A wireless sensor network consists of a large number of inexpensive micro sensor nodes deployed in the monitoring area, forming a multi hop self-organizing network system through wireless communication, mainly used for collecting, propagating, and processing sensor information.

Unlike traditional wireless self-organizing networks, wireless sensor networks have a large number of nodes and a dense distribution of nodes; Due to environmental impact and energy depletion, nodes are more prone to failures; Environmental interference and node failures can easily cause changes in network topology. In addition, the energy, processing capacity, storage capacity, and communication capacity of nodes are limited, so the primary design goal of wireless sensor networks is to efficiently utilize energy. The Media Access Control (MAC) protocol for wireless sensor networks must prioritize energy conservation and adopt a compromise mechanism, allowing users to make choices in extending the network lifecycle, improving network throughput, and reducing communication latency.

At present, researchers have proposed multiple MAC protocols from different aspects for different sensor network applications. CI871AK01 3BSE092693R1 lacks a unified classification method. Based on the use of fixed allocation channel or random access channel methods, sensor network MAC protocols are divided into Time Division Multiplexing (TDMA), Random Competition (RCA), and other MAC protocols. TDMA with fixed channel allocation can naturally perform low duty cycle operations on nodes, as they only need to enable wireless modules to transmit and receive within their own time slots. However, their scalability is poor, and time synchronization is a significant overhead for the system. Due to the low data rate and low latency requirements of wireless sensor networks, the current practical energy-saving MAC protocol is mainly based on competitive protocols. A large number of experiments and theoretical analysis have shown that the energy waste of wireless sensor nodes mainly comes from idle listening, conflict, crosstalk, and control. Therefore, combining the existing wireless sensor network MAC protocol and introducing the hierarchical topology control concept, an efficient and energy-saving wireless sensor network protocol is established, and analyzed, simulated, and verified, which has research significance.

Analysis of Competitive MAC Protocol

1.1 S-MAC protocol

The S-MAC protocol is a sensor network MAC protocol proposed based on the 802.11MAC protocol to meet the energy-saving requirements of sensor networks. The S-MAC protocol assumes that sensor networks typically have less data transmission, nodes collaborate to complete common tasks, data processing and fusion can be carried out within the network to reduce data communication, and the network can tolerate a certain degree of delay. Research has shown that sensor energy is mainly consumed by the passage between nodes, and idle listening accounts for about 1/3 of node communication energy. To achieve energy savings, the S-MAC protocol mainly adopts a low duty cycle mechanism of periodic listening/sleep, controlling nodes to be in a sleep state as much as possible to reduce node energy consumption. However, the S-MAC protocol has the following issues: all nodes in the same virtual cluster in the S-MAC protocol must simultaneously transition from sleep to active state, starting to compete for the channel, and a large number of nodes do not have data transmission tasks. These nodes waste a lot of energy in channel competition and idle listening.

1.2 T-MAC protocol

The T-MAC (Timeout MAC) protocol is proposed based on the S-MAC protocol. The cycle length of the CI871AK01 3BSE092693R1 protocol is limited by latency requirements and cache size, while listening time mainly depends on message rate. Therefore, in order to ensure the reliable transmission of messages, the cyclic activity time of nodes must adapt to the highest communication load, resulting in a relatively small network load and an increase in idle listening time of nodes. In response to this deficiency, the literature proposes the T-MAC protocol, which dynamically adjusts node activity time based on communication traffic while keeping the cyclic listening length unchanged, sends messages in a burst manner, and reduces idle listening time. However, due to the competition and idle listening of a large number of nodes that do not require data transmission, a significant amount of energy is still wasted. In addition, the execution of the T-MAC protocol can cause early sleep problems, leading to a decrease in network throughput. Therefore, it adopts two methods to improve the data throughput decrease caused by early sleep: (1) Future request sending mechanism. (2) Full buffer priority mechanism, but the effect is not very ideal.

Design of MAC Protocol Based on Topology Control Structure

All nodes in the S-MAC and T-MAC virtual clusters periodically transition from sleep to work, participating in channel competition and data transmission. However, most nodes do not have data transmission tasks, resulting in them being idle listening for most of their active time and wasting a large amount of energy. A new MAC protocol GS-MAC (Geographical SeNSor MAC) is proposed to address the unavoidable issues of S-MAC and T-MAC. After introducing the GAF topology control algorithm into the GS-MAC protocol, the number of active nodes is appropriately reduced to accelerate the convergence speed of the algorithm, reduce a large number of nodes’ idle listening and data collision on the channel, and thus achieve the goal of energy conservation.