Research on Power Line Communications

Power line communications (PLC) has recently gained widespread interest as a viable alternative technology for broadband communications. This interest stems from the fact that PLC does not require substantial new investment for the communications infrastructure, but uses the existing low voltage (LV) power line distribution network that already penetrates into every residential, commercial and industrial premises to carry voice, data and video traffic.

However, the power line medium presents an extremely harsh environment to operate a communication system as characteristics such as line impedance, noise and attenuation can be highly variable with time, frequency and location. It is therefore necessary to study the power line channel and understand its unpredictable characteristics in order to optimize its use for broadband communications.

This research program is initiated to identify and overcome potential issues/barriers to the successful deployment of PLC technology. Recent projects being carried out include:

Power Line Channel Modeling

A comprehensive and versatile computer model of the power line channel has been developed in terms of transfer function, impedance and noise. In this model, power line is approximated as a transmission line, of which two intrinsic parameters, the characteristic impedance and propagation constants, are derived based on lumped-element circuit model. Using these intrinsic parameters, transfer characteristics for a N-branch power distribution network are derived based on the scattering matrix method. The model has been verified with practical measurements conducted on actual power networks. It has shown to accurately determine the line characteristics under different network configurations and when different household appliances are connected. The model helps to raise the understanding of adverse channel conditions and aids in the design of PLC systems.

MAC Protocols for PLC Systems

To minimize possible electromagnetic interferences (EMI), PLC access networks have to operate with limited signal power, which in turn may reduce the system data rate. In order to compete with other access technologies, PLC systems have to ensure higher levels of network utilization. A medium access control (MAC) protocol that maximizes network utilization is thus desired. Both mathematical and simulation models have been successfully developed for MAC protocol performance analysis under impulsive noise interference. Currently, a new protocol is being designed that would optimize packet length to achieve maximum network utilization in different PLC environments.

PLC Systems with Low EMI Radiation

Electromagnetic fields radiated from power lines may cause disruption to existing critical radio communication services. To address this issue, the research group has been collaborating with Agilent Technologies in the development of PLC systems with low EMI radiation. Recently, the potential use of optical couplers for broadband power line modems to reduce EMI radiation has been demonstrated. Mathematical models are being developed to predict radiated electromagnetic fields from power lines under different cabling arrangements. The project is also expected to explore new signal-injection technologies for suppressing EMI radiation from PLC systems to safeguard the public interests.

Building Monitoring and Control System

This is a new project initiated to develop a reliable PLC-based in-building monitoring and control system of interest to Surbana Technologies (a subsidiary of HDB). The project will use existing power lines as a communication medium to transmit data for monitoring and control of building functions such as lift alarm, water pump alarm, switch room alarm, etc. in HDB estates in Singapore.

For more information on professional services and research collaborations, please contact:

Asst Prof So Ping Lam

Program Director (Power Line Communications)

Network Technology Research Centre

Research TechnoPlaza

4th Storey, Slab Block

50 Nanyang Drive

Singapore 637553

Tel: (65) 6790 5026

Fax: (65) 6792 6894

Email: eplso@ntu.edu.sg