A Comprehensive Performance Study of IEEE 802 . 15 . 4

IEEE 802.15.4 is a new standard uniquely designed for low rate wireless personal area networks (LRWPANs). It targets low data rate, low power consumption and low cost wireless networking, and offers device level wireless connectivity. We develop an NS2 simulator for IEEE 802.15.4 and conduct several sets of experiments to study its various features, including: (1) beacon enabled mode and non-beacon enabled mode; (2) association, tree formation and network auto-configuration; (3) orphaning and coordinator relocation; (4) carrier sense multiple access with collision avoidance (CSMA-CA), both unslotted and slotted; and (5) direct, indirect and guaranteed time slot (GTS) data transmissions. In non-beacon enabled mode and under moderate data rate, the new IEEE 802.15.4 standard, compared with IEEE 802.11, is more efficient in terms of overhead and resource consumption. It also enjoys a low hop delay (normalized by channel capacity) on average. In beacon enabled mode, an LR-WPAN can be flexibly configured to meet different needs, such as link failure self-recovery and low duty cycle. In both beacon enabled mode and non-beacon enabled mode, association and tree formation proceed smoothly and the network can shape up efficiently by itself. We also discuss some issues that could degrade the network performance if not handled properly.