Emulating co-channel interference in wireless networks using equivalent low-tap filters

Abstract

In emulating a multi-node wireless network, received interference can be represented by combining the multipath responses of the interfering links. Each multipath response can be described by a set of mean-squared amplitude of the multipath components and relative delays. The number of filter taps required per link to emulate the actual (`true') channel is a function of the channel bandwidth W and RMS delay spread τrms. Assuming each per-link channel to have an exponentially decaying power delay profile, this value is about 4Wτrms. We propose to emulate each link using n uniformly-spaced taps of equal mean-square gain. For this case, the required number of taps is only 2Wτrms, while maintaining the important characteristic (i.e., the CDF of total power, taken over the fading) of the true channel. We derive this result analytically and confirm it by simulation. Improving on this 50% reduction in required taps, we further show that the loss in accuracy is significantly low so long as the total number of taps is the order of 16 or more. For large values of Wτrms, this can lead to even more reduction in n and, thus, further limit the cost and complexity of emulators.