# Optimization of the AODV-Based Packet Forwarding Mechanism for BLE Mesh Networks
## 1 Introduction  
Bluetooth Low-Energy (BLE) is a Wireless Ad Hoc Network (WAHN) technology that is becoming increasingly popular among IoT devices that run on batteries. The Bluetooth Special Interest Group (SIG) introduced the BLE standard in Bluetooth Version 4.0, which was further improved in Bluetooth Versions 4.2 and 5 [1]. For multihop communications and network connections, BLE 4.x initially used the traditional Bluetooth-based Personal Area Network (PAN) paradigm. BLE 5 aims to address these flaws by implementing a flooding-based mesh architecture, which will enable better coverage of the network, standardized intercluster communications, and improved security [2]. The model, foundation model, and access, upper/lower transport, network, and bearer layers make up the BLE mesh system architecture, which sits on top of the BLE network stack [3]. Despite its many features, the BLE mesh protocol assumes the use of flooding for multihop communications. The flooding approach results in network overheads and delays due to continuous message broadcasting in the absence of a proper routing mechanism. Aside from the flooding-based protocol, numerous common routing protocols for wireless ad hoc networks exist, such as AODV [4], DSR [5], and others. AODV has been used in a wide range of applications and scenarios, demonstrating its dependability and robustness. For this paper, we considered a multihop mesh with a flat/nonhierarchical topology as a usage scenario and proposed a O-AODV protocol for BLE by replacing the network layer protocol in the BLE mesh architecture to improve communication efficiency and reliability over the current AODV and mesh protocols. The objectives of this research wereto: (a) optimize BLE mesh performance by reducing overheads and delays in comparison with the flooding approach and (b) improve the Packet Delivery Ratio (PDR) performance of AODV. Except for the work in [6] (the author tested with a single topology with six nodes (two hops)), there is no significant research available for improving the BLE mesh protocol. The AODV protocol was demonstrated to be the best among other ad hoc network protocols [7; 8]. As a result, as discussed in Sections 4.1.1, 5.1 and 5.8, we optimized the performance of the current version of the BLE-based AODV protocol for this article by reducing mainly the packets' retransmissions to reduce the delays, overheads, and traffic load. Furthermore, we conducted experiments with three topologies (linear--nine hops from the source to the sink with ten nodes, multipath--two hops from the source to the sink with multiple path availability with six nodes, partial mesh--four hops from the source to the sink with several paths with ten nodes) to evaluate the performance of our proposed protocol to that of the existing protocol. In addition, before moving on to the other sections of this paper, it is required to examine the application scenario of a BLE-based mesh network in order to increase the readability. Wireless Ad Hoc Networks (WAHNs) are gaining popularity as they require no infrastructure and low-power communication. When it comes to hospitals, infrastructure-less communication is required to deal with emergency situations, such as calling the staff in an emergency or normal condition from one location to another, message transfer, and patient convenience to obtain various types of information after entering the hospital's vicinity. Many technologies are available to make WAHN practical for hospitals, including ZigBee, Z-Wave, threads, BLE, and others. In light of the foregoing and following extensive research, Bluetooth Low-Energy 5 (BLE 5) is the most suitable technology for this kind of network because of its easy availability in mobile devices, low power, low cost, and mesh support characteristics. Due to the critical nature of the hospital, there is a requirement for a very efficient and robust BLE-based mesh communication network as the hospital is dealing with emergencies all the time.