Wi-SUN FAN Multi-hop Network in Coexistence of IEEE 802.15.4 FSK and OFDM Transmission Schemes

The wireless smart ubiquitous network field area network (Wi-SUN FAN) is a wireless communication standard for the Internet of things (IoT) in outdoor large-scale multi-hop networks. Currently, frequency shift keying (FSK) standardized in IEEE 802.15.4 is employed as the physical layer of the Wi-SUN FAN. Improving data rate of the physical layer is essential to realize expected requirements toward the next-generation IoT systems. In this paper, we introduce the orthogonal frequency division multiplexing (OFDM) standardized in IEEE 802.15.4 into the Wi-SUN FAN to improve data rate without increasing the system bandwidth. We evaluated the packet error rate (PER) characteristics under inter-signal interference in the transition period of the physical layer from FSK to OFDM through a computer simulation. Results showed that the new interference caused by the mixture of OFDM degraded the PER characteristics, in comparison with the interference between FSKs. However, the interference between different channels was limited because the required carrier-to-interference power ratio to achieve PER=10% was below –10dB. Furthermore, we evaluated the transmission characteristics of the Wi-SUN FAN in the media access control layer and verified that the introduction of the OFDM is effective for improving the maximum system throughput by 1.9 times when performing frequency hopping.