CogLEACH: A Spectrum Aware Clustering Protocol for Cognitive Radio Sensor Networks Rashad M. Eletreby, Hany M. Elsayed and Mohamed M. Khairy Department of Electronics and Electrical Communications Engineering, Faculty of Engineering, Cairo University, Egypt {reletreby,helsayed,mkhairy}@ieee.org Abstract—The integration of cognitive radios and wireless sensor networks enables a new paradigm of communication in which, sensor nodes can avoid heavily crowded transmission bands by tuning their transmission parameters to less crowded bands thanks to the cognitive radio capabilities. In such setting, sensor nodes act as a secondary user, opportunistically accessing vacant channels within a band originally licensed to a primary user. In this paper, we discuss the problem of how to cluster cognitive radio sensor nodes in a dynamic frequency environment set by the primary users. We introduce Cognitive LEACH (CogLEACH), which is a spectrum-aware extension of the Low Energy Adaptive Clustering Hierarchy (LEACH) protocol. CogLEACH is a fast, decentralized, spectrum-aware, and energy efficient clustering protocol for cognitive radio sensor networks. CogLEACH uses the number of vacant channels as a weight in the probability of each node to become a cluster head. We show that CogLEACH improves the throughput and lifetime of the network compared to the regular LEACH protocol that is operating in the same settings. Index Terms—clustering, cognitive radio, wireless sensor networks. I. I NTRODUCTION Due to the scarcity of the available radio spectrum and the rapidly growing demand, cognitive radios emerged as a solution to increase radio spectrum utilization. cognitive radios allow for the existence of a Secondary User (SU) system that is opportunistically accessing the vacant channels in a band originally licensed to a Primary User (PU) system [1]. The integration of cognitive radios with Wireless Sensor Networks (WSN) is introduced in [2]. In [2] authors identified that this integration could result in a new paradigm of sensor networks communication. In this paradigm, nodes can communicate (by tuning their radios to vacant channels) through a collision-free band instead of communicating through the heavily crowded unlicensed bands. This new communication paradigm opens the door to a new class of applications introduced by authors in [2], such as: • Multimedia applications where high bandwidth is needed. • Indoor sensing applications, where unlicensed bands are typically crowded. • Multi-class heterogeneous sensing applications, where networks with different objectives coexist together. However, this integration imposes a new protocol design constraint: spectrum-awareness along with the traditional Wireless Sensor Network (WSN) protocol design constraints (e.g. energy and computation constraints). Due to the energy limitation of a sensor node along with its possible operation in harsh environments, sensors are typically deployed randomly with large population and form a network in an ad-hoc manner. Such a scenario requires an energy-efficient routing protocol that accounts for scalability. Clustering is shown to achieve such constraints and generally enlarges the network lifetime [3]. The resulting network structure is composed of a two level hierarchy: Cluster Head (CH) nodes and member nodes. Each member node is attached to one of the CH nodes according to application-specific objectives (e.g. minimum distance CH to reduce transmission power) resulting in a cluster-shaped network. Member nodes send their data to their corresponding CH nodes instead of sending the data directly to the Base Station (BS) (i.e. reduce communication energy). Subsequently, CH nodes send these packets to the BS either in single-hop [4] or multi-hop [5]. In this paper, we introduce CogLEACH, which is a probabilistic clustering algorithm that uses the number of vacant channels as a weight in the probability of each node to become a cluster head. CogLEACH performs clustering with minimum number of exchanged messages, supports different network and PU models, and accounts for network scalability. CogLEACH is a spectrum-aware extension of the legacy LEACH protocol that is introduced in [4]. We show that CogLEACH improves the throughput and lifetime of the network compared to the regular LEACH protocol that is operating in the same settings. This paper is outlined as follows. In Section II, we survey the related research work. In Section III, we analytically introduce the CogLEACH Protocol. In Section IV, we describe our model parameters and assumptions, and evaluate the performance of CogLEACH through intensive Simulations. Finally, Section V concludes the paper. II. BACKGROUND Low Energy Adaptive Clustering Hierarchy (LEACH) [4] is considered the base line distributed clustering scheme for WSN. The operation of LEACH consists of cycles, where each cycle consists of N k rounds. In LEACH each node decides its state (CH or member node) autonomously through the CROWNCOM 2014, June 02-04, Oulu, Finland Copyright © 2014 ICST DOI 10.4108/icst.crowncom.2014.255370