Abstract
In this paper, we consider the optimization of wireless capacity-limited back-haul links in future heterogeneous networks (HetNets). We assume that the HetNet is formed with one macro-cell base station (MBS), which is associated with multiple small-cell base stations (SBSs). It is also assumed both the MBS and the SBSs are equipped with massive arrays, while all mobiles users (macro-cell and small-cell users) have single antenna. For the back-haul links, we propose to use a capacity-aware beam-forming scheme at the SBSs and MRC at the MBS. Using particle swarm optimization (PSO), each SBS seeks the optimal transmit weight vectors that maximize the back-haul up-link capacity and the access up-links signal-to-interference plus noise ratio (SINR). The performance evaluation in terms of the symbol error rate (SER) and the ergodic system capacity shows that the proposed capacity-aware back-haul link scheme achieves similar or better performance than traditional wireless back-haul links and requires considerably less computational complexity.
Highlights
Deploying small cell networks over existing macro-cellular networks, known as heterogeneous networks (HetNets), has emerged as a promising solution to deal with the increasing wireless traffic demands in generation 5G cellular networks [1]-[6]
In CR-HetNets, macro-cell users, which are considered as primary users (PUs) take the priority to access the channels, whereas small-cell users, which are considered as secondary users (SUs), can access the channels as long as the corresponding PUs do not use them
For the backhaul link we assume an multiuser multi-input multi-output (MU-MIMO) system with capacity-aware beamforming at each small-cell base stations (SBSs) and maximum ratio combining (MRC) detection at the macro-cell base station (MBS)
Summary
Deploying small cell networks over existing macro-cellular networks, known as heterogeneous networks (HetNets), has emerged as a promising solution to deal with the increasing wireless traffic demands in generation 5G cellular networks [1]-[6]. In CR-HetNets, macro-cell users, which are considered as primary users (PUs) take the priority to access the channels, whereas small-cell users, which are considered as secondary users (SUs), can access the channels as long as the corresponding PUs do not use them Under the assumption of very large number of antennas at the SBSs and the MBS, we derive semi-analytic expressions for the symbol error rate (SER) and the ergodic channel capacity, which quantify the reliability and spectral efficiency of the MU-MIMO based HetNet. The derived expressions are validated with Monte-Carlo simulation and used to evaluate the performance of the proposed PSO-based capacity-aware (PSO-CA) backhaul link.
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