Abstract: Routing protocols for wireless sensor networks are a hot research topic. Minimum hop count (MOH) routing guarantees a minimum number of packets within the network, is easy to implement, and has a wide range of applications. This paper proposes a routing protocol based on a reliable minimum hop count field to improve the network's data transmission success rate. The paper details the establishment process of the reliable minimum hop count field and the implementation method of the routing. Simulation experiments under the TinyOS operating system verify the correctness of the protocol. Keywords: wireless sensor network; routing protocol; TinyOS operating system [b][align=center]Research on reliable routing protocol based on minimum hop field LI Liang, LIU Lin-Lan, SHU Jian, CHEN Ying[/align][/b] Abstract: routing protocol of wireless sensor networks (WSN) is an important hotspot. The routing protocol based on minimum hop can efficiently reduce the number of messages to the lowest, and has the trait of easy implementation and wide application. For the aim of increasing the packet success rate, this paper proposes a routing protocol based on reliable minimum hop field, particularly introducing the building process of the reliable minimum hop field and the routing method. Simulation in TinyOS operating system shows the correctness of our protocol. Keywords: wireless sensor network; routing protocol; TinyOS operating system 1. Introduction Wireless sensor networks are composed of a large number of sensor nodes randomly arranged in the monitoring area, which can monitor the environment in real time and return monitoring messages to users in a multi-hop manner [1]. Because wireless sensor nodes are inexpensive, networks can be rapidly deployed, and they are highly resistant to destruction, they have broad application prospects in military reconnaissance, environmental monitoring, agricultural production, construction, and industrial production control. Routing protocols are an important research area in wireless sensor networks. Reference [2] provides a relatively detailed overview of routing protocols in wireless sensor networks. Due to the small storage space, short communication radius, limited computing power and energy of sensor nodes [3], implementing simple and low-energy routing protocols based on existing node hardware is the research focus of wireless sensor network research. Reference [4] proposes a minimum-hop-based routing protocol starting from reducing the number of messages in the network. In the monitoring area, sensor nodes in different areas send data to the aggregation node in the optimal way (with the fewest nodes traversed) while keeping the node communication radius unchanged. Nodes only need to record a certain number of node forwarding sets and their own hop count to achieve routing. The protocol is simple to implement, can reduce information transmission delay and reduce the amount of information in the network, and achieve low energy consumption of the network. However, the minimum-hop-based routing protocol has a significant shortcoming, namely, it does not take into account the influence of environmental and node factors. In the process of establishing a minimum hop count field, two adjacent nodes (with different hop counts but within each other's communication radius) establish a parent-child relationship. However, in reality, due to environmental influences and asymmetry in node communication, the packet loss rate on the link is high, and the link communication quality between nodes is very low. This paper proposes a routing protocol based on a reliable minimum hop count field to improve the packet transmission success rate of the network. It uses communication link quality as an evaluation method to establish a reliable minimum hop count field within the network. To verify the reliability of the algorithm, the authors conducted a series of experiments under the TinyOS operating system, proving the correctness of the algorithm. 2. Introduction to TinyOS Operating System TinyOS is a micro-operating system developed by the University of California, Berkeley specifically for wireless sensor networks. It is a programming framework suitable for networked embedded systems. By linking a set of necessary components within this framework, it is easy to compile an operating system for a specific application, which is crucial for systems with extremely limited storage resources. For wireless sensor networks with numerous nodes and high concurrency, this operating system adopts an event-driven architecture. Wireless sensor networks (WSNs) have diverse upper-layer applications and emphasize energy efficiency. Therefore, the system adopts a modular design that facilitates upper-layer application development and rapid program execution. The TinyOS operating system features an event-driven architecture; a single shared stack; and no kernel, process management, memory management, or virtual memory. TinyOS consists of numerous components, such as the main component, application component, actuator component, sensing component, communication component, and hardware abstractions. Users only need to write the relevant application-layer components, facilitating the development of new applications using existing components and significantly improving development efficiency. 3. Routing Protocol Based on Reliable Minimum Hop Count Field The routing protocol based on the reliable minimum hop count field includes two aspects: (1) establishing a reliable minimum hop count field within the network; (2) implementing node routing within the network. Establishing a reliable minimum hop count field further includes two aspects: (1) establishing temporary parent-child relationships between adjacent nodes; (2) quality assessment of temporary communication links. 3.1 Establishment of a Reliable Minimum Hop Count Field 3.1.1 Establishment of Temporary Parent-Child Relationships Between Adjacent Nodes Nodes in the protocol possess a unique network identifier, and the hop count of the sink node is initialized to 0, while the hop counts of the remaining nodes are set to a maximum value. After the network deployment within the monitoring area is complete, the sink node broadcasts a message M establishing a reliable minimum hop count field. M contains the following three items: Type; Message type ID; Node network identifier Hop; Upon receiving this type of message, a node in the current hop count network starts a timer Twait1. During this time period, the node continuously receives this type of message. After the timer Twait1 expires, the node selects the node with the smallest hop count among the message source nodes as its temporary parent node and stores the ID of the temporary parent node, while simultaneously setting its own hop count to the minimum hop count plus 1. For a node's temporary parent node, the node itself is called a temporary child node. Once the relationship between temporary parent and child nodes is determined, a temporary communication link between them is said to have been established. 