MIMO: Alcatel-Lucent regains its balance

(A sidebar to the Bell Labs special report, Reviving an icon)

In 1998, Bell Labs researcher Gerald Forschini unveiled a wireless radio technology called Bell Laboratories Layered Space-Time, or BLAST. BLAST divided up a wireless data stream into several sub-streams, which it would then transmit over separate but closely spaced parallel paths on the same radio frequency. Each of the separate signal streams arrived separate at the receiver where, where a powerful signal processor could then reconstruct them into the original data transmission.

The result was that far more data could be transmitted over the same wireless channel than hitherto thought possible. One of Claude Shannon’s theorems stated that interference or background noise limited the amount of error-free information that could be transmitted over any frequency channel. Much of communications research to date has been conducted to get closer to that boundary, and in wireless it was believed that limit had been reached. But BLAST pushed back Shannon’s limit, closing in on the maximum data rates allowed by the laws of physics.

The BLAST project became the basis for what we now know as multiple input/multiple output (MIMO) smart antenna technology. Sprint has championed the technology insisting that MIMO be a required element in its new nationwide WiMAX network. But when Sprint announced its plans in 2006, Lucent Technologies was not among its vendors. In fact, Lucent hadn’t even developed a product line. The contract winners, Motorola, Samsung and Nokia Siemens Networks, had all built their WiMAX gear using Bell Labs-developed technology, while Lucent sat on the sidelines.

Chief technology officer for Alcatel-Lucent’s wireless business group Hank Menkes readily admits that Lucent hasn’t worked well with Bell Labs in the past. There are technologies that have lain dormant on Bell Labs shelves that Lucent couldn’t find a market for, but Menkes said MIMO would definitely not be one of them.

The Alcatel-Lucent merger has given the company an immediate MIMO product outlet through Alcatel’s WiMAX base station line. Alcatel may not have won the Sprint contract, but it has landed several big deals in other regions of the world, Menkes said. The bigger MIMO opportunity, though, lies not so much with WiMAX, Menkes said, as it does with Long Term Evolution, the name given to the cellular network standard that the world’s GSM operators are expected to adopt.

Not only is Alcatel-Lucent utilizing Bell Labs’ MIMO expertise on the next-generation of wireless networks, Menkes said, it’s looking toward generations further out. Reinaldo Valenzuela, director of wireless communications research, and his team are exploring network MIMO, which--instead of using a single source to transmit multiple paths--will use multiple sources to transmit multiple paths. The future MIMO devices won’t receive data from a single cell tower, but multiple cell towers and eventually from other devices as each acts as a relay in a distributed network.

“Network MIMO will transmit a tremendous amount of information,” said Menkes, who has since retired from Alcatel-Lucent. “The infrastructure vendor who can deliver the greatest coverage with the highest throughput will win, that’s it.”