Abstract:
With the growth of different types of Internet traffic there is a compelling
need to provide better quality of service, especially, over the increasing
number of wireless networks. Expected Transmission Count (ETX) is a
high throughput route selection metric that measures link loss ratios. ETX
of a path reflects the total number of packet transmissions (including retransmission)
required to successfully deliver a data packet along that
path. Expected Transmission Time (ETT) is an improvement of ETX. ETT
of a path is a measure of the transmission time needed to successfully deliver
a packet along the path. ETT measures the loss ratio and the bandwidth
of the link. Both, ETX and ETT, in comparison to hop count, provide
better route selection for routing protocols widely used in Wireless Mesh
Networks (WMNs). Using minimum hop count to find the shortest path
has been shown to be inadequate for WMNs, as the selected routes often
include the weakest links.
This thesis presents a performance evaluation comparing hop count,
ETX and ETT when used with the Optimized Link State Routing version 2
(OLSRv2) protocol. This study is based on the wireless mesh topology of a
suburban residential area in New Zealand, and analyses the performance
of three common Internet traffic types in terms of throughput, end-to-end
delay, jitter and packet loss ratio, and presents findings that are closer to
the perspective of what an enduser experiences.
Also, a grid network of 121 nodes was used to analyze how the metrics
choose paths, the performance changes (for different path lengths) and
other conditions that affect the performance of the three metrics.
