Cognitive Radio Medium Access Control Protocols Research Articles

A reliability aware protocol for cooperative communication in cognitive radio networks

One of the challenging tasks in cognitive radio (CR) networks is to agree on a common control channel to exchange control information. This paper presents a novel medium access control (MAC) protocol for CR network which efficiently and intelligently establishes a common control channel between CR nodes. The proposed protocol is the first CR MAC protocol which is hybrid in nature and lies between global common control channel (GCCC) and non-GCCC family of MAC protocols. The dynamic nature of the protocol makes the CR nodes converge on a newly found control channel quicker whenever the interference from a licensed user is sensed. The analytical results show that the dynamic, hybrid and adaptive nature of proposed protocol yields higher throughputs when compared with other CR MAC protocols.

DCCC-MAC: A Dynamic Common-Control-Channel-Based MAC Protocol for Cellular Cognitive Radio Networks

We propose a novel dynamic common-control-channel-based medium access control (DCCC-MAC) protocol for cellular (centralized) cognitive radio (CR) networks. Specifically, unlike the traditional dedicated-control-channel-based medium access control (MAC) protocols, the proposed MAC protocol eliminates the requirement of a dedicated channel for control information exchange. During a given transmission frame, the common control channel (CCC) is selected by a cooperating set of secondary users (SUs) by using a support-vector-machine (SVM)-based learning technique. In the DCCC-MAC protocol, the frame duration is divided into four main phases as follows: spectrum sensing, CCC selection, data transmission, and beaconing. The SUs that participate in the CCC selection process are allocated channels for data transmission during a frame interval using a scheduling process, whereas the other SUs have to contend to access the channels. We present an analytical approach to calculate the minimum required number of minislots in the transmission frame for a given number of SUs in the CCC selection process. The saturation throughput of the proposed MAC protocol is analyzed in closed form. To this end, the numerical and simulation results are presented to quantify the performance of the proposed DCCC-MAC protocol. We also compare the performance of the DCCC-MAC protocol with that of two other state-of-the-art CR MAC protocols that use CCCs.

Energy-Efficient Hybrid CCC-Based MAC Protocol for Cognitive Radio Ad Hoc Networks

Transmitter power consumption and application throughput in cognitive radio-medium access control (CR-MAC) protocol has direct impact on control message overhead and common control channel (CCC). Hence, the design of CCC in CR-MAC plays a pivotal role in selecting an energy-efficient channel path for enhanced throughput. State-of-the-art CR-MAC protocols design CCC in in-band or out-of-band overlay spectrum bands. With in-band, imperfect node synchronization due to per-hop and group CCC coverage leads to multichannel hidden terminal and longer network access delays. Global coverage with dedicated out-of-band CCC is subject to saturation and intruder attacks, which results in single point of network failure and increased power consumption. To overcome existing problems, an energy-efficient hybrid CCC based CR-MAC protocol with omnidirectional control and directional data transmission is proposed to reduce power consumption due to link access overhead, multichannel hidden terminal, deafness, and spectrum mobility. In this paper, antenna index numbers through Global Positioning System and angle-of-arrival estimation are used for directional data transmission, whereas hybrid CCC is used to avoid interference due to multichannel hidden terminals. Experimental results reveal that the proposed hybrid CCC-MAC with directional antennas has increased network throughput and reduced transmit power consumption when compared with existing in/out-of-band omnidirectional CCC-based CR-MAC protocols.

A Novel Reservation-based MAC Scheme for Distributed Cognitive Radio Networks

This paper presents a novel medium access control medium access control (MAC) for distributed single-channel cognitive radio networks (CRNs) denominated cognitive radio reservation MAC (C2RMAC). C2RMAC is intended to be adopted by the nonlicensed users and introduces a double stage scheme to schedule each node's transmission. In this way, C2RMAC increases the use of the spectrum left free by the licensed users, when compared with other protocols. An important contribution of this paper is the assumption of a heterogeneous spectrum sensing condition, i.e., the assumption that different nonlicensed users may sense different levels of channel occupancy. We derive an analytical model to compute the performance of the proposed protocol by adopting innovative concepts to tackle the heterogeneous sensing condition. Several simulation results, including the aggregated throughput and the packet service time, evaluate the performance of C2RMAC and successfully validate the proposed model. Finally, C2RMAC is compared with other state-of-the-art cognitive radio MAC protocols, showing the effectiveness of the proposed solution.