3.1.2 Quality Assessment of Temporary Communication Links A temporary communication link does not necessarily indicate that the two corresponding nodes can communicate peer-to-peer, nor does it guarantee high communication quality. Therefore, the protocol uses a quality assessment method to measure the data transmission success rate of the temporary communication link, thereby evaluating its communication quality. During the assessment, temporary links with high data transmission success rates are retained and become fixed links, and the corresponding temporary parent-child relationship becomes a formal parent-child relationship; otherwise, the temporary link is discarded, and the corresponding temporary parent-child relationship is canceled. As shown in Figure 1, there is a temporary link between node 1 and node 2, where node 1 is the temporary parent node and node 2 is the temporary child node. After Twait1 times out, node 2 starts a timer T and sends N test messages to node 1. The message contains its own ID, the test message number, and the IDs of all temporary parent nodes of node 1. After receiving the test message containing its own ID, the temporary parent node starts a timer Twait2 and counts the received test messages to obtain a count value n. After Twait2 times out, node 1 sends a return message with the value n to node 2. Node 2 will calculate the data transmission success rate Pt (the ratio of n to N) to Node 1. When Pt is greater than or equal to the threshold P, the temporary link between them will be retained as a fixed link, and the two will form a formal parent-child relationship; if T times out or Pt is less than the threshold P, the temporary communication link will be canceled. The execution logic diagram of the temporary parent node and the temporary child node is shown in Figure 1: [align=center] Figure 1: Node Execution Logic Diagram[/align] After the quality assessment of the temporary communication link, the newly generated child node begins to generate and broadcast a message to establish a reliable minimum hop count field. All nodes with existing parent-child relationships will no longer accept this message, while all sensor nodes without parent nodes will participate in a new round of establishing a reliable minimum hop count field after receiving the message. When the parent-child relationships of all nodes in the network are determined, the establishment of the reliable minimum hop count field is also completed. 3.2 Implementation of Protocol Routing After the reliable minimum hop count field is established, each node in the network records all its parent nodes. When a message is sent, the node selects its parent node as the next hop in a round-robin manner. This is mainly based on two considerations: (1) reducing bottlenecks, as congestion can easily occur when multiple nodes choose the same parent node as their next hop; (2) the need for network load balancing, allowing more nodes to participate in sharing energy consumption and preventing individual nodes from dying due to excessive energy consumption. 4. Simulation Experiment and Result Analysis The authors simulated the establishment of a minimum hop count field under the TinyOS operating system. A topology diagram as shown in Figure 2 was obtained under different threshold values ​​P. As shown in Figure 2, node 0 is the sink node, and the other nodes are within its communication radius. When the threshold is small, the hop count of nodes 2, 3, 4, and 5 is 1, resulting in a topology diagram when the threshold P is 0.4. When P is 0.6, the links between nodes 4 and 5 and the sink node do not meet the requirements, and they choose nodes 2 and 3 as their parent nodes; when P is 0.8, nodes 2 and 3 choose node 1 as their parent node. Therefore, it can be seen that the network topology changes significantly under different threshold values ​​P. This paper also analyzes and studies the relationship between the maximum number of hops in the network during the establishment process and the latency of messages arriving at the network edge. The latency is related to the number of hops per node, the processing time of messages by nodes, and various timers set. [align=center] Figure 2: Network topology changes under different thresholds Figure 3: Relationship between latency and hop count[/align] Through experiments, we obtained a relationship diagram as shown in Figure 3. With Twait2 unchanged, the relationship between latency and Twait1 shows that when Twait1 decreases, the network latency can be significantly reduced. However, through experiments, we found that when Twait1 is very small, nodes may not receive the message from the node with the minimum number of hops to establish a reliable minimum hop count field, resulting in significant changes in the network topology. When Twait1 increases to a fixed value, the network topology changes will be very small. [align=center] Figure 4: Packet reception at the sink node under different thresholds[/align] Figure 4 illustrates the data packets received by the sink node under different thresholds P. Nodes in the network send a certain number of data packets to the sink node. As the threshold P increases, the sink node receives more data packets, indicating that less data packet is lost with a larger threshold P, thus verifying the correctness of the algorithm. 5. Conclusion Many fruitful works have been done on routing protocols for wireless sensor networks, resulting in numerous practical achievements. This paper proposes a routing protocol based on a reliable minimum hop count field, building upon the minimum hop routing protocol. It focuses on the establishment process of the reliable minimum hop count field, detailing the establishment of temporary parent-child relationships and link evaluation methods. Experiments under the TinyOS operating system show that the routing protocol based on the reliable minimum hop count field significantly improves data transmission success rate. The paper's innovations include: 1. Proposing the concept of a reliable minimum hop count field and studying its establishment. 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