GPRS and CDMA: how do they rate?

I had a chat last week with a chap who knows a thing or two about both GPRS and CDMA. He explained coherently how both networks will develop -- without any of the hype or spin the two telcos like to employ.

I had a chat last week with a chap who knows a thing or two about both GPRS and CDMA. I won't name him as the company he works for pitches for business with both Telecom and Vodafone.

He explained coherently how both networks will develop -- without any of the hype or spin the two telcos like to employ.

First things first. CDMA 1x is faster than GPRS. "There's no doubt about it," says my contact, which is good because now we can get on with our lives. But how fast is fast? Telecom's CDMA 1x should run, in the real world, at 60kbit/s to 90kbit/s. Vodafone's GPRS would probably hit the 30kbit/s to 60kbit/s mark.

Both companies have upgraded their entire networks nationwide -- Telecom from D-AMPS to CDMA and now to 1x and Vodafone from GSM to GPRS -- so there's no problem with coverage beyond the obvious blackspots.

If you talk to Telecom they'll tell you that Vodafone has to spend an absolute fortune upgrading its GPRS network to 3G standards. They'll also tell you that CDMA 1x is a 3G network already. Neither claim sits well with my contact. "So-called 3G isn't a technology, it's a service level."

A 3G network would be able to deliver all those oh-so-useful things like videoconferencing (does your brain switch off when you hear that phrase? It's one of those things they always tout but never deliver) and would run at megabit speeds.

CDMA 1x can't deliver megabit speeds so I think it's more properly referred to as a 2.5G network. It's fast enough for now, especially given the costs involved in moving to 3G around the world.

As for Vodafone, voice calls are still carried on the old GSM standard while bolted on underneath, so to speak, is the data-carrying GPRS. Vodafone has two options from this point on, says my contact.

"It can go to EDGE, which is in effect GPRS at four times the speed. The theoretical speed on that is 384kbit/s. Or it can go to wideband CDMA."

While EDGE would be a relatively cheaper option, W-CDMA isn't too expensive and could be rolled out piecemeal if the company so decided. Dense populations could get it first, then the rest of the network. The phones would be enabled to step down to GPRS where the higher speeds weren't available. Degradation of service is preferable to no service at all, I suppose.

At the moment Vodafone doesn't have to decide -- which is just as well, because as with most things in the technical world the two standards compete and are being variously touted by the Americans and the Europeans.

For Telecom, already knee-deep in the CDMA family, it's again a choice of two paths: W-CDMA or an amusingly named EV-DO. W-CDMA is the likelier of the two given Telecom's involvement with the Australian arm of Hong Kong telco Hutchison. Hutchison and Telecom have signed a deal to work together on 3G so that's probably what will happen here.

EV-DO (evolution data optimised) is something the Koreans are working on and should reach speeds in the realm of 2.4Mbit/s. It leads on to EV-DV (evolution data and voice), which will incorporate voice in the same network. Within the CDMA family voice is carried separately, as with the GSM network.

The ultimate goal for both companies is of course UMTS (universal mobile telephony service), which doesn't yet exist. It will unite the various arms of the cellular world into one standard, which should mean you'll need fewer phones for your travels.

Unfortunately, travellers will still have the problem of frequencies and the way they change around the world. In the US, for example, carriers use a different frequency for GSM than the Europeans. So you'll either need a phone that can hop or several handsets. And while GSM has more users and networks worldwide, if you travel exclusively in Korea or to Australia and the US, you might consider a CDMA-based phone to be more useful.

Then there are the services on offer -- but that's probably another column entirely.

Brislen is IDGNet’s reporter. Send letters for publication in Computerworld to Computerworld Letters.

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