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To: Joe NYC who wrote (20843)	1/5/1999 9:49:00 PM
From: Ramus	Respond to of 152472

Jozef, As I like to say, I think the ARIB W-CDMA proposal to the ITU says it best why the wireless world wants to move to CDMA..... 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. 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. 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. Improvement of multi-path resolution The RAKE diversity receiving technology improves the reception performance by combining the individual paths after they were received separately among multiple paths. The use of a wider band carrier can improve the capability to separate these multiple paths, which consequently reduces the required transmit power. This makes it possible to lower the transmit power of mobile stations, and at the same time brings down the interference power, which leads to further improve the spectrum utilization efficiency. Statistical multiplexing effect The use of a wider band carrier increases the number of channels accommodated in one carrier. Further improvement in the use of frequency can thus be expected, thanks to the statistical multiplexing effect. I've said before that this looks just like reasons to use IS-95 CDMA. I don't mean to imply that ARIB copied this from IS-95... I mean to imply that they are talking about CDMA! Regards Walt PS Your friends discussion about shorter wave amplitudes, shorter distances etc not really clear what he is implying but his assertions about more towers, weaker handoffs(whatever that means) don't apply to CDMA. In fact many of these things are enhanced by going to CDMA.

To: Joe NYC who wrote (20843)	1/5/1999 10:13:00 PM
From: Clarksterh	Read Replies (1) \| Respond to of 152472

Joe - Re CDMA - low energy, shorter wave amplitude, shorter distances, requires more towers, weaker handoffs between cells (???), more overall potential capacity, higher cost buildout. The person who wrote that post says it himself - he isn't a technical expert, and in fact as Walt points out much of the above sentence makes no sense (I don't mean just that it is wrong, but that it is gibberish). In general Walt's post, the cdg website and previous posts cover this pretty well. However, an interesting aside on his comment on cost of build-out. From a certain perspective it is true that CDMA is more expensive than TDMA. CDMA is significantly more complex than TDMA and thus connection per connection it involves more hardware and thus more cost. BUT: 1) Much of the hardware (and other capital costs) in a system is shared, and thus that cost gets split between more users. (Same thing is true of TDMA vs Analog). 2) The cell layout process for CDMA is, in theory, a much simpler process. This is a reasonably large percentage of the initial cost, and an even larger percentage of the cost to expand a system. (The only reason I say 'in theory' is that I know they were have problems initially, but I think that they have been overcome - I just don't know it.) Clark