SI
SI
discoversearch

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor.  We ask that you disable ad blocking while on Silicon Investor in the best interests of our community.  If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.
Technology Stocks : Qualcomm Moderated Thread - please read rules before posting
QCOM 172.98+1.1%Jan 2 9:30 AM EST
 Public ReplyPrvt ReplyMark as Last ReadFilePrevious 10Next 10PreviousNext  
To: Sully- who wrote (3132)9/15/2000 1:59:44 AM
From: engineer   of 197074
 
For all of you unfamiliar wiht the system design on CDPD, here are a few things about it.

CDPD was orginally made to sniff out unused 30 kHz channels in the analog spectrum which were not carrying voice calls. It listened to the airwaves and found those ones not activly using it. But it has to drop the chanel and not interfere in a short time when a voice channel is requested by a new call, so the channel can go away at any time. This is not so bad in a lightly loaded system. But as the system cpapcity grows and the system gets more loaded, there is less and less unused channels and the thruput of hte system goes way down. IF and WHEN you get a CDPD channel, then you get 19.2k bps, but this is a burst rate not sustainable over a long period of time, as you get bumped and then have to sniff and reassign a new channel. This can mean a down time of seconds in a loaded situation.

Now you can imagine that in a heavily loaded system such as AT&T one Rate plan where dropped calls come from not having enough capacity in the first place, there may be LONG periods of time where there are no unused voice channels, hence the CDPD system goes into a frozen queued state. So this may mean at peak times such as 5:00 PM, you may NEVER get a CDPD channel. If there are quite a few otehrs trying for the same non-existant channel, you all may block each other by queueing the sytem up so far taht it cannot unblock itself.

CDPD was great when analog systems were not used, but in todays heavy use places, it does not fair well at all. I would be surprised if anyone were able to sustain more than 1200 baud in any major metro area anywhere. I have heard thruputs of less than 300 baud in NYC where congestion is high.

"The king has no clothes".
Report TOU ViolationShare This Post
 Public ReplyPrvt ReplyMark as Last ReadFilePrevious 10Next 10PreviousNext  

HomeMailHotSubjectMarksPeopleMarksKeepersSettings
Terms Of UseContact UsCopyright/IP PolicyPrivacy PolicyAbout UsFAQAdvertise on SI
© 2026 Knight Sac Media.  Data provided by Twelve Data, Alpha Vantage, and CityFALCON News