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 174.69

0.0%

Dec 24 12:59 PM EST

Public Reply Prvt Reply Mark as Last Read File

Previous 10 Next 10 Previous Next

To: engineer who wrote (43368)	10/5/1999 4:08:00 PM
From: w molloy	Read Replies (1) of 152472

CDPD and GPRS CDPD is made as an overlay system to the existing analog network. what is does is watch the over the air radio signals and find call channels that are not in use. When it detects this, it then attempts to use this unsed channel for data. If another call channel comes along, then CDPD must detect this and drop off the air, even in mid packet. As the demand for bandwidth grows and the demand for data grows, these two will collide even faster than that described by BUX. CDPD works now only because it has a small following. If it is pushed to a large following and an large user base, then it will log jam not only itslef, but it would severely limit the capacity of the TDMA voice netowrk it is overlayed on. It must drop transmission during the most critical phase of a TDMA call, the data carrier timing burst. The demand for bandwidth might be infinite, but the bandwidth available isn't. In CDPD systems, the voice service is paramount. Lets say there is one spare channel - channel x. All other channels are servicing Voive calls. We begin transmitting packets on channel x. Another voice call comes along. Our CDPD service is bounced and the packet is dropped. At a random time period later, we try to resend the packet. We search for a channel. If one is available OK, if not, we wait for another random time period. The net effect is a reduction in the effective data rate that the application using the CDPD service sees. The nominal rate for CDPD is 19.2 kbps. This can be reduced to as low as 8kbps ( which I saw in a lab test with 12 CDPD units jostelling for service). There is no additional stress on the underlying network. All the stress is focussed on the CDPD service itself. I take your point regarding the packet being dropped during the carrier timing burst. Don't you think AT&T system engineers would have taken this into account before offering the CDPD service? (well - maybe not...) GPRS is the GSM equivalent to CDPD. From a software viewpoint it looks very similar indeed. There is no point in migrating from CDPD on IS-136 to GPRS on IS-136. w.

Report TOU Violation

Share This Post

Public Reply Prvt Reply Mark as Last Read File

Previous 10 Next 10 Previous Next