This article explains the minimum Wi-Fi signal strength requirements needed for stable operation of I-Series 2.0

When it comes to Wi-Fi signal strength, it typically does not fall to the device or OEM to specify a minimum requirement as this can vary purely based on the content you intend to display. A general rule to follow regarding connection reliability is that anything below -70dBm can potentially introduce connect/disconnect issues at the device level. For that reason, We recommend taking measures to ensure devices are connecting to the access points at or preferably above this value.
 
Between -30dBm and -70dBm, the content performance will vary depending on the demand of the content.
 
We always recommend testing your own deployments to ensure best performance. With Wi-Fi there are always environmental variables that could impact performance that you will need to account for.
 
Here is a link to a site which will help break this down into even more detail.