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New Technology Could Kill WiMax?
GolygyddMax writes "Techworld reports that a Florida-based start-up, xG, has developed a technology that's a 1000 times more efficient than WiMax and which could, in theory, lead to wireless LANs being powered by watch batteries. It is still in early development, but this technology could allow anyone to set up as an ISP. This could kill WiMax before it even gets off the ground." From the article: "At the demonstration with other reporters, we were able to verify that the signals were being sent wirelessly, and checked the distance by GPS, but had to take the 50mW base station - and its omnidirectional antenna - on trust, since it was at the top of an 850ft mast. The demonstration will be repeated for the US press next week. The system carried 7.4 Mbit/s per MHz per Watt, said Professor Schwartz. By comparison, GSM would have around 0.0058, and CDMA/EV-DO about 0.0085 Mbit/s per MHz per Watt. "
There had been some discussion here in the past about using cell phones as network relays as well as end-points to increase range and reach, but one of the conclusions was that having cell phones constantly retransmitting data would run down the batteries too quickly. This technology might change the equation, making it possible to have an ad-hoc networking system shuttling data between portable devices rather than needing a lot of infrastructure.
I've looked at this before. There's a lot of technbabble and nothing concrete. Some claims, such as "7.4 Mbit/s per MHz per Watt," are meaningless (distance is not part of the claim). The demonstration is not verifiable, "on trust, since it was at the top of an 850ft mast".
The only concrete claim, "3.7Mbit/s data signal to a radius of 18 miles across the suburbs of Miami, using 50mW and an omnidirectional antenna," is absurd...unless there is a REALLY BIG antenna at the other end.
Investors: avoid this like the plague!
My take is that they're using the difference in frequency between the carrier frequency and the generated sideband frequency to represent a value (ie. +10kHz = 0001; +15kHz = 0010; etc.). This seems awfully similar to the SSB modulation commonly used in shortwave radiocommunications to me.
Since they're operating in the license-free 900mHz ISM band, it also *must* implement some sort of frequency-hopping (or direct sequence, I suppose) spread spectrum stuff in order to be legal. Could be kind of an interesting technology. I'd like to play with a couple of the radios and a good spectrum analyzer to see what it looks like.
In the interests of full disclosure, IANARE (but I played one at a job once for awhile).
-Matt
Its all BS. Basically there is a standard MHz and a standard wattage that you really can't deviate much from. As well seval signals are being sent in neighboring MHz. Anyways the guy sent a 3.7Mbit/s signal using 1/20th of a watt using 900Mhz. To make the assumption that if use 20 times the wattage you could do anything but improve the distance/signal loss is rediculus.
Actually, increasing the transmit power *can* buy you greater data rates, as long as your data rate is limited by signal-to-noise ratio.
For example, let us build (in our minds) a transmitter/receiver pair which can encode/decode one symbol every second. OK? Every second we send one symbol (effectively a magic combination of waves which means something to a demodulator) from the transmitter, and every second we decode one symbol at the receiver.
If we have lousy SNR, we might only be able to differentiate between the most distinct two states of the transmitter (one bit per symbol: either 1 or 0), since all the noise impinging on our signal looks an awful lot like the more subtle states (or even worse, completely obstructs all states, making decoding impossible). This gives us a data rate of 1bps.
If we can increase the signal level at the receiver, thus increasing SNR (assuming we're not distorting the living hell out of our transmission, natch) but increasing our transmitter's output, we might be able to encode *two* bits per symbol (00, 01, 10 or 11) by adding two more symbols to the constellation. By doing this, we haven't increased our symbol rate (still only one symbol every second), but we *have* doubled our throughput.
Make sense?
-Matt
Was the demo mention in the summary fictional?
Pretty much, yes. In their demo, the alleged transmitter was up on an 850' tower. Reporters had to take it on faith that the signals reported by the recievers were really coming from that transmitter and that there wasn't a bank of car batteries and a 100W linear amp up there.
Until someone from outside the company can hook meters up to the transmitter and verify that it is really the source of the signal and that it's really using as little power as they claim, the demo is worthless.
0 1 - just my two bits
Since they're operating in the license-free 900mHz ISM band
Not a good band to be operating in for weak signal type stuff. The 300Watt paging transmitters operating in that band could cause them some trouble without the use of a helical front end on their receiver.
--fatboy
By comparison, GSM would have around 0.0058, and CDMA/EV-DO about 0.0085 Mbit/s per MHz per Watt.
In a world where CDMA EV-DO with Turbo Coding comes within 1-2dB of the Shannon Limit, xG claims their system is 1000x (60dB) better. Perhaps they are modulating the tachyon-neutrino field? Ensign, Crusher... evasive maneuvers!
