Unscrambling the networks

Section Editor Joni Blecher, a.k.a. the Cell Phone Diva

Q: What’s the difference between CDMA and AMPS? And should both be together in a phone? Can I send a message around the world to GSM phones using a CDMA phone?–Joao

A: Let’s start with the first half of the question. Here in the United States, we use CDMA (Code Division Multiple Access) and AMPS (Advanced Mobile Phone System), among other networks. In short, CDMA is a digital network; in the most basic terms possible, calls should come through pretty clear. But AMPS is an analog network, where calls aren’t always so clear. AMPS was the cellular network in use before the all-digital CDMA, TDMA, and GSM networks were deployed. For the most part, AMPS networks are still available, especially in rural areas, although you’ll pay dearly when making an analog roaming call off a digital network. As for CDMA, a few carriers support this network, the big players being Verizon Wireless and Sprint PCS.

I typically prefer a CDMA phone that supports AMPS, simply because it means more coverage. When I need to make a call, I can’t be bothered looking for a network or driving an extra 10 miles to find one. For example, if I’m stranded on the highway without a call box in sight and a phone that can’t get any service, an analog signal (AMPS network) is usually available, and I can use it to make a call if my mobile also supports AMPS.

Finally, text messaging: In general, the answer is yes, you can send a text message from a CDMA to a GSM phone anywhere. However, your best bet is to check with the carrier first; be sure to ask about text messaging plans so that you don’t end up with a devastating bill.