Police Tech & Gear
with Tim Dees
Really portable cellular service
Why depend on your mobile carrier’s cell tower when you can have your own in miniature?
Most of us have ceased to awe over the miracle of the cell phone. Within one generation, we’ve gone from bricks, bag phones, and car-mounted cellular phones to devices smaller than a pack of cards with the computing power of a desktop machine of yesterday. Many people have ditched their hardwired phone service in favor of a cell phone, but what happens when the cell tower loses power, is underwater, or just stops working? That’s inconvenient for most people, but it can be life and death in public safety.
AT&T’s Remote Mobility Zone
There are a couple of solutions to have a backup plan when regular cell service goes out or even when you need to bring service to an area that has a poor or nonexistent signal. First, the big guns: AT&T’s Remote Mobility Zone (ARMZ) can replace or substitute for a cell tower in any locale where AT&T has some licensed spectrum. If there’s no AT&T service in your county, chances are this isn’t an option for you. The hardware is dependent on having an AT&T-licensed wireless channel to use.
An ARMZ unit can be installed at a fixed location, mounted on top of a command vehicle, or shipped to where it’s needed in two or four hardened suitcases. There are two models: one that communicates with an overhead satellite, and one that connects to a hardwired local area network (LAN). In the case of the satellite, the system can use an AT&T bird or one you already have access to.
ARMZ can be set up by non-technical people in a few minutes. Depending on terrain and location of the transceiver, it will provide cell phone service for a radius of about half a mile. It will support 7 to 14 full rate or 14 to 28 half rate concurrent calls, the difference being whether you configure the system with one or two radios,. The distinction between full rate and half rate is one of clarity and sound quality; half rate also uses less power from the handset.
If you need cell service in an area that isn’t served by a cell tower, but has broadband internet access, the LAN option may be a good one for you. In this configuration, the “backhaul” (the data traffic between the cell tower and the hardwired network) goes over your internet connection. Bandwidth requirements aren’t especially high, with 256 Kbps for a single radio and 384 Kbps for a double radio unit. Pricing is set at $2,500 if you “bring your own” satellite or LAN service, and $2,700 when you use AT&T’s satellite.
Satellite time, of course, will be extra.
Femtocells Fill In Gaps
For routine communications in an area where cell service is poor, a femtocell may work for you. Femtocells are electronic boxes that look like and work like Wi-Fi access points, but communicate with cell phones rather than computers equipped with Wi-Fi. Many wireless telephone services are supplying femtocells to their customers when they can’t get a reliable signal at their homes or offices. The femtocells plug into your broadband, always-on internet connection in the same way a Wi-Fi access point does. Effective range from the femtocell to the cell phone is typically only 100 feet or so, but that’s sufficient to cover most homes and offices.
These are a great solution for offices where the cell tower signal is blocked by walls or other architecture. It’s also possible to configure a femtocell so that it will work with only the phones you designate, so you can provide a signal to Mary but not to Bob. How flexible these configurations will be is dependent on your cell service carrier.
Some carriers will provide a femtocell to you at no charge if you can show you live or work within their usual service area, but for some reason you can’t get a reliable signal. Otherwise, you can buy or lease the femtocell from the carrier for a nominal fee.