As an extension of the BEACO2N project out of Berkeley, our team at Strathclyde have had to perform a few tasks to get the system ready for deployment at our diverse range of deployment locations.

The deployment at Berkeley utilises an american power connection, and they usually have direct access to the an ethernet connection to provide access to the outside world. Our deployment locations are primarily schools, and as such it is difficult to get access permissions onto a school network. To address this issue, we decided to utilise off-the-shelf outdoor wifi routers and 4G sim cards to provide wireless access to each location.

With this switch to using 4G sims and a wireless router, we also had to update the configuration of the sensors to match. Over ethernet, the Berkeley team did not have a data limit (or at least not one they were likely to hit simply recording atmospheric measurements). However, on a 4G sim, we had to restrict the data backup scheme . Originally, the ’ethernet-mode’ backup did a full sync every 15 minutes; however, after running this for a brief time we realised that a network issue was preventing a correct differential backup from being calculated, which would have resulted in an excessive amount of data being transferred (and a very large phone bill!). We made some modifications to the synchronisation strategy to mitigate this differential backup, and also switched to only backing up every 4 hours.

The result: going from 1GB per month down to around 150MB per month transmitted per sensor. A significant decrease in data transfer, and well within budget for a mobile SIM contract.

All of this allowing us to deploy approximately 20 sensors around glasgow in this initial phase.