Optimal Relay Placement in Cellular Networks

Abstract

International audience<p>In this paper, we address the problem of optimally placing relay nodes in a cellular network with the aim of maximizing cell capacity. In order to accurately model interference, we use a dynamic framework, in which users arrive at random time instants and locations, download a file and leave the system. A fixed point equation is solved to account for the interactions between stations. We also propose an extension of a fluid model to relay based cellular networks. This allows us to obtain quick approximations of the Signal to Interference plus Noise Ratio (SINR) that are very close to 3GPP LTE-A guideline results in terms of SINR distribution.We then use these formulas to develop a dedicated Simulated Annealing (SA) algorithm, which adapts dynamically the temperature to energy variations and uses a combination of coarse and fine grids to accelerate the search for an optimized solution. Simulations results are provided for both in-band and out-of-band relays. They show how relays should be placed in a cell in order to increase the capacity in case of uniform and non-uniform traffic. The crucial impact of the backhaul link is analyzed for in-band relays. Insights are given on the influence of shadowing.</p

Scheduling Impact on the Performance of Relay-Enhanced LTE-A Networks

“…The problem of optimally placing RNs in a cellular network has been tackled in [22]. Paper [22] does not however consider PF scheduling at all and focuses on the structure of the optimal placement using Simulated Annealing, which is a computationally intensive meta-heuristic. The engineering insights obtained by [22] are used here to design a faster placement policy.…”

“…Popular meta-heuristics, such as Simulated Annealing (SA) or Tabu Search, have been adopted in e.g. [39], [22] for relay placement but they also require a high number of computations and anyway provide a sub-optimal solution.…”

“…In this paper, based on the experience acquired from our previous work [22], we propose a RN placement heuristic algorithm, which yields sub-optimal but very quick results. The first idea of our proposal is to perform an exhaustive search over a well chosen subset of all possible RNs placements.…”

Downlink outage probability analysis in two-hop relay-assisted cellular network

“…The outage probability at the MS under the combined effect of path-loss, shadowing and fast fading i.e., P;�� MS can be obtained by starting with (8). As in the previo�s case, we ignore fast fading on interfering links and consider that only direct link suffers from the fast fading effects.…”

“…In [4], a model for outage probability has been used to analyze the impact of spatial correlation of shadowing on the coverage of multi-hop cellular system. In [8], the authors used the fluid model to calculate the SINR and the outage probabilities.…”