The Effectiveness of QoS Constrained AODV Routing for Voice Support in Multi-Hop IEEE802.11 Mobile Ad Hoc Networks

Quality of service (QoS) support for real-time applications (e.g., voice) in mobile ad hoc networks (MANETs) has drawn much attention from researchers nowadays. Currently, most of the efforts are only concentrated on the routing algorithms. This paper shows that the design of QoS routing algorithms should not be treated in isolation but must also consider the feature of medium access control (MAC) layer and QoS metric collection schemes. We investigate the feasibility and effectiveness of voice support in multi- hop IEEE802.11 MANETs using the QoS constrained ad hoc on demand distance vector (AODV) routing protocol. Three main findings are presented in this paper. First of all, we found that, using QoS constrained AODV routing in multi-hop IEEE802.11 MANETs, voice communication can only be supported in a very limited manner (i.e., in a network composed of around a hundred nodes with pedestrian speed or less). Secondly, our simulations in OPNET and analysis show that IEEE802.11 performs poorly in multi-hop MANETs due to its hidden node problem, and is the major obstacle of voice support. Thus, new MAC protocols or improvements at the physical layer are needed to support voice with QoS guarantee in MANETs. Thirdly, we found that QoS routing metrics play an important role in determining the performance of a QoS routing algorithm, which should be selected with caution.