Abstract
As the market for internet of things (IoT) is growing and due to Ofcom's decision to reassign parts of the very high frequency (VHF) spectrum in the UK for IoT use, a propagation study has been conducted using the newly released VHF spectrum and the currently commercially operated ultra-high frequency (UHF) spectrum, in order to compare and contrast the suitability of the VHF spectrum for IoT use. The authors conducted their study in a number of different environments (rural, suburban, urban and dense urban), with measurement equipment deployed in a manner suitable for a portable IoT use case. Results are presented in comparison to other propagation studies available in the literature and widely used propagation models such as the Hata model. Shadowing and noise are also measured and examined. It is found that current propagation models do not provide adequate predictions within the considered use case, but found it is possible to calculate log-distance based models that provide good predictions. Path-loss is found to be constantly lower at VHF than UHF, but radio frequency noise is consistently higher. The newly released spectrum is found to be suitable for IoT deployments in all the examined environments.
Highlights
The internet of things (IoT) is a rapidly growing sector of communications technology, with 7 billion devices currently deployed and up to 22 billion devices expected to be deployed by 2025 [1]
Hata models are recommended for use in the ultra‐high frequency (UHF) frequency, so a better performance would be expected from the models at UHF than very high frequency (VHF)
It has been shown that the current mainstream propagation models do not accurately predict the propagation loss of an IoT deployment at the frequencies of 71 and 869.525 MHz within rural, suburban, urban or dense urban environments with RX antennas deployed close to ground
Summary
The internet of things (IoT) is a rapidly growing sector of communications technology, with 7 billion devices currently deployed and up to 22 billion devices expected to be deployed by 2025 [1]. The log‐distance propagation model given in (3) [22] is an established way to produce environment specific models in which the path‐loss increases with the log of the distance between the TX and the RX according to tailored variables This technique will be used with the measurements taken in this study to provide a new model for comparison to the existing models. Ð4Þ where σL = Standard deviation for a given length (dB) f = Frequency (MHz) This method is used to provide predictions which can be compared to the measurements taken in order to verify the validity of the method's possible use for the re‐purposed VHF bands examined here. PL71ðdBÞ 1⁄4 43:7 þ 21:1 log10ðdÞ þ X8:9 dB ð12Þ PL869ðdBÞ 1⁄4 48:9 þ 27:4 log10ðdÞ þ X7:9 dB ð13Þ Tables 1 and 2 show a summary of the path‐loss exponent (γ), channel constant (K), shadowing (σ) and the R2 fit for the straight line component of each model in the different environments
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