A quorum-based framework for establishing control channels in dynamic spectrum access networks

Abstract

Establishing a control channel for medium access control is a challenging problem in multi-channel and dynamic spectrum access (DSA) networks. In the design of multi-channel MAC protocols, the use of channel (or frequency) hopping techniques (a.k.a. parallel rendezvous) have been proposed to avoid the bottleneck of a single control channel. In DSA networks, the dynamic and opportunistic use of the available spectrum requires that the radios are able to "rendezvous"-i.e., find each other to establish a link. The use of a dedicated global control channel simplifies the rendezvous process but may not be feasible in many opportunistic spectrum sharing scenarios due to the dynamically changing availability of all the channels, including the control channel. To address this problem, researchers have proposed the use of channel hopping protocols for enabling rendezvous in DSA networks. This paper presents a systematic approach, based on quorum systems, for designing and analyzing channel hopping protocols for the purpose of control channel establishment. The proposed approach, called Quorum-based Channel Hopping (QCH) system, can be used for implementing rendezvous protocols in DSA networks that are robust against link breakage caused by the appearance of incumbent user signals. We describe two optimal QCH systems under the assumption of global clock synchronization: the first system is optimal in the sense that it minimizes the time-to-rendezvous between any two channel hopping sequences; the second system is optimal in the sense that it guarantees the even distribution of the rendezvous points in terms of both time and channel, thus solving the rendezvous convergence problem. We also propose an asynchronous QCH system that does not require global clock synchronization. Our analytical and simulation results show that the channel hopping schemes designed using our framework outperform existing schemes under various network conditions.

Quorum system and random based asynchronous rendezvous protocol for cognitive radio ad hoc networks

“…A cyclic QS is proposed in [15] and it is based on the cyclic block design and cyclic difference sets in combinatorial theory [16]. The last branch consists of either quorumbased, or difference set-based, or Latin Square-based protocols proposed for CRNs ( [17][18][19][20][21]). However, an asynchronous channel view (ACHv) is not explicitly handled in quorum-based schemes 2 and the channel heterogeneity is not considered in any related work approaches to the best of our knowledge.…”

“…Up to the best of the authors' knowledge there is only a couple of papers focusing on quorum based asynchronous rendezvous [6,17,20,22]. However, these papers as well as the aforementioned work dealing with the asynchronism, do not handle the channel heterogeneity in the generation of channel hopping sequences and do not handle the details of asynchronous operation and rendezvous between the devices.…”

CACH: Cycle-Adjustable Channel hopping for control channel establishment in cognitive radio networks

“…A CH scheme is called asymmetric if one SU can be identified as the sender and the other SU can be identified as the receiver. For asymmetric CH schemes (such as ACH in [18] and ARCH in [19]), the sender and the receiver can use different strategies to rendezvous and thus can achieve better performance than symmetric CH schemes (such as SSCH in [7], SYN-MAC in [8], QCH in [9] and DH-MAC in [10]), where both SUs have to follow the same strategy. Also, a CH scheme is synchronous if the indices of time intervals of both SU are the same.…”

“…As addressed in [9] and [19], there are three common metrics for evaluating the performance of a CH scheme: (i) degree of overlapping: the number of distinct channels for two SUs to rendezvous in each operation period, (ii) worst case time-to-rendezvous (TTR) (MTTR in [9]): the maximum time for two SUs to rendezvous (when there is no PU blocking), and (iii) system load: the maximum probability that an SU hops to a particular channel at a particular time interval. Clearly, for the PU long-time blocking problem, a CH scheme should have a large degree of overlapping, preferable the maximum degree of overlapping.…”

“…Finally, to mitigate the control channel saturation problem, a CH scheme should minimize its system load so that the average number of SUs that hop to the same channel at the same time interval can be minimized. As pointed out in [9], there is a tradeoff between worst case TTR and system load. In general, one can increase system load to reduce TTR and such a tradeoff can then be used to optimize system performance.…”