An important aspect of Voice over Wi-Fi (VoWFi) is cell phone seamless connectivity over wi-fi networks. T-Mobile USA (part of Deutsche Telekom) has something to say as well: mobile phones don’t have to break the bank, when you can make calls over both cell towers and Wi-Fi routers. T-Mobile claims calls made via cell phone won’t be dropped as you switch between cellular and Wi-Fi networks. Homes with poor cell coverage can still make calls if Wi-Fi access is made available, I say about time!

This is the culmination of the company’s Hotspot @Home initiative, which is going nationwide after several months of trials in the Seattle area. With this service users can make unlimited calls by adding $10 a month, or $20 a month for up to five lines on a family plan, to an existing T-Mobile phone account. The “unlimited” part only includes the VoIP calls made via Wi-Fi, of course – except if the call started on the Wi-Fi side. If the call then roams to the cell network, it remains unmetered (maybe this aspect will change soon).

This may yet be the most important “break-through” since introduction of cellular phones.

I’m sure, in the beginning there will be a small number of phone manufacturers offering dual mode phones, but as this service catches on, I’m sure other providers will jump on the dual mode band wagon.

Users are not limited to Wi-Fi calls on their home networks. The phones will work with any open Wi-Fi connection. T-Mobile will also be selling home wireless routers from Linksys and D-Link that it says are optimized for the service by supporting the WMM standard, part of 802.11e with a proprietary method for setting up a secure link. The routers will be free after a mail-in rebate. T-Mobile apparently won’t guarantee call quality with other routers, nor at non-T-Mobile hotspots. T-Mobile hotspots all have full T-1 lines for backhaul to the Internet, while typical public hotspots with open access are likely only to have DSL or cable connections with no service level agreements (SLA).

The Hotspot @Home network is powered by Unlicensed Mobile Access technology, which enables seamless hand-off from Wi-Fi to cellular and back. This technology has been used by networks overseas by BT in the UK and Orange in France.

The iPhone being a hot product it is, while offering Wi-Fi, will not support this kind of hand-off, as its exclusive carrier, AT&T, doesn’t offer this service. Wi-Fi on the iPhone will likely be used for data only, unless Apple introduces a VoIP application in the future, or people use a third party soft phone software but then I don’t see how seamless switch over will work.

Think of Femtocell as a mini base station for cell phones. It can connect via Wi-Fi or Ethernet to service provider’s network and handle a few cell phones.

Unlike a repeater or booster, that some people use to boost their cell phone signal, a Femtocell provides an alternate route to connect to service provider’s network in areas where you might have internet but no cell phone coverage.

There are obvious small business and end user benefits, another use maybe in hospitals where only specific handsets are allowed to connect to serve as a link between staff while general public has no signal.

As Femtocell’s capture the market, it will be as simple as deploying a Wi-Fi access point to extend cell phone coverage in areas where there is none. As you have probably already deduced, a Femtocell deployment requires your service provider to support it. We’ll keep an eye on this technology as it develops.

VoFi stands for Voice over Wi-Fi. Whenever you use your VoIP connection over a wireless connection, you are using VoFI. Do you have people connecting to the network via Wi-Fi connection and then using a soft phone to make a call? Then you are using VoFi.

For a few people, a regular data Wi-Fi connection works fine, but when you are planning on rolling out VoFI for a large number of people, a shared data Wi-Fi connection will not work.

To successfully use a Wi-Fi connection you need to make sure your corporate wireless connection has high bandwidth to host voice connections, low lag times and fewer hops. You may need a higher number of access points if you plan on using voice over the connection compared to plain data.

You can get away with using VLANs on same access points, some companies go a step further and setup a totally separate network for voice. Normally if a company is using 802.11b/g for data, they might want to consider using 802.11a for voice since they use different frequencies and this minimizes any chance of interference.

The best thing you can do is to perform an extensive and comprehensive wireless survey before rolling out VoFI. Take care of all the problem zones and if at all possible have a separate Wi-Fi infrastructure for voice side. Using a 802.11a connection would be better for voice and/or video since this standard offers more bandwidth and is less interference prone compared to the 802.11b/g standard.