A customer has several remote sites connected with their headquarters through microwave links. An engineer must propose a backup WAN solution based on these conditions: - A physical WAN solution is…

802.15.1 Bluetooth is a very short-range wireless technology unsuitable for WAN backup links between remote sites and headquarters.

LTE (Long Term Evolution) provides a wireless cellular-based WAN solution that meets the criteria of not requiring physical cabling, having relatively low implementation cost and quick deployment, and supporting low-to-moderate bandwidth requirements suitable for a backup link. It is widely available in many remote locations where wired solutions are not.

802.16 WiMAX is an older wireless technology that, while designed for metropolitan area networks, has largely been superseded by LTE/5G and is not as widely available or cost-effective for new deployments.

Laser link (Free-Space Optical communication) requires a clear line-of-sight and can be sensitive to environmental conditions like fog or rain, making it less reliable and more complex to implement and maintain as a backup solution for multiple sites.