Scheduling support for guaranteed time services in IEEE 802.15.4 low rate WPAN

Abstract

The explosive growth of embedded system in most electronic devices and the need of applications for connectivity of applications require the standardization. IEEE 802.15.4 standard defines PHY layer and MAC sub-layer to provide the embedded control and monitoring fields with the wireless connectivity. This considers WSN(wireless sensor network) as one of the main applications. An application monitoring the pressure of a tire may use this WSN. And WSN can be used in the application of a personal health care system. These kinds of applications require the timeliness as well as the proper functions IEEE 802.15.4 stipulates GTS(Guaranteed Time Slot) mechanism for exchanging time critical packets. But the standard is lacking in scheduling of time critical packets. Although the standard specifies several parameters which are related to guaranteed time service, it doesn``t present the way how to configure them. We propose a real-time message scheduling algorithm which is applied to schedule periodic real-time messages in IEEE 802.15.4 for LR-WPAN(Low Rate Wireless Personal Area Network). from the scheduling algorithm, we can get the standard specific parameters relevant to guaranteed time service. The LR-WPAN standard allows GTSs(Guaranteed Time Slots) in the optional use of a superframe structure in beaconenabled networks to be used to exchange real-time messages. To utilize these features of the standard efficiently, proper message scheduling algorithm is needed. The proposed message scheduling algorithm which is based on distance constrained scheduling generates the standard specific parameters for the superframe structure including BO, SO, and GTS information to schedule the given message set. The guaranteed time service using the schedule generated by the scheduling algorithm is implemented on CC2420DB which is a prototyping platform including an IEEE 802.15.4 compliant transceiver of Chipcon AS. The implementation shows that the guaranteed time works well wi...