Scientists Discover How To Boost Wireless Bandwidth - Canadian TV, Computing and Home Theatre Forums

Reply
 
LinkBack Thread Tools Search this Thread Display Modes

post #1 of 17 (permalink) Old 2012-03-02, 09:18 AM Thread Starter
HWP
 
Join Date: May 2010
Location: Toronto, East York (Greenwood & Mortimer)
Posts: 1,179
Scientists Discover How To Boost Wireless Bandwidth

Here is a very interesting story about how scientists in Sweden and Italy have successfully tested a hypothesis that OTA bandwidth capacity can be significantly boosted by adding a "twist" to the transmission signal.

'Twisted' waves could boost capacity of wi-fi and TV:
http://www.bbc.co.uk/news/science-environment-17221490

OTA, HD7697P, CM7778, Rotator, CM3218, TiVo, HDHomeRun
Apple TV, Netflix, Teksavvy, Unblock-us, Wind, MagicJack
HWP is offline  
Sponsored Links
Advertisement
 
post #2 of 17 (permalink) Old 2012-03-02, 06:17 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Heh, yeah I saw that this morning too. But the article I saw didnt really explain the difference between it and circular polarization, which has been around for a long time. I guess its the spacing of the "twists" that makes the difference.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #3 of 17 (permalink) Old 2012-03-02, 07:24 PM
Veteran
 
Join Date: Feb 2009
Location: The Dandelion City
Posts: 7,133
It does sound a little like polarization but vertical + horizontal, not circular. That has been done with satellite signals for years. The fact that they demonstrated only double the bandwidth makes me question the science behind the demonstration.

At 20 I had a good mind. At 40 I had money. At 60 I've lost my mind and my money. Oh, to be 20 again. --Scary
ScaryBob is offline  
post #4 of 17 (permalink) Old 2012-03-02, 08:32 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Its not increasing the bandwidth per se, but rather more like putting 2 lbs of crap in a 1 lb capacity bag, heh.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #5 of 17 (permalink) Old 2012-03-03, 12:11 AM
 
Join Date: Jun 2011
Location: Central Illinois U.S.
Posts: 108
found posted in 2009

I saw this posted else where by a fellow named Ai4i.
I've been trying to understand this for a while now, he said.


Quote:
A friend lived 200 Km from a CP TV station he enjoyed viewing, but an offending horizontal station was another 150 Km in the same direction, and whenever it got cold, the distant station would cause objectionable QRM. Using a vertical antenna would not resolve the issue because extended propagation always randomizes polarity. He built two CP receiving antennŠ, one CW and one CCW and connected them out of phase. They both received the linear station and their combined output was next to zero, but only one of them received the target station. It seemed counterintuitive, but connecting and disconnecting the second antenna had no effect on the strength of the desired station, but connecting it make the offending station go away
The reason I posted it here is how similar this is (two antennas connected out of phase ) to what the researchers did described in more detail here "Bo ThidÚ" is mentioned in both so I'm pretty sure it's the same experiment.

Quote:
The signal was collected equally by antennae A and B in phase and the signal of antenna A arrived at the signal adder 180░ out of phase with respect to that of antenna B because of the electric λ/2 cable delay, resulting in a difference signal configuration
Looks a lot like what I'm still not sure what they did new.
Wifi enthusiasts and others have known a long time that twice as many users can use the same frequencies if half use vertical polarized antennas and half use horizontal.

And I thought part off how N routers with "mimo" got more band width from a single channel was by decoding separate streams based on phase/time differences.

