MAC Performance Evaluation in Low Voltage PLC Networks Mehdi Korki † , Hai L. Vu * , Chuan Heng Foh ‡ , Xiao Lu ‡ , and Nasser Hosseinzadeh † * Centre for Advanced Internet Architectures, Faculty of ICT, Swinburne Univ. of Technology † Faculty of EIS, Swinburne Univ. of Technology, Melbourne, VIC 3122, Australia ‡ School of Computer Engineering, Nanyang Technological University, Singapore {mkorki, hvu, nhosseinzadeh}@swin.edu.au; {aschfoh, luxi0007}@ntu.edu.sg Abstract— Power line communication (PLC) system refers to the use of power distribution networks for communication purposes. In this paper, we investigate the performance of the low voltage (LV) power lines for smart grid applications involving data transfer in a specific narrow, low frequency band. We pro- pose an analytical approach to obtain the line’s transfer function and conduct simulation to determine the performance of the LV PLC system in terms of bit error rate. We then evaluate the performance of the medium access control protocol (MAC) for the LV PLC network taking into account its physical characteristic and performance limitation. We show by simulation that packet loss in this network can be significant even with a light traffic condition due to the noisy channel, and the goodput declines sharply once the individual transmission rate is high enough to congest the network. We also show that the channel errors can be reduced by adjusting the MAC parameters to allow the retransmissions recouping losses. Keywords-Low voltage power line communication; medium access control protocol; performance evaluation; orthogonal fre- quency division multiplexing I. I NTRODUCTION The efficiency, safety and reliability of the electricity trans- mission and distribution system can be much improved by transforming the current electricity grids into an interactive (customers/operators) service network or smart grid. Further- more, smart grid aims to take advantage of the existing power distribution networks to provide value-added services such as network management and control, broadband Internet access or intelligent home where devices are communicating via the electricity wires. The electrical power system network is comprised of high voltage (HV), medium voltage (MV) and low voltage (LV) transmissions lines. The different transmission lines carry different power levels over different distances using various gauge aluminium conductors steel reinforced cables for elec- tric distribution. The power transmission lines are known to be non-ideal for communication purpose due to noise and unpredictable impedance and attenuation, which vary with time, frequency and location. Despite that fact, power line communication (PLC) has been using in the past to send control signals within the electricity grid [1]. Recent develop- ment of more sophisticated modulation (e.g. spread spectrum or multiple carrier modulation) and stronger error correction schemes has overcome earlier obstacles and enabled PLC at speeds comparable to other wired communication mediums. Due to its pervasive nature, PLC now becomes a real contender for an alternative infrastructure in providing services that require data communication. In particular, advanced metering infrastructure (AMI) is one of the smart grid applications that recently attracts consider- able interest from both industry and the research community. It is because AMI provides consumers with the ability to use electricity more efficiently and at the same time enables utilities to monitor and repair their network in real time. Early version of AMI has already been implemented (e.g. in part of Victoria, Australia [2]) using wireless technologies to collect meter readings remotely and automatically. In this paper, we investigate the use of LV transmission line as a medium for data communication between electric meters and the substation as a data concentrator point located on different parts of the distribution network. The recommended frequency band for communication in the AMI application is a narrow, low frequency band between 9 and 490 kHz [3]. Although the choice of LV line for AMI communication is natural as it connects pole-mounted transformers to individual homes associating with the electric meter, its characteristic and network performance from the medium access control point of view are not well understood in the literature. It is because the majority of the work in this area was focusing on indoor PLC network and at the high frequency band applicable for high- speed broadband access [4]. Note that if the PLC is to be extended beyond substation transformers to the MV network, data transmission should then bypass those transformers that have a great impact on PLC in the frequency range of interest. To this end, our contributions is twofold. We first describe in this paper an analytical model that enables us to obtain the transfer function of the LV PLC lines at the above specified frequency band for generic distribution networks (i.e., includ- ing outdoor transmission lines). Based on the obtained transfer function, we then investigate the performance of the LV PLC network as a data communication medium via simulation in terms of bit error rate (BER) versus the signal to noise ratio (SNR). Another major contribution of this paper is the evaluation of a medium access control (MAC) protocol for the LV PLC network based on our understanding of its physical characteristic and performance limitation. Both contributions are useful in designing and optimizing the PLC performance 135 ENERGY 2011 : The First International Conference on Smart Grids, Green Communications and IT Energy-aware Technologies Copyright (c) IARIA, 2011. ISBN: 978-1-61208-136-6