Research On A New Method And Its Application Of Micro-power Wireless Automatic Meter Reading System Design

Wireless automatic meter reading (AMR) system has become one of the most potential applications of modern technologies. And its communication technologies and methods are becoming a hot reseach subject in smart meter reading field. There are three core issues on communication technologies of wireless AMR. The first issue is the low cost. Because the wireless meter reading system involves thousands of users, its own cost directly affects the user’s acceptance. The following one is low power consumption. The power of most meters is supplied from batteries. So energy-saving is a precondition for designing the network communication technologies and protocols. The last one is self-organizing network. To ensure that measured data of meter and commands of control center are transfered in time and accurately, the reliablility and self-healing capability are important requirements for wireless AMR network. Regarding a hierarchical architechure of wireless AMR as the research object, the dissertation focused on the communication methods for the three core issuses.(1) according to the meter reading architechure consisting of concentrators, collectors and meters, and the network characteristics completing the user specified meter reading tasks by wireless communication, the dissertation established a wireless meter reading network communication model including physical layer, MAC layer, network layer and application layer.(2) In order to get rid of dependence on foreign high-priced chips and reduce the cost of implementation of communication nodes, the physical layer of micro-power wireless network concentrated on algorithms and their implementations of digital signal modulation and demodulation, which were aimed for simple and low-cost characteristics. The dissertation studied on the modulation and demodulation algorithms which were realized simply and easily, and it would provide theoretical basis for the design of low-cost and low-power communication chips. The dissertation analyzed the OQPSK modulation scheme with half-sine shape, put forward a simplified method of modulation algorithm, which could reduce the realization cost of the modulator. To compensate for channel distortion by noise disturbance and eliminate inter-symbol interference by time dispersion, a variable step adaptive equalization technology was proposed to improve the communication quality. According to the data-aided LS algorithm citeria, a frequency offset estimator was derived to adapt multipath interference channel. And frequency offset could be obtained by lookup table. According to the phase characteristics between adjacent codes of OQPSK with half-sine shape, the differential detection method for demodulation with one bit correction capability was proposed. In order to save energy for the baseband processor, the frame detection mothod was put fowoad to start other signal processing work of the baseband.(3) The main task of MAC protocol is to adjust the access time of sharing channels among the various nodes, and reduce the probability of packets collision to decrease power consumption. According to the carrier sense multiple access with collision advoidance (CSMA/CA) which obtains the right to use communication channel in a competitive way in IEEE802.15.4, the dissertation proposed a CSMA/CA modified scheme that could effectively avoid collision or reduce the probability by analyzing the underlying information of clear channel accessment. The modified scheme could improve system throughput, energy consumption etc.(4) The routing algorithms of network layer are mainly to ensure nodes’ effetive communication and maintain the connectivity between nodes’ transportation path. The majority of nodes do not communicate directly with cencentrators, so they need forward data to concentrator with the help of intermediant nodes by means of multi-hop route. If the selection strategy for relaying nodes is unsuitable, it will lead to excessive use of a small number of nodes which will result fast energy consumption, then the nodes will break down finally. For reducing enery consumption and energy balance, an energy-efficient multi-level clustering algorithm was proposed. A mathematical model was set up to deduce optimal clusters among tiers and probablity of single-hop or multi-hop in cluster’s nodes. According to the optimal number of cluster heads to determine the number of collecctors, the cost of system implementation could be saved. At the same time, adopting single-hop and multi-hop hybrid communication method to transit data to cluster heads, the dissertation proposed routing implementation based on tree structure. The method could effectively disperse the energy consumption of nodes and extend the network lifetime.(5) For the verification difficulty of point-to-point communication capability and system performance, the dissertation gived a detailed verification method for the success rate of once communication and self-organizing capability. And the verification results were carefully analyzed. Furthermore, field results of the micro-power wireless AMR system relying on design methods have shown that the meter reading system was stable and reliable.For network characterics of micro-power wireless AMR network, the dissertation researched the communication methods of physical layer, MAC layer and network layer. And it effectively solved some issuses in micro-power wieless AMR system and process in industrialization. The results perfected and enriched the theory of AMR, and provide the theoretical basis and realization means for the design and development of micro-power wireless AMR.