moat - I'll try to give this a shot...if I'm wrong, hopefully Clark Hare, Eric L, engineer etc will correct me.
I have a very theoretical question: According to information theory, is CDMA at the theoretical limit in terms of efficiency?
No, CDMA is an access method...how to share a resource (e.g. cell with many mobiles). In terms of information theory, there is source coding and channel coding. Information theory is a difficult and involved subject...however, Shannon proved that a channel has a fixed capacity. That rates above this capacity are impossible. And error free communication is possible for rates below this capacity. In addition, he also showed that there is a lower limit to the amount of compression (source entropy) for perfect reconstruction (lossless data compression).
Why ask such question? In the very long-run, will someone else be able to invent a better mouse trap?
Sure, why not. This is a fast big money game and a lot of R&D dollars are being spent. Qualcomm realizes this and IMO is responding accordingly. However, as Eric L has pointed out, keeping an eye on GPRS, EDGE, etc. is important.
At the theoretical limit, CDMA is 3-4 times more efficient than TDMA right?
Yes, that is my understanding.
What's the current state of the technology at in the field?
See above (GPRS, EDGE, OFDM, CDMA2000, HDR, W-CDMA etc). Also as Gregg Powers has pointed out, establishing a standard is a difficult process.
regards Scott |
