A struggle has emerged in the mobile phone industry, between competing approaches to “fixed mobile convergence,” or FMC. One approach provides consumers with a single number for calls routed over both “fixed” WiFi access points and “mobile” cellular radio networks. The other works with access points that are not carrier-controlled.

FMC phones incorporate both mobile and WiFi radios, and deploy various least-cost routing schemes to ensure that the less expensive access mode is used when available. The more advanced FMC solutions allow simultaneous call standby modes on both radios, and seamless call hand-off between wireless networks, for example when entering a building equipped with a WiFi hotspot.

Two competing FMC schemes seem to be emerging. One is “IMS” (integrated multimedia system), a slightly misleading acronym for a specification aimed at fostering interoperability between wireless cellular and IP (internet protocol) networks. IMS is maintained by the 3GPP (third-generation partners program) industry group.

The other FMC scheme is called UMA (unified mobile access). It offers the advantage of allowing a single phone number to be used on both fixed and mobile radio networks. The downside is that UMA only works with UMA-certified CPE (customer premises equipment), whereas IMS-based FMC schemes support ordinary WiFi access points.

Don Brown, marketing and communications director for FMC software supplier LongBoard, says, “Most agree that UMA is not IMS-compliant.”

Brown explains, “UMA and [IMS-based FMC] use the same dual-mode handsets, just with different software. Mobile phone carriers are backing UMA, because if [they] put out a dual-mode handset with untethered access to WiFi, what's to stop [users] from loading Skype, and not needing the carrier anymore?”

Brown calls UMA a “dead end,” from a technical perspective. “It's a transport technology, to ensure the longevity of wireless network operators,” he says.

At the same time, Brown acknowledges that IMS-based FMC faces challenges. “The problem with [VoIP applications today] is that [they're] not very easy to use… I want to be able to walk along, and when I walk into range of commercial, WEP-secured, or open hotspot, have the call routed over IP without intervention.”

Whether and when such technology appears, of course, may ultimately be up to the carriers, since they, more than anyone, control mobile phone technology — a fact noted in a story at The Register predicting that UMA will kill VoIP.

LongBoard's IMS FMC products

LongBoard's IMS-compliant “OnePhone” SIP client currently supports mobile handsets running Windows Mobile, Brown says, and the company is working with “a major carrier” on implementing a Symbian version. The Linux version is described as “under finalization.” LongBoard, then known as Persona, announced a Linux version of OnePhone in September of last year.

The OnePhone clients work in tandem with LongBoard's main product, an IMS application server called LongBoard Mobile Application Server (LMAP). LMAP supports Solaris, because, many carriers are still most comfortable with “what they know,” according to Brown. “There's an attitude like, 'Until all the old Bell-heads die…'” he said. The company currently has no plans to port LMAP to Linux, that Brown is aware of.

In addition to its 3G, IMS-based application server, LongBoard also offers FMC application servers for legacy 2.5G networks, Brown notes.

Another vendor, Bridgeport Networks, also demonstrated an IMS-compliant FMC platform that works in conjunction with Linux-based smartphones from E28, at 3GSM this year. The Bridgeport solution is based on SS7 signaling, an older circuit-switched line protocol, according to Brown.

Dual-mode 3G/WiFi Linux smartphones have been available in Japan for some time.

 
This article was originally published on LinuxDevices.com and has been donated to the open source community by QuinStreet Inc. Please visit LinuxToday.com for up-to-date news and articles about Linux and open source.