T-Mobile HotSpot@Home Review

When is a cell phone not a cell phone? When it makes calls over a WiFi connection. That's the promise of T-Mobile's new Hotstpot@Home service; for an extra $9.99 a month on top of your existing phone bill, you get unlimited calls using your home WiFi connection. That could be a huge draw for those looking to replace a home phone with a cell phone, and it also works at T-mobile HotSpots on the road; a big plus for frequent travelers.

We tested the Hotspot@home service using the Samsung SCH-T409 and a Linksys WRT-54G-TM router supplied by T-Mobile; they also offer the Nokia 6086 and a D-Link router, and there are rumors that the T-Mobile BlackBerry Curve will also support Hotspot@Home. The SCH-T409 costs $49.99 with a 2-year contract, and the Hotspot@home service costs $9.99 a month for unlimited calls.

Before we get into the review, a quick overview on how the service works. It uses a new standard called UMA (Unlicensed Mobile Access), which allows a cell phone to send audio data over a WiFi connection. When you are in range of a WiFi network, the cell phone uses this to connect to the Internet and T-Mobile's servers. They communicate with the phone, and when you dial a number on the phone, they set the call up, receiving the audio data over the Internet from the cell phone. The cell phone keeps an eye on the WiFi signal, and if the signal gets weak, it notifies the servers and starts transmitting  over to the digital cell phone network instead. The T-Mobile servers keep the call going while this switch occurs, and start receiving the audio data that the cell phone is now transmitting over the cell network, switching the call from WiFi to a cellular connection automatically. All of this happens without the person being called knowing or caring if the call is coming over the WiFi or cell network. It's very clever stuff that has been in development for several years.

Audio Quality

To test the quality of calls made over both WiFi and cellular connections, we used the same professional testing system that we use on normal cell phones to test the quality of calls made using both WiFi and cell connections, and found some interesting results. As far as the frequency response goes, we found the two connection methods were identical; the differences were so small as to make the two sets of curves almost indistinguishable.



This is, perhaps, not surprising when you know that the two connection methods use the same method of compressing the call, and transfer the same amount of data (both methods use the AMR-FR codec running at 12.2kpbs for you cell phone geeks).

We were also pleased to find that making calls over the WiFi connection didn't introduce much of a delay. All cell phones introduce a certain delay as they compress and transmit the sound; usually between 300 and 400 milliseconds (about .3 to .4 seconds). We measured the delay of the SGH-T409 making calls using the T-mobile cellular network at 382 milliseconds for the sound sent and 382 milliseconds for sound received by the t409. For calls made over the WiFi connection, this delay was 405 milliseconds for sound sent from the t409 and 457 milliseconds for sound received by the t409. That's a pretty small difference that would be barely noticeable. Considering that the call data has to navigate the Internet before it reaches the T-mobile network, it's pretty impressive.

We did find, however, that on some busy Internet connections, the call got somewhat choppy as the data was delayed by other traffic. Cell phones can switch down to a compression system that sends less data (called AMR Half Rate, which only sends 6.6kpbs of data), but the SCH-T409 we tested can't do this over the WiFi connection; it can only use the full rate codec. This might be an issue if you were trying to use a busy connection (such as the press room at a big convention or a Starbucks filled with laptop users streaming audio), but you can switch over to the cell network with relative ease. And a clogged Internet connection is an extreme example; on most connections, the call quality was fine.

Switching Networks

We found that the process of switching from a WiFi connection to a cell network is as simple as T-Mobile claims; when you make a call over the WiFi connection then walk out of range of the WiFi network, the switch is seamless from the callers point of view (or point of hearing, rather). The caller doesn't have to do anything; the T-Mobile system handles the switch from WiFi to cell network automatically. The person on the other end might notice something, though; a slight gap in the call and a second or so of partially interrupted speed. To show how this works, we ran the following test: we set a short clip from an audio book playing repeatedly, then made a call using the WiFi connection. We then took the cellphone for a walk, leaving the range of the WiFi network so that the phone switched over to the cell phone network. You can see the result of this test in the video below; the call starts on a WiFi connection (in our office), then switches to the cell network, then back onto a HotSpot at a local Starbucks.


