However, in the machine world where machines do not tend to have the intelligence of computers, there are many benefits to fixed IP:

Airtime costs
It is a private range of Internet addresses that are issued to users. These are not Public IP addresses - you will not get lots of usage travelling up or down to your devices (public addresses are known by spammers and users are liable from virus attacks)

Better monitoring
For Business 2 Business applications users can fix the SIM card to a Private IP address at network level either to the SIM or via a dynamic pool of Fixed IP addresses allocated on a per user basis. This enables monitoring which means as the data routes through the APN network, usage can be monitored at a network level and routing. 
This service gives machines greater control of their routing policy and uptime of their connectivity and management of their field based machines. Each device can be allocated with a static IP (Fixed) address, allowing interrogation of the device at a moment’s notice, without having to wait for contact to the host computer.

Fixed IP benefits
-Lower airtime costs
-Easier to manage and control usage
-Easy to route two way and to multiple locations
-No spam or virus attacks
-No need to route across the internet
-No need for added security levels as authentication with username and password from the Fixed IP address from and to the Firewalls.
-By having a closed environment Wireless Logic can route SIM cards in machines to multiple locations depending on certain criteria.