[time-nuts] The future of Telecom Frequency Standard surplus
jimlux at earthlink.net
Wed May 31 23:47:30 EDT 2017
On 5/31/17 8:47 AM, Tom Knox wrote:
> I think many of us Time-Nuts have played with the wide range of
> frequency standards surplussed from the Telecom market.
> My questions is, will the quality of future surplus offerings go up
> or down as 4G and in the more distant future 5G surplus Frequency
> Standards hit the market? It seems with higher data rates stability
> and phase noise demands will increase, but will other advances find
> ways around the expense of a high end Frequency Standard. I know some
> early telecom systems even want as far as Cesium Standards, but more
> robust network tolerances seems to have reduced the need for that
> level of performance. So which way are we headed?
In general, higher data rates don't have as stringent close in phase
noise/ADEV requirements - if you look at published jitter specs, they
use phase noise from something like 10kHz to several MHz.
We encounter this all the time with deep space telecom, where
historically, they'd do radio science with the carrier. When you're
sending 8 bits/sec, you need a good quiet carrier so your receiver loop
bandwidth can be small (to improve SNR). When you're sending 100 Mbps,
not so much.
Higher carrier frequencies make things like Doppler more important -
some of the high rate point to point links actually have problems with
tall buildings moving in the wind. As a result, the modulation schemes
and detection methods are moving towards more highly adaptive techniques
which don't require as good performance for the oscillators.
> Any thought? I imagine some members are actually involved in design
> and implementation of the next generation telecom technologies and
> will have direct knowledge.
> Thomas Knox 1-303-554-0307 actast at hotmail.com
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