Experimental Evaluation of the Long-Range MIMO Outdoor Channel at 2.4 GHz

Low Power Wide Area Networks (LPWAN) technologies in the 2.4 GHz band offer the opportunity to employ multiple antennas at the sensor, which can be used to create antenna diversity. In this paper, we present our software-defined, interference-robust, and highly mobile channel sounder architecture and experimentally evaluate the long-range outdoor-to- outdoor MIMO channel in a typical Smart City environment. Analyzing the measurements we have obtained over a wide area, we estimate path loss, coherence bandwidth, and antenna correlations. Link budget calculations show that, despite the higher frequency compared to popular LPWAN technologies such as LoRa or SigFox, multi-kilometer links are feasible. Furthermore, the comparison of an IEEE 802.15.4 PHY designed for LPWANs with a recently proposed multi-antenna scheme indicates that considerable performance gains are possible through antenna diversity schemes, even with rather high antenna correlation.