This month I'm focusing on the terms associated with wireless wide area networks (WWANs) -- primarily cellular systems, but, as you'll see below, these technologies overlap other wireless systems as well.
What's driving the development of advanced WWAN technologies is 3G, or third-generation cellular. First generation (1G) was analog, and 2G was digital. 3G is also digital, but designed for higher speed. 3G makes more efficient use of the radio spectrum, which means users have a better shot at getting a call through on the first try; this was the original motivation for going digital in the first place. 3G allows higher data speeds; the strict definition of 3G includes raw performance from 144 kilobits per second (Kbps) up to 2 megabits per second (Mbps). The actual performance will usually be less than this, but more than adequate for email, Web browsing and almost all enterprise applications. But in addition to packing more bits into the bandwidth allotted, 3G improves reliability, especially critical when mobility is a factor. Radio conditions can vary dramatically as a subscriber moves, so keeping up to date is the name of the game in WWANs.
The most important WWAN technology is Code-Division Multiple Access (CDMA). This is the core technology used by Sprint PCS and Verizon Wireless, and also forms the basis of all 3G systems worldwide. CDMA allows multiple users to transmit on the same set of frequencies and at the same time without interfering with one another. That's what the "code" does -- each user has a unique one. By analogy, suppose you are at a cocktail party at the United Nations. The acoustic environment is filled with people speaking many different languages, all potentially interfering with one another. The reason that they usually don't is that each person is listening only for the language or languages they know (their codes), and all the other noise can be safely ignored. Of course, the din can get so loud that individual conversations are drowned out. For this reason, a properly functioning CDMA system needs to carefully control the power emissions of each transmitter associated with it so that can't happen. In fact, a CDMA base station can update the transmit power level of every handset connected to it 800 times per second.
There are two terms associated with CDMA -- 1XRTT and 1xEV-DO. Both of these were intended as internal names for the technology, but somehow made it into marketing literature. With 1XRTT, you can expect from 60 Kbps to 80 Kbps throughput, and 1xEV-DO bumps this up to 300 Kbps to 500 Kbps. Again your throughput will usually be less because there will seldom be an optimal relationship between where you are and the base station you're talking to, and, more importantly, latency due to congestion or other weak links in the network will result in delay, just as it does on any other network.
The other major cellular technology is the Global System for Mobile Communication (GSM), which is the most popular cellular system in the world with roughly 1.2 billion users in close to 200 countries. GSM is not based on CDMA, but its 3G upgrade, which is called Universal Mobile Telecommunications System (UMTS), and, given that 80% of the 1.5 billion people using cellular worldwide use GSM, UMTS is also going to have a major impact. Cingular and T-Mobile are the GSM carriers in the United States.
It's good to understand these technologies, but what is most important is your company's choice of carrier and plan, based on pricing, availability and the quality of the service a carrier offers.
Craig J. Mathias is founder of the Farpoint Group, an advisory firm specializing in wireless communications and mobile computing.