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Software-Defined Radio Could Unify Wireless World
mjdroner writes "Technicians in Ireland are testing a device capable of skipping between incompatible wireless standards by tweaking its underlying code. The article states: 'The device can impersonate a multitude of different wireless devices since it uses reconfigurable software to carry out the tasks normally performed by static hardware. The technology promises to let future gadgets jump between frequencies and standards that currently conflict. A cellphone could, for example, automatically detect and jump to a much faster Wi-Fi network when in a local hotspot.'"
I've been researching similar technologies over the past few years because I believe we can see an amazing communications "utopia" by deregulating (or at least minimizing regulations) all the frequencies we're blocking for specific uses.
Software radios are not new technology, but the implementation has been fairly worthless as frequencies are set up for specific purposes. At any given moment in any given area, there is a ton of bandwidth going unused. Frequency hopping is already pretty well documented in how to maximize its use, and power allocation specifications have been out since pre-cell phone days. Combine that with a much wider bandwidth and we can see higher data rates, lower battery usage and maximum bandwidth allocation everywhere you go.
I know the FCC will never give up the bandwidth to the open market -- it is too lucrative for the few who are in cahoots with the licensing body. But I see so much happening just in the WiFi "unreglated" spectrum that I would really love to live in a world where all that analog TV, digital TV, analog radio, digital radio, CB, HAM and every other heavily regulated piece of spectrum could be allocated to being used for just information transmission. Software radios would set themselves to the best frequency possible to maximize transmission distance (as needed) and minimize power consumption (as needed).
What we have now is more kludge than efficiency. Can you imagine how incredible the Internet would be if we had nearly infinite spectrum to use (compared to the limited spectrum we have now)?
Sure, some people will say "What prevents Megacorp YYY from blasting 100,000 watts over every frequency?" That's pretty simple -- energy costs make it prohibitive to transmit anything but profitable data. The FCC has existed long past its useful life, maybe it is time to open up little bits of unregulated spectrum piece-by-piece and let's see what happens. These software radios are a huge step in the right direction.
Do you believe in faries too?
Seriously, ou are right, the FCC isnt going to give up control of anything, as there is far too much $ to be made. Besides, when does a government give up control? ( unless of course its during a revolution )
---- Booth was a patriot ----
didn't have enough bugs.
Sigh...
What's the big deal here? The US military and public safety sectors have been using radios with software defined waveform capability for over a decade. Expensive, but Moore's Law will drive the cost down to make devices using this technology commerically viable.
I've found it slightly puzzling that my wifi dongle's drivers don't make channels 12 and 13 accessible in 'US' mode, something I found out after my devices kept randomly switching from channel 13 to 11 every so often, despite the fact that I'd specified the channel my Wifi network is on. I realise there is an FCC restriction on those last two channels (in the UK 1-13 are perfectly legal) but it's always seemed totally arbitrary to me. Why has this decision been made?
Before the FCC auctions off the analog TV spectrum for new proprietary, old technological uses (and filling the U.S. government's coffers), the technological community should educate the masses on why doing that could be a bad thing for new radio transimission/reception technologies.
At least the FCC is recognizing some of the newer radio technologies, like Ultra Wideband, and conditionally approving their use (within specified spectral ranges).
I'm not much of a hardware person, so maybe I'm missing something, but aren't different types of antennas needed for different applications? Isn't the best size of antenna a function of its frequency? I understand how you can use software to replace some of the active circuitry, but how are you going to change the size and shape of an antenna via software?
The RF engineering crowd can enlighten us, but wasn't the idea of plasma antennas kinda in the same vein? The idea being that the device could modify itself on the fly to have wireless ubiquity.
[RIAA] says its concern is artists. That's true, in just the sense that a cattle rancher is concerned about its cattle.
Perhaps GNU Radio is of a worthy mention here.
Banu
Can you imagine what will happen when people find the free hotspots they're providing are constantly saturated by cell phone connections? At least until they firewall whatever protocol a phone would be using to wrap the equivalent of VoIP.
Since we're talking about Software Defined Radio, I urge everyone with an interest in the subject to look at the GNU Radio project. They have designed a front end board using generic cable TV tuners feeding an FPGA to perform some initial processing, such as decimation and filtering. The data is then transferred over USB to the host, whose software performs the demodulation and decoding. It's a fascinating project and a great stepping stone into the field.
To really get started on SDR, check out the Ten-Tec RX320D shortwave receiver. It outputs a 12 kHz-wide IF signal from the front end to an audio jack, which can then be fed to a PC soundcard. There are a number of packages that can take this data and demodulate it, including DREAM, an open source DRM (Digital Radio Mondiale) decoder which allows you to listen to the new digital shortwave transmission standard that many of the world's broadcasters are beginning to experiment with.
