In my last post, SIP Trunks: Rescue the Customer, I noted our use of fixed cellular gateways. These gateways are available in numerous configurations and uses, including backup dial tone to an on-premises solution, primary dial tone for alarm and monitoring systems, and even for home/vacation dial tone solutions. Some of these gateways are also used as a means to curb landline-to-cell costs.
A key consideration is what you want the fixed cellular gateway to provide dial tone for: alarm system, monitoring system (water, gas, relays), backup service, primary routing (cost deterrent), VPN, ATM, modems or POS. Because of the range of fixed cellular gateways, you need to nail down the purpose and use so that you can make sure the product is the right fit for what you want to accomplish.
Next, consider whether your provider is compatible with the device's underlying cellular technology: CDMA (EVDO/3G/4G/LTE) or GSM (GPRS/E/3G/4G/LTE). Also, some providers require registration (notification of usage) of the device in addition to the SIM card(s).
The existing on-premises solution (usually a PBX) needs to provide ARS/LCR (Automatic Route Selection/Least Cost Routing) capability. Specifically, you need at least 6-digit screening capability for the NPA-NXX, to route your cellular carrier calls across the cell gateway when dialing to your users/customers on that same carrier. This provides cell-to-cell connectivity and usually with chosen plans, there is no additional billing against the minutes of either plan.
Other important considerations include reception, the ability to connect an antenna, and the type of antenna used. Limitations by some equipment manufacturers with fixed cell gateways that have an onboard antenna may preclude the extension of an antenna to a different location for better reception. There may also be some other limitations such as cable length and antenna type, which needs to be suitable for outdoor use.
It will be important to determine signal strength beforehand and perform a site survey to determine it is a suitable and secure location for the gateway, as well as to determine its proximity to the served equipment, how to power-protect, and whether a small battery UPS will be required. External antenna use requires grounding of the cable along with power/lightning protection. The UPS means that in the future there will be service calls or maintenance on replacing the battery in the UPS. Then, check that the gateway is positioned in a secure location to avoid vandalism or theft--it may need to be installed out of sight along with the power (AC receptacle).
The next consideration should be around compatibility with the equipment using the fixed cellular gateway for dial tone. It sounds easy, but there's caution from past experiences. Some gateways provide "simulated dial tone" and some don't. This is an issue with older alarm and monitoring systems that "expect" dial tone before they will initiate the dialing string (i.e., calling the preprogrammed telephone number).
During the initial site survey, collecting interconnected equipment inventory, contacts and model and part numbers will help decipher details regarding compatibility when talking to the providers of the other gear. When public safety is a factor, testing the services multiple times is an essential part of the process to ensure that call completion is consistent and the interconnected gear is working properly with the cellular gateway. This often requires coordination with the service (monitoring) provider, and they will need to test for remote access connecting to the gear for service and monitoring.
Last, really consider which cellular provider service plan to use, especially for single-point-of-use applications. Alarm and monitoring, generally speaking, require low usage. Then, remember to register the telephone number(s) of the fixed cellular gateways with the alarm and monitoring companies to ensure that they have the number matched correctly to the proper address.
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