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 173.96

+1.4%

Nov 11 3:59 PM EST

Public Reply Prvt Reply Mark as Last Read File

Previous 10 Next 10 Previous Next

To: mmeggs who wrote (19714)	12/15/1998 1:32:00 AM
From: Ramus	Read Replies (2) of 152472

mmeggs, Your logic is correct here. In fact, I thought I would give you a little direct evidence showing that W-CDMA is not as robust or state of the art as CDMA-2000. This is not my opinion or the opinion of the CDG. These are the conclusions of the people who wrote the ETSI UTRA W-CDMA proposal and the CDMA-2000 proposal<gg>. In response to question A1.3.1.5.2 in part "what is the information capacity per cell"... to break this down we can look at the Erlangs/MHz/Cell for the Uplink and Downlink Erlangs/MHz/Cell RL / FL W-CDMA 26.1/21.4 see page 131 of proposal CDMA-2000 29/36.7 see page 241 of proposal *higher numbers mean higher capacity This is for voice services and means that the CDMA-2000 Cell can support more voice calls than W-CDMA. Now, consider that this is based on an 8kbps vocoder rate for W-CDMA and a 9.6kbps vocoder rate for CDMA-2000. This means that the CDMA-2000 cell supports more users and they are using a higher data rate. This implies that the CDMA-2000 cell has an even greater data capacity than the W-CDMA cell. The really neat thing to realize is that the CDMA-2000 cell uses 10% less spectrum than the W-CDMA cell in doing this. Plus, with the ability to mix and match 1XRTT and 3XRTT the CDMA-2000 system will be much more efficient and versatile than W-CDMA in any spectrum allocation. What? This can't be true can it? Why? Well here are some reasons. Question A1.4.9 asked about signaling overhead. "Describe the estimated fixed signaling overhead" In other words, some of the system capacity will be used for internal use...to configure the system. W-CDMA states:2.8% up to 25% in downlink and 5.9 to 33% in uplink. CDMA-2000 states: about 5% (do you suppose 2.5% each for UL/DL) Another possible reason is the use of asynchronous signaling in W-CDMA. It is well known that asynchronous signaling yields higher bit error rates(reduced system capacity) than synchronous signaling (as used in IS-95 and CDMA-2000). And another possible reason: The W-CDMA proposal stipulates the use of concatenated Reed-Solomon/convolutional coding. And mentions that more state of the art "Turbo" coding schemes are under consideration but are not implemented. The CDMA-2000 proposal specifies the use of "Turbo" codes and specifically describes their implementation. This item struck me when I first read it. W-CDMA is being touted as a new technology that is leading the pack into 3G. On the contrary, This type of concatenated Reed-Solomon/convolutional coding scheme was (to my knowledge) first used in deep space probes going back to the 1960's. I worked at a company some years ago ( building V-sat data modems) where concatenated Reed-Solomon/Viterbi convolutional coding was used. In fact, DirectTV which was developed in the early 90's uses this type of coding scheme. On the other hand Turbo codes represent the state of the art. I can't imagine why ETSI UTRA W-CDMA would consider using anything less than Turbo codes. Especially when they tout W-CDMA as being so advanced. So mmeggs, your conclusions are correct "ergo ipso facto, no reason cdma2000 cannot be THE converged standard." Walt

Report TOU Violation

Share This Post

Public Reply Prvt Reply Mark as Last Read File

Previous 10 Next 10 Previous Next