Karma: Excellent Birds (mostly as a result of listening to Laurie Anderson)
Once upon a time, it used to be that only the military could fark up my garage door opener.
Now everybody will be able to.
Thanks Ireland.
[Fuck Beta]
o0t!
I agree. A few minimum guidelines should be set: X-Y mHz is for emergency use only, Y-Z is for military use only, please reserve A-B for research, now go have fun!
[Fuck Beta]
o0t!
A cellphone could, for example, automatically detect and jump to a much faster Wi-Fi network when in a local hotspot.
Hopefully, this will keep your calls connected more reliably than they do now, it will be interesting to see what happens next.
He who knows best knows how little he knows. - Thomas Jefferson
It is because it is basically a software defined radio. You have a DPS and a set of AD/DA converters and a baseband (low freqency) to RF (high freqency) converter.
Only difference here is that they are hacking the firmware for their Atheros wifi cards a bit more than the rest of us.
I think you need to remember that the RF spectrum is a finite resource and as such needs to be managed to prevent noise. Deregulate and you would have people lusing HF to go across town and I didn't pass the ham exams to have some bitch in kentucky's email to her boyfriend blocking DX when he lives down the street.
First, how are you going to get the dynamic range you need for RF intense areas if the radio front end has to remain wide open for octaves?
Second, energy costs for radiating Kilowatts are relatively cheap.
Third, what about the near-far problems with spread spectrum?
Fourth, how do you regulate narrowband emergency frequencies in a spread spectrum world?
Fifth, if you're going to push everyone to unlicensed spread spectrum, how do we resolve interference disputes?
I could go on, but I think you can figure out where I'm coming from. The problem is that if we didn't have radio and we were starting from scratch, you might be able to make a case for this technology. But since you clearly don't know how the standards got to where they are today you have no technical basis for trashing them.
Keep dreaming until you get a clue...
Nearly fifty percent of all graduates come from the bottom half of the class!
Well with the advances in Field programmable gate arrays so we will have software defined hardware defined software algorithm defined radio
Some drink at the fountain of knowledge. Others just gargle.
In Korea, Software-Defined Radio is only used by the elderly.
echo "This is not a lame sig generated through a pipe." | cat - >
Look on this thread for a lot of naysaying, negative posts from supposed slashdotters, who would theoretically by anything but tech-luddites. But software radio could hurt a lot of established wealthy quasi-monopolies. So, they likely already have astroturfers posting on most big forums, setting up these issues.
I read a metafilter post this week from someone who interviewed for such a job. THey were expected to post multiple times a day, and this marketing company had dozens of such astroturfers. I will try to come up with a link to that post.
But I doubt that sort of astroturfing is all that effective--most slashdotters never seem to read many of the posts.
But what do I know...
eat shiat and bark at the moon
Sure, some people will say "What prevents Megacorp YYY from blasting 100,000 watts over every frequency?" That's pretty simple -- energy costs make it prohibitive to transmit anything but profitable data. The FCC has existed long past its useful life, maybe it is time to open up little bits of unregulated spectrum piece-by-piece and let's see what happens. These software radios are a huge step in the right direction.
That's just nonsense. With no regulation at all, no frequency would be safe from a fly-by-night operation disrupting service. TiVos would fly right out of the window because they're all dependant on a show being broadcast on a designated channel at a designated time. If TV channels could be jammed by absolutely anybody, TV as we know it would cease to exist. Radio as we know it would cease to exist. DirecTV, Dish Network, Sirius, and XM would all have their investments in satellites wasted. (Only cable would be safe, because cable network signals spend most of their distance traveled on fiber anyway, and they can sheild the "last mile" of coax against anything given a thick enough wire.)
Of course, your answer to that would be that's the whole point, you want the existing license-holders evicted to free up everything for one big utopian mesh network. That's great on the chalkboard, but fails to stand up to real-world attacks. Just how are you going to avoid man-in-the-middle attacks and eavesdropping? "Encryption!" you say? That's nice, but you can't encrypt routing data. You have to put the address you're headed to outside of the enveleope, otherwise it's not going to get there. Basically, every partisipating router is a chance to be logging, and worse yet tampering with every packet. Meshes don't work as soon as somebody intent on not playing fair joins.
You basically want to obsolite nearly every RF telecom device in existance, and in that system's place subsitute chaos. It's just not gonna fly. Don't bother.
but aren't different types of antennas needed for different applications? Isn't the best size of antenna a function of its frequency?
from TFA:
Although software-defined radio devices use a normal antenna and amplifier to receive a signal they are fundamentally different from conventional radio-based equipment. An analogue-to-digital converter changes the signal into a digital format, which can be then be processed and manipulated by the software.
