A number of vendors will be showing off systems and devices designed to combine cellular and voice-over-Wi-Fi at this year's 3GSM trade show in Barcelona next week - and this time around, many of the offerings have already benefited from testing in the real world.

The idea of building Wi-Fi into mobile phone handsets is to give a single device access to both mobile and fixed telephony, in other words, fixed-mobile convergence (FMC). The idea has been around in various forms for some time now, but vendors say this year's systems are more practical for real-world usage.

Atheros, BridgePort, Convergin, Calypso, CSR, Qualcomm and UTStarcom are among the companies introducing FMC systems at the conference.

Atheros on Friday announced a collaboration with Qualcomm that will see the two companies developing interoperability between Atheros' ROCm single-chip Wi-Fi/cellular product and Qualcomm's Mobile Station Modem (MSM) chipsets. Initially, ROCm will work with the MSM6550 for CDMA2000 networks and the MSM6280 chipsets for WCDMA (UMTS) networks, the basis of 3G in Europe.

Qualcomm is one of the leaders in cellular technology, while Atheros's chips are used by a large number of PC, networking equipment and handset manufacturers. The two companies will demonstrate the initial ROCm and MSM system at 3GSM next week, and the products should become commercially available in June.

Chipmaker CSR and Calypso Wireless will also be demonstrating converged handsets at the conference. CSR is demonstrating its UniFi-1 single-chip Wi-Fi silicon for consumer electronic devices alongside a Bluetooth HV3 connection to a headset, proving that the two wireless connections can coexist in close proximity.

UniFi-1 is designed for integration into handsets and other pocket-sized devices, but CSR will be demonstrating it embedded in a Wi-Fi/Bluetooth combination card plugged into a PDA, which will make a Wi-Fi Voice-over-IP call using a Session Initiation Protocol (SIP) client and terminating in another SIP client.

Calypso will be showing a converged mobile phone, the C1250i, based on its patented ASNAP technology, Intel PXA application processor and Windows CE 5.0. The C1250i has the added distinction that it will connect via Skype for long-distance calls.

'Seamless' handoff
Other companies will be concentrating more on the back-end acrobatics needed to hand off a call between Wi-Fi and cellular networks. UTStarcom, which has been making converged handsets for some time, this week introduced the "Continuity" end-to-end system for carriers, including the FMC Feature Server (FMC-FS), based on the company's handset and its mSwitch IP softswitch platform.

UTStarcom claims mSwitch already has a solid track record, supporting more than 48 million subscribers around the world, and that the Continuity architecture will allow operators to keep adding in feature servers for CDMA, WiMax and other future services. The system supports both single and dual numbers.

The company also said this week that it has completed successful trials of Continuity with Brasil Telecom, a fixed-line and mobile operator with more than 12 million subscribers in Brazil. UTStarcom will be providing its F1000 Wi-Fi phone for customers of RabbitPoint, a UK-based firm setting up an international Wi-Fi network to allow users to make international calls free of roaming charges.

Convergin and BridgePort Networks will also be demonstrating new hand-off systems at the conference.