## 3 Integration of WSN Node Sleep Scheduling into the CSMA/CA Mechanism  
The traditional CSMA/CA mechanism is widely used for Medium Access Control in WSNs. However, it does not inherently account for energy conservation, which is crucial in sensor networks where nodes are often battery-powered. By integrating a sleep/activate mode, nodes can conserve energy by switching to a low-power sleep state when not actively transmitting or receiving data. [PERSON] et al. (2016) proposed an extended Markov-based analytical model for the IEEE 802.15.4 slotted CSMA/CA algorithm, incorporating sleep mode to reduce power consumption in WSNs. The study focused on the impact of sleep mode on throughput and power consumption. The model considers active/sleep transitions of sensor nodes, enabling significant energy savings by shutting down the radio during sleep mode. Various duty cycles are analyzed to optimize power usage without severely affecting throughput. Numerical simulations validate the model, showing that it accurately matches performance metrics like throughput and power consumption. The results demonstrate that enabling sleep mode effectively reduces power consumption while maintaining satisfactory network performance, making it a valuable addition to the IEEE 802.15.4 standard ([PERSON] et al., 2018). [PERSON] et al. (2018) addressed performance issues of the standard IEEE 802.15.4 CSMA/CA scheme under heterogeneous buffered conditions by proposing two transmission schemes: One Service a Time Scheme (OSTS) and Bulk Service a Time Scheme (BSTS). These schemes aim to enhance delay, fairness, throughput, and energy efficiency in time-critical buffered networks with heterogeneous, unsaturated traffic. The study used modified semi-Markov chains and macro-Markov chains combined with M/G/1/K queue theory to model these schemes, evaluating throughput, packet delay, and energy consumption. Simulations of OSTS and BSTS showed significant improvements in delay and fairness, with superior throughput and energy efficiency compared with other non-priority schemes. The analysis and simulation results align well, confirming the effectiveness of the proposed schemes. [PERSON] and [PERSON] (2018) proposed an enhancement to the Clear Channel Assessment (CCA) mechanism within the IEEE 802.15.4 standard, which is crucial for the slotted CSMA/CA protocol. The Enhanced Clear Channel Assessment (ECCA) mechanism optimizes channel access by incorporating additional checks and adaptive strategies to reduce collisions and improve channel assessment accuracy. ECCA performs multiple checks to ensure the channel is clear, considering factors like signal strength and interference. Simulations showed that ECCA significantly improves throughput, packet delay, and energy consumption compared with the standard CCA method. The results demonstrate that ECCA reduces collisions and retransmissions, leading to more efficient channel use and lower energy consumption for sensor nodes. The comparative analysis of the three works (Table 3) underscores substantial advancements in the performance and energy efficiency of IEEE 802.15.4 CSMA/CA schemes by leveraging features at the Data Link Layer and Physical Layer. [PERSON] and [PERSON]'s Enhanced Clear Channel Assessment (ECCA) mechanism introduced enhanced CCA checks and adaptive strategies, significantly improving channel assessment accuracy, reducing collisions, and enhancing throughput and energy efficiency. [PERSON] et al. 's study proposed the One Service a Time Scheme (OSTS) and Bulk Service a Time Scheme (BSTS), which address performance issues in heterogeneous buffered conditions. These schemes improve delay, fairness, throughput, and energy efficiency through effective buffer management and adaptive sleep scheduling. [PERSON] et al. [36] incorporated sleep mode into the IEEE 802.15.4 CSMA/CA mechanism using an extended Markov-based model, optimizing duty cycles to reduce power consumption while maintaining satisfactory network performance.