Channel Assignment With Access Contention Resolution for Cognitive Radio Networks

Abstract

In this paper, we consider the channel allocation problem for throughput maximization in cognitive radio networks with hardware-constrained secondary users. Specifically, we assume that secondary users (SUs) exploit spectrum holes on a set of channels where each SU can use at most one available channel for communication. We present the optimal brute-force search algorithm and its complexity for this non-linear integer optimization problem. Since the optimal solution has exponential complexity with the numbers of channels and SUs, we develop two low-complexity channel assignment algorithms that can efficiently utilize spectrum opportunities on these channels. In the first algorithm, SUs are assigned distinct sets of channels. We show that this algorithm achieves the maximum throughput limit if the number of channels is sufficiently large. In addition, we propose an overlapping channel assignment algorithm, that can improve the throughput performance compared to the nonoverlapping channel assignment counterpart. In addition, we design a distributed MAC protocol for access contention resolution and integrate it into the overlapping channel assignment algorithm. We also analyze the saturation throughput and the complexity of the proposed channel assignment algorithms. Moreover, we have presented several potential extensions including greedy channel assignment algorithms under max-min fairness criterion and throughput analysis considering sensing errors. Finally, numerical results are presented to validate the developed theoretical results and illustrate the performance gains due to the proposed channel assignment algorithms. Index TermsChannel assignment, MAC protocol, spectrum sensing, throughput maximization, cognitive radio. I. INTRODUCTIONEmerging broadband wireless applications have been demanding unprecedented increase in radio spectrum resources. As a result, we have been facing a serious spectrum shortage problem. However, several recent measurements reveal very low spectrum utilization in most useful frequency bands [1]. Cognitive radio technology is a promising technology that can fundamentally improve the spectrum utilization of licensed frequency bands through secondary spectrum access. However, transmissions from primary users (PUs) should be satisfactorily protected from secondary spectrum access due to their strictly higher access priority.Protection of primary communications can be achieved through interference avoidance or interference control approach (i.e., spectrum overlay or spectrum underlay) [1]. For the interference control approach, transmission powers of SUs should be carefully controlled so that the aggregated interference they create at primary receivers does not severely affect ongoing primary communications [2]. In most practical scenarios where direct coordination between PUs and SUs is not possible and/or if distributed communications strategies are desired, it would be very difficult to maintain these interference constraints. The interference avoidance approach instead prote...

Channel Assignment Algorithms in Cognitive Radio Networks: Taxonomy, Open Issues, and Challenges

“…The channel sets come in two types: orthogonal channels and overlapping channels [116]. The orthogonal channels do not interfere with one another, even if they are simultaneously active in the same coverage area; whereas, overlapping channels interfere with one another, if they are being simultaneously used in the same coverage area.…”

“…(b) Access contention resolution: Overlapping and non-overlapping channel assignment algorithms are employed in [116] to maximize the throughput within the CRAHN. In the non-overlapping channel assignment algorithm, a distinct set of channels is assigned to the SUs.…”

A Distributed Dynamic Channel Assignment and Routing Framework for Cognitive Sensor Systems

“…Since Urban-X uses simultaneous transmission of two data transceivers in different channels, it is costly for cognitive radio sensor networks. Tan and Le [2] have investigated the channel assignment problem for cognitive radio networks with hardware-constrained SUs, and presented the optimal bruteforce search algorithm to solve the corresponding problem. Wang et al [3] have proposed a heuristic centralized scheme to assign channels among secondary users.…”

“…Shi et al [6] have studied the problem of periodic sensor scheduling with limited sensor energy and communication bandwidth. However, [2]- [4] do not consider multihop communication between sensor nodes.…”

“…The use of simultaneous transmission on different channels also makes the protocol design complex and increases the channel switching incurred delay. A multi-hop communication is not considered in [2]- [6].…”