A New QoS Resource Allocation Scheme Using GTS for WPANs

IEEE 802.15.4 (for low-rate Wireless Personal Area Networks??WPANs) (IEEE 802.15.4 Standard-2003) and IEEE 802.15.7 (for Short-Range Wireless Optical Communication Using Visible Light) (IEEE 802.15.7 Standard??2011) are two typical standards for WPANs that support Quality-of-Service (QoS) through a Guaranteed Time Slot (GTS) mechanism to allocate a specific duration within a superframe structure for a time division multiplexing transmission. The low bandwidth utilization problem may occur in the GTS mechanism when the allocated bandwidth is less than the available bandwidth. However, this problem has not been resolved thoroughly in any of the standard or current research thus far. This paper analyzes GTS performance in QoS-guaranteed transmission and proposes a new GTS allocation scheme named Unbalanced GTS Allocation Scheme (UGAS), which improves the bandwidth resource efficiency. Our scheme tries to solve the bandwidth under-utilization problem by using Network Calculus theory based on the fluid model and greedy algorithm. The UGAS scheme divides the Contention-Free Period into time slots of different durations to support various bandwidth requirements. Time slots are allocated using an approximation QoS model to minimize under-utilization. Compared with the standard GTS allocation scheme, UGAS makes an efficient bandwidth allocation with the QoS-guaranteed model and without breaking the standard protocol. The numerical results show that the average bandwidth utilization using UGAS can be improved by 30 % as compared with the standard scheme.