Modeling and analysis of network protocols for automatic meter reading systems using power line communications

Utilities now look at the deployment of automatic meter reading (AMR) systems to reduce the operating costs, improve meter reading accuracy, eliminate man-made errors and improve efficiency through demand management. The inherent communication infrastructure presented by power line communications (PLC), which significantly reduces the cost of building a new communication network, makes PLC a favorable solution for AMR communication networks. Power supply networks, however, are not designed for communication because the PLC channel is characterized by large, and frequency-dependant attenuation, changing impedance and fading as well as unfavorable noise conditions. Therefore it is important to develop a robust and stable network protocol that meets the working conditions and requirements for PLC channels in order to make PLC network systems competitive with other access technologies. The objective of this thesis is to investigate suitable network protocols for use in PLC based AMR systems and to study their performances using narrowband and broadband PLC technologies. One of the typical problems associated with PLC-based AMR systems is the “hidden node” problem. A “hidden node” is a meter unit that cannot communicate directly with the data concentrator (DC). The “hidden node” problem is not caused by a meter’s own malfunction but because of the significant signal attenuation along cables, the noisy power line environment and the varying in-home impedance. These affect the efficiency and reliability of PLC-based AMR systems. Furthermore, the impulsive noise interference on the PLC channel also considerably influences the performance of the AMR system. Over the years, much research has been done on the mitigation of impulsive noise interference through physical (PHY) layer or PHY/MAC cross-layer designs. There also has been some research on the fundamentals of AMR systems using PLC. There is, however, no significant research on the effect of impulsive noise interference on AMR system performance. Phase 1 of this research seeks to develop analytical models to analyze the performances of the two AMR protocols, namely clustered simple polling (CSP) and neighbor relay polling (NRP), under impulsive noise interference. The performance analyses show that the NRP protocol performs better than the CSP protocol in terms of throughput but requires longer data collection delay to cater for re-polling of failed meter units. Both the CSP and NRP protocols do not perform well under heavy impulsive noise interference, resulting in a drop to 0.2% of successful metering data collection. However, high throughput can be achieved for moderate and heavy impulsive noise interference environments by reduction of the packet size of the AMR system. Phase 1 of the research demonstrates that the delay associated with the polling-based protocol is generally higher and increases with the number of nodes connected to the DC. Furthermore, polling-based protocols lack the important capability for automatic association of new devices to the system. Therefore, Phase 2 of the research proposes a new and effective communication protocol for implementation in PLC-based AMR systems and presents analytical models to study its performance. The protocol utilizes a novel packet routing system which combines “Request” and “Data” packets that enable meter units to send their metering data to the DC and at the same time re-broadcast the “Request” to other meter units. The protocol ensures significantly lower data collection delay than the NRP protocol. It will be able to achieve 100% throughput for light and moderate impulsive noise interference environments and 75% throughput for a heavy impulsive noise interference environment using broadband PLC with a cluster size larger than 60. The protocol does not require a central controller to initiate all data transmission unlike polling based protocols and can be applied to PLC systems with unstructured networks. Finally, with AMR being part of an advanced metering infrastructure (AMI) in smart grid technology, Phase 3 of the research proposes a communication infrastructure for implementation of AMI in the Intelligent Energy System pilot project at Nanyang Technological University, Singapore and presents analytical models to study its performance. The proposed AMI communication infrastructure utilizes a hybrid PLC and Worldwide Interoperability for Microwave Access (WiMAX) technology for the last mile and backhaul communications respectively. The PLC-based communication employs the packet routing protocol developed in Phase 2 of this research. The WiMAX-based communication operates on the 3.5GHz licensed band satisfying the Standford University Interim (SUI) model for path loss prediction. The proposed AMI completes the data collection of 1250 meter units in less than 205 seconds. The proposed AMI achieves 100% throughput for Pg > 0.5 in environment without impulsive noise interference, where Pg is the probability that a meter unit can directly communicate with the DC or a relay meter unit. It is also able to achieve less than 5% drop in throughput for light and moderate impulsive noise environments.DOCTOR OF PHILOSOPHY (EEE