So from what i see in the above quotation, the standard antenna will work, with software providing the necessary adaptations. I'm curious to see how big the box will be for this type of tech., and I'm wondering if a typical consumer cell phone has an antenna capable at detecting broadcast radio signals from the same distance as, say, a walkman...any ideas?
Thank you Dave Raggett
It's easy to see where this will go.
1. They'll be successful, and the world will benefit from their tool.
2. Some two-bit company from Podunk, Indiana, will claim that they have a patent on the technology. A lawsuit causes the court to issue an injunction against using software radio.
3. Some other two-bit company from South Podunk, Iowa, files a suit claiming that software radio diminishes trade opportunities. The US government agrees and bans the technology. They try to get the EU to ban it as well, and a tussle ensues.
4. Large corporations take over the technology and introduce a tiered system of access.
5. Microsoft says they were planning it all along.
In the end, no one benefits from the groundbreaking technology.
Or, at least, that's how these things seem to be going these days.
Did I mention the patent infringement lawsuit?
-- The reason it's called the right wing? Irony.
Isn't that what would probably happen with software radios too?
glorious economic history.
Sure, some people will say "What prevents Megacorp YYY from blasting 100,000 watts over every frequency?" That's pretty simple -- energy costs make it prohibitive to transmit anything but profitable data.
No, it's not practical to blast 100,000 watts over ever frequency. I'm not worried about such a shot-gun approach. What I'm much more worried about is the "sniper" approach. Let's say that you're using the newly-deregulated spectrum to provide some service. Perhaps your trying to operate a local public interest radio station, or providing internet service, or selling wireless telephone service of some sort. Now somebody with an interest in preventing _you_ specifically from providing your service comes along. Maybe they don't like the message from your radio station, or are your competitor in the ISP/phone market. All they have to do to keep you off the air is tranmit a signal which degrates the SNR of your signal sufficiently to render it useless. If they're willing to pay a little more for the power to produce their signal then you are for the power to produce your signal, they'll win.
I'd much prefer minimal regulation (i.e. just enough to force licensees to co-operate to avoid and resolve cases of interfearance.) to no regulation.
Come test your mettle in the world of Alter Aeon!
The technology promises to let future gadgets jump between frequencies and standards that currently conflict.
So, in one fail swoop they've automated the radio dial and the AM/FM button? Science rocks.
It would be nice except Slashdot has been posting something about software radio for years and still nothing. Other factors to consider:
1) Power consumption on software radios will be much less efficient than their analog counterparts
2) band limited to certain frequencies - relevant because higher powered transistors at higher frequencies are becoming available, pushing beyond the 2.5 GHz limit we have right now (compliments of Gallium Nitride and Gallium Arsenide).
Same old anarchic anti-government trolls, huh dada21?
Yes, because of all the legacy equipment still in-use. You can't phase it out overnight can you? Everyone is bitching that the FCC is forcing broadcasters to shut-off their TV signal, all the while saying the FCC should be much quicker in forcing OTHER PEOPLE to replace all their radio equipment... no, that's not hypocritical at all.
Actually, it's quite ironic that the organization you want to do-away with has, in-fact, been the force gradually making companies reduce their spectrum use through newer technologies.
Sure, if you take the bandwidth away from somebody else, and use it for your own purposes, you'll get better data rates...
And "maximum bandwidth allocation is just a euphamism for noise all across the spectrum...
No, I can't imagine it being all that wonderful really. How does that solve any of the problems of the internet? Bandwidth would be somewhat cheaper, and you wouldn't be tied-down to a landline, but that wouldn't stop spam, trolls like yourself, DDoS attacks, worms, etc. It wouldn't really increase the content on the web, make it more useful, or make it more accessible to people in poor nations.
While not completely unregulated, the CB band is wide-open, and getting practically no use. Before you start complaining that you don't have enough spectrum for public use, why not try utilizing what is available first?
Slashdot gets worse every day... Pipedot: News for nerds, without the corporate slant
What prevents Megacorp YYY from blasting 100,000 watts over every frequency?
.. or well political groups may do it to silence broadcasts etc.
Well miscreants may do it
It's better to simply ban intentional misuse and place a wattage cap for license free broadcast. Also open up more spectrum for WiFi and devices that are non parasitic (fine people who don't follow spread spectrum rules etc. if they are broadcasting above a certain wattage).
I would really love to live in a world where all that analog TV, digital TV, analog radio, digital radio, CB, HAM and every other heavily regulated piece of spectrum could be allocated to being used for just information transmission.
That's the way it is today. Except a corporation known as government owns it and uses / rents it out to make money. Shareholders in govt. are called "taxpayers". You are pro entity ownership right?
wireless winmodems
Why on Earth would the cellular companies ever sell you such a device, or allow one on their networks? Sure, it's a pretty idea, but the gatekeepers of the big wireless networks will have none of this.
