Comparison between Channel Hopping and Channel Adaptation for Industrial Wireless Sensor Networks

One of the differences between the new standard IEEE 802.15.4e, in comparison to the previous IEEE 802.15.4 standard, is the use of multiple channels. The Time-Slotted Channel Hopping (TSCH) mode employs channel hopping, and the Deterministic and Synchronous Multi-channel Extension (DSME) mode employs channel hopping or channel adaptation, during the contention free periods. When using the channel adaptation as the channel diversity technique, a pair of nodes communicate using the same channel while the channel quality is good enough in terms of signal-to-noise ratio. Thus, it is necessary to evaluate the quality of the links, in order to proper use this mechanism. In this paper, three different approaches, based on the DSME protocol, were implemented and evaluated through a simulation study. The first one (CH-DSME) is based on a simple channel hopping mechanism, the second one (CA-DSME) employs channel adaptation, and the third one is a novel hybrid approach (H-DSME), that uses both channel hopping and channel adaptation. The H-DSME outperformed the other two approaches for the scenario in consideration, which shows that the use of channel adaptation is better than channel hopping for the transmission of unicast packets, when the quality of the links are monitored continuously. However, for packets transmitted in broadcast by the coordinator, the use of channel hopping is a good alternative to deal with the spatial variation in the quality of the channels.