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To: Robert Sheldon who wrote (23586)	3/1/1999 2:39:00 PM
From: Ruffian	Respond to of 152472

Qcom & Ericy Talk> rcrnews.com

To: Robert Sheldon who wrote (23586)	3/1/1999 9:49:00 PM
From: Drew Williams	Read Replies (3) \| Respond to of 152472

<<Anyway, I think we are getting too far off topic. >> This is really funny when you are talking with Mqurice. Don't you know that hardly anything on this thread is really off-topic? <g>

To: Robert Sheldon who wrote (23586)	3/4/1999 9:38:00 PM
From: Maurice Winn	Read Replies (1) \| Respond to of 152472

On topic - VCO discussion - how to make handsets Getting back on topic, although I bet Ramsey's DNA is fascinating, here is a follow on to the VOC issue. Robert, you said: ----------------------------------------------------------------- "My point rests in that the demands placed on next generation VCOs are much greater than existing VCOs. Currently if a VCO fails to retain the signal properly the call is dropped. No big deal if you are just on a phone conversation. If you are transferring data this could become the downfall of handset based data transfer. I believe that we will eventually see VCOs (that become components of PLLs) that were traditionally utilized in base stations become ubiquitous in broadband handsets too. Currently, one supplier of VCOs (VARL) supplies ~95% of this market (the % is from industry infrastructure producer estimates)." ------------------------------------------------------------- Here is some information from somebody who seems to know about these things. Check it out folks - you'll be an expert on VCOs in no time. ---------------------------------------------------------------- Regarding the different "qualities" of VCOs in basestations versus handsets and signal quality; basestations have the luxury of being able to be "tied" to a very reliable frequency reference. This is done because the basestation serves many users and has to maintain reliable communications for all these users over a variety of conditions (even power lost) and over a long lifespan relative to the handset (commodity item). Handset frequency dependent components are selected not only for their frequency but also size as this does have some relationship on consumer appeal. The handsets are locked to a small oven-controlled reference that while "good" is nothing compared to basestation references. A basestation can "dump" an errant mobile. Yes, data transmission can suffer from poor frequency control, but data transmission is far more flexible in the manner in which it is transmitted. The error and compression software tends to find and correct errors before the signal is reassembled at the received end. The same thing is done with digital voice signals. But humans are sensitive to conversation delays, so the correction time slot is narrow for voice. For data, the software can just keep retransmitting the corrected data until the receiver acknowledges good data. Data is also easily broken up into smaller chunks for transmission and can easily be fitted into "dead spaces" in the transmission scheme. Voice is time-sensitive and must take precedence in the scheme. So data is far less sensitive to VCO drift than one might think. Short cut example: think Morse code for data. The signal tends to get through no matter how poor the transmission medium, whereas modulated voice signals break up to garble fairly easily. Regarding demands on VCOs, yes, the VCOs used today are far better than what was used for instance on high quality military gear just 20 years ago. We [Ed: Not me, the writer] are demanding that the available bandwidth be cut into finer and finer slices to serve all the bandwidth demands. So our "knife" (VCO) must permit finer and finer cuts. The frequency stability of today's consumer equipment is fantastic 10^-12 or better (frequency drift over time) compared to yesterday's "high tech" gear 10^-6 or so. I don't know if VARL is one of the big suppliers for VCOs in the handsets but I know that we [Ed, again, not me!] are constantly looking for smaller and better. ---------------------------------------------------------------------- So there are a few of the little details that go into the day to day designs. Thanks to my consultant for this timely advice. All contributions welcome. Email: Mqurice@EudoraMail.com Mqurice --