We propose a four-stage hierarchical resource allocation scheme for the downlink of a large-scale small-cell network in the context of orthogonal frequency-division multiple access (OFDMA). Since interference limits the capabilities of such networks, resource allocation and interference management are crucial. However, obtaining the globally optimum resource allocation is exponentially complex and mathematically intractable. Here, we develop a partially decentralized algorithm to obtain an effective solution. The three major advantages of our work are as follows: 1) as opposed to a fixed resource allocation, we consider load demand at each access point (AP) when allocating spectrum; 2) to prevent overloaded APs, our scheme is dynamic in the sense that as the users move from one AP to the other, so do the allocated resources, if necessary, and such considerations generally result in huge computational complexity, which brings us to the third advantage: 3) we tackle complexity by introducing a hierarchical scheme comprising four phases: user association, load estimation, interference management via graph coloring, and scheduling. We provide mathematical analysis for the first three steps modeling the user and AP locations as Poisson point processes. Finally, we provide the results of numerical simulations to illustrate the efficacy of our scheme.
A more realistic simulation-based study of small-cell deployment in a heterogeneous network was reported by @cite_34 . The results suggest either coordination among layers or orthogonal spectrum allocation to improve outage rate. The authors of @cite_33 propose a combination of fractional frequency reuse (FFR) and orthogonal spectrum allocation in a two-tier network differentiating between commercial and home-based femtocells.
@cite_34 @cite_33
2073851917 1978180069
The main objective of the paper is to investigate and compare the downlink performance of different LTE heterogeneous network (HetNet) deployment solutions. By adding small cells to the existing macro overlay, network coverage and capacity can be significantly enhanced to accommodate the fast growth of mobile broadband traffic. Emphasis is put on how to optimally assign the spectrum for the different networks layers in an evolved HetNet including outdoor and indoor small cells. The study is conducted for a "Hot-Zone" scenario, i.e. a high-traffic area within a realistic dense urban deployment. A broadband traffic volume growth by a factor of 50 compared to today's levels is assumed. The investigated deployment schemes are outdoor pico-only, indoor femto-only and joint pico-femto deployments, all combined with an overlay macro layer. The results indicate that the best network coverage performance with a minimum user data rate of 1 Mbps is achieved when deploying small cells on dedicated channels rather than co-channel deployment. Furthermore, the joint pico and femto deployment turns out to be the right trade-off between increased base station density and enhanced network capacity. Heterogeneous networks consisting of small cells (e.g. femtocells) are capable of achieving high capacity and improving indoor cellular coverage area, while the fractional frequency reuse (FFR) scheme has been proposed for upcoming and future cellular systems to improve spectral efficiency in cellular OFDM networks. In two-tier networks of macrocells layered with femtocells, the resource allocation will most likely be sharing the same licensed spectrum. In this paper, we formulate a simple femtocells resource allocation strategies that allows a femtocells base station (FBS) to allocate more resources (co-channel) in high usage areas such as commercial FBS (cFBS) and orthogonal resource allocation for randomly deployed home user FBS (hFBS). We analyze our strategy in a multi-cell systems using area spectral efficiency (ASE) in composite fading consisting of Nakagami-m fading, path-loss and log-normal shadowing. Analytical and simulation results show that our simple resource allocation strategies are able to reduce inter-tier interferences and to offer an improvement in the overall spectral efficiency of the two-tier systems.