XCon: Cross layer topology controller for energy efficient LTE networks

In this study, we aim to design a controller (XCon) which optimizes energy-efficiency in the over-provisioned indoor 4G cellular networks for under-utilized eNodeBs. In this manner, we propose a novel energy efficiency coefficient (EEC) which covers conventional bits=joule energy efficiency metric and additionally contains parameters such as channel utilization and SINR. Moreover, we define an optimization problem which aims to maximize total EEC w.r.t network capacity and point-to-point delay (p2p). However, the introduction of the multi-parameter EEC increased the complexity of the optimization problem. In order to solve this problem, we propose a novel heuristic called “Two Phase Enhanced Branch and Bound” (TPEBB). This heuristic manipulates the network topology by closing underutilized eNodeBs during the first phase and forcing to offload an UE without closing any eNodeB during the second phase. Finally, we have compared the XCon with greedy and sleep-mode approaches under real-time and non real time traffic models in the evaluation section and shown that it provides moderate solution in terms of p2p delay and energy consumption.

I. Introduction

The efficiency of the energy usage in the current network technologies is becoming essential due to the proliferation of the smart devices. There are considerable number of studies which tries to optimize the energy consumption of the LTE networks [1]–[5]. But, none of these studies uses a cross layer approach which considers both interference and QoS demands of users. Most elementary solution to this problem is to implement sleep mode for the under-utilized or non-utilized eNodeBs. However, sleeping an eNodeB brings about many problems such as decreasing coverage area, and increasing interference [6]. This forces end-users to offload to another eNodeB with unacceptable QoSs. To increase energy efficiency and remove these negative effects, the dynamic mechanism is required that both guarantees keeping QoSs at acceptable levels and reduce energy consumption of network infrastructure. For this purpose, we propose the XCon which utilizes a novel as the objective function in an optimization problem in order to reduce energy consumption of the network while considering QoS constraints. uses additional parameters such as channel utilization and SINR. A cross-layer topology controller XCon has been proposed due to utilization of . XCon uses the proposed low-complexity TPEBB algorithm in order to solve the defined optimization problem. This algorithm manipulates the network topology by closing under-utilized eNodeBs during the first phase and forcing to offload an without closing any eNodeB during the second phase in order to acquire green topology. We also defined two different traffic types by using Markov models to validate XCon.