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Sunday, May 16, 2010

A problem with WiFi-based offload?

In general, I'm a fan of using WiFi to reduce load on 3G macro networks, especially for laptops used with 3G USB dongles and smartphones like the iPhone. Where the connection manager works well, there are various models which can permit the device to connect to home/office or public WiFi.

In particular, I'm seeing a fair amount of mobile operators use their own, or partners' networks of public WiFi APs. Most notably, AT&T acquired Wayport and has other footprint for use in iPhone offload, while Vodafone has cut a deal with BT OpenZone in the UK.

However, there is one problem as the density of such offload points increases. As well as the main public OpenZone points in London, I can also use the BT Fon "virtual hotspots" as an extension of my home broadband account.

While this is great for my laptop, it's causing me difficulties on my smartphone. The density of BT / Fon / OpenZone access points in central London is so high (in homes and offices or other locations) that as I walk down the street, my iPhone keeps attempting to register. But by the time I've got online, I've walked past it and onto the next one along the street with stronger signal.

If I walk 5 minutes from home to my local tube station, I need to switch off WiFi temporarily, if I actually want to use mobile data - otherwise I have a constant stream of pop-ups from the connection manager on-screen, and no reliable connection.

It probably wouldn't help with a high density of femtocells either, until there's a reliable way of doing femto-to-femto handoff as you walk down the street.

Food for thought.

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@micronauta said...

Hi. There are easy solutions for both phenomena you describe:

The iPhone can be switched to stop asking you for each network it finds without having to turn off Wifi. It will however connect to Wifi networks that you have already connected to if you keep the Wifi interface on and don't let the device sleep.

I usually turn of Wifi when walking around the city but for a different reason: battery life. Even though theoretically Wifi will usually cost lest power than 3G when in use, searching and registering eats the battery fast and slows down the whole device.

You might also have noted that unless you have heavily modified a jail-braked iPhone or connected an external battery, it will keep Wifi off when the screen is off and the device sleeps, so it's a non-issue when the device is in your pocket.

As for femtocells, they are usually set up in such a way as to only allow pre-registered phones to connect, so it's a non-issue except with some public setups in subways, malls and such where their deployment is usually as carefully planned as the rest of the network and can do graceful handoffs.

This is all data. I have not used UMA-enabled smartphones like some Blackberries, which can offload GSM voice calls to Wifi. It's a very cool technology for which there is something in the 802.11 spec and I believe the iPhone's Wifi stack supports it but it is network provider dependent and nobody seems to be doing it with the iPhone yet. Still, in that case it will be the same, if you set the iPhone to only connect to known networks you won't run in to any problems as the handoff to Wifi would only happen to known hotspots.

Dean Bubley said...

The problem is that I now have both BT Openzone and BT FON [its open-access service for home broadband] as "known hotspots" - and so if I walk down the street (using the phone) it is likely to see them repeatedly.

I probably notice it because I tend to do things like RSS updates, download email etc while walking to the tube, so it's not asleep in my pocket.

Fair point on femtos - although that will change once there is a move to "open access" mode rather than just closed to specific subscribers, which may occur in the near future.

UMA is something I've written about since its inception in 2004. It does some things very well, but other things exceptionally badly.

Anonymous said...

Dean, this is a good point and becomes more of a problem in the home when in-home WiFi is used for video streaming and gaming. There is certainly a business case for managed high QoS wireless data services - there seems to some talks on this at the up-coming Femtocell World Summit

Raman said...

In Singapore we have this public free WiFi access in all major shopping centers, libraries, some parks etc. and they have an authentication based on user-name password at WiFi level (without launching the browser, that is) and it seems to be working very well on my iPhone. It is called Wireless@SGx and there is a little auto-configuration programs for PCs as well wherein you need to authenticate only once. Something like that should solve it, no ?

Dean Bubley said...

Large, single operator public Wifi is relatively easy when it's implemented in a unified way. But that's unusual - normally you have thousands of independent hotspots or shared-access home Wifi operated by multiple different operators, with no central control or standardised SSIDs.

It's easy to think that public hotspots are the most important manifestation if Wifi, but really they are a small sideshow compared to personal or business access points.