Distributed Robust Scheduling and Power Control For Cognitive Spatial-Reuse TDMA Networks

Abstract

We investigate the distributed robust transmission scheduling and power control problem in a cognitive spatial-reuse time division multiple access (STDMA) network. In particular, we address the problem of minimizing the transmission length (in terms of time-slots) of the secondary links under their minimum quality-of-service (QoS) requirements without violating the maximum tolerable interference limit for the primary receivers. Traditionally, the joint transmission scheduling and power control problem only considers the average link gains; therefore, QoS violation can occur due to improper power allocation with respect to instantaneous channel gain realization. To overcome this problem of QoS violation, our problem formulation takes the channel gain uncertainty into account. Since an optimal solution cannot be obtained due to the NP-completeness of the problem, we propose a novel distributed two-stage algorithm based on the distributed column generation method to obtain the near-optimal solution for the robust transmission schedules in an ad-hoc cognitive radio network. To demonstrate its relative efficiency, our algorithm is compared with previously proposed algorithms. For the proposed algorithm, we also derive the bounds on the probability of signal-to-interference-plus-noise ratio (SINR) constraint violation and the expected number of additional time-slots required to satisfy the traffic demand requirements of secondary links.