IP: NTT Researchers Predict 10Gbps Wireless

[David Farber <dave () farber net>]

http://www.theregister.co.uk/content/5/23809.html

NTT researchers predict 10Gbps wireless
By ComputerWire
Posted: 24/01/2002 at 11:50 GMT
[]
NTT Corp, Japan's incumbent telco, claims to have raised the ceiling on
wireless bandwidth, after achieving a peak data transfer rate of 2.5Gbps in
laboratory trials. The previous highest wireless transfer rate was 1Gbps,
but NTT's researchers believe they can ultimately take wireless
communications up to 10Gbps.

Given that wireless equipment manufacturers are struggling to build
equipment that can realize 2.5Mbps, and fixed-wire equipment makers are
struggling to sell switches that already support 10Gbps of sustained
capacity, pushing wireless to these dizzy heights might seem a little
superfluous.

However, even if there is no immediate need for gigabit wireless links,
NTT's researchers are at least exploring technology that uses spectrum that
has so far not been utilized by anything else. In a world where radio
spectrum is becoming increasingly congested, that alone might be a reason
why NTT's efforts could well pay dividends in future.

For instance, the 2.4GHz and 5GHz radio bands, spectrum previously used
largely for background telemetry and monitoring tasks is quickly being
occupied by IEEE 802.11x WLANs and Bluetooth interconnect links. Further up
the scale, wireless local loop technology is colonizing the 20GHz and 40GHz
bands, the new Wireless 1394 home multi-media standard will operate at
60GHz, and automotive navigation and in-motion information systems are
targeting the 76GHz band. Probably the only reason higher bandwidths have
not been exploited is that until now electronic gear hasn't been up to
driving signals at frequencies that are starting to approach the optical
spectrum.

NTT's solution has been to harness new electronic and optical technologies
to access the empty 120GHz radio band. Optical systems are used to generate
the original signal which is passed, using amplitude modulation to a 300GHz
photodiode, which creates an electrical signal that is passed to a direct
slot antenna. The key to the whole process is the 300GHz photodiode, which
harnesses optical technology, in this case the Lithium Niobate substrate
originally designed for light switching, to the business of generating an
electrical signal.

Inevitably, there is great deal to do before NTT's 120GHz wireless
technology becomes commercially viable. At the moment, for instance, the
sustained 1.25Gbps signal generated in the laboratory has a range of just
50cm. But as spectrum becomes ever scarcer over the next several decades,
the motivation to refine this technology will undoubtedly intensify. 

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