Abstract-Service discovery is an important part of realization towards ubiquitous computing with self-configurable mobile ad hoc networks. However, it is faced by the challenge of network dynamics due to node mobility. In this paper, we propose a signal strength based service discovery framework in mobile ad hoc networks. Service discovery is carried out selectively along reliable links by monitoring the qualities of wireless connections to neighbor nodes. We show by simulation that, compared to non-selective distributed service discovery, our approach achieves higher service success ratio, less message overhead and shorter service discovery latency. I. INTRODUCTION Service discovery in Mobile Ad hoc NETworks (MANET) is an important part of realization towards service access anytime, anywhere. However, it poses greater challenges than in traditional distributed systems, since service failure more often results from disconnection due to host migration [1] . Therefore, transient wireless medium and device roaming require a dedicated service discovery approach in MANET. The basic criteria for evaluating a service discovery scheme is the effectiveness with which: (1) service clients are able to find a service provider and (2) the service provider will successfully deliver the requested service. Since connections can be broken with nodes moving, the most important factor affecting service delivery success is the qualities of wireless connections along the service path between service provider and requester. Connectivity can be determined according to the relative distance (e.g., Euclidean distance) of the geographical positions of the nodes. For instance, physical proximity of service providers to service seekers has been proposed as a metric for service selection [2] . However, position acquiring is luxury and comes at a price. From current state of the art, one way to obtain (geographical) position is by using GPS. But GPS is an extra hardware and suffers from poor signals in indoor environments. Another way is by measuring relative locations from fixed, position-known base stations [3] . But We propose in this paper a simple, yet efficient, service discovery framework, based on signal quality. To our knowledge, our approach is the first effort to select mobile services in MANET based on link quality. The rest of this paper is organized as follows. Section II examines the wireless communication background and surveys related work. Section III proposes and elaborates our service discovery framework based on signal quality. And then Section IV presents simulation-based evaluation results. Finally, the paper finishes with concluding remarks and future work. A. Background The radio wave (signal) propagation is generally modeled by the combination of large scale and small scale propagation models [5] . Node movement over short distances (e.g., a few wavelengths) may cause the received signal strength, which is the sum of contributions of multiple components, to fluctuate rapidly, giving rise to small scale fading. As the node moves over longer distance, the local signal strength average (i.e., average of signals measured over a distance from 5A to 40A -about from 0.6m to 5m for 802.1 lb) gradually decreases. We call the distance locality distance and large-scale propagation model estimates the average signal over the locality distance. Large scale is of interest here because the aim of our work is to capture the movement tendency of the nodes, and thus to discover services that are less likely to fail because of movement-induced network disconnection. However, small scale fading makes it difficult to recognize the node's moving tendency and cannot be simply ignored. Small scale fading can be modeled by Ricean fading (with line of sight) or Rayleigh fading (with no line of sight) [5] . During signal transmission, the transmitter sends the signal with certain transmission power. Subject to large-scale and small-scale fading, the signal arrives at the receiver with certain power, along with the interference from background noise and other parties who share the same band. Each receiver has a receiver sensitivity, which is the power of the weakest signal that can be reliably heard and demodulated by the receiver, and a threshold Signal to Noise Ratio (SNR), defined as the 978-3-8007-
In REF , the authors exploit the variation tendency of signal strength to detect the relative movement between nodes, which is utilized to identify leaving and thus unreliable neighbors.
Signal strength based service discovery (S3D) in mobile ad hoc networks
2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications
2005 IEEE 16th International Symposium on Personal, Indoor and Mobile Radio Communications
Computer Science