P1 Technology Helpdesk
with John Rivera
P1 Tech Help: Wireless connectivity 101
There are a ton of acronyms, numbers, and silly names like like 802.11, Wi-Fi, iGSM EDGE, UMTS, and CDMA2000, wireless connectivity is really not magic
As you start your shift you turn on your MDT, MCT, or whatever terminology you use for your patrol car computer — I know some of you call them names I cannot print here. Your CAD (Computer Aided Dispatch) comes online and the other software you regularly use starts up as well. Once the connectivity is up, you start to receive dispatches and your day begins. Some of you wonder how this is voodoo occurs. I’m sure we know people who asked themselves the same question when they saw their first TV transmission. But even if there are a ton of acronyms and numbers and silly names involved in this stuff, it’s really not magic.
Cellular Data Options
Many agencies use a cellular wireless provider’s “3G” network — so named because it is the third generation of mobile data technology. There’s an alphabet soup of options on the market, like GSM EDGE, UMTS, and CDMA2000, and depending on the provider your agency has a contract with, your car could be connecting to the Web via any one of these.
We’ve come a long way from the earliest cellular or wireless connectivity. When cellular telephones first came out towers were sparse at best — one of the reasons why cellular service was so expensive. Now towers and cell sites are everywhere and come in different sizes and shapes. You may have seen the typical cellular tower standing over a building. You may have seen them driving past a building, the familiar metal grid that looks much like an iron gate with triangles on it. Yup, that’s a cell tower.
This availability and the sheer numbers of these cell sites are what allow Law Enforcement to connect to dispatch and other officers from other agencies connected to the same dispatch system and service the community faster and more efficiently. This option can be fairly expensive — typically an agency can figure that each car (a.k.a. subscriber), can cost about $50 per month — but the benefits of getting all that information to your squad car wirelessly and immediately are priceless.
Another wireless connectivity option for police agencies is Wi-Fi — this can be part of a city’s municipal wireless infrastructure (also known as Muni Wi-Fi) which can serve schools, businesses and the general public with wireless Internet connectivity, or via a proprietary, purpose-built network intended only for public safety and selected other city services. Either way, Wi-Fi is a little different from cellular data networks.
A Brief history of 802.11
Wi-Fi is a trademark of the Wi-Fi Alliance. This alliance is associated with WLAN (wide local area networks) devices using the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards.
Simply put, the IEEE 802.11 is a global standard that carries out transmissions over the air in several bands in the gigahertz frequency range. When the 802.11 standard was first developed it only supported a bandwidth that maxed out at 2 megabytes per second. This is considered extremely slow for the applications we use today and 802.11 was expanded to today’s commonly used 802.11b; which supports up to 11 megabytes per second and uses the 2.4 megahertz frequency.
The frequencies have since been updated to the faster 3.6 and 5 gigahertz bands.
The cost for the 802.11 standard is low, the signal range is good and connectivity stays constant. Although some home appliances may interfere with the unregulated frequency band, I have never had any personal experience with any home appliances blocking my wireless signals.
All of the new wireless routers are manufactured for the 802.11 standard and most if not all new laptop computers that have an internal antenna that uses the 802.11 standard. The external antennas that you can purchase just about anywhere use this or a variation of the 802.11 standard.
Logging onto a Virtual Private Network (VPN)
A typical computer network used by private businesses and Police agencies work using the same 802.11 standard. You must log into a computer network, type in your user name and password, and then the system recognizes your log in information, allowing you to enter the “Private Network.”
The wireless network works in the same manner as a wired network, only it uses cellular type transmissions to connect to the network. The antennas used to transmit and receive information from your patrol car are cellular as well but can be of a different configuration. Some agencies have the typical cellular antenna added to the patrol car and some agencies have small domes installed atop of the patrol cars. Some may have better aesthetics than others but they all work the same. The antenna connected on top of your patrol car is wired to the computer mount in your patrol car therefore given better connectivity.
Once logged into the computer, the networking software installed on your computer automatically executes itself. The computer antenna detects a signal and the networking software automatically dials a preset number entered by your IT department. This process is done almost in an instant and once connected the username and password already authenticated allows you to access the private network and gives the ability to log into the CAD software.
Much like a cellular telephone, your vehicle’s computer antenna constantly updates its connectivity by finding the nearest tower to give you the best signal while you move about in your patrol area.
I hope this has helped you somewhat understand how your MCT functions while you are patrolling your area.