Why yes, I AM a rocket scientist!
Cognitive radio is a concept very related to this discussion. I googled a little about SDR and cognitive radio and came across some interesting paragraphs. Short Definition of SDR: Software defined radios are making it possible to change waveform properties and applications while operating in the field via the addition or upgrade of software. For SDRs, reprogramming or upgrading a single radio or a radio network takes about as much effort as upgrading a computer's operating system or program options. US Army interest : For its part, the U.S. Navy is likely to be the largest consumer of software defined radios with the military's Joint Tactical Radio System Initiative (JTRS) radios following closely behind. For the Navy, the software-based Digital Modular Radio (DMR) is replacing a roomful of radios with a single rack of DMRs. The DMR is a four-channel, full-duplex system that is essentially four radios in one. Currently operating on submarines and surface ships around the world, the DMR (AN/USC-61) is successfully demonstrating the viability of software defined radios on active duty. Cognitive radio: The cognitive radio, as its name implies, builds on Software-defined radio to carry a level of cognition or intelligence that permits decision-making and learned patterns of behavior. According to IEEE, the cognitive radio is a radio transmitter/receiver that is designed to intelligently detect whether a particular segment of the radio spectrum is currently in use and to jump into (or out of) the temporarily-unused spectrum very rapidly without interfering with the transmissions of other users.
Wow. Hostile much?
Why yes, I AM a rocket scientist!
This isn't all that new. It's just becoming cheap enough that it's worth doing for single-channel units.
A winmodemish wireless network card.
That's the best argument for deregulation I've heard yet!
I don't care if it's 90,000 hectares. That lake was not my doing.
Everyone on this thread seems to be pointing out only hardware advances for this field. Recent tool development for standards like SCA and CORBA have made software many times more approachable when addressesing the software defined radio world. US military companoes (like boeing) just rescently announced working radio's build on the spec ... which all SDR radio's must implement in the future according to the JTRS.
For some really interesting reading on software defined radios, do some research on the DoD's program called Joint Tacticle Radio System (JTRS). The goal is to replace ALL radio's in the DOD and other government agencies (think police, fire, ems, homeland defense, fema, etc as well as coalition countries) with a JTRS radio (in a few different form factors) using standard waveforms that are kept in a single library to ensure compatibility. The basic chasises will use pluggable modules for both "standard" waveforms as well as others that require either highpower, atypical freqs, as well as modules for encryption. the base system will be able to act as a gateway for compatible msg types on different wave forms allowing joining of systems that previously are not able to share traffic.
... as well as some other very nifty features.
... and those are IMPOSSIBLE to get without a "if we don't have this now troops will die YESTERDAY" justification.
Then of course there is the Wideband Networking Waveform (WNW) which will also go on the JTRS radio. THAT is an interesting beast that is VERY ambitious. Not sure how much info is out there open source (even the unclass stuff) but whatever is out there should prove intersting. WNW is planned to be the SINGLE waveform for all DOD use after they phase out the others sans uber special ones like ULF for subs, etc. Think a completly networked battlefield for text, voice, video, and data on land sea and air, that can dynamicaly heal and reroute itself as nodes come on and off the network (for whatever reason be it "death" or loss of connectivity) all while keeping special forces hidden (but still connected), ground pounders situationally aware of where other friendlies are and where we know the enemy is via a networked display, instant access to survielence at the lowest levels and doing it all while under electronic attack
To put it in perspective of how serious they are: NO ONE in the DOD is allowed to buy ANYTHING that isn't JTRS compliant without a waiver from the SecDef level
I find it sad that the first post rated "Informative" is almost all political.
Can't we look at this technology without the technology government bashing and utopian (and ignorant) libertarian rants?
SDR is not a new technology, but it is rapidly becoming a good way to do things, as the hardware (digital and analog) to enable it is being designed and built.
Cell phone companies are (or will soon be) using SDR to much more efficiently handle their multichannel cell sites. Instead of having a radio per conversation, or a radio per channel, they can have one or a few radios containing very high speed DSP SDR code. This saves cost and has the obvious flexibility of field upgradeability.
GNU ( http://www.gnu.org/software/gnuradio/doc/exploring -gnuradio.html#software ) has had an SDR project going for quite a while (I do wish they would do APCO P-25 reception, since I don't have the time). Hams have been doing various forms of SDR also - for example, the very narrowband systems that use a PC to do the DSP for HF data communications.
Contrary to what some might think, SDR doesn't give magical powers to radios - the ability to operate on all frequencies at once. Radios have hardware filters in them for reasons that cannot be solved in software: to compensate for the non-linearities in the analog (or digital) software - which especially causes problems in high dynamic range situations. Radios may have to separate signals that differ in power by factors of 10^12 or more, which are relatively close in frequencies. Transmitters have to avoid emitting spurious signals at similar ratios to their output power.
