## 1 Introduction  
Many wireless sensors must be connected to the Internet, ensuring that the static information of products to which sensors are attached and the dynamic sensing information of the environment where sensors are deployed are delivered and utilized for efficient decision making to realize a ubiquitous computing society. An increasing number of wireless sensors are connected to the Internet for public security and health data monitoring because of the development of wireless LAN technologies, such as IEEE 802.11 ah and IEEE 802.11s, and other non-802.11 technologies. Developing an efficient Medium Access Control (MAC) protocol that harnesses the radio resource of wireless sensor networks with a large number of sensors is a vital part of the success of wireless sensor networks in the future. The connectivity-based multipolling MAC protocol was developed to improve the efficiency of the multipolling MAC protocol by reducing the multipolling frame transmissions [1; 2; 3; 4]. Using connectivity and interference information among nodes, a simultaneous polling method was proposed to allow multiple direct data communication between nodes to be carried out [1]. The backtracking algorithm was introduced to derive the connected multipolling sequence [2]. Frame aggregation and connectivity-based multipolling techniques were combined to efficiently collect Radio Frequency Identification (RFID) tag information from nodes [3]. The combined clustering and sequencing method was proposed for a heuristic approach for deriving the connected multipolling sequence of RFID readers [4]. However, in some cases, a scheduling algorithm based on the Traveling Salesman Problem (TSP) model, which is employed by the connectivity-based multipolling MAC protocol, requires too much time to obtain the minimal number of serially connected multipolling sequences in cases where a large number (e.g., >100) of nodes exist in wireless LANs [1; 2; 3; 4]. An efficient real-time implementable algorithm should be developed for deriving serially connected multipolling sequences of nodes when a large number of nodes exist in wireless LANs. In this study, an efficient node insertion algorithm is proposed by modifying the existing scheduling algorithm based on the TSP model to construct serially connected multipolling sequences of nodes for the connectivity-based multipolling MAC protocol. The next node can be selected to be added to a serially connected multipolling sequence based on the connectivities from recently added multiple nodes. The nodes simultaneously connected from the most recently added nodes are not skipped. They are selected to be added to the serially connected multipolling sequences using the proposed node insertion algorithm. Therefore, a smaller number of serially connected multipolling sequences of nodes can be derived to cover all Wi-Fi sensor nodes in a wireless LAN. In densely populated wireless LANs, a single serially connected multipolling sequence can be derived for all Wi-Fi sensors, which will be shown by the simulation results later in this paper. Although the previous scheduling algorithm may backtrack to obtain a smaller number of serially connected multipolling sequences, the proposed node-insertion algorithm does not backtrack to derive a near-optimal number of serially connected multipolling sequences in real time. The existing backtracking algorithm has the computational complexity of \(O(l)\), where \(l\) is the number of sensors in a wireless sensor network, while obtaining the minimal number of serially connected multipolling sequences. The proposed node insertion algorithm almost eliminates the computational time uncertainty from the backtracking algorithm because the proposed node insertion algorithm has the computational complexity of \(O(l^{3})\) in deriving a near-optimal number of serially connected multipolling sequences.