| Bluetooth technology is an open global standard for short range wireless data and voice communication. Based on low cost short distance wireless communication, Bluetooth becomes a communication technology that provides special connections for fixed and mobile devices. It has many intriguing characteristics, such as low cost, low power, small size, and free spectrum. With the development and popularization of Bluetooth, there is increasing interest in wireless ad hoc networks built from portable devices equipped with Bluetooth. But the communication and network roles of Bluetooth make the new challenge in constructing and managing a wireless Ad Hoc network with the Bluetooth devices.The Bluetooth personal area network, which is composed of multi-devices, is one of the typical Ad Hoc. The Ad Hoc wireless mobile network based on Bluetooth is self-construction, self-organization and self-management wireless mobile network without additional network devices or manual configuration. There are two kinds of network formations, piconet and scatternet. It applies frequency-hopping spread spectrum technology in the MAC layer, so Bluetooth devices are not able to communicate unless they have previously discovered each other by synchronizing their frequency hopping patterns. Each piconet has its own frequency-hopping sequence. Within a piconet, a Bluetooth device can be either a master or a slave, each piconet has only one master and up to 7 active slaves, the communication between devices obeys on a centralized master-slave mechanism. Multiple piconets can co-exist in a common area and piconets can be interconnected via bridge device to form a larger , flexible and complex ad hoc network known as a scatternet. The Bluetooth personal area network is designed for the application scences of home and small offices. It can be used for voice communication, data communication, the connection and automatic information exchange of electrical devices and etc. The Bluetooth specification has not had feasible introduction on scatternet topology formation , packet routing, channel or link scheduling and access point. There is not an algorithm could achieve the best performance of Bluetooth network, so these questions are all current leading and import research issues of Bluetooth technology.To construct a Bluetooth Ad Hoc network topology, Bluetooth devices are inquired to discovery each other, and then to construct peer-to-peer physical connection in order to synchronize their frequency-hopping sequence and exchange their essential address and clock information. Better Ad Hoc topology construction algorithm can fastly carry out these steps to make devices within communication range form steady networks in a short time. Once Bluetooth Ad Hoc topology is constructed, as the base of network routing and scheduling, it will considerably influence on the whole network performances of the routing and scheduling.In this paper, we analyze the Bluetooth protocol, the characteristics of frequency hopping and master-slave mechanism, and then addresses the fundamental problem of Ad Hoc network formation, i.e., the problem of the self organization of Bluetooth devices into a multi-hop network. The whole work is devided into five parts:First, the basic concepts of Bluetooth technology ,Bluetooth PAN and the hot issues of Bluetooth technology were summarized. Then reviewed the Bluetooth Ad Hoc network construction algorithms. Finally, the main research work of the thesis were specified. Second, the basic concepts, characteristics and the scope of application of the Ad Hoc self-organized networks were introduced, then detailed analyzed the Bluetooth core protocol stack and application framework, and the supporting on the PAN network of the core. Focused on two physical links and the establishing process of communication link in Bluetooth. Then summarized the forms of the Bluetooth network and the application models of Bluetooth PAN, and analyzed the contacts and distinction of the Bluetooth PAN network and the Ad Hoc network. Finally, introduced other technologies of short range wireless communication.In the third part, several typical Bluetooth Ad Hoc network formation algorithms and their formative processes in literature were introduced and analyzed, anddescribed the algorithm of Bluetooth chain topology and took the dynamic simulation experiments and performance analysis. then compares the performances of the network construction algorithms above. The standards to evaluate an algorithm was about: (1) the connectedness of the formed network(2) average degree of the devices(3)delay of the network(4) the number of de- vices in each piconet(5) the number roles assumed by each node(6) self healing of the network(7)multi-hop characteristics(8) the average number of piconets(9) routing robustness(10) time complexity(11) network diameter(12) message complexity. Then pointed out the advantages and disadvantages of the various algorithms. Finally, concluded the demands of an algorithm and gave the important bridge node working mode.The fourth chapter is the kernel of this paper, a dynamic maintenance Bluetooth Ad Hoc network topology algorithm. The algorithm is based on the Bluetooth symmetric link, the algorithm is distributed, devices are independent each other, they are located at random and know none messages about their neighbors. This algorithm doesn't demand that the devices are in communication range. The core of the algorithm, through the nodes mutual discoveries, to elect the master control device according to their remainder energy and information processing capability of nodes, the master control device compute the number of piconets and masters of the network according to the algorithm. Then establish the role of the candidate master nodes, and then connect the temporary candidate master nodes to form the temporary master piconet. The master control node transfer the information of the slave and bridge nodes, which belong to every candidate master node. Next each master construct their piconet at the same time, then interconnection the network with bridge nodes. Finally a set of Bluetooth devices which are unknown quantitatively, distributed evenly at random, independent for each other and not located within communication range connect each other and form connected Bluetooth Ad Hoc network. After the formation of a Bluetooth scatternet, network operated the dynamic maintenance strategy, the master control device adopted the mechanism of master nodes alternation, each piconet adopted monitoring and back-up mechanism, when the maser or bridge nodes quit or malfunction, the mechanism would guarantee the network connection. This enhances scatternets'self-healing ability. The algorithm adapts to dynamic Ad Hoc network.Finally, we adopted BlueHoc Bluetooth network simulation software platform based on NS2 in Linux operating system to simulate the Bluetoothtopology algorithm of this paper, and analyzed the performance of the network. The result proves that the algorithm can be easily implemented. The formed scatternet has fewer piconets, network diameter is O(logN), the number of slaves in each piconet presented saturation, message complexity is O(N).The network performance was good and it's a practical Bluetooth Ad Hoc network topology algorithm.A conclusion for the entire thesis was made in the last of the thesis, and prospected what need to be investigated in the future. |
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