Presentation Information
[B-15-42]VHF Band Multipath Propagation Delay Estimation for DR-IoT Systems
〇ryuta Kato1, Ginji Ikenoya1, Kouki Hirakawa1, Tetsushi Ikegami1, Susumu Ishihara2, Masakatsu Ogawa3, Arata Kato4, Mineo Takai5 (1. Meiji Univ., 2. Shizuoka Univ., 3. Sophia Univ., 4. Space-Time Engineering Japan, 5. Osaka Univ.)
Keywords:
Multipath propagation,DR-IoT(Diversified-Range IoT),Power delay profile,VHF band
In DR-IoT (Diversified-Range IoT) systems using the 220 MHz VHF band for disaster response, packet errors presumed to be caused by multipath have been confirmed in high-bit-rate transmission at 320 kbps. Conventionally, wideband signals such as PN-sequence PSK or OFDM signals are used to obtain a multipath delay profile, but employing them is difficult in DR-IoT testing. We therefore verified a method for estimating the power delay profile from the frequency response of the received power, obtained by transmitting an unmodulated carrier while switching its frequency. The profile was estimated by applying an IFFT to the frequency response data, with peak extraction and Gaussian reconstruction. In an experiment in the Kakuto Basin, Ebino City, Miyazaki, a frequency-swept signal from 216 to 222 MHz was transmitted at 5 W and received at three stationary points: Rx1 and Rx2 in line-of-sight (LoS) and Rx3 in non-line-of-sight (NLoS). In the LoS environments, the relative power of delayed waves remained below −20 dB relative to the main wave, whereas at Rx3, obstructed by hills, reflected waves above −20 dB arrived continuously for 5 μs after the first wave, with strong reflections continuing thereafter. These results show that the method can estimate delay profiles from frequency response data. We plan to further evaluate its accuracy and apply it to transmission test evaluations.