RID: radio interference detection in wireless sensor networks

In wireless sensor networks, many protocols assume that if node A is able to interfere with node B´s packet reception, node B is within node A´s communication range. It is also assumed that if node B is within node A´s communication range, node A is able to interfere with node B´s packet reception from any transmitter. While these assumptions may be useful in protocol design, they are not valid, according to the real experiments we conducted in MICA2 platform. For a strong link that has a high packet delivery ratio, the interference range is observed smaller than the communication range, while for a weak link that has a low packet delivery ratio, the interference range is larger than the communication range. So using communication range information alone is not enough to design real collision-free media access control protocols. This paper presents a radio interference detection protocol (RID) and its variation (RID-B) to detect run-time radio interference relations among nodes. The interference detection results are used to design real collision-free TDMA protocols. With extensive simulations in GlomoSim, and with sensor network application scenarios, we observe that the TDMA which uses the interference detection results has 100% packet delivery ratio, while the traditional TDMA has packet loss up to 60%, in heavy load. In addition to the scheduling-based TDMA protocols, we also explore the application of interference detection on contention-based MAC protocols.