Turn on, Tune in, Crank up the Speed
By Andrea Orr, Thu May 17 00:00:00 GMT 2001

The head of wireless communications research at Bell Laboratories explains how their new BLAST antenna technology addresses the biggest obstacle 3G networks face: speed.

Lucent Technologies thinks the mobile Internet will succeed or fail based on how fast it is able to move data. It says its new BLAST technology will offer mobile operators a way to increase traffic and speed over their networks without adding expensive, unsightly base stations.

Six years ago, when wireless usage had only just begun its steep ascent and most consumers still had no thought of using a cell phone for anything other than carrying on a voice conversation, engineers looked into the future and saw a trap. The industry was enjoying explosive growth in demand, but the supply of transmission base stations was limited, and efforts to build new ones were usually met with aesthetic or financial objections.

Basic laws of supply and demand said it would not be easy to build enough new transmission towers to keep up with the growth in wireless usage. The engineers who were tackling the problem understood the actual math to be much more daunting than supply and demand. Without a new and improved technology, they knew, capacity would have to be brought online much faster than demand was growing.

The (non) economies of scale

In reality, the demand for transmission capacity grows at an accelerated rate to the amount of material being transmitted. Because every receiver has to overcome a certain amount of intrinsic noise before it can transmit the sound intended to be sent, each time the data load increases a little bit, the amount of transmission capacity must expand a lot – about ten times more rapidly.

“Very soon, you run out of capacity,” says Reinaldo Valenzuela, Director of the Wireless Communications Research group at the Bell Laboratories division of Lucent Technologies. “It gets very impractical very quickly.”

According to these ratios, when the amount of data being transmitted increases by a factor of ten, the transmission capacity can go up by a factor of one thousand. Apply those standards to so many of the new media-rich and interactive services that have been proposed for wireless devices, and they begin to sound quite impractical. “Any time you want to do something a thousand times, things get very nasty,” says Valenzuela. “That is just completely outside of any practical reality.”

A new discovery

A Lucent research project called BLAST, which has recently been identified as one of the most promising solutions for 3G wireless networks, was born out of that trap Bell Labs researchers identified years ago. The premise behind BLAST is to increase capacity by using multiple antennas at the transmitter and the receiver, which have traditionally housed only a single antenna each.

This system, which Lucent just this month incorporated into its 3G wireless base station platform, does more than just increase capacity. It appears to solve the problem of the exponential growth in transmission capacity relative to the material being sent. When a second antenna is added at the transmission and receiving points, the amount of data that can be sent doubles. Ten new antennas will increase capacity ten times, and so forth.

“To our total amazement, we discovered that you can keep adding speed as fast as you add antennas,” said Lucent’s Valenzuela. “In classical thinking, this is total nonsense.”

If the multi-antenna solution seems too logical to be classified as a breakthrough, consider what happens to wireless radio waves once they are in transit. Far from moving directly from the transmitting antenna to the receiving one, the waves bounce and scatter randomly, and don’t always get put back together again even when just one single antenna is involved.

How it works

Traditionally, this random, or multi-path system of transmission had been a big impediment to accurate communications because the bits of data arrive at the receiver at slightly different times. Conventional wisdom long held that multiple transmitters would only compound this problem. But when the researchers at Bell Labs began to test the BLAST method, they were stunned to discover that multiple antennas actually enhanced rather than degraded transmission accuracy.

It appears the approach provides what the company calls a “spatial parallelism” that enables each antenna to see all of the transmitted data as a whole rather than separately, significantly improving transmission rates and accuracy.

Although BLAST is the result of years of research, it remains to be tested in real world conditions. A number of critics doubt the one-to-one ratio between added capacity and added transmission potential will hold up outside of the lab.

What does seem clear is that even if its real world performance is a lot worse than has been demonstrated in a controlled setting, it will still mark a notable improvement over traditional systems. Instead of having to construct massive new base stations every time new wireless services are introduced, BLAST could do for wireless devices what the motherboard has done for the PC, enabling it to unobtrusively add on incremental capacity as needed.

Putting it to use

Lucent, which now is working aggressively to have BLAST incorporated into third generation wireless standards in Europe, sees strong demand for systems that can move more data at faster speeds. The company says it expects some form of the multiple antenna technology could be used by mobile service providers to increase their capacity, or could be incorporated onto consumer products like Personal Digital Assistants to improve the speed at which they can receive data.

Although early versions of BLAST, most incorporating a triple antenna format, have had a somewhat cumbersome design of horizontal and vertical antennas, the company believes it could eventually be simplified into three small metal strips lying in a flat patch and glued to the back of a laptop. And if the design is improved, the two or three or four-antenna approach could possibly be expanded further.

“I think we are going to see an explosion of new applications of Internet services,” says Valenzuela. “Not so much new services, as some of the things like wireless stock quotes and wireless chat that people have already been suggested for the current generation of wireless data. A lot of these services haven’t yet taken off because they are just too slow.”

“I’d like to think that in the not too distant future, we can move well beyond four antennas.”

From Silicon Valley, Andrea Orr covers developments in the mobile world for TheFeature. She is also a correspondent for Reuters in the Palo Alto, California, bureau.