Scarry bob said
Quote:
It does sound a little like polarization but vertical + horizontal, not circular
actually in the link(above) it looks like one was linear and one was circular( but then they seem to contradict themselves). I to share your skepticism of actual throughput improvement. And wonder if the "test " could have been conducted with any two oppositely polarized antennas (linear or circular)

I also noticed they tested over water, think a ridge detraction might hurt the effect ?
Still wading.

my gain reports and models are here
GHZ24 is offline  
post #6 of 17 (permalink) Old 2012-03-03, 12:04 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
Wifi enthusiasts and others have known a long time that twice as many users can use the same frequencies if half use vertical polarized antennas and half use horizontal.
And I thought part off how N routers with "mimo" got more band width from a single channel was by decoding separate streams based on phase/time differences.
Well, the multi-user data through-put capacity of Ethernet, whether on Cat-6 cable or a single wifi channel, is limited by the number of collisions. More collisions, less net data through-put. Anything that minimizes collisions will increase the multi-user data through-put.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #7 of 17 (permalink) Old 2012-03-03, 12:12 PM
Veteran
 
Join Date: Feb 2009
Location: The Dandelion City
Posts: 7,133
Quote:
actually in the link(above) it looks like one was linear and one was circular
I also forgot that circular polarization can be reversed. Either way, I'm not yet convinced this "discovery" is anything new.

At 20 I had a good mind. At 40 I had money. At 60 I've lost my mind and my money. Oh, to be 20 again. --Scary
ScaryBob is offline  
post #8 of 17 (permalink) Old 2012-03-03, 12:17 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Quote:
Either way, I'm not yet convinced this "discovery" is anything new.
Yeah, and I dont think this "discovery" could possibly work in practice for long distance DTV signals with only small changes in existing equipment.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #9 of 17 (permalink) Old 2012-03-03, 03:15 PM
Veteran
 
Join Date: May 2009
Location: Mississauga
Posts: 6,488
Quote:
whether on Cat-6 cable or a single wifi channel, is limited by the number of collisions
There no collisions on Ethernet these days, with switches and full duplex commonly used. Collisions occured on the old coax and hub based networks. With switches, there is no longer a collision domain to worry about.

Quote:
I also forgot that circular polarization can be reversed
I also get the impression they're talking about circular polarization.
JamesK is online now  
post #10 of 17 (permalink) Old 2012-03-03, 04:23 PM
 
Join Date: Jun 2011
Location: Central Illinois U.S.
Posts: 108
Jamesk is right on the ethernet but 802.11 abg and I think N use (CSMA/CA) to deal with collisions and all devices within ~3 channels share a collision domain.
Just to clarify my statement about Wifi, the devices can tune to twelve channels +or - depending on your country but only 3 are far enough apart to not interfere, without large attenuation channel 3 interferes with
1 - 6 and 9 with 6 -12. But with the attenuation provided by opposite polarization channels 3 and 9 can be used like this ch. 1-VP. ch. 3-HP. 6-VP. 9-HP 12-VP effectively adding 2 more usable channels/wires. This works good outdoors with LOS but not so much inside buildings where multiple reflections can totally jumble the polarization.
I think that's what's happening when you rotate your biquad and see no drop in signal it's because the signal got jumbled (polarization wise) before it finds it's way to the window and out.
Theoretically 1, 6. and 12 could all have two transmitters on each, one HP and one VP and not even see each other. (but those are spherical chickens in a vacuum)

Meanwhile back on the subject : I have to agree that this technique is unlikely to help long distance tv. The refraction of 1 edge likely kills the
signal integrity beyond recovery. And it's hard to imagine a tropo signal that would tolerate a big null (singularity ) at the boresite.
They picked over water for a reason.
IMHO It is more likely to kill DX reception if used for tv transmission hopefully it will be relegated to LOS data links and microwave relay stations ect. not TV.

I do think they have discovered something, remember someone "discovered " America and electricity and in both cases it wasn't the first person to see or notice it !

