月曜日, 12月 26, 2005



In march of 2000 Jean Tourrihles posted the excellent document Wireless Overview in which he said, "In fact, many people have been thinking of universal radios, which can be simply reprogrammed to receive (and transmit) any radio standard. The main idea is having a big block of reprogrammable logic on the card and to download a new configuration for each protocol that the system wants to use, making it a fully digital radio.

To achieve that goal, we need to go one step further down, and be able to adapt to any modulation and bit rate. Most implementations of common wireless LANs used fixed analog components in the modem, so are not suitable. So, a digital radio needs to digitise (with a fast AToD) the whole bandwidth and to feed that the fast super DSP or EPLD (Electric Programable Logic Device, like Xilinx or Altera) and to work entirely in the digital domain to demodulate (and modulate) the signal. Unfortunately this is not really cost effective and doesn't work that well at the frequency we are talking about (GHz)." Now, to me there is several things that immediately pricked my attention. The first being that he said many people, so I wanted to research the many people that where proposing this idea, which is very revolutionary. The second being that he said Unfortunately... OK, if you understand who Jean Tourrilhes is (only one of the greatest goldmines of info for wireless users on the Linux OS) then you know that before you argue anything with this guy you had better be a pretty smart. Well, Im not flamming him, (only in the true spirit of A.Einstein that the important thing is not to stop questioning) only curios what his opinion on that quote is now that things have changed so rappidly in 6 years.

Jeffrey H Reed in his book Software Radio: A modern approach to radio engineering says that " Software radios represent a major change in design paradigm for radios in which large portion of the functionality is implemented through programmable signal processing devices, giving the radio the ability to change its operating parameters to accommadate new features and capabilities. A software radio approach reduces the content of radio frequency (RF) and other analog components of traditional radios and emphasizes digital signal processing to enhance overall receiver flexibility. This change in the paradigm for new radios has occured so rapidly that it has left a significant void in the educational material available to train new radio engineers. Traditional radio engineering textbooks emphasize analog component level design with little mention of the increasingly important role of digital signal processing in performing the central functions of the radio transceiver. Individual references covering the key analog and digital subsystems tend to be insufficient in that they fail to provide a full understanding of the interaction between these subsystems."

He goes on to say" I became acutely aware of this void when conducting research into the developement of novel high-performance radios for the Defence Advanced Terrorist Agency AKA DARPA." oops , the defence advanced research projects agency-- my bad.. anyway he continues " while constructing radio prototypes, I found there was no comprehensive resource to which I could point my students for more information"....yada yada so he wrote the book--

"Software radios are emerging in commercial and military infrastructure. this growth is motivated by the numerous advantages of software radios.
1) Ease of design
2) Ease of manufacture
3) Multimode operation
4) The use of advanced signal processing techniques
5) Fewer discrete components
6) Flexibility to incorporate additional functionality
(all of the above mentioned points he elaborates of course)

Given these clear advantages and increasing processing power available in commercial digital signal processing devices, I anticipate that radio engineers that software radios will become the standard approach for radio design"

So what is apparent to me and anybody that has there eyes open I surmize, is the merging of so many previously disparate realms of science. Being headed that direction in education it is a clear sign of the symbiosis of RF and Digital Signal Processors, software and hardware knowledge both is crucial to the future tech job market.

I wish I could just download information directly into my brain like Neo, theres not eneough bloody time in the day to learn things. And here Im struggling to understand the well documented wireless tools interface on my Ubuntu box. :-) some wifi ninja I am.

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