Comparison of two routing metrics in OLSR on a grid based mesh network

Abstract

a b s t r a c tPredicting the performance of ad hoc networking protocols for mesh networks has typically been performed by making use of software based simulation tools. Experimental study and validation of such predictions is a vital to obtaining more realistic results, but may not be possible under the constrained environment of network simulators. This paper presents an experimental comparison of OLSR using the standard hysteresis routing metric and the ETX metric in a 7 by 7 grid of closely spaced Wi-Fi nodes to obtain more realistic results. The wireless grid is first modelled to extract its ability to emulate a real world multi-hop ad hoc network. This is followed by a detailed analysis of OLSR in terms of hop count, routing traffic overhead, throughput, delay, packet loss and route flapping in the wireless grid using the hysteresis and ETX routing metric. It was discovered that the ETX metric which has been extensively used in mesh networks around the world is fundamentally flawed when estimating optimal routes in real mesh networks and that the less sophisticated hysteresis metric shows better performance in large dense mesh networks.

Performance analysis of variable Smart Grid traffic over ad hoc Wireless Mesh Networks

“…The steepness in the degradation of HWMP can also be attributed to the large overheads generated by HWMP as well as the PREQ travel distance from the data concentrator (root node) as the network scales. This demonstrates a clear indication of the advantage of OLSR's MPR in achieving better reliability across larger multi-hop network [17] [18]. Fig.…”

Evaluation of mesh routing protocols for wireless community networks

“…Third, the path metric used by the olsrd.org implementation is based on the expected transmit count (ETX) metric [40] which, compared to the originally proposed hop count metric, provides a better reflection of the real path cost for transmitting a packet via wireless links. Although controversy on the best parameterization of this protocol exists (such as the findings published by Johnson and Hancke in [41] on the performance of ETX and the hysteresis-based hop count metric), we decided to base our experiments on the defaults of this implementation because their current selection still represents a common ground that reflects the experience from its usage in several community networks over many years.…”

Multipath optimized link state routing for mobile ad hoc networks

“…It has been extensively used in mesh networks around the world. In [33], the authors present a comparison between OLSR-RFC default hysteresis/hop count metric and OLSR-ETX metric in a mesh network testbed. However, their results reveal the ETX metric to be fundamentally flawed when estimating optimal routes in large dense mesh network and worse than the OLSR RFC standard.…”