IEEE 802.15.4g/4x-Based Orthogonal Frequency-Division Multiplexing Transmission Scheme for Wide-Area and Mobile IoT Communication Systems

Radio communication systems using the frequency-shift keying (FSK) scheme standardized by the IEEE 802.15.4g standard can realize low-power consumption and highly reliable communications and are mainly adopted for smart metering as part of the Internet of Things (IoT). However, smart metering has recently broadened its application expectations, with broadband and long-distance communications now required. To fulfill these requirements, orthogonal frequency-division multiplexing (OFDM) has been incorporated into the IEEE 802.15.4g and 802.15.4x standards. However, comprehensive transmission performance analysis of OFDM under static and multipath fading environments has not been conducted. In this article, we first evaluated the packet error rate (PER) of OFDM assuming fixed communications using computer simulations. We then evaluated the transmission distance of OFDM and showed that OFDM can communicate at transmission distances up to 3.0 times longer than those specified in IEEE 802.15.4g FSK. Next, the PER in a mobile communication environment was evaluated using computer simulations. When only the long training field (LTF) was used to estimate multipath radio channels, the required PER of 10% was not achieved, even in a mobile communication environment at a speed of several km/h. To solve this problem, we proposed a receiving scheme which included a new channel estimation scheme. This scheme successively utilized not only the LTF but also pilot signals inserted into the transmitter to estimate radio propagation characteristics. Computer simulation results showed that the required PER was achieved even in a mobile communication environment at 30–40 km/h by using the proposed scheme.