HotSpot @Home Delivers Wireless Convergence

Review: As the first Wi-Fi/cellular convergence system to be offered by a U.S. carrier, T-Mobile's HotSpot @Home could be more important than Apple's headline-grabbing iPhone.

It almost seems as if T-Mobile wanted to make sure no undue attention was drawn to its revolutionary HotSpot @Home converged wireless system. The system was announced just before Apples iPhone (but well after iPhone hype had taken over the media) and positioned as a consumer-only product. Even the name screams "consumer-only."

This is, of course, hogwash. After spending over a week testing the various components of the T-Mobile @Home components and service, it is clear that this is a set of products and services that is more than ready for the small to midsize enterprise, albeit with some caveats. It is, in fact, a fully formed, fully functional Wi-Fi/Cellular convergence system that is the first in the United States to be offered by a carrier. In the grand scheme of things, this could be more important than the iPhone, despite the hype.

What T-Mobile USA, a unit of Deutsche Telekom, is offering is a phone that can connect to its network either through the standard GSM cellular system or through a Wi-Fi connection to the Internet. While T-Mobiles new handsets arent the first with this capability, HotSpot @Home is the first offering to add support for moving seamlessly between these two modes, during a conversation, without interrupting anything and without having to buy anything but the phone. In addition to the two phones, T-Mobile is also offering a pair of Wi-Fi routers that are optimized to prioritize voice traffic.

While T-Mobiles HotSpot @Home can be used with any Wi-Fi access point, it wont work on networks that require advanced authentication. As a result, an enterprise RADIUS server will keep the phones from working except (perhaps) through guest access. And, of course, the phones wont support log-in portals.

T-Mobiles service wont plug into a corporate PBX, as all the convergence in this GSM-over-IP service takes place on the carrier end. Whats more, as with the consumer-focused iPhone, companies may have trouble reconciling the individual user service plan structure of HotSpot @Home with their corporate T-Mobile accounts.


However, if users can live with the limitations, the T-Mobile HotSpot @Home service could be a real benefit to a business. Users get unlimited Wi-Fi use (if they sign up for the right plan, which costs $19.95 per month). The Nokia 6086 and Samsung t409 phones that support the service cost about $50 with a two-year contract. The voice-optimized D-Link and Linksys routers also cost about $50 apiece, but are currently available for free with a mail-in rebate.

/zimages/7/28571.gifClick here to read more about T-Mobiles convergence system.

T-Mobile is reportedly working on a similar converged system more geared to business users, but in the meantime, the company has delivered an actual, working converged system, which is something no other carrier has managed to do. At the very least, its worth a serious look.

Converged testing

The part of the HotSpot @Home offering users will see first is one of the two phones that are being offered with the ability to make the GSM/Wi-Fi transition. Other T-Mobile phones that are Wi-Fi enabled, such as the Dash smart phone, can work on both Wi-Fi and GSM, but they cant move between them. Currently the Samsung t409 and the Nokia 6086 are the only phones that work with T-Mobiles converged service.

For this test, T-Mobile sent both the Samsung and Nokia phones, as well as a T-Mobile-branded Linksys WRT54G-TM router. The Samsung phone arrived first, so I began my testing with the Samsung handset and a Linksys SRX 400 router that isnt optimized for voice, but does feature a MIMO (multiple input, multiple output) antenna system for enhanced throughput and range. Because eWEEKs Washington lab has cell phone service from T-Mobile that could charitably be described as "spotty," testing the transition wasnt possible. However, the Wi-Fi calls worked perfectly, and were at least as clear as a cell phone call. The calls exhibited little latency (about .5 second).

Rather than install the T-Mobile/Linksys router with a direct connection to the Internet (as the company recommends), I installed it as it would probably be used in a business. It was behind the firewall and the main router, and it got its DHCP (Dynamic Host Configuration Protocol) and DNS (Domain Name System) information from an internal server running Novell NetWare 6.5. Going through the setup process was exactly like every other Linksys setup, and used the same wizard software. Getting the router to work inside and existing network was not a problem.

Initial tests with the Samsung t409 showed that T-Mobiles converged solution can work very well indeed. Since cellular coverage was unavailable at the lab, I retreated to a nearby Starbucks and later to a Borders, both of which feature T-Mobile HotSpots. A series of test phone calls made while moving into and out of the Wi-Fi coverage area confirmed that the transition between Wi-Fi and GSM is transparent. The only way to tell thered been a change was by looking at the screen for the carrier information.

