Abstract
New wireless network paradigms will demand higher spectrum use and availability to cope with emerging data-hungry devices. Traditional static spectrum allocation policies cause spectrum scarcity, and new paradigms such as Cognitive Radio (CR) and new protocols and techniques need to be developed in order to have efficient spectrum usage. Medium Access Control (MAC) protocols are accountable for recognizing free spectrum, scheduling available resources and coordinating the coexistence of heterogeneous systems and users. This paper provides an ample review of the state-of-the-art MAC protocols, which mainly focuses on Cognitive Radio Ad Hoc Networks (CRAHN). First, a description of the cognitive radio fundamental functions is presented. Next, MAC protocols are divided into three groups, which are based on their channel access mechanism, namely time-slotted protocol, random access protocol and hybrid protocol. In each group, a detailed and comprehensive explanation of the latest MAC protocols is presented, as well as the pros and cons of each protocol. A discussion on future challenges for CRAHN MAC protocols is included with a comparison of the protocols from a functional perspective.
Highlights
The current wireless networking paradigm consists of the connectivity of many heterogeneous devices through links operating under dynamic environments
The Worst Feasible Channel Medium Access Control (MAC) (WFC-MAC) is a protocol based on Carrier Sense Multiple Access (CSMA) for multi-hop Cognitive Radio Network (CRN), which is based on the distributed scheme
Several cognitive functionalities directly depend on the MAC protocol performance such as spectrum sharing and allocation and spectrum mobility
Summary
The current wireless networking paradigm consists of the connectivity of many heterogeneous devices through links operating under dynamic environments. As can be observed from existing surveys, most of the concentration is given to spectrum management functionalities, and less attention is given to the MAC protocols, especially for decentralized networks, concluding that there is no comprehensive survey paper on MAC protocols for CRAHN. Based on the analytical study of the existing MAC protocols, we have provided a discussion on the open research topics to be investigated more deeply in the future. It provides a comprehensive survey of the CR spectrum functions of sensing, decision, sharing and mobility together with their connection to MAC protocols. It reviews the state-of-the-art MAC protocols in CRAHN.
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