Boffins outline 24Mbps mobile phone chip design

Not due until 2006

Boffins at Lucent Technologies' Bell Labs has come up a blueprint for a mobile chip, designed with 3G mobiles in mind, which works at a blistering fast 24Mbps.

The chip, which is 10 times faster than anything available today, is unlikely to be deployed anytime before 2006.

Nonetheless the technology behind Lucent's chip merits closer examination.

The turbo decoder chip is described as the first silicon for third-generation (3G) wireless data terminals that supports the evolving High Speed Downlink Packet Access (HSDPA) standard.

HSDPA is an enhancement to Universal Mobile Telecommunications System (UMTS) spread-spectrum technology, also known as wideband code division multiple access (W-CDMA). The chip is fast enough not only to support first-generation HSDPA systems, which will offer transmission speeds between 5 and 10 Mbps, but also future Multiple-Input/Multiple-Output (MIMO) HSDPA systems, which are expected to achieve peak data rates up to 20 Mbps.

So what's in the design of the chip that makes it so fast? Over to Lucent for an explanation:

The chip achieves this extraordinary speed in part thanks to a unique implementation of turbo codes - powerful software programs that perform error correction by adding - to each bit of data transmitted - several redundant bits that help the decoder reconstruct the original signal without errors at the receiving end. In addition, the chip also can be reconfigured for different packet sizes and data rates on the fly, making it compatible with the variable data rates arising from Adaptive Modulation and Coding (AMC) - a key capacity-enhancing feature of HSDPA.

A Bell Labs research team in Sydney, Australia, designed the turbo decoder - the same team that last October announced the industry's first chip that incorporates Bell Labs Layered Space Time (BLAST) MIMO technology for mobile communications. The BLAST chip enables terminals to receive data at 19.2 Megabits per second (Mbps) in a 3G mobile network.

The design team chose a highly parallel architecture for the turbo decoder chip and employed a new compression technique that enables it to operate at a low clock frequency and yet still achieve high data rates. By operating at low clock frequencies, the chip consumes very little power.

Dynamic power reduction techniques have also been incorporated that adjust the amount of power the decoder consumes depending upon how and where the chip is being used - for example, offering more power if a user is driving in a car than if he or she is stationary in an office. This technique guarantees maximum performance while creating less of a drain on the terminal's battery.

Architectural and performance details of Bell Labs' decoder chip were described in public for the first time at the IEEE International Solid State Circuits Conference, in San Francisco, earlier this week.

Lucent hopes to license the chip to manufacturers of wireless data terminals and smartphones.

Additional technical details about the chip can be found in the researchers' recently published paper, A 24 Mbps Radix-4 LogMAP Turbo Decoder for 3GPP-HSDPA Mobile Wireless, available here. ®

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