Energy Efficiency and Capacity Tradeoff in Cloud Radio Access Network of High-Speed Railways

Shichao Li,Siyu Lin,Lei Xiong,Xiaoyu Qiao,Qian Gao,Gang Zhu,Weiliang Xie

doi:10.1155/2017/5816862

Abstract

To meet the increasing demand of high-data-rate services of high-speed railway (HSR) passengers, cloud radio access network (C-RAN) is proposed. This paper investigates the tradeoff between energy efficiency (EE) performance and capacity in C-RAN of HSR. Considering that the train location can be predicted, we propose a predictable path loss based time domain power allocation method (PPTPA) to improve EE performance of HSR communication system. First, we consider that the communication system of HSR only bears the passenger information services (PISs). The energy-efficient power allocation problem with delay constraint is studied. The formulated problem is nonconvex. To deal with it, an equivalent convex problem is reformulated. Based on PPTPA, we propose an iterative algorithm to improve the EE performance. Second, we consider that the PISs and the train control services (TCSs) are all bore. A capacity optimization problem with joint EE and services transmission delay constraints is formulated. Based on PPTPA, we propose a hybrid power allocation scheme to improve the capacity of the system. Finally, we analyze the effect of small-scale fading on EE performance. The effectiveness of the proposed power allocation algorithm is validated by HSR channel measurement trace based emulation results and extensive simulation results.

Highlights

In the past couple of years, high-speed railways (HSR) are expanding rapidly all over the world
We firstly evaluate the EE performance of the proposed QoE Constrained EE Power Allocation (QCEPA) power allocation solution, and we analyze the impact of the service processing capacity of Virtual Machines (VMs) μ, channel fading factor m, data arrival rate λ, and different train speeds V on the EE performance
As can be seen, when the EE performance reduces from 100% to 95%, the capacity is increased by 11.76% compared to 5% EE loss

Summary

Introduction

In the past couple of years, high-speed railways (HSR) are expanding rapidly all over the world. The railway communication system plays a key role in HSR to bear the train control services (TCSs) and passenger information services (PISs) [1, 2]. Distributed antenna system (DAS) is consisted with radio remote units (RRUs) and base stations (BSs), but the radio resource cannot be shared between the RRUs, which limits the centralized processing gain of DAS. To mitigate this issue, cloud radio access network (CRAN) is proposed based on DAS structure [4, 5], in which a baseband unit (BBU) pool is instead of the distributed deployed BSs to handle the complex computational tasks. C-RAN can provide extensive radio coverage via super cell to limit the handover frequency

Objectives

Results

Conclusion