Kỷ yếu Hội nghị Quốc gia lần thứ VIII về Nghiên cứu cơ bản và ứng dụng Công nghệ thông tin (FAIR); Hà Nội, ngày 9-10/7/2015 CAEER: CHANNEL ASSIGNMENT AND ENERGY-EFFICIENT ROUTING PROTOCOL IN COGNITIVE RADIO ADHOC NETWORK Nguyen Duy Tan 1 , Nguyen Dinh Viet 2 1 Faculty of Information Technology, Hung Yen University of Technology Education 2 Faculty of Information Technology, University of Engineering and Technology, VNU, Hanoi tanndhyvn@gmail.com, vietnd@vnu.edu.vn ABSTRACT - One of the main challenging factors for designing routing protocols in cognitive radio ad-hoc network (CRAHNs) is how to select route for which can save energy battery for devices and avoid interference to primary users (PU). To solve this problem. In this paper, we propose channel assignment and energy-efficient routing (CAEER) protocol in multi-hop and multi-channel CRAHNs. The proposed routing scheme suggests an intelligent multi-channel selection function, which is used to assign an appropriate channel for link to build route based on interference avoidance to PUs. Moreover, our routing metrics also consider necessarily the path which reduces energy consumption and control overhead. Our simulation results show that CAEER performs better than weighted cumulative expected transmission time (WCETT) and Multi-radio Multichannel Ad-Hoc on-Demand Distance Vector (MM-AODV) protocols in term of energy consumption and the control overhead. Keywords - Cognitive radio, Ad-hoc, Channel assignment, Interference avoidance, Energy-efficient, Routing. I. INTRODUCTION In recent years, the fixed radio spectrum for wireless networks is becoming ineffective and wasting precious spectrum resources. According to the Federal Communications Commission (FCC) report that most of fixed spectrum bands (licensed bands) are of low utilization [9], [11] while unlicensed spectrum bands are more and more crowded. For instance, the licensed spectrum includes the UHF/VHF TV frequency bands. The unlicensed spectrum, which user can access freely, includes the industry, scientific and medical (ISM such as IEEE 802.11, IEEE 802.15.4, wireless local area network (WLANs), Bluetooth and ZigBee) and unlicensed national information infrastructure (U-NII) [8]. To solve this problem, cognitive radio (CR) [1], [16] has been considered as a promising technology for using the valuable spectrum frequency band opportunistically without harmful interference to the PUs. CR devices can identify sense, transfer and access the unused portion of the available spectrum band called spectrum opportunity. Cognitive radio ad hoc networks (CRAHNs) consists of a collection of PDA, Pocket PC, laptop, etc., that work on different spectrum bands (channels) and usually use battery energy. There are two types of users in CRAHNs: one is primary user (PU), which works on its licensed spectrum band (e.g., TV broadcast bands and some cellular bands). The other is cognitive user or secondary user (SU), which is equipped multi-interface with capabilities of sensing the available channel (or spectrum hole), to select the best band for communication. Furthermore, in CRHNs, the CR nodes can be self-organized, self-reconfiguration radio frequency and access the licensed band opportunistically when no PU uses that band and vacate the band as soon as PU start working on it. On-demand routing in multi-hop multi-channel CRAHNs faces several new challenges. An essential challenge is the collaboration between the channel assignment (channel decision) and route selection because of random occurring of PU in SU working area and avoiding interference to PUs. Nodes may dynamically work on different available channels. Therefore, routing algorithm should assign available channel for links in order to avoid interference to the PUs on the same channel. Another challenge is the energy management. Energy-efficient routing algorithm can be achieved high performance and long network lifetime. It also reduces the network partition caused by the energy exhaustion of the intermediate SUs. The third challenge is the route maintenance and recovery the broken link. Link failure in multi-hop multi- channel CRAHNs can happen due to the mobility of nodes, the sudden appearance of PUs or dead node. Consequently, how to improve the efficiency of using available spectrum bands and reduce energy consumption for wireless devices is still an open direction for researchers. In [11], Probabilistic Path Selection in Opportunistic CR Networks (PPSO) was proposed a novel routing metric, which determines probability lognormal cumulative distribution function (CDF) of the PU-to-CR interference on given channel. Let C i kj , D and P i I,j be the maximum channel capacity given by Shannon, the rate demand and the total PR-to-CR interference at CR node j over channel i, respectively. The routing metric is calculated as following: [ ] ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎣ ⎡ − − ≤ = ≥ 0 / , 1 2 Pr Pr N P P D C i w D i rj i j I i kj (1) Where N 0 , P i rj , W i denotes the power of the white Gaussian noise, the power of the received signal and bandwidth on channel i, respectively. The route selected will have the highest probability lognormal CDF to become the most probabilistically stable route to the destination node.