Qualcomm Incorporated (QCOM) Message Board

STOCKTALK

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 Incorporated (QCOM)

QCOM 166.06

+0.6%

1:50 PM EST

Public Reply Prvt Reply Mark as Last Read File

Previous 10 Next 10 Previous Next

To: Ramus who wrote (3753)	8/24/1997 4:58:00 PM
From: chuckj	of 152472

<<chuckj, you are correct about what is understood to be a 3dB(doubling) increase in noise power results in a 2 fold decrease in capacity.>> Thank you for acknowledgement. This basic misuse of Shannon formula, is the first order flaw in CDMA the rest of the stuff they do to increase capacity of the CDMA, the biggest one the VOCODER, are second order to the capacity equation. TDMA folks are and can further increase their capacity by using more sophisted vocoder. The reason they havent developed a much more sophisticated vocoder is because they haven't needed it. <<fragile power management.."which is prone to breakdown"? Would you care to enlighten us? >> Once again thank you for the opportunity. The power management is fragile because the base station has to manage the power level of all of the thousands of the handsets that are within one cell. If one handset malfunctions and does not respond to the base station to lower its power, the rest of the handsets will have to talk louder and therefore the capacity collapses, because the noise figure in the denomenator shoots up(remember this one from the Shannon formula). A reminder for those BSEE folks, this phenomenon in engineering term is positive feedback and extremely unstable. Of course in a desperate attempt to resolve this situation, Qualcom claims that they have a remedy for this in their VOCODER. Supposedly in this situation, the base station will command all of the coders within the cell to reduce their sampling rate (and temporary slash the quality of all of the calls), and walla they resolve the situation. Meanwhile the CDMA police force are sent on the road to find and disable the offending handsets. As the number of the handsets increase the chance of having offending handset grows. This is why CDMA's power management infrastructure is fragile. There is scientific wisdom behind GSM and TDMA. Good luck to all, on this grand pipe dream of qualcomm. Your immediate concerns should be that qualcomm is cash strapped and without a significant lay off it is not even a going concern.

Report TOU Violation

Share This Post

Public Reply Prvt Reply Mark as Last Read File

Previous 10 Next 10 Previous Next