Analysis of the Competition Between Wired, DSL and Wireless Users in Access Networks
This paper analyzes the performance of a large population composed of
several classes of long lived TCP flows experiencing packet losses due
to random transmission errors and to congestion created by the sharing
of a common tail-drop or RED bottleneck router. Each class has a
different transmission error rate. This setting is used to analyze the
competition between wired and wireless users in an access network,
where one class (the wired class) has no or small (like BER in DSL)
transmission error losses whereas the other class has higher
transmission error losses, or the competition between DSL flows using
different coding schemes. We propose a natural and simple model for
the joint throughput evolution of several classes of TCP flows under
such a mix of losses. Two types of random transmission error losses
are considered: one where losses are Poisson and independent of the
rate of the flow, and one where the losses are still Poisson but with
an intensity that is proportional to the rate of the source. We show
that the large population model where the population tends to infinity
has a threshold (given in closed form) below which there are no
congestion losses at all in steady state, and above which there is a
stationary limiting regime in which we can compute both the mean value
and the distribution of the rate obtained by each class of flow. We
also show that the maximum mean value for the aggregated rate is
achieved at the threshold.
Philippe Nain
Last modified: Tue Mar 15 14:50:21 MET 2005