It's interesting that the switch from WiFi to cell is a little glitchy, but the switch from cell to WiFi is pretty much flawless; you barely notice when it happens. We suspect that this is because the switch from WiFi to cell network happened when the WiFi signal dropped to low levels; some of the data may have got lost before the system realized there was a problem and switched to the cell network instead. The switch the other was was glitch-free because it didn't happen until the phone had a strong signal from the new WiFi network.

We did also have occasional dropped calls when the system was trying to switch, and again these seemed to be connected to the WiFi signal strength dropping off quickly. And this could be due to the metal-framed building that we tested in (which tends to eat WiFi signals); when we ran the same test in a wood-framed house, the switchover happened without problems.

One interesting thing to note here is that, as long as a call starts on the WiFi connection, it doesn't matter if it switches over to the cellular network; T-Mobile still allows unlimited calling. So, if you're planning to make a long call, start it on the WiFi connection and then leave the house and it won't count against your plan minutes. This does make the dropped call issue a bit annoying; if you start your call on WiFi, and it gets dropped, you'll have to call again on the cell network, which will use your cell minutes.

Calls can also switch the other way: if you walk into range of a WiFi connection that your phone has previously connected to, it will detect this after about 30 seconds and switch over to the WiFi connection. Again, you don't have to do anything for this to work; the phone does it automatically, and the only indication is a change in the logo on the screen. However, the unlimited calls doesn't count in this case; if the call starts on the cell network, it is charged as a normal call.

It's also important to note that the T409 doesn't automatically connect you to new WiFi networks; you have to go into the WiFi menu, scan for networks and pick the one you want to connect to. The exception to this is T-mobile hotspots; as they all have the same SSID (the name of the network), the T409 automatically detects them and switches over to them if possible. In our video of the test above, the second switch happened when our call switched over to a hotstpot in a local Starbucks when we walked past it.

One thing to clarify here: if you are making a voice call over Wifi at a T-Mobile hotspot, you don't have to pay the access fees that T-Mobile usually charges; that connection is free. You cannot, however, use this to browse the web on your phone. But while you don't get free web browsing, frequent travelers can use Hotspot@home to make unlimited calls if the places you visit have hotspots. And, with hotspots in most Starbucks, many hotels and other locations, this could be a big selling point for road warriors.

On The Road Again

We also tried making calls over WiFi at a number of locations with T-Mobile hotspots, such as coffee shops and hotels, and we found the process to be quick and easy. As noted above, the T409 automatically connected to T-Mobile hotspots, bit with other networks, you'll have to connect to them manually, using the Menu>settings>WiFi>Add New Network option, then selecting the wireless network from the list of found networks. This is pretty easy to do, and when you've connected once, it will remember the details. The only issue is if the network uses encryption; you then have to enter the network key using the phone's keypad, which is rather awkward. The exception to this is if you use encryption on a network with a T-Mobile supplied router; in this case, you press the key button on front of the router and it goes into a special mode that allows some devices (such as phones that support Hotspot@home) to connect without having to enter the key.

Conclusions

Hotspot@home could prove to be a revolutionary service; it's obvious that T-Mobile is looking to use it as a way to persuade people to dump their home telephone lines. And it is an attractive prospect; $10 a month is affordable, and the sound quality is good. And generally speaking, it works pretty well; the icon on the phone screen shows you what type of connection you are on, and dialling is the same either way. But there are a few glitches still to be ironed out; the dropped calls are a pain, and the switching process sometimes causes an audible glitch. These are annoying, but they aren't enough to make the service unusable. Basically, it works pretty well, and the Hotspot@Home service will be a very attractive option for those who travel a lot, or who are sick of their home phone company jacking up the rates again.