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Technology Stocks : Qualcomm Incorporated (QCOM) -- Ignore unavailable to you. Want to Upgrade?

To: Joe NYC who wrote (20850)	1/5/1999 10:48:00 PM
From: engineer	Read Replies (3) \| Respond to of 152472

Hey, keep the questions coming. Asking good questions when you don;t know is a great thing. I love responding and trying to help everyone understand the system aspects. The thing that guy does not understand is coding gain. Having 3 receviers in the chip and listening to multipath along with using error correction and some DSP coding gain tricks, you can get much more signal than TDMA, even if the transmitter is alot weaker. since TDMA is a single timing refernce system, doing multipath is a tough problem, and not one that can be easily done in the current TDMA systems in the world. Just a historical note, while Bill Frezza was blasting Qualcomm for CDMA not working, TDMA was not working at all to spec. It seems that since it was designed by committee without alot of real world experimentation, they pushed the limit on the front end symbol equalizer and the timing refernce in the phones could not get the timing in the symbols allowed. they had to back off and instead of having 3 times slots, they had to back off to two times slots for awhile until the equalizer techology caught up with the expectations. If they were to try to split time down once again, they would come back to the theoretical limit for this critical part. As far as sectorization, think of it as a round circle and if you can control this circle by splitting it into 3 parts at 120 degrees apeice, then you can create different code areas on the same hardware, thus have almost 3 times as many users in the same cell area. If you can then spend a little more on antennas which have very narrow beams, then you can split it down even further and have 6 sectors. Thus you can get about 5.5 times as many users on a cell than if you just had one big omni-directional cell. Each sector would use the same frequency, but would use a differnt CDMA code. the loss from 6 times to 5.5 times is for handoffs between sectors, since you may be driving around the cell pole and going between them (like one in the middle of a shopping center at Christmas time...). You have to reserve some capacity to handle this.