Backoff Algorithm in Cognitive Radio MAC Protocol for Throughput Enhancement

In this paper, we have explored a novel concept of the medium access control (MAC) protocol for the distributed cognitive radio network. We have implemented the backoff algorithm in the self-scheduled multichannel cognitive radio MAC (SMC-MAC) protocol for the contention solving among the cognitive users and, hence, reserve the licensed channels for data transmission. In this control channel protocol, the cognitive users share the sensing results with each other, and each channel is divided into four intervals such as idle, sensing–sharing, contention, and data transmission. However, the backoff algorithm has been implemented during the contention interval to enhance the number of successful users and, hence, has increased the throughput of cognitive radio network. The backoff algorithm has significantly minimized the competition and, hence, collision among the cognitive users while reserving the unutilized licensed channels.

Preemptive Opportunistic MAC Protocol in Distributed Cognitive Radio Networks

A preemptive opportunistic cognitive radio (CR) medium access control (MAC) protocol, which is called PO-MAC, is proposed for distributed CR networks. PO-MAC consists of three main phases: network initialization, reporting, and contention. The primary user (PU) channel exclusively assigned to each secondary user (SU) is sensed during the sensing period, and the sensing result is then reported to all other SUs without collisions during the reporting phase. Using the sensing results, SUs can preempt and make use of free channels via a contention method during the contention phase. It is demonstrated that PO-MAC outperforms existing CR MAC protocols in terms of the end-to-end delay and throughput performance. Further, it is shown that PO-MAC effectively operates when used in real-time services such as voice over Internet protocol.

Issues in Realization of Cognitive Radio Sensor Networks

Recently, significant growth in the applications of the wireless sensor networks (WSNs) operating in unlicensed spectrum bands has been made. In the meantime, existing unlicensed bands are becoming congested and overcrowded. On the other hand, Cognitive Radio (CR) technology has been proposed as the key technology for future wireless communication that exploits dynamic spectrum access strategies. Since this offers more flexible way to utilize the wireless spectrum than traditional radio technology based on a fixed spectrum access policy, it is thought that the key feature of cognitive radio, i.e., dynamic spectrum access can be applied in WSNs to access the underutilized spectrum bands to transmit their readings in an opportunistic manner to the next hops and finally to the sink. In cognitive radio sensor networks (CRSNs), obtaining the information about spectrum holes on channel, negotiating among primary users and secondary users for spectrum allocation, synchronizing transmission parameters are the important functions of CR medium access control protocols. In this paper, we mainly focus on investigating the major issues to be considered with the existing communication protocols and algorithms devised while realizing the cognitive capability into wireless sensor networks. We also discuss the main challenges on the basis of dynamic spectrum management and extra energy expenditure to apply the cognitive capability into wireless sensor networks.

Design and Analysis of an OSA-BR MAC Protocol for Cognitive Radio Ad Hoc Networks

Cognitive Radio (CR) is a new communication network paradigm introduced to solve the problems of spectrum scarcity and inefficient spectrum usage. Basically, it allows the Secondary Users (SUs) to utilize the Licensed Channels (LCs) of the Primary Users (PUs) in an opportunistic manner without causing any harmful interference to the PUs. However, there are many challenges associated with cognitive radio networks, such as the CR Medium Access Control (CR-MAC) protocols. An important issue for CR-MAC protocols is to identify whether the spectrum is licensed or unlicensed. In addition, the sudden appearance of the PU is the most important feature of the distributed CR-MAC protocols. In this paper, a multichannel CR-MAC protocol, which reacts efficiently to the appearance of the PUs, is developed. The proposed protocol is named Opportunistic Spectrum Access with backup channel and Buffered data with Resume (OSA-BR). The OSA-BR is an unaided rendezvous, asynchronous, and contention-based MAC protocol. The proposed protocol operates in heterogeneous environment, where the SUs utilize both LCs and unlicensed channel (ULs) and the activities of the Classical Users (CUs) are taken into consideration. In addition, the concept of the backup channel and the buffer with resume are introduced. The simulation results show that OSA-BR accomplishes 35% throughput gain over the SWITCH protocol and 55% over other CR-MAC protocols.

