Comparison of routing metrics for static multi-hop wireless networks

Abstract

Routing protocols for wireless ad hoc networks have traditionally focused on finding paths with minimum hop count. However, such paths can include slow or lossy links, leading to poor throughput. A routing algorithm can select better paths by explicitly taking the quality of the wireless links into account. In this paper, we conduct a detailed, empirical evaluation of the performance of three link-quality metrics-ETX, per-hop RTT, and per-hop packet pair-and compare them against minimum hop count. We study these metrics using a DSR-based routing protocol running in a wireless testbed. We find that the ETX metric has the best performance when all nodes are stationary. We also find that the per-hop RTT and per-hop packet-pair metrics perform poorly due to self-interference. Interestingly, the hop-count metric outperforms all of the link-quality metrics in a scenario where the sender is mobile.

Quality-Aware Routing Metrics in Wireless Mesh Networks

“…It has also been illustrated in different platforms (e.g., [13]) that in the presence of link variability, which is a common phenomenon in wireless mesh networks, minimum hop fails to have a satisfactory performance. …”

“…It is originally built as a part of a Multi-Radio Unification Protocol (MUP) -a channel assignment protocol for community networks-. Its application as a routing cost metric is implemented in [13].…”

“…In [13], the RTT metric is experimentally analyzed in a 23 node network in which every node pair initiates a long TCP session. The median of the average throughputs of all the sessions may be 75% lower when RTT is used instead of the simple hop count (which achieves around 1100 Kbps).…”

“…PktPair is built by [13] in an effort to modify per hop RTT, which is shown to be problematic due to two issues. First one is the self interference and the second one is the relative significance of the queueing delay compared to the transmission time in the overall cost.…”

“…It was shown in [13] that the ETX metric improves the average throughput of the TCP flows in the 23 node network (to 1357 Kbps) by 23.1% over the hop count metric. Also the frequency of the changes in the calculated optimal paths is only 3 times as much as the hop count, which implies that the effects leading to self interference are mostly suppressed.…”