Adaptive VoLTE and Data Traffic Offloading with Cell Range Expansion in LTE-A Heterogeneous Networks

在第四代行動通訊系統中，有效分流可提高使用者效能。基地台提供服務多元，包括語音服務與上網服務，且服務所使用的是共用資源。過載的基地台會提供差的語音品質服務及低速率的上網服務。 毫微型基地台被使用在傳統蜂巢式網路周圍，形成異構性網路，讓負載可分流至毫微型基地台，但減低過載基地台的負載成效不大，所以最近毫微型基地台擴展被使用在增加分流的人數。 而我們使用粒子群聚演算法，得到在混合流量之下在異構性網路的毫微型基地台擴展的偏壓數值，改善語音品質服務及低速率的上網服務情形。As all-IP network is deployed in the near future, voice over LTE (VoLTE) is considered as a solution to provide voice service in LTE network. The explosion of demands for mobile data also spurs LTE to maintain the data rate of cell-edge user. Allocating resource for data and voice usage properly is important. In thesis, there are two kinds of resource of downlink air interface. One is resource block (RB) and another is control channel (CCH) which is used to assign RBs for a user. We use semi-persistent scheduling (SPS) to simulate the result of resource allocation with voice traffic. And we compare the metrics as MOS, R-value and capacity with dynamic scheduling (DS). The number of CCH resources which we needed is significantly reduced by using SPS. Cell range expansion (CRE) is a newly discussed cell association method, and we formulate the solution as an optimization problem which is aim to maximize the summation of two Jain’s fairness indices (JFIs) fractions of virtual load and log normalized throughput by adjusting the CRE bias. The approach is to adjust CRE bias with constrained particle swarm optimization (PSO) to maximize the goal. The aim is to get a proper CRE bias to let voice capacity and 5%-tile data rate increase.1 Introduction 1 2 Background And Related Work 5 2.1 LTE Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2 LTE Channel and Throughput . . . . . . . . . . . . . . . . . . . . 9 2.3 Cell Range Expansion . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4 Voice over LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.5 Voice Codec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.6 Scheduling Method . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.7 Delay Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.8 Performance Metric for Voice Packet, VoLTE User, Serving BS . . 31 2.9 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 3 Problem Formulation 37 3.1 Network Topology . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.2 Load Balance Index for VoLTE Users PRB . . . . . . . . . . . . . 42 3.3 Load Balance Index for Data Traffic Users Throughput . . . . . . 43 3.4 Problem Formulation . . . . . . . . . . . . . . . . . . . . . . . . . 44 4 Methodology 47 4.1 Proposed Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 47 4.2 Constrained Particle Swarm Optimization . . . . . . . . . . . . . 50 5 Simulation Results 53 5.1 Simple Scenario for VoLTE Users . . . . . . . . . . . . . . . . . . 53 5.2 Simulation Environment . . . . . . . . . . . . . . . . . . . . . . . 61 5.3 Simulation Result . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 6 Conclusions 81 Bibliography 8