Rendezvous In Cognitive Radio Networks Research Articles

Quality of Service Aware Channel Hopping Rendezvous in Cognitive Radio Networks for Internet of Things

Quality of Service Aware Channel Hopping Rendezvous in Cognitive Radio Networks for Internet of Things

On Heterogeneous Sensing Capability for Distributed Rendezvous in Cognitive Radio Networks

Cognitive radio networks (CRNs) have been proposed to solve the spectrum scarcity problem. One of their fundamental procedures is to construct a communication link on a common channel for the users, which is referred to as <i>rendezvous</i> . In reality, the capability to sense the spectrum may vary from user to user. We study distributed rendezvous for heterogeneous sensing capabilities in this paper. The licensed spectrum is divided into <inline-formula><tex-math notation="LaTeX">$n$</tex-math></inline-formula> channels, <inline-formula><tex-math notation="LaTeX">$U = \lbrace 1,2,\ldots,n\rbrace$</tex-math></inline-formula> . We denote the sensing capability of user <inline-formula><tex-math notation="LaTeX">$i$</tex-math></inline-formula> as <inline-formula><tex-math notation="LaTeX">$C_i \subseteq U$</tex-math></inline-formula> and the set of available channels (i.e., the channels not occupied by paying users) as <inline-formula><tex-math notation="LaTeX">$V_i \subseteq C_i$</tex-math></inline-formula> . Due to hardware differences, the users may have different sensing capabilities: <inline-formula><tex-math notation="LaTeX">$C_i \ne C_j$</tex-math></inline-formula> , and this is called <i>heterogeneous sensing capability</i> . In this paper, we propose efficient algorithms for two scenarios: the fully available scenario where <inline-formula><tex-math notation="LaTeX">$V_i = C_i$</tex-math></inline-formula> and the partially available scenario where <inline-formula><tex-math notation="LaTeX">$V_i \subseteq C_i$</tex-math></inline-formula> . Our idea is to utilize two ‘pointers’ to traverse the sensing capability set, which sets our algorithms apart from the extant rendezvous algorithms. Considering any two neighboring users <inline-formula><tex-math notation="LaTeX">$a, b$</tex-math></inline-formula> , we propose the Traversing Pointer (TP) algorithm that guarantees rendezvous in <inline-formula><tex-math notation="LaTeX">$O(\max \lbrace |C_a|,|C_b|\rbrace \log \log n)$</tex-math></inline-formula> time slots for the fully available scenario. This result is only <inline-formula><tex-math notation="LaTeX">$O(\log \log n)$</tex-math></inline-formula> larger than the theoretical lower bound. Moreover, it removes an <inline-formula><tex-math notation="LaTeX">$O(\min \lbrace |C_a|,|C_b|\rbrace)$</tex-math></inline-formula> factor when compared to the state-of-the-art result ( <inline-formula><tex-math notation="LaTeX">$O(|C_a||C_b|)$</tex-math></inline-formula> in S.-H. Wu <i>et al.</i> For the partially available scenario, we propose the Moving Traversing Pointers (MTP) and Prime based Moving Traversing Pointers (P-MTP) algorithms that can guarantee rendezvous within <inline-formula><tex-math notation="LaTeX">$O((\max \lbrace |V_a|,|V_b|\rbrace)^2\log \log n)$</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">$O(|V_a||V_b|\log \log n)$</tex-math></inline-formula> time slots respectively, where the latter one combines the pointers and a common technique of plugging in a prime number. The proposed algorithms work more efficiently than the previous best result ( <inline-formula><tex-math notation="LaTeX">$O(|C_a||C_b|)$</tex-math></inline-formula> in C.-C. Wu <i>et al.</i> under various circumstances. We also conduct extensive simulations and the results corroborate our analyses.

Channel Hopping Using ${p}$ -ary m-Sequence for Rendezvous in Cognitive Radio Networks

Rendezvous is a process that assists nodes in a cognitive radio networks (CRNs) to discover each other. In CRNs where a common control channel is unknown and a number of channels are given, it is important how two nodes find each other in a known search region. In this letter, we have analyzed a channel hopping sequence considering ${p}$ -ray m-sequence by which each node visits an available number of channels. We analyze the maximum and expected time-to-rendezvous (TTR) mathematically. The proposed sequence performs significantly better compared to the existing ones in term of maximum and expected TTR.

Multi‐radio channel rendezvous in cognitive radio networks

In decentralised cognitive radio (CR) networks, establishing communication sessions between a communicating pair requires them to meet each other on a common channel via a `rendezvous' process. Devising distributed CR rendezvous protocol is a challenging task as cognitive nodes are not necessarily synchronised, and may have different perceptions of channel availability. In this study, the authors present M-Rendezvous , an order-optimal rendezvous protocol exploiting the performance gain brought by having multiple radios at cognitive nodes. As a distinguished feature, M-Rendezvous is a unified rendezvous protocol that can operate in both homogenous case where both of the rendezvous nodes are equipped with only one radio or multiple radios, and heterogeneous case where one of the rendezvous nodes has single radio and the other has multiple radios. In both cases, by rigorous analysis, the authors demonstrate that M-Rendezvous can guarantee rendezvous over every channel with bounded and order-minimal delay even when rendezvous nodes have asynchronous clocks and asymmetrical channel perceptions.

