Gugrajah_Yuvaan_ Ramesh_2003.pdf

Adaptation ofthe Fixed Point Approximation to Ad Hoc Networks
Figure 5-4. Network topology used to obtain results
Chapter 5
The average blocking probability for the network for varying mean arrival rates per
node pair is shown in Figure 5-5. The mean arrival rate of calls for each node pair is
identical and the average blocking probability for the network is calculated as
(5-23)
In Figure 5-5 the call activity probability p, labelled as "rho" in the graphs, was
varied to investigate the effect of call activity probability on the blocking probability.
The ratio of the weighting factors, Wratio is 2. As expected, the larger the probability
of activity of a call, the larger the blocking probability for the network, however the
large difference in blocking probability for different p values is worthy of further
consideration. In the analysis of a communications system, when a node is assumed
to be transmitting with a certain probability while engaged in a call, it is important to
able to adequately characterise the value ofp based on experimental data. Due to the
lack of experimental data for ad hoc networks, p =0.45 is used for the results that
follow. Another striking feature of the graph in Figure 5-5 are the oscillations that
occur for a high probability of call activity. The analytical model becomes unstable
5-12