Ken Nakaoka

LQHR: A Link Quality-based Hybrid Routing Protocol for Wireless Ad Hoc Networks

This paper proposes a link quality-based hybrid routing (LQHR) protocol for wireless ad hoc networks. LQHR takes account of link quality such as SNR between adjacent nodes and the link utilization level of each node. In LQHR, each node maintains routing information produced by OLSR, which is a proactive routing protocol for ad hoc networks. When a source makes a communication request, it finds a route to the destination node on the basis of the link quality. We implemented LQHR on an experimental network, where laptop PCs were arranged on the same floor of a building, and audio-video streams were transmitted along a route selected by LQHR. To evaluate the effectiveness of LQHR in audio-video transmission, we compared application-level QoS of LQHR with that of the standard OLSR in the presence of another traffic flow in the network. As a result, we found that the routes selected by LQHR can provide shorter transmission delays and lower loss ratios in the transmission of the audio-video streams than those selected by the standard OLSR

Application-Level and User-Level QoS Assessment of Audio-Video IP Transmission over Cross-Layer Designed Wireless Ad Hoc Networks

SUMMARY This paper performs application-level QoS and user-level QoS assessment of audio-video streaming in cross-layer designed wireless ad hoc networks. In order to achieve high QoS at the user-level, we employ link quality-based routing in the network layer and media synchronization control in the application layer. We adopt three link quality-based routing protocols: OLSR-SS (Signal Strength), AODV-SS ,a ndLQHR (Link Quality-Based Hybrid Routing). OLSR-SS is a proactive routing protocol, while AODV-SS is a reactive one. LQHR is a hybrid protocol, which is a combination of proactive and reactive routing protocols. For applicationlevel QoS assessment, we performed computer simulation with ns-2 where an IEEE 802.11b mesh topology network with 24 nodes was assumed. We also assessed user-level QoS by a subjective experiment with 30 assessors. From the assessment results, we find AODV-SS the best for networks with long inter-node distances, while LQHR outperforms AODV-SS for short inter-node distances. In addition, we also examine characteristics of the three schemes with respect to the application-level QoS in random topology networks.