An enhanced routing metric for ad hoc networks based on real time testbed

摘要

The deployment of wireless ad-hoc networks compared to traditional infrastructure based networks offers several advantages such as fully distributed mobile operation, easy discovery of joining wireless devices and quick cheap network setup. The design of an effective routing protocol is one of the main challenges in the ad-hoc networking paradigm and the utilisation of an adequate link cost metric is essential. In this paper, the validity of ETX (Expected Transmission Count) as a link cost metric is investigated by studying its behaviour in real-time testbeds. In our performance evaluation, the ETX performance was studied in different distance scenarios. Subsequently, the main observation was that ETX values was not steady over time and usually fluctuated for a fixed scenario. Fluctuation in the ETX values affects a routing protocol in wrongly identifying the best path based on current ETX link cost and therefore new methods for ETX calculation are proposed in this paper. These different methods for ETX link cost calculation are compared with each other and the best link cost formula has been proposed as a new method for ETX calculation towards the end of the paper. The new ETX calculation is called AETX that could be used as a link cost in routing protocols that reflects the balance required between the consistency of a link metric value over time for fixed scenarios and the flexibility required to detect actual changes in link metric values. We finally provide conclusions about our research and some avenues for future work.