Effect of Interference in Relay-Assisted Cellular Networks

Valentine A. Aalo, PI; Student: Constatntine Mukasa

Motivated by the increasing demand for higher data rate, broader coverage, and lower infrastructure cost in wireless systems, a major effort is being made to study the use of relay stations in wireless networks. Base stations require considerable infrastructure cost whereas relays require very low-cost, operate at low power, and have no connection to wired infrastructure. Thus, the use of multi-hop relaying can provide considerable performance improvement to a wireless network through coverage enhancement, range extension and capacity enhancement, at relatively low cost to the service provider. Studies have shown that that use of relaying technology is a reliable way to improve the performance through cooperative diversity and extend the coverage of many wireless communication systems. The performance of a multi-hop relaying system with amplify-and-forward (AF) transmission in which the transmitted signal propagates through cascaded nodes, with each node amplifying and forwarding the received signal from the previous node to the next node, is sometimes of interest.

project16-interferenceThe effect of interference on the performance of multi-hop relay networks has not been studied extensively in the literature. In this work, we develop an analytical tool to study the performance of a multi-hop transmission system with AF relays operating in a generalized fading environment in the presence of co-channel interference and thermal noise.

We assume that the transmitting terminals in a wireless network are distributed in a plane according to a homogeneous Poisson Point Process (PPP). The statistical characteristics of the aggregate interference power at each relay node depends on the statistics of the individual signals, the randomness of which depends on such system characteristics as propagation effects, location of interferer, mobility patterns, and user activity. When the interfering signals sum incoherently, then the aggregate interference can be modeled as a shot noise process whose distribution follows an a-stable distribution under certain conditions. Based on this interference model, we derive the performance of a multi-hop relay network in the presence of thermal noise and interference in a generalized fading environment. The main objective of this work is to quantify the effect of interference on the performance of multi-hop relay networks. To this end, we derive the statistics of the end-to-end signal-to-interference-and-noise ratio (SINR) and several performance metrics in the presence of co-channel interference. Specifically, our goal is to achieve the following: (i) develop a statistical framework to characterize the statistics of a multi-hop relay transmission system in which the relays employ the amplify-and-forward protocol and are located in a series network, (ii) derive closed-form expressions for relevant performance metrics in the presence of interference and noise in a fading environment, (iii) explore ways to cancel or mitigate the detrimental effect interference on system performance and (iv) validate the analytical results with extensive computer simulation using Matlab.

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