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NB-Fi showed 32 kilometers range in harsh urban environment

WAVIoT trials in China showed 32 km signal transmission range in harsh urban areas

WAVIoT has successfully completed a number the real-life trials of its LPWAN technology which anticipates the massive roll out of the NB-Fi based smart metering IoT solution. The field test took place in one of the Chinese megalopolis in a harsh urban environment with a pretty built-up surroundings. Here are the brief details of our test. As our experience shows, the exact location for installation of the LPWAN antenna is obviously one of the key success factors for ensuring a long range wireless communication.

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Initially, we planned to install the base station on top of the 230 m skyscraper building, but the circumstances allowed us to set the antenna only on top of the 25-story building with the total height of 60 meters.

Based on the theoretical calculations, the line of horizontal sight from 60 m building is about 30 kilometers. That is the distance which signal will pass till it gets stuck on earth.

  • One sector antenna has been installed on top of the building with recommended tilt of 7 deg to the vertical line. Surrounding environment included a lot of skyscrapers and other concrete buildings which were much higher than base station installation spot. The measured noise level in the place of installation was significantly high -133 dBm in 50 Hz band.

    After the base station installation, WAVIoT team with customer representatives got in a car and started moving away from the spot. The team has been making the check measurements of signal strength every 3-5 kilometers. Reference 17 dBm signal has been sent from the standard testing modem which is equipped with a button.

    Maximum signal transmission range observed by the team with no omission errors reached 30 kilometers. At this range, the signal strength comes down to the noise floor of -133 dBm. But it was not the end.

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One of the key technical benefits of the NB-Fi protocol is that the signal can be reliably received even at the level of -3 dBm below the noise floor. Since the modem has already passed the line of direct sight and the signal went down below the noise floor we expected that further movement will not give any results. But as this practical experiment showed, the base station continued to receive data packets with some omission errors.

The final packet has been received at a range of 32 kilometers which is beyond the line of sight. We assume that some reflections from the hi-rise buildings took place. By that moment, signal strength went down the noise floor at -3 dBm.

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