Police Tech & Gear
with Tim Dees
A primer on mobile broadband
The alphabet soup of standards makes it hard to know what does what
Between the blending and mergers of mobile communications companies, the variety of services they offer (and the variety of names they use for them), and the mix of cell phone platforms such as Android, iOS, and Symbian, the typical consumer operates at a disadvantage. It seems that every carrier claims to have the fastest or the biggest or the most widely used network, and yet it’s rare to find a customer who is nearly as enthusiastic about their service as are those smiling folks in the commercials. Is there a combination of hardware, network and technology that is truly superior to all the others?
The simple answer is, “yes,” although that winning combination differs considerably with location. Mobile data carriers have been furiously expanding their networks over the past few years, and they aren’t anywhere close to being done. With the exception of a few markets with very high population and user density (New York City, Los Angeles, Washington D.C., etc.), one carrier usually has an advantage over the others in most of the country. Further, there are still portions of the country where you will have difficulty making a cell phone call, and you can forget about getting a data connection. Like real estate, data networks are largely about location, location and location.
Evolving Standards and Technology
To understand where we are and where we’re going, it helps to know where we’ve been. When cellular telephone service started became widely available about 25 years ago, signals were all analog, as opposed to today’s digital signals. Analog signals require considerably more power than digital, which is why most of the early cell phones were either permanently installed in cars or carried as “bag phones.” The transmitters put out as much as three watts, and only a single conversation could be carried on a channel. Charges of $0.50 to $0.75 per minute, even for local calls, were commonplace.
This service was called Advanced Mobile Phone Service or AMPS, and is now also known as “1G” or “first generation” service.
The second generation or 2G service gave us digital signals, much smaller handsets with lower-powered transmitters, and a greatly-expanded carrying capacity for voice calls. The increased capacity or multiplexing came about through the use of TDMA and CDMA technologies, for Time-Division Multiple Access and Code-Division Multiple Access. TDMA allows a single channel to be used for multiple conversations by sending Call 1 for a fraction of a second, then sending Call 2, Call 3, and so on, until it gets back around to Call 1 again and restarts the sequence. CDMA accomplishes the same magic through spread-spectrum technology and encoding each conversation so that it reaches the proper handset and is rejected by all the others on the channel. CDMA has a potential greater carrying capacity than TDMA for the same bandwidth, and persisted when TDMA had been abandoned.
The move into 2G also marked the diversion of standards of cellular service between the U.S. and Canada and most of the rest of the world. Most of North America used a standard called Personal Communications Service or PCS, which identified each handset to the network via a permanent electronic serial number, or ESN. The rest of the world used the Global System for Mobile Communications (GSM), which relies on a replaceable Subscriber Identity Module or “SIM” inside each handset. SIMs, which are the size of a fingernail or smaller, contain all of the information associated with a phone account: number, carrier subscription, airtime purchased, etc. If you take your GSM phone (a couple of U.S. carriers use GSM) to Europe, you can buy a SIM at a kiosk for a few dollars and have a local phone for use in that country, with a number reachable from any phone in the world. When you come back home, swap out that SIM with the original one from your carrier, and you’re back in business.
A few 2G phones had the capacity for text messaging and very limited data transmissions. You’ll know what I mean by “very limited” if you have ever tried to use your smartphone for data communications when you’ve been on an EDGE network. EDGE is short for “Enhanced Data Rates for GSM Evolution,” and compared to what most of us have gotten used to, it’s s-l-o-w.
Typical EDGE data speed is around 22 Kbps, where a 3G experience might be 2Mbps, or 100X as fast.
Third generation or 3G is where most of us not residing in rural areas are today. 3G satisfies most data needs, and will support streaming video and audio at low resolution — say, a picture the size of the one on your smartphone. You may know of landline telephone service that runs over your home or office internet connection, called Voice over Internet Protocol, or VoIP. With a 3G phone, all calls are VoIP. Your phone is more of a mini-computer than a telephone, and can double as a wireless modem for your computer, although your carrier will probably charge you extra to do it.
Now the race is on to provide the best 4G network. 4G and LTE or “Long Term Evolution” are terms that are sometimes used interchangeably and even combined. Most networks now claiming to be LTE are actually at a transitional level of development, called 3GPP (3rd Generation Partnership Project) Long Term Evolution. LTE promises true broadband service with speeds rivaling or even exceeding what we’ve become used to over hardwired cable and fiber networks. Download peak data rates are or will be in the neighborhood of 100 Mbps, with upload speeds of 50 Mbps. The fastest service available from the cable provider in my community is 60 Mbps.
The promise of 4G is of special interest to public safety agencies, as the FCC plans to reserve a portion of the 700 MHz spectrum for a nationwide 4G network. Implementation of this system would permit fire, police, EMS and other emergency management operations to communicate and share data seamlessly, irrespective of location or devices. The FCC has indicated that 10 MHz of this frequency band will be adequate for both normal and emergency communications and data. Even so, the FCC proposes to implement a plan where public safety would get priority access and roaming in the commercial portions of the 700 MHz band. That kind of access would provide redundancy to normal channels and networks in extreme situations.
True mobile broadband will mean access in the field to the same resources an officer has in the station — telephony, data, video, and anything else you can think of. That data stream won’t just flow to the car, but to handheld devices as small as the Smartphones of today, and future devices that will be built into helmets, headsets and even uniforms. You’ll be more connected than ever before.