The 10th International Conference on Ubiquitous Robots and Ambient Intelligence (URAI 2013) Oct. 30 – Nov. 2, 2013 at Ramada Plaza, Jeju, Korea Link Quality Aware Route Selection in Heterogeneous Wireless Sensor Networks Adnan Fida, Nor Tuah Jaidi and Trung Dung Ngo Universiti Brunei Darussalam The More Than One Robotic Laboratory 11h8401@ubd.edu.bn, norjaidi.tuah@ubd.edu.bn, ngo.trungdung@ubd.edu.bn Abstract - This paper studies the problem of opti- mal route selection in heterogeneous wireless sensor net- works. The link quality aware route selection strat- egy is proposed by integrating realistic communication model depicting the underlying dynamics of wireless links. The Rician/Rayleigh fading environments consid- ers communication channels with both dominant Line of Sight (LOS) and non-dominant LOS (NLOS) where the desired signal between two sensor nodes is represented by Rician fading channel while the interfering signals are modelled by Rayleigh fading channel. Link quality is portrayed by reception probability i.e. probability of successfully received packets over a communication link. Reception probability of Rician/Rayleigh fading channel is utilized as a metric for link quality aware route selec- tion. Rician/Rayleigh metric based performance is com- pared with conventional route selection metrics based on simplified communication models. The simulation results demonstrate that incorporating Rician/Rayleigh metric based link quality in route selection process pro- vides routes with optimal end-to-end throughput. Keywords - Route selection, Rician fading, link quality, throughput 1. Introduction Wireless sensor networks (WSNs) are envisioned to have a significant impact on wide range of applications such as rescue operations [1], surveillance missions [2], and habitat monitoring [3]. Fundamental operations of wireless sensor network require acquiring information through sensing and transferring the collected informa- tion to peer nodes or base station. The sensor nodes re- quires reliable communication with other neighbouring nodes in an ad-hoc network to form multihop routing of wireless sensor nodes acting as relay forwarding data to other nodes. In the scope of this paper, it is assumed that sensor nodes have collected environment exploited data through their sensing capability and collected information must be transferred to peer nodes or base station through self- organized ad hoc network. WSNs borrow the existing routing literature available for ad hoc networks. The vari- ation in signal strength due to fading is an overlooked fact in conventional route selection strategies based on simpli- fied assumptions and unrealistic communication models. As the monitoring area becomes smaller, the effects of the channel impairments become different from the tradi- tional ones such as shadowing and doppler effects. The dominant effect in such scenarios is characterized by Ri- cian fading which appears when there is a line of sight between transmitting and receiving nodes. The received signal is considered as a set of scattered components plus a dominant component, thus interference characteristics in heterogeneous networks are significantly different than in homogeneous networks. Different interference scenar- ios in heterogeneous networks are provided in [5] and it can be inferred that it is highly probable to have a situ- ation where the desired signal experiences line-of-sight and interfering signals experience non-line-of-sight con- ditions. In this paper, link quality aware route selection scheme is proposed to estimate the quality of communication us- ing realistic communication links in Rician/Rayleigh fad- ing environment. This scheme uses reception probabil- ity as a metric to search for high end-to-end throughput routes. This integration of link quality and route selection is necessary to realize the realistic capacities of wireless sensor networks. 2. Related Work The conventional wireless route selection schemes in multihop networks are based on simplified communica- tion models such as binary link model where nodes per- fectly communicate within a transmission radius [6]. The Hop Count (HC) metric is based on the concept of binary link model and is widely used in ad hoc networks [7] [8] because of its simplicity in implementation. Hop Count metric aims to minimize the number of hops on the route between source and destination nodes. Another popular approach is to use Euclidean Distance (ED) as route se- lection metric utilizing the geographic position of nodes [9]. This metric relies on disk graph models where sig- nal strength decays according to distance [10] [11][12] neglecting the fact that link quality can change drasti- cally due to fading. The route selection metrics based on simplistic communication models does not generate routes with higher throughput as it neglects the sensitiv- ity of wireless links. [13] show that variations of wire- less links in realistic environment strongly influence the performance of ad hoc wireless networks. Furthermore, [14] explained that simplistic assumptions of disk models yields unrealistic inclusions and limitations. Recently, link quality incorporation with route selec- tion is considered to find the high quality routes. A link quality estimation based routing protocol (LQER) is pre-