Abstract
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.
Highlights
In the existing literature, the radio spectrum is divided into licensed and unlicensed bands
OSA-BR is developed based on the following assumptions: 1) The Common Control Channel (CCC) which used as a rendezvous channel by Secondary Users (SUs) is selected in a dynamic manner from the idle Primary Channels (PCs) which are licensed to Primary Users (PUs)
Spectrum Allocation Based on the gathered sensing information, the spectrum allocation data structures, residing in each SU, make an adaptive decision on the operating channel defined by the center frequency and the time duration of using such a channel according to the activities of PUs, Classical Users (CUs) and other SUs in its vicinity
Summary
The radio spectrum is divided into licensed and unlicensed bands. Time-slotted MAC protocols need a global synchronization between SUs where the time is divided into slots for both the control channel and the data transmission. Examples of this category are the Cognitive MAC (C-MAC) protocol [9] and the Opportunistic Spectrum Access (OSA-MAC) protocol [10]. SWITCH uses the concept of Backup Channel (BC) to cope with the appearance of the PUs. In this paper, we present a modified protocol from the existing SWITCH protocol named Opportunistic Spectrum Access with backup channel and Buffered data with Resume (OSA-BR).
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