Abstract

In this paper, a self-organizing cloud radio access network (C-RAN) is proposed, which dynamically adapt to varying network capacity demands. A load prediction model is considered for provisioning and allocation of base band units (BBUs) and remote radio heads (RRHs). The density of active BBUs and RRHs is scaled based on the concept of cell differentiation and integration (CDI) aiming efficient resource utilisation without sacrificing the overall quality of service (QoS). A CDI algorithm is proposed in which a semi-static CDI and dynamic BBU-RRH mapping for load balancing are performed jointly. Network load balance is formulated as a linear integer-based optimization problem with constraints. The semistatic part of CDI algorithm selects proper BBUs and RRHs for activation/deactivation after a fixed CDI cycle, and the dynamic part performs proper BBU to RRH mapping for network load balancing aiming maximum QoS with minimum possible handovers. A discrete particle swarm optimization (DPSO) is developed as an evolutionary algorithm to solve network load balancing optimization problem. The performance of DPSO is tested based on two problem scenarios and compared to genetic algorithm (GA) and the exhaustive search (ES) algorithm. The DPSO is observed to deliver optimum performance for small-scale networks and near optimum performance for large-scale networks. The DPSO has less complexity and is much faster than GA and ES algorithms. Computational results of a CDI-enabled C-RAN demonstrate significant throughput improvement compared to a fixed C-RAN, i.e., an average throughput increase of 45.53% and 42.102%, and an average blocked users reduction of 23.149%, and 20.903% is experienced for proportional fair and round Robin schedulers, respectively.

Highlights

  • T HE SURGING volume of mobile data traffic witnessed in the recent years is triggered by the dramatic growth in smart mobile devices, diverse mobile Internet enabled applications, and ever increasing wireless access demands

  • The instantaneous Signal-to-Interference-and-Noise-Ratio γ based on Channel Quality Information (CQI) received from user k in cell i served by remote radio heads (RRHs) n at the pth Physical Resource Block (PRB) of subframe τ is expressed as γkin,p(τ ) = N0 +

  • A load prediction model is considered for pro-active network scaling of base band units (BBUs) and RRHs

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Summary

INTRODUCTION

T HE SURGING volume of mobile data traffic witnessed in the recent years is triggered by the dramatic growth in smart mobile devices, diverse mobile Internet enabled applications, and ever increasing wireless access demands. Unlike conventional cellular networks, where the base stations are not always in peak time and often work in idle states with their resources not fully utilised, in C-RAN, suitable resource allocation schemes can dynamically adjust the logical connection between BBUs and RRHs. It is necessary for a system to optimise its resources according to varying traffic environments. In C-RAN the problem of resource wastage is overcome by dynamically allocating the shared and centralised BBUs resources to the RRHs. significant cost and energy savings can be achieved by dynamically scaling the BBUs concerning varying traffic caused by uneven user distribution in the network [9]. Significant energy savings can be achieved if the RRHs and BBUs are turned on/off in such a way that the QoS of the network is not degraded In this context, a two-stage design is proposed in this paper for efficient resource utilisation in a self-optimised CRAN with real time BBU-RRH mapping.

RELATED WORK
SELF-OPTIMISING CLOUD RADIO ACCESS NETWORK FRAMEWORK
C-RAN Architecture
System Model Constraints
Channel Model
LOAD PREDICTION AND BBU ESTIMATION
Load Prediction Based on Wiener Processes
Number of BBUs Required in the Network
DYNAMIC BBU-RRH CONFIGURATION AND FORMULATION
Key Performance Indicator for Load Fairness Index
Key Performance Indicator for Network Throughput
Key Performance Indicator for Handovers
Performance of DPSO Algorithm
Complexity Comparison
Performance Analysis of CDI Algorithm
Findings
CONCLUSION

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