FF-MAC : Fast Forward IEEE 802.15.4 MAC Protocol for Real-Time Data Transmission

This paper presents a Fast Forward MAC layer designed for hard real-time applications in wireless sensor networks. This protocol is an enhancement to the IEEE 802.15.4 standard MAC layer proposed for Low-Rate Personal Area Network. The energy conservation mechanism proposed by the current standard is quite efficient and very flexible. This flexibility comes from the ability to configure different duty cycles to meet specific application’s requirements. However, this mechanism has a considerable impact on the end-to-end delay. Our approach resolves the energy delay trade-off by avoiding the storage of the real-time data in the coordinator during sleep time. A new superframe structure is adopted and a deterministic reception scheduling is used. All the simulations were done using the network simulator 2 ‘NS-2’. The simulations outcomes show that this new proposed protocol performs better than the current standard and reduces considerably the end-to-end delay even in low duty cycle networks. Our protocol can also provide a delay bound for all network configurations which allows a better choice of the duty cycle for the required delay. Keywords-component; IEEE 802.15.4; WSN; Superframe; star topology; delay; Duty cycle; D-GTS