The Nokia 6086 performed just as well during the transition between GSM and Wi-Fi. However, that does not mean that these two phones were equally useful. In fact, their performance was quite different, and some of those differences will be critical to anyone wishing to take advantage of the HotSpot @Home service.

The phones

The Samsung t409 is a nice but not spectacular flip-phone. A 1.2 megapixel camera is its main distinguishing feature. The t409 ships with T-Mobiles annoying MiFaves user interface, but, fortunately, this is an optional feature. The handset does not include a memory card slot. More importantly, Samsung did not set up the phones software so that it could transition from one Wi-Fi router to another. According to T-Mobile, the handset must make a GSM connection before it can move to the next Wi-Fi connection.

The Nokia 6086 ships with the same user interface as the t409, but the differences are significant when you look beyond that. The Nokia handset includes a MicroSD memory card slot, for example. More important, the Nokia phone can transition from one Wi-Fi router to the next directly, which means you can use it in areas that dont have good cell coverage and still maintain a conversation.

I tested the phones in a variety of business settings, and again differences emerged. The Samsung could see Wi-Fi routers that the Nokia missed, and the Nokia could see some that the Samsung missed. There was no discernible pattern.

What was more important was that the Samsung phone could not be used with some WEP (Wired Equivalent Privacy) or WPA (Wi-Fi Protected Access) systems, because the user cant type in the right characters for pass phrases. For example, when I tested both phones at a local Acura dealership that offers free Wi-Fi for customers, the Samsung was unable to accept a "0" as a part of the password. The Nokia worked fine. Since the number 0 is a legitimate part of a security password, this hurts the Samsungs usefulness outside of its local setting.

Both phones are unable to use log-in portals, common at some public Wi-Fi locations and some hotels. This means, for example, that when I tried to use the phones at a Barnes & Noble, which uses an AT&T hot spot, I couldnt get past the hot spots log-in portal.

Neither phone will pull in a Wi-Fi signal as well as a laptop will. In fact, neither phone did as good a job receiving GSM signals as other phones Ive tested. A T-Mobile version of a Motorola RAZR handset I had on hand would typically show one or two bars of signal before either test phone would register the presence of the cellular network. However, the Wi-Fi reception of the Nokia phone was consistently better than that of the Samsung phone that I tested.

The routers

T-Mobile is offering a pair of routers, one from D-Link and one from Linksys, that are optimized for voice traffic. This means that they add QOS (quality of service) prioritization to voice traffic, and otherwise package the GSM-over-IP packets so that they get preferential treatment over data packets. According to T-Mobile, this means better voice quality and longer battery life while using Wi-Fi. Both of these claims held up in testing. While voice quality is subjective, the difference in battery life with Wi-Fi was dramatic. A standard Wi-Fi router would drain the phones in a day. T-Mobiles version, which uses UAPSD for power conservation, would let the phones last for two or three days.

While the T-Mobile routers do provide priority for voice calls, I was unable to find any performance difference when compared with routers without this feature. Considering that the GSM-over-IP calls consume a mere 72K bps, this isnt surprising. T-Mobile didnt place any upper limit on the number of handsets that can work with one router, saying only that it depends on the bandwidth of the Internet connection.

The service

Clearly, the T-Mobile network is doing most of the heavy lifting in this converged service. There is nearly constant communication between the handset and the network in regard to relative signal quality, which GSM connection is nearby, which signal is better and the like. As a result, the phone has the transition ready before the user needs it, which explains the smoothness of the transition.

As youd expect, theres a lot of infrastructure in the background to support all of this, including a network of media gateways, updated cell site controllers and updated Wi-Fi routers in all of T-Mobiles 8500-odd commercial HotSpots in the United States.

The service will only work on T-Mobiles network using phones designed for the service that are also using T-Mobile USA SIM (Subscriber Identity Module) cards. While you can use T-Mobile phones nearly anywhere in the world, and while you can use the Wi-Fi feature at with any open Wi-Fi router, the transition between services currently only works in the United States. Also, the Nokia, as a quad-band phone, is the only one thats truly global.

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Wayne Rash

Wayne Rash

Wayne Rash is a freelance writer and editor with a 35 year history covering technology. He’s a frequent speaker on business, technology issues and enterprise computing. He covers Washington and...