A Survey on MAC Protocols for Cognitive Radio Networks

인지 무선(CR) 기술은 동적 스펙트럼 접근 방식을 이용한 미래 무선 통신의 핵심 기술로 제안되었다. 이 기술은 고정 된 스펙트럼 접근 방식에 기반한 기존의 무선 기술보다 무선 스펙트럼을 더욱 유용하게 사용할 수 있다. CR 네트워크는 채널의 유휴 자원에 대한 정보를 얻으며, 스펙트럼 할당에 대한 주 사용자와 보조 사용자간의 상호 규칙이 존재하며, 동기화 전송 매개 변수는 CR 매체 접근 제어 프로토콜이 중요한 기능이다. 본 논문에서는 기존 CR MAC 프로토콜을 직접 액세스 기반(DAB) MAC과 동적 스펙트럼 할당(DSA) MAC으로 분류하였고, 그 체계에 대하여 살펴보았다. 또한, 기본적인 CR 기술의 특색, 장점, 설계 요소 및 단점과 함께 DAB MAC 프로토콜에서 최근 기술동향에 대하여 설명하였다.

Vulnerabilities of cognitive radio MAC protocols and countermeasures

Cognitive Radio (CR) is a promising technology for opportunistically accessing underutilized licensed spectrum to achieve higher spectrum efficiency and communication throughput. These performance gains are contingent upon the efficient coordination of channel access to the idle portion of the spectrum, an operation performed at the Medium Access Control (MAC) layer. In this article we identify various vulnerabilities of state-of-the-art CR MAC protocols, exploited by selfish/malicious CR users for gaining an unfair share of the available network resources. Furthermore, possible countermeasures for detecting and mitigating these vulnerabilities are discussed.

Cognitive radio networking and communications: an overview

Cognitive radio (CR) is the enabling technology for supporting dynamic spectrum access: the policy that addresses the spectrum scarcity problem that is encountered in many countries. Thus, CR is widely regarded as one of the most promising technologies for future wireless communications. To make radios and wireless networks truly cognitive, however, is by no means a simple task, and it requires collaborative effort from various research communities, including communications theory, networking engineering, signal processing, game theory, software-hardware joint design, and reconfigurable antenna and radio-frequency design. In this paper, we provide a systematic overview on CR networking and communications by looking at the key functions of the physical (PHY), medium access control (MAC), and network layers involved in a CR design and how these layers are crossly related. In particular, for the PHY layer, we will address signal processing techniques for spectrum sensing, cooperative spectrum sensing, and transceiver design for cognitive spectrum access. For the MAC layer, we review sensing scheduling schemes, sensing-access tradeoff design, spectrum-aware access MAC, and CR MAC protocols. In the network layer, cognitive radio network (CRN) tomography, spectrum-aware routing, and quality-of-service (QoS) control will be addressed. Emerging CRNs that are actively developed by various standardization committees and spectrum-sharing economics will also be reviewed. Finally, we point out several open questions and challenges that are related to the CRN design.

Medium access control protocols in cognitive radio networks

AbstractIn cognitive radio (CR) networks, medium access control (MAC) protocols play an important role to exploit the spectrum opportunities, manage the interference to primary users (PUs), and coordinate the spectrum access amongst secondary users (SUs). In this paper, we first introduce the challenges in the design and implementation of CR MAC protocols. Then, we make a comprehensive survey of the state‐of‐the‐art CR MAC protocols and categorize them on the basis of spectrum sharing modes, i.e., overlay and underlay modes. We also introduce some other classification metrics such as architecture (centralized or distributed), sharing behaviors (cooperative or non‐cooperative), and access modes (contention based or contention free). Through the study, we find out that most CR MAC protocols are designed for the overlay mode. The CR MAC protocols in underlay mode could yield higher spectrum utilization efficiency with the cost of more complicated power and admission control schemes. The centralized CR MAC protocols are more suitable to do spectrum sensing using quiet period of whole network, while the distributed CR MAC protocols are more flexible to deploy. We identify several future directions, such as more practical CR MAC protocols for underlay mode, MAC protocols considering security, MAC protocols considering heterogeneous coexistence, etc. Copyright © 2009 John Wiley & Sons, Ltd.

A survey on MAC protocols for cognitive radio networks

In cognitive radio (CR) networks, identifying the available spectrum resource through spectrum sensing, deciding on the optimal sensing and transmission times, and coordinating with the other users for spectrum access are the important functions of the medium access control (MAC) protocols. In this survey, the characteristic features, advantages, and the limiting factors of the existing CR MAC protocols are thoroughly investigated for both infrastructure-based and ad hoc networks. First, an overview of the spectrum sensing is given, as it ensures that the channel access does not result in interference to the licensed users of the spectrum. Next, a detailed classification of the MAC protocols is presented while considering the infrastructure support, integration of spectrum sensing functionalities, the need for time synchronization, and the number of radio transceivers. The main challenges and future research directions are presented, while highlighting the close coupling of the MAC protocol design with the other layers of the protocol stack.