Gugrajah_Yuvaan_ Ramesh_2003.pdf

EvaLuation ofNetwork Blocking ProbabiLity
Chapter 4
EVALUATION OF NETWORK BLOCKING
PROBABILITY
4.1. Introduction
Chapter 4
Due to the frequently changing and unpredictable topology of ad hoc networks, an
efficient, distributed and dynamic routing protocol is required to ensure economical
usage of the bandwidth available. The routing protocols that have been proposed are
usually evaluated using discrete event simulators. One of the aims of the research
described in this dissertation is to develop a mathematical model for ad hoc networks
that can be used to evaluate the routing protocols and their resultant end to end
blocking probabilities. The blocking probability of a network is the probability that a
call offered to the network will be blocked due to insufficient resources. Analytical
methods for evaluating blocking probability can potentially generate estimates orders
of magnitude faster than simulation, and once refined can be used to determine
optimum bandwidth, power requirements, network user density and other factors
relevant to the development of viable ad hoc networks.
Throughout the 20 th century telecommunication engineers have employed loss
networks to model the performance of telephone systems [Ross95]. In a loss network
each call requires a fixed amount of bandwidth on every link on a route between the
source and destination. The call is admitted to the network and holds the requested
capacity for a certain amount of time if each link on the route has enough bandwidth
to satisfy the requirements. The call is rejected otherwise, and the blocking
probability is the probability that the call is rejected.
4-1