Scheduling Master-Slave Wireless Networks in the Presence of Interference

Industrial wireless sensor networks are often implemented as master-slave type configurations. In this paper, the problem of scheduling transmissions and retransmissions by the master node in order to meet real-time deadlines in the presence of interference is considered. When interference is present retransmissions may be necessary in order to increase reliability of delivery. As packet losses often occur in correlated bursts, it is often useful to insert a gap before attempting a retransmission in the case of failure. In this paper, it is suggested that in many practical cases, the use of a two-stage earliest deadline first scheduler by the master node to assign transmissions and retransmissions to the available slots gives close to optimal performance. Retransmissions are treated as aperiodic requests which are handed by a simple but effective server. An example illustrates the application and effectiveness of the proposed method, and indicates that it performs favorably when compared to two related approaches also based upon deadline scheduling.