Cross-Layer Control for Utility Maximization in Multihop Cognitive Radio Networks Long Bao Le INRS-EMT, University of Quebec Montreal, Quebec, Canada long.le@emt.inrs.ca Abstract. We investigate the cross-layer control problem for utility maximization in a multihop cognitive radio network. Specifically, we consider a scenario where wireless links of a secondary multihop wire- less network opportunistically exploit a frequency band for data delivery when their neighboring primary users do not access it. We assume that the busy/idle status of the underlying channel in view of any partic- ular secondary wireless link follows a two-state Markov chain and this information is only available at each secondary wireless link within one time slot delay. We develop a joint flow control, routing and scheduling algorithm that can achieve the total network utility arbitrarily close to optimality. In addition, we show that the proposed algorithm can main- tain stability of all network queues while keeping collision probabilities with primary users below predetermined desirable values. To the best of our knowledge, this paper is the first attempt to design optimal control algorithms for multihop cognitive radio networks. Keywords: Network control, routing, scheduling, utility and backlog tradeoff, stability/throughput region, cognitive radio, multihop wireless networks. 1 Introduction Recent measurements have shown that spectrum utilization on many frequency bands is very low [1]. This has motivated a great deal of research interests from FCC, wireless industry as well as academia [2], [3], [4], [5], [6]. These research interests are mostly driven by growing bandwidth demands of emerging broad- band wireless applications. In general, wireless technologies that aim at improv- ing spectrum utilization through efficient spectrum sharing/allocation techniques are commonly referred to as cognitive radio technologies. In fact, the first stan- dard that specifies physical, MAC and air interface for spectrum sharing in the TV broadcast band has been under active development [4]. There have been growing research activities on information theoretic, protocol and system engi- neering issues of cognitive radio systems. Although the cognitive radio can be very broad and abstract in concept [3], research activities in this area mainly focus on developing efficient hierarchical spectrum sharing techniques between primary and secondary users/networks X. Zhang and D. Qiao (Eds.): QShine 2010, LNICST 74, pp. 28–40, 2011. c  Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2011