# A Reconfigurable Formation and Disjoint Hierarchical Routing for Reshapeable Bluetooth Networks
###### Abstract  
In this paper, a reconfigurable mesh-tree with a disjoint hierarchical routing protocol for the Bluetooth sensor network is proposed. First, a designated root constructs a tree-shaped subnet and propagates parameters \(k\) and \(c\) in its downstream direction to determine new roots. Each new root asks its upstream master to start a return connection to convert the first tree-shaped subnet into a mesh-shaped subnet. At the same time, each new root repeats the same procedure as the designated root to build its own tree-shaped subnet, until the whole scatternet is formed. As a result, the reconfigurable mesh-tree constructs a mesh-shaped topology in one densely covered area that is extended by tree-shaped topology to other sparsely covered areas. To locate the optimum \(k\) layer for various sizes of networks, a peak-search method is introduced in the designated root to determine the optimum mesh-tree configuration. In addition, the reconfigurable mesh-tree can dynamically compute the optimum layer \(k\) when the size of the network changes in the topology maintenance phase. In order to deliver packets over the mesh-tree networks, a disjoint hierarchical routing protocol is designed during the scatternet formation phase to efficiently forward packets in-between the mesh-subnet and the tree-subnet. To achieve the energy balance design, two equal disjoint paths are generated, allowing each node to alleviate network congestion, since most traffic occurs at the mesh-subnet. Simulation results show that the joint reconfigurable method and routing algorithm generate an efficient scatternet configuration by achieving better scatternet and routing performance than BlueHRT (bluetooth hybrid ring tree). Furthermore, the disjoint routing with rechargeable battery strategy effectively improves network lifetime and demonstrates better energy efficiency than conventional routing methods. bluetooth; scatternet formation; topology configuration; routing; energy harvesting +
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can be used in several applications, such as home networking, environment monitoring and sensor or _ad hoc_ networks. With centralized infrastructures, many message delivery services are distributed via active Internet connection. Using smartphone applications, individual users can conduct packet transmissions to interested users over Bluetooth _ad hoc_ wireless connections, while methods for sharing information over delay-tolerant networks (DTN) are being developed [4] in order to achieve social routing over Bluetooth low energy (BLE) multi-hop scatternets. Increasingly, many BLE data applications are emerging in our daily lives, such as personal area networks, body area networks, sensor networks, _etc._ However, these applications pose some important research challenges, such as connecting BLE devices to share information between users, and forming the desired network configurations for various types of network applications. Bluetooth wireless technology makes it possible to transmit time-constraint video/audio in mobile and pervasive environments. Most wireless sensor network (WSN) applications are event-driven. The main WSN architecture has a multi-level network topology with a large number of sensor nodes deployed within a geographic area, often communicating to an external network through a gateway node. The information communication between the sensor nodes and the gateway node is a multi-hop architecture to extend the network coverage. Typical WSN applications with such Bluetooth topology include: video streaming transmission [5], health monitoring [6] and data collection [7]. However, the performance of WSNs is constrained by limited battery capacity. To date, several approaches have been introduced to reduce the energy consumption and correspondingly maximize the lifetime of WSNs, such as data aggregation, green routing and sleep scheduling mechanisms.