Merged GSM/Wi-Fi Scheme Proposed

TTPcom will outline its concept for the optimal architecture for converged cellular and wireless-LAN (Wi-Fi) devices during a seminar on GSM evolution to Edge at the show. Many other companies are exploring the convergence concept. Analog Devices Inc., for example, is also working on a way to combine the two technologies, said Christian Kermarrac, vice president of RF and wireless systems.

There is no pull from carriers or phone manufacturers for a fully integrated solution, however, said Doug Grant, director of marketing for Analog Devices (Norwood, Mass.). "The radios will remain separate for some time, as the investment required to respin an ASIC that integrates the two is prohibitive at this point," he said. "Carriers want to remain flexible."

Greg Matthews, contract fulfillment manager at TTPcom, agreed, noting that this separation will remain especially true for laptops. "You don't need a lot of functional integration between the two GSM and 802.11 there, as Wi-Fi is already in there, almost as part of the specification for laptops these days," he said. (802.11 is the IEEE standard for Wi-Fi devices.)

Matthews also talked about the complementary nature of cellular and wireless technology. "When you're on the move and just need short bits of info, GSM/Edge is perfect," he said, "but when you're involved in a more data-intensive, immersive application, that's where WLANs can take the load off the cellular network."

As device sizes shrink down to PDAs and then smart handsets, however, the integration requirements will increase. "The simple phone with cellular and Wi-Fi access for voice-over-Internet Protocol is the biggest driver toward wireless integration. If you want to put 802 into a phone, you have to use more optimized chips," Matthews said, referring to size and power consumption.

While some companies are addressing that-most notably Broadcom, with its recent announcement of a low-power 802.11b solution for embedded applications-Matthews believes that they may be off base somewhat. "The baseline for Wi-Fi is 802.11g now," he said, "plus, it's more power-efficient at the higher data rate, which means it'll consume less power, as the transmit mode is the most power-hungry portion." The real question, he said, is whether it'll be .11g only or .11a/g: "No hotspots are doing 5 GHz .11a right now, but that'll change when the number of hotspots increases and interference becomes an issue at 2.45 GHz."

While the radios will essentially remain separate, Matthews intends to lay out in his description of the proposed architecture, called GSM.11, a means by which some components, such as crystals and clocking circuitry, can be shared to reduce space and cost. "You can't achieve much commonality between the radios, because 802.11 standards were defined without any reference to any other standard," he said. This contrasts sharply with 3G, he said, which was "very carefully designed so you can have a lot of commonality between the GSM and 3G sides." But Matthews did see the potential for a migration of the WLAN digital functions onto the GSM chip.

The GSM.11 architecture, which Matthews said has already received interest from at least one semiconductor manufacturer, comprises a GSM side and an 802.11 side. The GSM component has two processing cores: a DSP for the radio and a microcontroller for control and protocol processing. Memory is included. The 802.11 side comprises a separate chip for the modem, followed by high-speed logic for protocol processing and a special processor for lower-level media-access control processing.

"You need the high-speed logic for the very fast control and protocol processing needed at 54 Mbits/second," said Matthews, who added that the 802.11 side would also need about 64 kbytes of local RAM for software and data, though voice-over-IP (VoIP) might have its own memory requirements. "The remainder would reside on the host," he said, which would also take care of the mobility aspect.

"Today, the system for VoIP would have to be shut down and rebooted as a user migrates between networks, but in the future it'll be seamless," he said. For data connections, seamless roaming is much closer. "Separate GSM and 802.11 cards can do it today," he said.

For the interface between the GSM and 802.11 components, Matthews said that it will be configurable "to match up to each of our various GSM partners."

John Haines, head of research at TTPcom, said Matthews will present at the show TTPcom's vision of how Wi-Fi and 3G technologies will interact. Matthews will describe how Wi-Fi could be used by carriers for voice calls using VoIP in areas where the wide-area network can't reach. This use, Haines said, makes Wi-Fi particularly complementary to the newer 3G technology, which has shorter reach per basestation. Wi-Fi could be used to fill out coverage. "There's good reason to believe that the operators will leverage all these techniques to achieve coverage," Haines said.

Those same carriers are under pressure to create revenue from 3G-like technologies, said Malcolm Burwell, the company's general manager of North America, "even though 3G won't be with us for a number of years."

Debate about the place of Wi-Fi in 3G technology is not new. At a panel held at the recent Communications Design Conference, panelist Craig Barratt, CEO of Atheros Communications, said carriers "will dominate the Wi-Fi market."

Another panelist, Andy Seybold, analyst and president of Outlook 4Mobility, took it a step further. "Anyone who's solely in the hotspot business is not going to make it," Seybold said. That merging of the two services is still a ways off. "The back end infrastructure between them won't be there for another three years," he said. "First you'll have individuals signing on, then you'll get full roaming between them with combined billing."

According to Barratt of Atheros, the handsets will have the capability long before the infrastructure does, with businesses leading the way with free voice access over their network.

This story courtesy of TechWeb .