This paper talks about ETX metric that ensures finding high-throughput paths in a wireless network. The authors argue that most protocols in wireless networks concentrate on minimizing the hop count when choosing paths for routing. Minimum hop count can maximize the distance traveled in each hop and large travel distances are likely to increase losses due to loss in signal strength. They propose ETX that requires few expected number of transmissions required to deliver packets to the destination.
As stated in the paper "ETX of a link is the predicted number of data transmissions required to send a packet over that link including retransmissions. ETX of a route is the sum of the ETX of each link in the route". Each link's ETX is calculated using forward and reverse delivery ratios of the link. Delivery ratio is the measured probability that a packet(data or ACK) successfully arrives at the recipient.
The main thing to take away from the paper is that the performance of a route is dependent on the packet delivery rate of the links. The packet delivery rate takes into consideration both the directions of communication where one direction is used to sending data and the other is used for sending ACKs.
The ETX metric performs better than shortest hop count routing protocols. It considers lossy links, asymmetric links and interference while choosing the routing path. The issues that still remain unanswered are network load (it does not consider congestion) and adaptiveness to mobility.
ETX is computed by each node broadcasting a probe packet every second. The probe packets sent are of fixed size at an average rate of T. These packets may not depict the same loss rate that the data packets may face. This can happen because data packets may be coming at a much higher rate and their size may be different as well.
As stated in the paper "ETX of a link is the predicted number of data transmissions required to send a packet over that link including retransmissions. ETX of a route is the sum of the ETX of each link in the route". Each link's ETX is calculated using forward and reverse delivery ratios of the link. Delivery ratio is the measured probability that a packet(data or ACK) successfully arrives at the recipient.
The main thing to take away from the paper is that the performance of a route is dependent on the packet delivery rate of the links. The packet delivery rate takes into consideration both the directions of communication where one direction is used to sending data and the other is used for sending ACKs.
The ETX metric performs better than shortest hop count routing protocols. It considers lossy links, asymmetric links and interference while choosing the routing path. The issues that still remain unanswered are network load (it does not consider congestion) and adaptiveness to mobility.
ETX is computed by each node broadcasting a probe packet every second. The probe packets sent are of fixed size at an average rate of T. These packets may not depict the same loss rate that the data packets may face. This can happen because data packets may be coming at a much higher rate and their size may be different as well.
No comments:
Post a Comment