Advantage GSM Carriers: Simultaneous Voice & Data

Now that Verizon Wireless is getting traction with the iPhone 4 on their CDMA network AT&T is left trying to find ways of differentiating itself. While it’s too early to know how much of a bloodletting AT&T will suffer, it’s clear that in many parts of the country Verizon’s much touted network supremacy will win over a significant number of frustrated AT&T customers, even if it means buying a new CDMA capable iPhone4.

Perhaps the biggest difference between the two carriers is the type of networks they operate. Networks based upon GSM standards, like AT&T and T-Mobile here in the US, allow the simultaneous use of voice and data. In marked contrast, CDMA networks like Verizon’s, simply don’t do this.

The rumor is that AT&T is working with Apple to allow iPhone 4 users to use their iPhones as mobile wifi hotspots. This practice has been possible for some time with “jail-broken” iPhones, but frowned upon by AT&T. In the past they simply didn’t want user placing additional burden on their network. It seems that now they may be counting on such capability to retain some of their high-value iPhone user base.

Some people have commented that the real need for simultaneous voice and data is slight, so it might not be a compelling capability. I’m here to tell you that such assertions are very simply wrong.

T-Mobile has been offering tethering for some time. I’ve made considerable use of it via my G2.

This past week I was staying at a Hyatt in New Brunswick, NJ. Hyatt’s are normally beyond my travelling budget, but we use Hotwire.com for hotels so we often end up in really nice places at reasonable rates. The trouble is that the nicer hotels still usually charge $10-15/day for internet access.

At such rates per day one can very quickly justify paying the monthly cost of a Mifi type device or USB 3G stick. This is how I convinced my employer to cover the cost of my Sprint 3G Mifi about eighteen months ago. I’m coming to the end of a two year contract on that service and I’ve long decided that I will not renew the service.

Since the November firmware update to my G2 I’ve been able to use it as a hotspot, making T-Mobile’s HSPA+ network available to my laptop and netbook. This can be considerably faster than Sprint’s 3G service.  I have still made some use of the Mifi due to differences in the coverage areas between the two carriers.

Curiously, while T-Mobile announced that there would be a $15/mo option to permit tethering, I don’t see that being added to my monthly bill. They seem to be allowing tethering for free on existing accounts.

This past week when I visited the Hyatt logon page and saw the $10.95/day rate for access I knew exactly what to do. I plugged my G2 into a charger and enabled the hotspot mode. I also enabled the Bluetooth radio and got out my Plantronics Voyager Pro UC headset. So arranged I was able to work online for many hours at a time, making and receiving calls as desired.

I see great value in the ability to use voice and data simultaneously. Not usually when I’m walking down the street with the phone, but typically when I’m working somewhere that doesn’t offer suitable internet access. Suitable might mean at the right price, or perhaps a matter of reliability or speed. Down market hotels often provide free internet access based upon wifi, but both reliability and performance can be highly variable.

Perhaps this sort of thing is only useful to a road warrior like myself. I suspect that there are enough of us that it will be a significant factor in the carriers marketing plans.

There was also a rumor that Verizon would implement a Voice-Over-EVDO-RevA strategy, allowing them to offer simultaneous voice and data. Some see this this as a natural step in the migration to LTE, where the core network is IP-based and voice just an application.

It sure is amusing to watch AT&T and Verizon slug it out, all the while enjoying T-Mobile service. I’m not an iPhone user, but if I were I’d certainly want to be able to tether and talk at the same time.