FROM EDN EUROPE: Module speeds 802.11a to 162 Mbps

You can cut the time it takes to build a WLAN (wireless-LAN) device using a module from Agere Systems. The system integrates all RF and baseband functions for IEEE 802.11b into one 25×25-mm package. The WL1141 includes the baseband circuitry, direct-conversion radio receiver, antenna switch, and power amplifier, and the use of the package eases type approval. You can treat the BGA-mounted device as a single component, offering a "two-chip" approach to a basic 802.11b when you pair it with a suitable MAC (media-access-controller) chip. Agere also offers a chip set that supports dual RF channels using antenna diversity for more robust WLAN performance in difficult signal conditions.

Despite all the coverage the press has recently given to the 5-GHz standard 802.11a, Agere's business development director, Roman Polz, believes that no alternative currently exists for a cost-effective system to today's 802.11b standard. The company sees a migration directly to a multimode environment that will use coexisting 11a and 11b standards; the environment will also include facilities for 11h, 11g, and other variants. Agere is working with Infineon on chip sets and Ericsson on laptops, handhelds, and interworking between WLAN and 2.5G or 3G cellular systems. The company plans by mid-2003 to provide a multimode system for 11a, 11b, and 11g at a price equal to or lower than today's 11b offerings.

Agere has also announced that it has exploited research it performed at Bell Labs under the name BLAST (Bell Labs Layered Space Time) to achieve a data rate of more than 162 Mbps over one channel in the 5-GHz band. The technology, also known as MIMO (multiple-input multiple-output) uses multiple RF channels and multiple antennas; it demultiplexes raw data into as many streams as there are RF channels and feeds a separate stream to each antenna. Each transmits on the same frequency, and the system exploits the time differences that natural multipath effects add between the transmitter and the receiver to identify and reconstruct the multiple signal streams, which it then remultiplexes back into their original form. You can achieve a linear increase in a channel's capacity by increasing the number of antennas, Agere says. In practice, for 802.11a/g, you use a coding scheme with 75% efficiency for greater robustness, yielding 162 Mbps with three RF paths but one channel. Agere plans to commercialise the technique for use with 11a- and 11h-standard variants.

Agere Systems, +44 1344 296400, www.agere.com.