Wireless - You never cease to amaze me. Your response must have taken considerable time, thought, and effort. It is deeply appreciated.
I was troubled, by the third or fourth day after asking the question, by another thought: "Perhaps this is a dumb question, that simply does not deserve a response."
So, inspired by the silence, I began research, still not complete, into IS 54, IS 136, UWC 136, CDMA 1, CDMA 2000, GSM, D-AMPS, vocoders, relative infrastructure cost, and who knows what all. As you can guess, it was an unending string of questions, each created by the answer before it. What prompted the search was the comment by Dr. Levy that CDMA was not particularly spectrally efficient.
How could that be? In a comparison of D-AMPS to CDMA 1, the call-carrying capacity of CDMA was clearly superior. It seemed logical to assume that the greater capacity derived from greater spectral efficiency.
WRONG
However, the search produced a huge amount of information, which I am trying to assemble into a whole that is presentable, in our discussion of the Mobile Last Mile. The islands of information were not linked, however, by the deep understanding that you have of the subject. In one post, you have answered a mountain of questions.
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I am reminded of the post you made last fall, on the efficacy of various modulation techniques, in the context of frequency, multipath interference, atmospheric attenuation, etc., as we searched for an answer on the relative merits of VOFDM and WOFDM.
The sense that I recall was that there is no best, under all conditions. It comes down more to a question of suitability to usage, conditions, and environment.
Later, I began to understand Mike's informed point of view on the importance of legacy infrastructure in the cost equation of infrastructure buildout.
In between there, somewhere, Dave gently corrected me on a naive interpretation of an AB whitepaper, and I began to understand the interplay of competitive forces for consumer mindshare.
And of course, Ray's post, which hangs on my wall...
"Those who can dash you hopes are the purveyors of slideware, vaporware, disputationware, mirrorware, thegreatestthingsinceslicedbreadware, wereinventedthewheelware, snakeoilforthemilleniumware and a few Wehrs that occured on the other side of an unforgiving pond.
Dash your hopes. You betcha, and smash delusions in the process."
Friday night, I discovered posts by Frank, discussing the problems inherent in network design that properly encompasses mobile solutions. So much for my "original" thoughts!
The point is, that the conclusion I reached is the same one I reached on the WOFDM/VOFDM debate: the CDMA/TDMA debate does not need to be resolved. Each technology will find a place in the RF infrastructure, that place to be determined by questions of cost and suitability in the particular requirement. There will be thousands of analyses of the optimal answer, in thousands of places, and the circumstances themselves will dictate the proper decision (notwithstanding the verbal fistfights between stockholders in competitive modulation camps, prompted by the "insights" of technology seers).
Cementing that conclusion was the fact that Moore's Law, advances in DSP, ASICs, and SOCs, will make software radio a viable, cost-effective concept. The requirement then becomes to extract the data stream from whatever RF modulation scheme has been chosen as most suitable to the area one is in.
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Thanks, wireless.
Best regards,
Jim |