Anybody want a peanut?
Joe Bobier is behind this technology, and it's not his first time of trumping up "new" ideas.
His last venture was to "revolutionize" wireless networks by "inventing" Wireless to home users. He did this in Parkersburg WV using Wirefire Internet Service. It worked moderately well, though line of sight transmissions caused a problem, since the system required bulky exterior antennas, and trees blocked signal nearly universally. He claimed to have invented the system, even though the equipment was actually off the shelf Breezecom cards and radios talking to APs housed on terrestrial based radio and water towers.
Before Megafire (as it was known) failed, he convinced a Sarasota company iDigi to buy it. iDigi was owned in part by the Mooers company, referenced in the article. They funded the creation of a company named Island Labs, who's sole purpose was the create wireless that worked.
Joe is a smart guy, but he takes too much credit for things he didn't do. This may be another of those cases. I have heard of another technology very similar to this that didn't work either. I'm going to try to find it. If I do, it will be a reply to this post.
Either this is vaporware, or so innovative that Big Brother and his cousin The Man will crush this before it even gets off the ground. .005 of the world population is even using it, even though it's faster and easier to implement than Cable/DSL so we're told....
Don't expect to see this for another 20 years if it even exists....
How long has powerline internet been in the works, and only
My lecturers teach me one thing. Whenever something new comes out that seems to be so fantastic as to be miraculous ask one question
Whats the catch?
I'm doing engineering and i'm alway wary about such claims
where else/how much have they tested it?
How much does weather affect its operation?
How much will it cost?
Of course. i'm not saying that they are lying, they have achieved an engineering marvel that can only change things for the better. can you imagine how useful this would be in the developing world and rural areas where bandwidth is expensive or non-existent
Not a good band to be operating in for weak signal type stuff. The 300Watt paging transmitters operating in that band could cause them some trouble without the use of a helical front end on their receiver.
That's the whole point. It's fairly conventional technology, but they've developed MAGIC TECHNOLOGY at the reciever that filters out the BAD signals (i.e. NOISE). Low operating frequency plus incredibly low S/N ratio equals efficiency equals range. They state on their website that they don't violate Shannon's Law (which was awfully considerate of them.) It's the MAGIC WAVEGUIDE TECHNOLOGY required on each reciever that looks pretty unlikely to me.
To ensure perfect aim, shoot first and call whatever you hit the target
There is a simple fix for that: use the phone's built-in GPS receiver.
No consumer-level data network (WiFi, WiMax, etc.) is aware of its location. Since VoIP goes through data networks which may be re-routed through other networks (someone routing calls using SSL to some other machine), it is impossible to determine the exact location based on the traffic's apparent point of origin.
100% 911-compliant VoIP is unlikely to ever happen because the 'line' is not tied to any fixed infrastructure. Cell phones have the towers, cable/dsl/phone have the coax/phone cable but VoIP is not tied to any particular endpoint/network/etc. anywhere on the planet. Even if a GPS receiver is built into the VoIP phones, these still depend on being able to detect the satellites and will fail to provide a location if there are a few reinforced concrete buildings around the area. Even if the GPS is cell-assisted, even cell phones stop working inside larger reinforced concrete buildings and there are dead zones all around towns too.
VoIP is not for critical calls. AFAIK, it was never intended to be and never will be. For VoIP to work, you have to trust that:
1) Your WiFi handset will work
2) Your WiFi router will work
3) Your ADSL/Cable/whatever modem will work
4) Your ISP link will work
5) Your VoIP company's servers will work
6) etc.
VoIP has more than double the number of middle-men compared to land lines and cell phones. Every link is a potential point of failure and any failure is very likely to lead to a dropped call, assuming the failure did not prevent you from placing the call in the first place. Last thing you want to have to do when you need to make an urgent call is troubleshooting your network.
Actually, how many bits you can cram in 1Hz of bandwidth depends on the SNR.
From Shannon: bps = BW * log2(1 + S / N)
So, with a 30dB SNR you get BW * log2(1+1000) = you could almost encode 10bits of data per Hz of bandwidth... a little under 10Mbps per 1MHz.
Since this modulation has smaller sidebands, more energy gets packed in a narrower band, enhancing the signal's strength while reducing the amount of noise picked up. It makes sense and I imagined something like this years ago. It looks basically like a single-cycle version of FSK or PSK but I think these should not look quite as clean as they did on their plots. (Well, they did stop at 100kHz resolution.)
As far as the signal generation goes, I am guessing they used an FPGA to drive an ADC and DAC for their prototypes and their 50mW is only the DAC's power output, not the entire receiver/transmitter power. They insist a lot on the signal's power but they say nothing about the system used to generate, transmit, receive and decode the signal.