Study On Energy-Saving Methods In LR-WPAN Based On Network Layer

ZigBee technology is a low data rate, low power consumption, low cost wireless networking protocol targeted towards automation and remote control applications. IEEE 802.15.4 committee started working on a low data rate standard a short while later. Then the ZigBee Alliance and the IEEE decided to join forces and ZigBee is the commercial name for this technology. IEEE and ZigBee Alliance have been working closely to specify the entire protocol stack. IEEE 802.15.4 focuses on the specification of the lower two layers of the protocol: physical layer and media access control layer. On the other hand, ZigBee Alliance aims to provide the upper layers of the protocol stack:network layer and application layer. LR-WPAN is just based on this protocol. Compared to WLANs and other WPANs, the main features of LR-WPAN are simple network structure, low cost, very low power consumption, and low data rate. At present, the main research focus in LR-WPAN is to save energy.Comprehensive research work on the ZigBee protocol for LR-WPAN was made in this paper. A series of algorithms and corresponding ways were proposed, which is on the existing problems of the routing and ZigBee network connecting of the network layer. The creative work of the whole paper includes three aspects: 1) Because of the Tree routing is not flexible and low efficiency, the improvemened neighbor-routing algorithm by using the neighbor table had been proposed: finding the common neighbor nodes between the source nodes and destination nodes; establishing a strategy on selecting neighbor nodes with the routing cost, which avoided the same nodes with reducing complexity and memory. The algorithm could save more energy for the original Tree routing in ZigBee network. 2) It was the first time that we proposed a kind of energy optimization routing way for ZigBee in the view of node characteristics, according to the percentage of RN- nodes impacting the ZigBee network performance with the different data flows. It could provide instructive theoretical reference for ZigBee practical applications. 3) The improved orphan nodes-reduced mechanism was presented based on the orphan nodes during ZigBee network connecting period. This mechanism adjusted the connecting process of the joining nodes and potential parent nodes, which could improve network connectivity and avoid redundant network overhead. It established the theory foundation for practical node energy-saving deployment in ZigBee network and wireless sensor network.This thesis consists of six chapters:The research development for several key contents, important research objectives and characteristics of LR-WPAN were summarized in the first chapter. The main research work and the chapter structure of this thesis were specified.In the second chapter, the IEEE 802.15.4/ZigBee protocol was introduced. They are the physical layer and media access control layer in IEEE 802.15.4 standard, the network layer and application layer in ZigBee specification respectively. Then the ZigBee device types and the network connecting were summarized. The corresponding theories provided research foundation for the following chapters.In the third chapter, the ZigBee energy-saving tree routing algorithm was studied. Based on deeply studying the tree routing in ZigBee, we found that Tree routing is simplified routing where the node communication is restricted to parent-child links only. There is no any routing discovery and any routing overhead in the tree routing. However, one drawback is that it may not be flexible, especially in the large scale network, which resulting in transmission imbalance, low efficiency and energy consumption. So the improvemened neighbor-routing algorithm (NTR) by using the neighbor table had been proposed in this paper: finding the common neighbor nodes between the source nodes and destination nodes; establishing a strategy on selecting neighbor nodes, which could ensure that the selected nodes were different ones. The strategy avoided the same nodes which brought redundant complexity and memory. The NTR algorithm could reduce the network costs and end to end delay, resulting in the energy conservation and the real time of the network enhancement.In the fourth chapter, it was the first time that we proposed a kind of routing way for ZigBee in the view of node characteristics for the purpose of energy consumption. In ZigBee network, the routing algorithms about the two kinds of nodes RN+ and RN- had been deeply studied in this paper, meanwhile the energy optimization routing way had been proposed in the view of node characteristics. We studied that the gradually increasing ratio of RN- nodes impacted network performance, such as end to end delay, packet delivery ratio and residual energy etc with different data flows. The test showed the more the data flows are in the network, the smaller the respective packet delivery ratios are. The packet delivery ratio already reduced to below 39.79% with above 20 data flows in the network especially. With the increasing number of RN- to the total routers, the end to end delays do not change obviously. While the residual energy is the most as to different data flows with the 40% percentage of RN-. The results showed that the 40% percentage of RN- is more excellent in deciding routing performance and energy optimization. It also could provide instructive theoretical reference for ZigBee practical applications.In the fifth chapter, the ZigBee network orphan node-reducing connecting mechanism was proposed. For ZigBee network and wireless sensor network deployment could produce orphan nodes, bringing about increasing network cost, we proposed an improved orphan node-reducing network connecting mechanism. By deeply studying ZigBee connecting network process, we found that address assignment algorithm in the specification restricted the value Cm and Lm, resulting in some orphan nodes without address network. This mechanism adjusted the connecting process of joining nodes and potential parent nodes according to the reserved bits of beacon payload and the added commands. This could reduced the number of orphan nodes in the process of connecting network, improve network connectivity and avoid redundant network overhead without adding additional length of beacon payload. This mechanism might reduce network costs and energy consumption.A conclusion for the entire thesis was made in the sixth chapter. And the issues that needed to be investigated and solved in the future research on LR-WPAN were pointed.