Reclaiming the efficiency of opportunistic routing in wireless multi-hop networks

Abstract

145 probability from any forwarding candidate, which is different from traditional routing only relying on pre-defined path such as dynamic source routing (DSR) [2]. Therefore, OR can cope well with the fluctuant link quality that is typical characteristic of wireless networks.Cooperation mechanism is employed to coordinate the behaviors of forwarding candidates. Based on the mechanism used, existing ORs are divided into three groups: timer, network coding [3] and token [4]. Since no extra tokens or encoding modules are involved, timer-based OR is the most straightforward approach and could be implemented easily [1].One of the important issues for timer-based OR is transmission efficiency. To address this issue from theory, we propose an analytical model. Since more duplicate transmissions lead to longer queue delay and ineffective back-off mechanism causes larger back-off time for transmission (BTT), time overhead in this proposed model can well represent the efficiency. Accuracy of this model is validated by the accordance between theoretical values and experimental results. By applying the model to evaluate two typical ORs, named extremely opportunistic routing (ExOR) [5] and network layer broadcast with confirmed opportunity routing (NBC-OPP) [6], we find that coordinating the candidates without priorities or exclusively using a single priority for the cooperation is inefficient. Therefore, a Abstract: Opportunistic routing (OR) is an effective way to guarantee transmission reliability in wireless multi-hop networks. H o w e v e r, l i t t l e r e s e a r c h f o c u s e s o n transmission efficiency. Thus, an analytical model based on open queuing network withMarkov chains was proposed to evaluate the efficiency. By analyzing two typical ORs, we find duplicate transmission and collision avoidance overhead are the root reasons behind inefficiency. Therefore, a new scheme called dual priority cooperative opportunistic routing (DPCOR) was proposed. In DPCOR, forwarding candidates are configured with dual priority, which enables the network to classify forwarding candidates more effectively so as to reduce the back-off time and obtain more diversity gain. Theoretical analysis and simulation results show DPCOR achieves significant performance improvement with less time overhead compared with traditional routings and typical ORs.