On Call: Finding 3G

Q: I currently have an iPhone 3G but I'm considering purchasing the Sony Ericsson C905. This would be my first time using an unlocked phone and I'm a bit skeptical that it will work. What steps do I need to take in order to make the switch go as smoothly as possible? And will I be able to use AT&T's 3G network?
- Nacor

A: Buying an unlocked phone needn't be complicated as long as you consider a couple of points. Most importantly, the phone will need to support the GSM bands used in the United States. Since the C905 is a quad-band GSM phone, you'll be able to make calls here without any problem. Just pop in your AT&T SIM card and you can start dialing. Yet, the 3G compatibility is another story. Sony Ericsson makes two versions of the C905, each with support for different 3G bands. The C905i will support only European 3G bands, while the C905a will work with AT&T's 3G network. So when buying your phone, you'll need to make sure you have the correct model.

Once you get the phone, you'll also need to program it with the correct multimedia settings to send picture messages and browse the Internet. The settings are unique to every phone and carrier but you should be able to download them from the support section on Sony Ericsson's Web site.

Q: I'm new here in the United States, and I would like to know if I can use a prepaid SIM from Verizon Wireless. Is that possible?
- Chaya

A: Verizon Wireless is a CDMA carrier, which means that its phones don't use SIM cards. Verizon does offer prepaid phones, but you'll need to purchase a phone from the carrier if you want to use the service. And in any case, Verizon does its best to downplay its prepaid service.

If you already have a prepaid SIM, I would recommend using it with either an unlocked GSM phone or a handset purchased from AT&T or T-Mobile. The two carriers also offer prepaid SIM cards of their own.

Q: I have just purchased a Nokia 6555, but I'm confused about whether it has 3G. While FIDO (my retailer) says it doesn't have 3G, Nokia's Web site says it does. Can you help? And what constitutes a 3G phone? - Ed

A: Rest assured, Ed, the Nokia 6555 is indeed a 3G phone. But there is one important point to consider. While it is compatible with AT&T's 3G network, it is not compatible with T-Mobile 3G network (the two carriers use different bands). You will be able to make calls with both networks, but you'll only be able to use 3G at AT&T.

In answer to your second question, 3G, which stands for third-generation, is a wireless technology for transmitting voice and data at broadband speeds. While your average cell phone is comparable to a dial-up connection, a 3G handset will surf the Web and download data at about the same speed as you might find on a computer with a DSL or cable Internet connection. The benefit is a faster connection and a phone that can deliver more content and services. For example, a 3G phone can offer streaming video and wireless music downloads, while a 2G or 2.5G handset can't offer much beyond a basic Web browser and multimedia messaging. There are several types of 3G, but any phone that supports UMTS, HSDPA, or EV-DO technologies is a 3G phone.

Kent German, CNET's cell phones guru, answers your questions about cell phones, services, and accessories and reports on the state of the industry. Send him a question.