Gugrajah_Yuvaan_ Ramesh_2003.pdf
Gugrajah_Yuvaan_ Ramesh_2003.pdf
Gugrajah_Yuvaan_ Ramesh_2003.pdf
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Adaptation ofthe Fixed Point Approximation to Ad Hoc Networks<br />
Chapter 5<br />
ADAPTATION OF THE FIXED-POINT<br />
APPROXIMATION TO AD HOC NETWORKS<br />
5.1. Introduction<br />
Chapter 5<br />
In this chapter an analytical model is proposed to evaluate the call blocking in a<br />
wireless ad hoc network employing CDMA. In the literature [Kaufman8l],<br />
[Kelly94], [Ross95], the reduced load method, in particular the' fixed-point<br />
approximation, has been used to evaluate blocking probability in wired networks<br />
modelled as loss networks. The call blocking probability in wireless CDMA systems<br />
has been evaluated using the Erlang capacity of the CDMA system and is based on<br />
the total interference being experienced by the base station. There is nothing in the<br />
literature, as far as the author is aware, that attempts to analytically evaluate the<br />
blocking probability in an ad hoc network due to the routing protocol that is<br />
implemented. The analytical model proposed is a combination and modification of<br />
the blocking probability methods used for wired networks proposed in [LiuOO] and<br />
the blocking probability evaluation of wireless cellular CDMA systems as proposed<br />
in [Gilhousen91], [Viterbi93], [Miller95], [Viterbi95] and [Narr99]. The blocking<br />
probability evaluation of wired networks and wireless cellular networks are<br />
discussed in Chapter 4.<br />
Since the ad hoc network is a wireless environment, it is assumed that congestion is<br />
due to the number of simultaneous calls being handled by a particular node, instead<br />
of using the capacity of links as the limiting factor. Nodes in an ad hoc network<br />
receiving transmissions from other peer nodes in the network are analogous to a base<br />
station in a cellular network receiving transmissions from mobiles within its cell.<br />
Since the only transmissions in an ad hoc network intended for a target node are<br />
5-1