More specifically, if you put two signals (assume sine waves for now) into a non-linear device, it is the equivalent of putting those time-domain functions into a polynomial of degree 2 or more. This means that those sine waves will be multiplied by each other and themselves (and a coefficient which you try to make as small as possible). The result is output at the sum and difference frequencies and the harmonics of the original signals. Non-linearity can crop up in surprising ways. The most common one seen in radio is receive and transmit amplifiers, which are *always* non-linear. In addition, parasitic devices (such as two wires touching each other somewhere nearby) can act as non-linear mixers, generating spurious signals. Anyone who has worked on systems at crowded radio sites knows the fun of tracking down "intermod" signals (which are the result of this process). SDR's do nothing to improve this situation. On the contrary, they may require wider bandwidth amplifiers, which increases the odds of spurious signals. Furthermore, the very process of sampling with non-infinite bit-width A/D's and D/A's is itself a non-linear process that generates mixing.
So SDR still has to deal with the issues at the antenna that analog radios deal with.
Where it gets cool is at the baseband - in other words, at the modulation=baseband level (or in the case of multi-channel receivers/transmitters, at an intermediate level). This is where you take the information you want to send/receive, and convert it into/from the RF representation of that information. A simple example is FM modulation (used in most older land mobile radios - police, fire, cell phones, ham repeaters, etc, and in TV and FM radio broadcast). Here the SDR will take the modulation (voice or music or whatever), and use it to generate the signal equivalent to having it quickly alter the frequency of a carrier wave. Depending on the system, it may literally output a sine wave modulated this way. In other systems, it may generate some intermediate representation that then goes to the radio.
But a far more interesting system might be a trunked narrow-band digital public service radio system (which US public safety organizations are converting to at FCC insistence). These systems are designed for improved flexibility (
The only good weather is bad weather.
I know that the black hatters are salivating about this one, you get lots of points for hacking one of these software defined receivers. Hack the receiver AND the computer behind it, get triple points in the software trashers sweepstakes.
Vornan23
Just being a jerk here but luddite refers to an english group of textile workers who feared new technology (Industrial revolution) would detroy their jobs. A "Tech-luddite" is a redundent phrase as all luddites fear technology by definition. The coloquial phrase is now known to mean "Fears technological change."
I want a software-tuned phased-array. That's my idea of a universal radio: any frequency, all frequencies, multiplied by all the points from which transmissions originate, across several GHz of spectrum, suited to a mobile device. Finally bandwidth to compete with a stationwagon loaded with backup tapes.
--
make install -not war
In software radio utopia the bitch down the street would have a software radio that would automatically range the boyfriend and select a band that allowed for the most efficient and localized transmission. Which I sincerely doubt would be your precious highly regulated HF band.
In software radio utopia the radios would only invade low bit per second "buggy whip" HF bands when something like a category 5 Hurricane Zelda struck and knocked out the local high bandwidth high frequency ISP nodes.
And even then a UHF or VHF band would be more likely to reach a functioning ISP node. So don't get your HF panties in a bunch.
One huge issue I see with software radios is buggy software.
The radio is going to need a very goof proof hardware enforced watch dog that will whip Microsoft's code back into line when it crashes and sits there spewing noise down the antenna.
And even then I wouldn't be comfortable buying one with Microsoft code in it. The last thing I need is to come home to find the FBI waiting for me because my computer has been spewing junk into the VHF satellite rescue band.
Here in Seattle I've often found my Verizon EVDO is faster than T-Mobile's Starbucks or Border's WiFi hot spots.
And what if I'm on the bus traveling down the street: 3G, WiFi, 2.5G, WiFi...
The decision to switch from 3G to WiFi will have to be made on more complex criteria than simply "Oh look WiFi!!"
Right now my Tablet PC can't even handle going "Hey Wifi!" reliably, although Mac's do it quite well.
And I can't even begin to picture how one would handle a TCP hand off with out using IPv6. RIght now Verizon and CIngular both suck at handing off seamlessly from 3G to 2.5G and back to 3G when running around in a bus on their own networks (where they have control over IP addresses' and routing).
I submit that these issues push things further out than you think to achieve your utopia.
Expensive, but Moore's Law will drive the cost down to make devices using this technology commerically viable.
Arrgh... Thats not Moore's Law... Which is about transistors doubleing every 18 months or so, but you are thinking of Law of Accelerating Returns.
"I am the king of the Romans, and am superior to rules of grammar!"
-Sigismund, Holy Roman Emperor (1368-1437)
They're going to find me lucky charms! They're magically delicious!
