Hi Stephen,
The true test of any digital system is its ability to accurately replicate visual images and auditory sounds that are, by nature, innately analog. And therein lies the irony of discussing the merits of digital vs. analog.
Of course, with travel over great distances and the time lapse implied by such due to propagation, analog signals deteriorate due to the influences of phase shift and the introduction of noise and other artifacts stemming from nonlinearities, etc., all of which having the effect of distorting those signals by the time they reach their destination. It's therefore necessary to digitally encode analog signals, ship them over the longer distance, and then explode them back to their original analog form for presentation to the human (sensory) interface.
This, I suppose, is what the fuss is all about over on the Gilder board: the fact that the human interface can only appreciate the analog signal form, and if this is so, it could be argued, then why not just perfect analog as opposed to going through all of the hullabaloo of digital. Not to diminish the validity of this notion, ther are good reasons, from a price performance angle, to continue to employ analog techniques in niche situations. Just as free-space optics are still highly justified as opposed to planar techniques for certain applications. Such as in certain opto-electric camera applications, and for short haul video links, as I note below.
It makes for some interesting reading, if nothing else, especially when plausible methods are suggested that would support doing so. But this doesn't diminish the importance of the other reasons to digitally encode, and those have to do with the ability to manage, route, store, process and transmit these signals in any of a near-infinite number of a ways. Doing so in the analog realm just hasn't been addressed to the same degree (historically, such features used to manipulate analog signals were only possible through relatively "manual, or electro-mechanical" means), much less perfected, except under the control of systems that use digital processing techniques.
I recall working on the engineering necessary to deliver the original Bloomberg terminals to a large brokerage back in the early Nineties. Bloomberg's screen quality was by far the most impressive, in terms of luminance, color and crispness, of any of the fifty or sixty market data vendors who we worked with at the time. And they were using a classical RGB/S cabling scheme between the screen and the closet controller (big fat black cabling that we converted to optical), as opposed to the LAN-fed, local cpu-based digital approaches that the others had begun using at the time, as opposed to the video-switch based analog systems.
Of course, on the Bloomberg system each color rode over its own multiplexed super-high resolution FM/FDM channel that was superimposed onto a multimode fiber wavelength, and each (color) enjoyed its own 300 to 600 MHz of bandwidth. This was hardly the cheapest way to get news and quotes to the trading desk, but that was the price one paid at that time for super-high-resolution video.
Commercial TV broadcast studios are forced to live with the same dichotomy. For very short haul use, analog systems are still very much in demand, and still offer better price-performance than digital when the objective is to merely capture and port images over short haul distances. But when distances reach a certain threshold and begin to affect signal quality, they revert to digital forms of encoding and transmission over longer haul section(s), and then convert back to analog at the remote site or intermediate drop-offs along a network's backbone.
re: "What do you think about the most recent ADSL systems? How much life can be breathed back into copper. My guess is quite a bit."
I've been impressed by some of the claims made by those developing ADSL2 products. Not so much for the increased speeds they offer, which are obviously also important, but for the added functionality that they support at the customer premises location, some bordering on the ability to double as routers and gateways, should they elect to offer those capabilities. But the potential to do so is there, nonetheless.
Whether these new bit bangers can actually scale when pushed to the limit of HDTV expectations over the next couple of years is equally a function of how their dslams operate, as it is the ability to recover from modulation at the home. Dave Burstein has done some writing on this subject recently making some valid observations, imo, which I think is only appropriate for me to point out. His DSLPrime reports can be viewed at:
dslprime.com
In a more general sense, how do I feel about pursuing ever greater speeds over greater lengths using xDSL? I think that at some point we reach a point of diminishing returns, when viewed against the capabilities of competing technologies. Yes, where there is no hope for ftth or cm over an identifiable interim period, sure, dsl is the way to go. It's a lot better than having to live with V.90 or ISDN, for example.
One problem that I see with taking this approach, however, is that it removes any incentive by the carriers/service providers to go the extra step and install a more robust platform in the future, for fear of prematurely abandoning one (in this case, xDSL) that has not yet paid for itself.
And as Burstein so aptly points out, the CM camp will be readying itself with a new arsenal of bandwidth and enhanced features that the DSL camp will find very difficult to compete against. Likewise, I might add, this same form of disadvantage will be brought upon the xDSL camp by those who are forging ahead with broadband wireless and ftth access platforms, as well. So, where will this leave xDSL in two years time, even at the higher speeds now being touted? I don't know for sure, but I'll bet they will be somewhere behind the 8-ball in comparative terms, even more so than they are now.
What do you and others think about this?
FAC |
