Tree TDMA MAC Algorithm Using Time and Frequency Slot Allocations in Tree-Based WSNs

Wireless Pers Commun Tree TDMA MAC Algorithm Using Time and Frequency Slot Allocations in Tree-Based WSNs Jae-Hyoung Lee 0 Sung Ho Cho 0 0 Department of Electronic and Computer Engineering, Hanyang University , Seoul 04763 , Korea In this paper, we propose a tree-based time division multiple access (Tree TDMA) media access control (MAC) algorithm based on the IEEE 802.15.4 PHY standard. The method involves the simultaneous use of two algorithms, a time slot allocation algorithm (TSAA) and a frequency slot allocation algorithm (FSAA), at low power consumption to support voice and data communication to solve the problems afflicting prevalent MAC protocols in tree topology networks. The TSAA first generates routing paths through the control channel in a super frame prior to transmitting packets, and allocates time slots for each node to transmit packets. The FSAA then allocates frequencies to each path according to the routing paths generated following its application. The overhearing problem and the funneling effect in TDMA as well as carrier sense multiple access with collision avoidance (CSMA/CA) MACs are resolved by these two algorithms because a given node and its neighbors are orthogonal in terms of time and frequency. The problem of inter-node synchronization is addressed by periodically sending a beacon from higher to lower nodes, and the issue of low power is solved by leaving unsigned time slots in an idle state. To test the effectiveness of the proposed algorithm, we used a MATLAB simulation to compare its performance with that of contention-based CSMA MAC and non-contention-based TreeMAC in terms of network throughput, network delay, energy efficiency, and energy consumption. We also tested the performance of the algorithms for increasing number of nodes and transmission packets in the tree topology network. IEEE802; 15; 4 topology CSMA/CA TDMA TreeMAC TDMA MAC Tree 1 Introduction Early wireless sensor networks (WSNs) were considerably limited in the provision of services such as voice or multimedia communication because the main function of media access control (MAC) at the time was to monitor sensor data from devices without guaranteeing successful or timely delivery. The representative MAC protocol featuring this characteristic is carrier sense multiple access with collision avoidance (CSMA/CA). It incurs a significant overhead according to the depth of the relevant tree topology network and the funneling effect. The funneling effect is typically generated when packets are transferred from a lower node to a higher one in a tree topology network. It leads to packet transmission delays and inefficient energy consumption, with the consequence that successful and timely delivery cannot be guaranteed. Time division multiple access (TDMA)based MAC has recently been proposed to solve the above problem. However, it has not been widely used in WSNs because it can reduce packet transmission efficiency while trying to prevent packets from being overheard and adjusting inter-node synchronization according to the topology at hand. Among WSNs using CSMA/CA MAC, ZigBee has been widely used. It is based on the IEEE802.15.4 physical layer (PHY) and the CSMA MAC. It exhibits poor performance in terms of data transmission efficiency unless the MAC of ZigBee dynamically manages the channel by designating active and inactive intervals to reduce energy consumption. Moreover, ZigBee struggles to support voice communication, and invariably incurs a delay because of limited bandwidth and the delay characteristics of sensor networks. Nonetheless, because it can be simply implemented using the IEEE 802.15.4 MAC, and it supports low energy consumption as well as the star, tree, and mesh topologies, it is among the most widely used sensor network protocols. The ZigBee Alliance has recently begun distributing CSMA/CA network-based standards for automation, remote control, smart energy profiles, ZigBee healthcare, home automation, input devices, light links, retail services, and telecom services to expand ZigBee’s field of application in order to compensate for the limited service due to CSMA/ CA. Of these, telecom only provides service between devices. However, research is underway on providing Voice over IP (VoIP) services that utilize codecs and the Session Initiation Protocol (SIP). The commonly used tree topology sensor network is classified into a sink node and a general node. It is a widely used topology for data monitoring that requires variation from low to high speed owing to the generation of tree-form traffic while transmitting data from the general node to the sink node. Traditional MAC protocols, such as ALOHA and CSMA, that do not have traffic channel control at traffic generation create a funneling effect [ 1 ] that increases traffic congestion as packets approach the sink node in the tree sensor network by increasing the number of reattempts as well as the backoff time. This causes a sudden incr (...truncated)