On the simulation of fixed wireless users in NS-2

In this article we propose a new simulation module for NS-2 able to reproduce the performance of fixed terminals operating in a wireless network with one or more antennas at the receive end, based on empirical models validated on the literature. This is relevant to perform accurate cross layer analyses of fixed wireless systems as Wireless Local Loop, relay networks, WiMax for fixed or repositionable users or sensor networks. To the best of our knowledge, published modules for NS-2 assume that all the stations are moving during the simulation or that published PHY models for mobile systems are also applicable to the fixed case. We show that while the latter method may be valid as a first approach, the shape of the Doppler spectrum for both cases differ significantly and performance metrics as packet loss rate will not be predicted well in all cases when using an inappropriate channel model. We also show that (as expected) a maximum ratio combiner with uncorrelated antennas achieves a higher throughput than equal gain or selection combiners.