# ACE: A Routing Algorithm Based on Autonomous Channel Scheduling for Bluetooth Mesh Network
## 8 Related Works  
**Bluetooth Mesh Evaluation and Analysis:** As a relatively new technology, most research works on Bluetooth Mesh have focused on the analysis or evaluation of its performance [2; 5; 14; 20; 21; 22; 23]. The experimental results showed that Bluetooth Mesh is vulnerable to external interference when using only 3 out of the 40 Bluetooth low-energy frequency channels [5]. However, the achievable average delay is relatively low [5; 22], and it will be negatively impacted when the network is more sparse [22]. However, the scalability is especially challenging for Bluetooth Mesh since it is prone to suffer broadcast storm, hindering the communication reliability for denser deployments [5; 20; 22]. The optimization of Bluetooth Mesh network parameters such as retransmission parameters, buffer size, random backoff values, and TTL parameter [14] can be hot topics in the future. High energy consumption is a big issue for Bluetooth Mesh due to continuous scanning. An analytical model on important energy performance parameters of a battery-operated low power node is presented [21], and BMADS [24] is an asynchronous dynamic scanning mechanism designed to reduce the overall energy consumption of the mesh network. Even though the above works have done various experiments and explored the disadvantages of Bluetooth Mesh, most of them do not propose improvement measures in terms of its deficiencies, such as collisions. ACE, in contrast, provides a novel routing algorithm for Bluetooth Mesh and improves its performance realistically. **Routing-based BLE mesh network:** Before the Bluetooth Mesh standard was released in 2017, some research works have already been studied on a routing-based BLE mesh network. For example, a static tree topology over Bluetooth 4.0 is presented in [25; 26], and Real Time BLE (RT-BLE) [26] is intended to enable bounded message delay for BLE mesh networks. MHTS [9] was designed over Bluetooth 4.0, based on next-hop, on-demand routing over the GATT layer. BLE Mesh Network (BMN) [10] uses the Directed Acyclic Graph (DAG) structure as a basis for routing, inspired by the IPv6 Routing Protocol for Low power and lossy networks (RPL). An on-demand routing for Bluetooth 4.1 was presented for forming scatternets in [27]. However, these BLE mesh solutions are not designed over the standard Bluetooth Mesh network and can introduce an unacceptable latency due to connection-oriented routing. ACE, in contrast, support routing algorithm for standard Bluetooth Mesh in a completely connectionless way, and it is more practical for its simplicity, timeliness, and scalability. **Ad Hoc Network Routing Protocols:** Existing routing protocols for ad hoc networks can be classified either as proactive or reactive. Classic proactive protocols include DSDV [28], TBRPF [29], and WRP [30]. These protocols continuously evaluate the routes within the network so that the route is already known when a packet needs to be forwarded. Also, there are Artificial Intelligence based management algorithm for improving high-dynamic network performance [31]. In contrast, reactive or on-demand protocols invoke a route determination procedure by an on-demand route query. Examples of reactive protocols include AODV [12], DSR [32], and TORA [33]. The on-demand discovery of routes can result in much less traffic than proactive schemes; however, the route acquisition delay can be significant. We do not apply any of the above protocols directly to Bluetooth Mesh network. Instead, we explored the features of Bluetooth Mesh protocol and customized the routing protocol for it with the essence of the above classic ad hoc network routing protocols. **Synchronous Transmissions:** Synchronous transmission is a recent direction in low-power wireless networks for its high reliability, low latency, and energy efficiency. By exploiting constructive interference and capture effect, Glossy [34] can flooding by precisely timing transmissions. Even in the presence of duplications, the receiver can successfully receive packets.