On Cooperative Channel Rendezvous in Cognitive Radio Networks

In cognitive radio (CR) networks, establishing communication sessions requires the communicating pairs to meet each other on a common channel via a “rendezvous” process. Designing distributed rendezvous protocols without common control channels is a challenging problem due to the dynamic and opportunistic spectrum access paradigm. The existing protocols, mainly based on channel hopping, suffer from the rendezvous difficulty due to asymmetric channel perceptions and significant rendezvous delay when the system scales. In this paper, we exploit a long-neglected opportunity for enabling rendezvous in CR networks-the cooperation among cognitive users. We develop a novel cooperative rendezvous mechanism by introducing the cooperative cognitive nodes serving as “bridges” between communicating pairs to facilitate their rendezvous process. We establish a mathematics framework to study the rendezvous delay and robustness and derive the performance limit in asymptotic scenarios. Our analytical results are further confirmed by the simulation results showing the performance improvement of the developed cooperative rendezvous protocol with only small overhead.

Symmetric Channel Hopping for Blind Rendezvous in Cognitive Radio Networks Based on Union of Disjoint Difference Sets

In order to exchange control information without relying on any fixed control channel, neighboring cognitive users (CUs) in a multichannel cognitive radio network (CRN) can tune their transceivers to hop among a common set of spectrum channels and communicate when they rendezvous at a common channel in the blind fashion. Based on the combinatorial concept of the union of disjoint difference sets ( UDDS ), the present paper proposes two novel symmetric channel hopping (CH) schemes, namely UDDS-SCH and UDDS-ACH , for CUs with or without a synchronized time clock, respectively, to achieve blind rendezvous. By deriving their performance metrics, we then point out that both UDDS-SCH and -ACH can be optimized by adopting a special UDDS, which can be partitioned into mutually disjoint minimal difference sets ( MDSs ) as many as possible. This stimulates us to further develop exhaustive and heuristic solutions for searching the optimal and suboptimal numbers of mutually disjoint MDSs at high and low computational complexities, respectively. Based on these searching results, we finally show that both UDDS-SCH and -ACH can achieve better performance metrics than most existing symmetric CH schemes and remedy one major shortcoming of the best known ones, i.e., incapability to rendezvous at an arbitrary number of spectrum channels. Numerical simulation demonstrates that, when primary users may appear at part of or all rendezvous channels, the proposed CH schemes will outperform the existing ones in terms of the average transmission throughput and time of the CRN.

Multiple Radios for Fast Rendezvous in Cognitive Radio Networks

Rendezvous is a fundamental operation in cognitive radio networks (CRNs) for establishing a communication link on a commonly-available channel between cognitive users. The existing work on rendezvous implicitly assumes that each cognitive user is equipped with one radio (i.e., one wireless transceiver). As the cost of wireless transceivers is dropping, this feature can be exploited to significantly improve the rendezvous performance at low cost. In this study, we investigate the rendezvous problem in CRNs where cognitive users are equipped with multiple radios and different users may have different numbers of radios. We first study how the existing rendezvous algorithms can be generalized to use multiple radios for faster rendezvous. We then propose a new rendezvous algorithm, called role-based parallel sequence (RPS), which specifically exploits multiple radios for more efficient rendezvous. Our basic idea is to let the cognitive users stay in a specific channel in one dedicated radio and hop on the available channels with parallel sequences in the remaining general radios . We prove that our algorithm provides guaranteed rendezvous (i.e., rendezvous can be completed within a finite time) and derive the upper bounds on the maximum time-to-rendezvous (TTR) and the expected TTR. The simulation results show that i) multiple radios can cost-effectively improve the rendezvous performance, and ii) the proposed RPS algorithm performs better than the ones generalized from the existing algorithms.

Channel-Hopping-Based Communication Rendezvous in Cognitive Radio Networks

Cognitive radio (CR) networks have an ample but dynamic amount of spectrum for communications. Communication rendezvous in CR networks is the process of establishing a control channel between radios before they can communicate. Designing a communication rendezvous protocol that can take advantage of all the available spectrum at the same time is of great importance, because it alleviates load on control channels, and thus further reduces probability of collisions. In this paper, we present ETCH, efficient channel-hopping-based MAC-layer protocols for communication rendezvous in CR networks. Compared to the existing solutions, ETCH fully exploits spectrum diversity in communication rendezvous by allowing all the rendezvous channels to be utilized at the same time. We propose two protocols, SYNC-ETCH, which is a synchronous protocol assuming CR nodes can synchronize their channel hopping processes, and ASYNC-ETCH, which is an asynchronous protocol not relying on global clock synchronization. Our theoretical analysis and ns-2-based evaluation show that ETCH achieves better performances of time-to-rendezvous and throughput than the existing work.