# Combined Sweeping and Jumping Method to Enhance Node Insertion Algorithm for Wi-Fi Sensor Networks
## 4 Discussions  
Originally, the connectivity-based multipolling MAC protocol was proposed to optimize the mutipolling sequence of nodes in Wi-Fi networks using the backtracking algorithm, which is one Artificial Intelligence (AI) technique. However, the backtracking algorithm is inappropriate to be applied to wireless sensor networks, where a large number of sensors exist, because it sometimes takes too much time to derive the minimal number of serially connected multipolling sequences. The node insertion algorithm was proposed for the connectivity-based multipolling MAC protocol to be more easily applied to wireless sensor networks by cutting down the computational complexity and the actual time taken for deriving the pseudo-optimal number of serially connected multipolling sequences even in wireless sensor networks with up to 1000 sensors. The combined sweeping and jumping method is proposed to significantly reduce further the computational complexity and the actual time taken for deriving the pseudo-optimal number of serially connected multipolling sequences. As far as is known to the author, the combined sweeping and jumping method is unique in enhancing the node insertion algorithm for the connectivity-based multipolling MAC protocol for wireless sensor networks. As stated in [4], all the MAC protocols for wireless sensor networks based on Wi-Fi networks are categorized into the contention-based and polling-based MAC protocols. The contention-based MAC protocols suffer from the immense interference among sensors in wireless sensor networks where a large number of sensors exist. On the other hand, the polling-based MAC protocols can effectively avoid the interference among sensors because APs grant uplink transmission opportunities to sensors in a centralized manner. The connectivity-based multipolling MAC protocol modifies the PCF protocol, which is the basic polling-based MAC protocol for Wi-Fi networks, so that the transmission overhead is minimized; therefore, the polling efficiency is maximized. The connectivity-based multipolling MAC protocol, which is powered by the node insertion algorithm with the combined sweeping and jumping method, is unique in maintaining the framework of the original polling-based MAC protocol for Wi-Fi networks and achieving the maximized efficiency of the polling-based MAC protocol. As illustrated in [13; 14], the connectivity-based multipolling MAC protocol can be employed for the efficient direct communication between nodes and the reliable multicast transmission in Wi-Fi networks. However, due to the lack of the scalability of the backtracking algorithm that was used to derive the minimal number of serially connected multipolling sequences, the direct communication and reliable multicast MAC protocols that were specified in [13; 14] cannot be easily applied to wireless sensor networks where a large number of sensors exist. Thanks to the node insertion algorithm with the combined sweeping and jumping method, the connectivity-based multipolling MAC protocol can be directly applied for the direct communication between sensors and the reliable multicast transmission in wireless sensor networks where a large number of sensors exist. Even though the node insertion algorithm with the combined sweeping and jumping method was experimented for wireless sensor networks with up to 1000 sensors in the previous section, it was also found that the node insertion algorithm with the combined sweeping and jumping method on the average produces 1.02 and 1.0 serially connected multipolling sequences within 102.5 and 175.0 ms in the circular and donut-shaped service areas of wireless sensor networks with 10,000 sensors, respectively. The node insertion algorithm with the combined sweeping and jumping method can be implemented in about 40 lines of the Java program; therefore, the hardware can be developed for implementing the node insertion algorithm with the combined sweeping and jumping method without much difficulties.