"I think you need to remember that the RF spectrum is a finite resource and as such needs to be managed to prevent noise." LOL @ scarce resources. My technological utopia I live in will charge the RF spectrum with rainbows, sunbeams and pure human happiness. And if that fails I always have monkeys who shall deliver messages via unicorn. You crazy managers with your economic theories of scarcity.
It'd might be a nice easy way of avoiding the Verison, Comcast, Baby Bell crunch if enough people become interested. (Verison is an immoral company---www.deadwomen.com... yup....)
One question? With the new planned subscription based internet proposed by the big three. Does liability become an issue if a crime is committed across "their" networks? Heh,... "A Safer (downstream) Internet for all"
you are a fucking moron. You have no idea what the reprocussions would be...
Can you imagine how incredible the Internet would be if we had nearly infinite spectrum to use (compared to the limited spectrum we have now)?
You never will, dumbass. The spectrum is limited. Can you imagine how great your internet connection will be when the jerk next door is using the same frequency to broadcast his own shitty talk radio station? Switch to a new frequency? Oops... they're all taken up because no one is regulating it and your stuck with your thumb up your ass.
Software radios would set themselves to the best frequency possible to maximize transmission distance (as needed) and minimize power consumption (as needed).
Software radios mostly just change modulation and keep the frequency the same. You run into a shit load of physical problems if you don't have the right filters setup at the antenna.
God damn.... read a book.
I think you need to remember that one of the benefits of Software Defined Radios is that all parameters can be adjusted, including power levels. Sending an email down the street could be, and would be, done at a very low power level under a new regulatory regime that takes into account modern technology. Current regulations provide no incentive to use less than than the maximum legal power, so excessive power is the norm.
Tell me again why you are opposed to lowering interference with your use?
As the Esperantinos would say: Bonvolu alsendi la pordiston? Lausajne estas rano en mia bideo!
Agreed, and "jcgf 688310"...too much caffeine?
;)
Get over the fact that the past does not always (sometimes,yes) translate to the future (or present for that matter).
By your reasoning, I should be upset over the time I spent learning to chip/flake flint into arrowheads because some asshat came up with 'nukes.
Get over it....use your ham exams until it pains you, then slap it between bread with cheese so you can enjoy a Ham and Cheese sandwich.
Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti
Well, after 3 years, I still do not get any mod points to give out, but if I had some...for you I would do this:
:)
+2 funny
+3 insightful
+4 informative
Sadly, this is all I can offer- not worth s*it most likely, but my heart is in it.
Down With Slashdot BETA!!! I've been around the corner and seen the oliphant; you can only abuse me from your perspecti
I actually worked on a literal all-band/all-access (look up access in a Communications textbook) communications system once.
But it was 1985, and it was all in hardware.
It was basically a mobile shelter containing every kind of radio you've ever heard of, your local ham club has ever heard of, your local military base has ever heard of, and one or two nobody has heard of.
Right after that I went into software and haven't looked back.
So the world is 20 years behind me. Explains a lot.
Well, there goes my terrestial HDTV due to RF polution.
he's probably bemoaning about the morse requirement being dropped because it means that more people can get through the exam...
he probably thinks his precious spectrum will be like usenet the day after AOL let their subscribers in...
well, software radio won't be like that, because, unlike usenet, where a message gets to every server in the world that carries that group, software radio will only send a message as far as the recipient and with only enough power to reach him/her... and if things are set up right, then we'll have an interlocking mesh of nodes so the power requirements can be kept extremely low purely for node-to-node message passing.
Donald 'Duck' Dunn: We had a band powerful enough to turn goat piss into gasoline.
nice reply, saved me the trouble...
Donald 'Duck' Dunn: We had a band powerful enough to turn goat piss into gasoline.
Intel's WLAN solution used in Centrino laptops, namely the ABG-compliant mini-PCI card has the ability to send and receive in frequencies from 600MHz to 7.2GHz with up to 500mW transmit power.
;)).
/. in the park now.. there are tall buildings on the way but if I can't reach my home network at 1.8GHz, I'll try 685MHz, 907MHz or 3.23GHz or join one of the ad hoc networks :)
However, the open source drivers for Linux are deliberately crippled to very low transmit power (32mW) and narrow frequency bands by forcing Linux users to download and install a closed binary part. This closed DRM part is NOT present in Windows drivers and there exists at least two (albeit very expensive) programs that allow the card to be used as a signal generator with up to 500mW power and any frequency that the card is physically capable of. (please note that some brand name laptops include hardware filters to restrict the frequency range, my Acer does not)
My question is this: usually Open Source drivers allow me MORE control than using Windows so why do did the driver programmers decide to add DRM to the drivers?
Fear of the authorities in some countries? Agreements signed with Intel in exchange for source code?
