Chipsets from startup Engim that allow one Wi-Fi access point to carry data on multiple channels may help bring wireless networks to airplanes.
The Acton, Massachusetts company introduced this week its new generation of both silicon and access points for vendors to incorporate into wireless LAN offerings. Engim's EN-3001 Wideband Wireless LAN chipset and access point reference designs for 802.11b and 802.11g are designed to use three channels at once. This enables more clients in a single area to simultaneously use Wi-Fi, says Scott Lindsay, Engim's vice president of marketing.
Managing Channels
Engim is adding to its lineup a thin access point, priced to system makers at about $100, in which packets are processed in the chipset rather than on a separate processor. Also new is a feature in Engim's radio chip called "transmit cancellation," which can prevent interference that an access point's transmitting antenna can cause to the same access point's receiving antenna, Lindsay says.
At the heart of Engim's approach is multichannel capability. The 802.11b and 802.11g standards use spectrum in the 2.4GHz band that offers at least 11 bands, but generally can support only three because of interference from channel overlap. Each access point typically can only use one channel, and simply putting three access points in one place with each on a different channel--or building an access point with three chips on different channels--won't provide good performance because they will interfere with each other, Lindsay says.
That means the zone covered by an access point, typically about 300 feet, can only be served by one channel, leaving two channels unused, says analyst Craig Mathias, founder of Farpoint Group. That's a waste of spectrum, one that is not a big problem today but is likely to become one in the future, Mathias says.
As more clients in a given space start to use Wi-Fi, access points increasingly will have to make use of those other two channels, he said.
Engim built the silicon for three channels into a single chip, with technology that finds interference and subtracts it out to provide a clear signal, Lindsay says. A radio for 802.11a, due in two or three months, will support three 802.11a channels simultaneously.
Wi-Fi on Board
Airliner cabins may benefit from this network technology optimized for high-density use, according to Jim Pristas, founder and CEO of Matrx Aerospace Broadband Technologies, a startup in Arlington Heights, Illinois. Matrx is using Engim's chipset to demonstrate an in-flight wireless infrastructure it is developing, called Galaxy. Matrx plans to work with airlines, aircraft manufacturers and other partners to install the systems, Pristas says.
Several airlines are looking into such technology; Pristas would not disclose Matrx's aerospace partners.
Galaxy can use multiple wireless bands as well as multiple channels within each band, according to Pristas. Planned for late 2005 is a version geared primarily to passenger Web access and e-mail over Wi-Fi. Some airlines already offer those services, but because Galaxy is designed for airplane cabins, it will perform better--partly because of the multichannel capability, Pristas says.
A second version of Galaxy, for 2006 release, will offer a wider range of services and support proprietary wireless systems as well as Wi-Fi, Pristas says. Matrx envisions wireless delivery of multimedia services including video on demand to screens on seat backs, eliminating the weight and the maintenance costs of data cables in every seat. The system could also be useful to surveillance cameras, crew communication, handheld point-of-sale devices, and even in-flight wireless phone calls, he says.
Besides suppressing interference from other Wi-Fi channels, the Engim chipset can gather information about anything going on in the spectrum band. For example, it can detect interference from other technologies, such as Bluetooth and cordless phones, and pinpoint locations so network managers adjust those sources of interference, Lindsay says.
