All,
I thought you all might enjoy the following excerpt from one of the W-CDMA proposals to ITU. I enjoyed reading it because it states the case very well why the world would want to move to CDMA and away from other technologies. It's particularly interesting because the W-CDMA people know why they want CDMA...they just have to convince the world that their version is better than CDMA-2000<GG>. However, for some reason the following sounds just like an ad for IS-95...a few years back... For you doubters, just message me and I will tell you exactly where to find this document. You can read it for yourself. Please remember as you read this it was submitted to ITU last June 1998!!
Cheers
Walt
o Highly Efficient Spectrum Utilization
In order to improve spectrum utilization efficiency, different technologies such as transmitter power control or VOX technology, where signals are transmitted only when there is speech, can be applied to CDMA. The adoption of these technologies makes it possible to achieve an effect equivalent to when a sophisticated technology such as dynamic channel assignment, etc., is employed in other radio access schemes. In other words, this means that a system with high
spectrum efficiency can be realized easily.
o Release from frequency management
Since CDMA allows the use of the same frequency in adjacent cells, a frequency assignment plan becomes no longer a necessity. With FDMA and TDMA systems, however, frequency assignment is necessary. In particular, in a real environment where base stations are deployed, it is quite difficult to assign frequencies while giving considerations to irregular propagation patterns and the impact from geographic topology. In addition, while imperfect frequency assignment design could rather lead to lowering the spectrum utilization efficiency,
CDMA can get rid of such concerns.
o Low mobile station transmit power
By means of technologies such as RAKE receiving, CDMA can improve the
reception performance, thus, the required transmit power at the mobile station can be reduced with CDMA systems when compared to TDMA systems. Since intermittent transmission is employed in TDMA, the peak power to send information symbols will increase in relation to the number of timeslots. On the other hand, the peak power for CDMA can be kept low since continuous transmission is adopted. This is also advantageous in terms of keeping the impact in electromagnetic environment to a minimum.
In TDMA, where various transmission rates are supported by setting up the number of timeslots to be allocated, the same level of peak power as the power needed for transmitting the highest rate service will be needed even for mobile terminals dedicated for voice service. |
