# MTRSRP: Joint Design of Multi-Triangular Ring and Self-Routing Protocol for BLE Networks
###### Abstract
Another innovation is the dual-ring tree topology [7], which is suitable for distributed scatternet construction in single- or multi-hop communication scenarios. Furthermore, efforts are underway to integrate mesh and ring subnets and explore a hybrid mesh ring topology [8] to optimize mesh links within a single configuration. Efficient routing within a scatternet is crucial and has led to the development of various routing protocols tailored for Bluetooth networks. These protocols include proactive [3; 6], reactive [9; 10], and hybrid schemes. Proactive protocols utilize local or global routing tables to create spanning tree scatternets, thereby facilitating packet forwarding. In contrast, reactive protocols dynamically discover routes that are effective in small-scale networks but may suffer from increased overhead as the network size increases. To mitigate this concern, a cluster-based flooding scheme reduces packet flooding during route discovery, thereby improving the routing performance. In addition, a self-routing protocol combined with a layer-based formation algorithm and preconfigured parameters minimizes route discovery overhead, enhancing network scalability and routing efficiency [11]. In this paper, we propose a multi-triangular ring and self-routing protocol (MTRSRP), which is a decentralized strategy designed to improve throughput and network efficiency in multi-ring scatternets. MTRSRP comprises two phases, namely, the leader election phase and the scatter formation phase, which together establish an efficient multi-triangular ring topology. During the leader election phase, the nodes exchange messages to gather node IDs, update tables, and elect a coordinator through a competitive process. Simultaneously, the scatternet formation phase determines the rings based on the coordinator information and predefined rules. The master nodes with the highest neighbor counts initiate unicast connections by following a role table to form piconets within the scatternet. The intra- and inter-bridge nodes then interconnect the piconets, creating a multi-triangular ring scatter net. MTRSRP also includes a self-routing addressing scheme that optimizes the packet transmission efficiency. The key contributions of MTRSRP are summarized as follows:  
1. Decentralized Control  
MTRSRP employs decentralized topology control, enabling nodes to autonomously elect a coordinator and form a multi-triangular ring structure. 2. Competitive Leader Election  
MTRSRP uses a competitive leader election process to ensure robust and efficient coordinator selection based on neighbor node information. 3. Multi-Triangular Ring Scatternet  
MTRSRP dynamically determines the number of rings and selects the master nodes with the highest neighbor counts during scattering, facilitating a cohesive multi-triangular ring structure. 4. Dual Bridge Connections  
The protocol utilizes dual intra-bridge and inter-bridge connections for seamless communication within and between piconets, thereby enhancing network connectivity and coverage. 5. Self-Routing with Shortest path  
MTRSRP integrates self-routing functionality within the triangular ring architecture, optimizes packet transmission paths, and reduces overhead by leveraging the established master/slave relationships during scatternet formation. Overall, the primary contributions of MTRSRP include enhancing the transmission rate, optimizing routing paths to reduce end-to-end delay, and improving network efficiency in multi-ring scatternets compared with other schemes, such as cluster-based on-demand routing protocol (CORP) [12] and Bluetooth low-energy mesh (BLEmesh) [13], through decentralized control and self-routing. The remainder of this paper is organized as follows. Section 2 provides an overview of the related research on topology construction and routing methods specific to BLE networks. Section 3 explores the design rationale, discusses piconet and scatternet designs, and defines the objectives of the MTRSRP network.