I think this makes foul of the GPLv2, I could modify the sources all I want but the closed DRM part still enforces arbitrary restrictions for me, so I won't break the rules of some other country's radio spectrum regulatory body.
Where I live I have the legal right to transmit on ANY frequency with up to 1000mW transmit power omnidirectionally*1 on my own property and in public spaces*2 without any licence. Yes, that includes TV, cell phone, commercial radio frequencies. The TV/phone/radio companies have leased monopolies to transmit on those frequencies using OVER 1000mW power in my area.
Simply put, there is no chaos. There isn't a tumor in my brain from all the radiation either (at least not yet
In case you are wondering the police and other emergency workers have 5W-25W handhelds/car radios along with special cell phones (that have priority access in congested nodes) for emergency use.
In my city of 200000 there's no chaos from all this "wild" use of limited spectrum. Here's a free hint why some would like you to believe otherwise: it has got to do with bank accounts and numbers with many 0's after them.
A direct result from the quite free use of the spectrum (when compared to USA and most EU countries) is the available commercial broadband options. Here are some of the options I had when I moved to my new place:
1. 12Mbit/6Mbit wireless (limit 250GB upload) 45USD
2. 12Mbit/2Mbit wireless (limit 100GB upload) 30USD
3. 10Mbit/512kbit cable (connection may be "throttled" after 600GB down) 30USD
4. 10Mbit/512kbit cable 77USD (a bit cheaper with cable TV service)
5. 6Mbit/256kbit cable (connection may be "throttled" after 300GB down) 18USD
6. 4Mbit/4Mbit SDSL 40USD
7. 2Mbit/1Mbit ADSL 16USD
8. 24Mbit/2Mbit ADSL (limit 1000GB down, no commercial servers) 45USD
9. 24Mbit/2Mbit ADSL 100USD
10. 100Mbit/100Mbit fiber (limit 2TB/500GB d/u, no limit on local (citywide) transfers) 70USD not available on suburbs
11. 256kbit/128kbit wireless 8USD
12. ?/? satellite 30USD
Free competition=good for the customer? Do you agree?
What are the prices and options like when compared to your country?
Unless otherwise noted, all examples have unlimited bandwidth*3.
It's a sunny day outside, I think I'll get my laptop and go browse
(I have one software WLAN card connected to three antennas, cycling between the four frequencies in 250ms intervals until it hears a transmission with my laptops MAC. No, it's not secure but that's what simple VPN+Privoxy is for. I have an open AP like most others so no need to hack for 'net access anyway).
*1 using a directional antenna places further limits to the transmit power but the increased gain more than makes up for it. This is to done to make
Capitalization is the difference between "Helping your uncle jack off a horse" and "Helping your uncle Jack off a horse"
Too smart to be really used by industry.
Infact manufacturers would then have fewer ways to convince customer to buy newer and better devices as a replacement of the older ones.
Maybe Computers will never be as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]
FDR = Franklyn Delano Roosevelt = Liberal = one of the most politcally charged sets of initials in American politics.
SDR = software defined radio = not really a question of politics
a revealing lapsus??
ooooh, yes, he does. This isn't a "noise" issue where, you're right, coding gain would help. This is a "nonlinearity" (e.g., blocking and intermodulation) issue, where coding gain is irrelevant or inadequate, and the "obvious workarounds" typically don't work well in practice. A digression:
Blocking occurs when you're trying to receive some desired signal, at some reasonable signal strength, and at least one strong, undesired signal, on an arbitrary frequency, also reaches an active stage of the receiver. If the undesired signal is strong enough, it can corrupt the dc bias of the active stage. The small-signal gain of the receiver drops, often by 80 dB or more, so the desired signal (and all others, often including the undesired signal that caused the problem in the first place) simply disappears. It's an impressive thing to see in action. Essentially no signal reaches the backend of the receiver, where the correlators are that produce the coding gain. You can experience blocking for yourself by listening to a station on a car AM radio and then driving close by (~200 m) the antennas of a second AM radio station. The signal from the first station fades out as you approach the second, leaving you with no signal at all. Just...silence.
Blocking is most easily prevented in conventional receivers by providing passive filters before the active circuits (i.e., the LNA), filtering out the strong signals elsewhere in the spectrum before they have a chance to affect the active circuits. (The filters are why the AM radio test above doesn't affect your car FM radio.) However, this produces a narrowband radio (unless one is willing to make really complicated tracking and switching RF filters, as seen in early shortwave receivers), which is not suitable for SDR. Less efficiently, one can increase the dc bias power of the active circuits, so that stronger undesired signals are needed to produce blocking, but the tradeoff is dB-for-dB, so a 10 dB improvement in blocking performance is achieved by a 10x increase in receiver power consumption. Not a pleasant trade, in most applications.
