On the performance of 802.15.4e in the real world

To make wireless sensor networks more robust, an amendment was added to the IEEE802.15.4 standard: IEEE802.15.4e. This work studies one of the operational modes described in this amendment: Time-Slotted Channel Hopping (TSCH). This protocol is more robust due to the use of channel hopping. When channel hopping is used, every time communication fails, the nodes switch to another channel for retransmission. This way the resilience to interference increases. To be able to analyze this protocol, some environments are characterized. These serve the purpose of evaluating the operation of TSCH in real circumstances. To characterize these environments the signal strength (RSSI), 802.15.4 link quality indicator (LQI), bit error rate (BER) and packet loss (PL) are measured. A first conclusion derived from the results is the asymmetry in interference between nodes. The nodes do not see an equal amount of interference on the same channel. Secondly the characteristics of the channels vary during the day. Therefore, a communication schedule that takes these spatial and temporal variations into account is very important to optimize TSCH performance.