a system utility concave function. This optimization needs a long time of processing, which leads to a constraint in practical implementation. In this paper, we present an alternative solution, by using a weak control on the opportunistic selection. Thus, the selected user would combine a good channel condition and a low user performance. Therefore, if the user reaches a minimum level of performance and experiences an instantaneous transmissible rate greater than a predefined threshold, he would be selected for receiving packets. If the user with the worst case performance has a transmissible rate lower than the threshold, he would be selected, if he owns the max instantaneous transmissible rate compared to other users in the same conditions. The switching between these two groups of users is defined by the result of a logical function that indicates the group of the user that has a critic performance. Accordingly, the proposed algorithm can be viewed as the opportunistic scheduling algorithm under adaptive weak control of the QoS requirements. The system used for this analysis is the downlink of a single cell. A selection of numerical results is presented to compare the proposed scheduling algorithm to other scheduling schemes.