In the GP's discussion of intermodulation, the P is right, coding gain will help overcome intermodulation distortion--but he's wrong in saying "as long as I can get a few dB of coding gain." The difficulty is that intermodulation products frequently are very much stronger (~30 dB or more) than the desired signal. A simple definition of direct sequence coding gain is the ratio of the chip rate to the bit rate; to get 30 dB of coding gain the chip rate has to be a thousand times the bit rate, so your moderate-performance 1 Mb/s system requires a chip rate of 1 Gc/s--nice, if you have an open channel wide enough to put it in (along with the power to code and decode it); a bit of a bother otherwise. And that's for only 30 dB of protection.
Let's discuss workarounds.
One "obvious" workaround to avoid intermodulation is to reduce the gain of the receiver front end when strong signals are detected by the receiver via some kind of AGC (and assuming this can be done without reducing the overall receiver intercept point). This has the attraction that the receiver bandwidth must be wide to ensure that the undesired signals reach the AGC detector, something compatible with the SDR concept. The receiver gain is set high when no or weak signals reach the AGC detector, and low when strong signals reach it.
What happens in a blocking environment, though? In a blocking environment, the receiver's "analog stages" are "overloaded", so that no signal reaches the AGC detector. The AGC system responds as designed, and attemps to maximize the gain of said analog stages. This ensures that they remain overloaded! Note that it's difficult for the SDR algorithms to figure out what's going on, be
Irish government has also allocated a large chunk of RF spectrum for research purposes, specifically related to this project. Ireland can afford to do this because it is an island, and also because it doesn't waste so much spectrum on military/security reservations (but it does have an army, air-corps and naval service, as well as polic, Civil aviation etc..). This allocation of spectrum is, it appears, the largest such allocation in the world, and puts Ireland in a very strong position to leverage investment in R&D in this sector. Already, many US, European and other R&D groups are clamouring for access to this spectrum to conduct R&D over a large geographic area using this spectrum allocation.
Where are you located? 1 Watt allowed no questions asked is very interesting for testing new Modulation! Thanx
http://jtrs.army.mil/
Care about electronic freedom? Consider donating to the EFF!
I find it sad that the first post rated "Informative" is almost all political.
Welcome to the new and improved slashdot.
With the re-election of Bush jr we've seen that someone in the high ups of slashdot has a chip on their shoulder so anything that can be done with a political spin makes it to the front page and try to post an a-political post? Please. These vultures will find any crack in the sidewalk to take seed and make everything seem like it's somehow politically motivated.
It's starting to suck bad.
And what's worse is that slashdot now also has the "has-been entertainer syndrome".... That's my term for the odd phenomenon that overtook "news" sites like MSNBC and CNN that anytime an old face from TV, movies or music came out and said "I hate George W" they got into the headlines. Not to say they don't have their right to an opinion but frankly what some one hit wonder from 1982 thinks about the political climate of anyplace (let alone the US) is NOT news. The decision of these sites to carry this crap as news shows how much of a slant there is to the "news" media.
But on slashdot it's even better. All you have to do is claim that some political figure or party is for/against something or that they're abusing government power and you get auto-Insightful mods... even if the government isn't even involved. Most of the idiots here are too stupid to read the article and are too quick to use political slogans. Sadly most of them also believe what they say and so do the lemmings around here.
Enough of my rant.
Dedicated Cthulhu Cultist since 4523 BC.
Could you stop using such big words you assholes?
Stop invalid scientific research. Ask your local scientists to feed their lab rats with a phytoestrogen-free chow.
The other poster summed up the issues of preamp nonlinearity pretty well.
I'll address coding gain - Yes, it's possible to improve performance of a given system at a given SNR by employing some sort of error correction coding. That said, there are pretty hard limits on performance of a communications system no matter what coding scheme you use. (Refer to Shannon's Law). Thus, it is still VERY beneficial to have a preamp with a very low noise figure if it is practical to do so. Given two systems using identical coding schemes, the one with the noisier preamp will perform worse.
retrorocket.o not found, launch anyway?
I once got sent to the office for discussing capacitors with a friend way back in high school. We were looking at building a pretty big Leech amp, and the guy writing the guide we were looking at kept referring to how mnay "dog feet" the capacitor had; how far the potential energy of the cap could hypothetically throw his black lab.
We found some 10 farad 60V caps on Fair Radio Supply. Never bought any, too cheap to work. Course, my college roomate was best friends with the campus supply depot, so he had some eighty pound 600V and 1kv caps that he wanted to turn into a coilgun someday.
I'd like to see what an open astroturfer has to say.
Tech Public Policy stuff
What Windows software allows such things to do with the Intel wireless adapter?