I guess the split does something but not polarization (diffraction?) because it says both signals were linear, My mistake. I should alter a parabola like they did to see if what nec shows going on
(if it shows anything). I don't think the split causes circular polarity (I thought the feed was CP).

my gain reports and models are here

Last edited by GHZ24; 2012-03-04 at 02:05 AM. Reason: correction
GHZ24 is offline  
post #11 of 17 (permalink) Old 2012-03-04, 07:51 AM
 
Join Date: May 2007
Posts: 258
I saw the story too. Am I correct in thinking that everybody would need to buy new receivers if broadcasters were to start to use this ?
ppauper is offline  
post #12 of 17 (permalink) Old 2012-03-04, 08:00 AM
Veteran
 
Join Date: May 2009
Location: Mississauga
Posts: 6,488
^^^^
Given how vague the description is, I expect we'll have to see something far more concrete before we have to worry about anyone switching.
JamesK is online now  
post #13 of 17 (permalink) Old 2012-03-04, 11:33 AM
 
Join Date: Jun 2011
Location: Central Illinois U.S.
Posts: 108
off the shelf

I managed to finish the article (that doesn't mean I caught it all ) and I picked up a few facts.

Quote:
Am I correct in thinking that everybody would need to buy new receivers if broadcasters were to start to use this ?
No they use all "COTS" equipment that's "consumer off the shelf" (except the split dish)

It's all in the "interferometer" (two yagis connected 180 degrees out of phase) and the separation distance between and aiming of the two yagis determines what signal is left for the tuner to pick up.

With one yagi you would have heard both tones/signals.

Quote:
Already with this setup, one can obtain four physically distinct channels on the same frequency by additionally introducing the use of polarization (SAM), which is independent of OAM. A further five-fold multiplicative factor from implementing multiplexing would yield a total of 20 channels on the same frequency. The utilization of multiport techniques (e.g. MIMO) could increase the capacity further.
So I was wrong it's not the same as either polarization or mimo.

This PDF is the same report I think.

http://iopscience.iop.org/1367-2630/...4_3_033001.pdf

I'm still not sure what the exact effect of the split dish but if (that's a big if)edge diffraction imparts similar qualities in the signal then this could be used to not just attenuate offending co-channel interference but pick which channel to receive (if both signals were strong enough).

my gain reports and models are here
GHZ24 is offline  
post #14 of 17 (permalink) Old 2012-03-04, 12:08 PM
Veteran
 
Join Date: Mar 2008
Location: Somewhere in Delaware on the flat side
Posts: 7,360
Thanks for the link.

Helicoidal parabolic antenna is what he calls his new antenna.



It does seem like it may be good for tower to tower LOS applications. But in practical terms, I think it would mean a separate antenna for each channel on the same frequency, which would mean the number of channels would be limited by the size of the tower ??

And there would be no such thing as a broadband helicoidal parabolic antenna ?? (but multi channel maybe ?)

As usual, the solution for one problem may cause a host of other problems, heh.

My builds/plans (not the latest models) are located here.
300ohm is offline  
post #15 of 17 (permalink) Old 2012-03-05, 05:45 PM
Veteran
 
Join Date: Nov 2008
Location: San Diego, CA
Posts: 2,514
OAM (Orbital Angular Momentum), aka "Radio Vorticity" aka "Twisted Radio Beams":

OAM is a fairly well-known capability for Lasers and has been observed in Space.
But Tamburini's 1Mar2010 article is the FIRST report of a public On-Air Test using
Radio signals (2.4 GHz Wi-Fi Band).

Generating a OAM signal can be accomplished with a circular array of antennas, each
fed with the same signal, but adjacent antennas have a phase difference = 2*Pi*l/n,
where n=number of antennas and l=integer (e.g. 1, 2, 3, 4, 5, etc), so that the
phase rotation around the entire circular array is 2*Pi*l.

The Venice Experiment injected OAM by using a Horizontally Polarized Parabolic
Antenna cut from the outer edge to the center and separated by 6.25-cm at the outer
rim, thereby generating the increasing phase difference for l=1. Yagi's would be l=0.
They only built one Parabolic to generate l=1. If they had used two additional
Parabolic Antennas with the Gap twice and three times as big, they could have
transmitted THREE orthogonal OAM signals on the same frequency, thereby
TRIPLING total capacity.

At the receiver, two identical, Horizontally Polarized Yagi Antennas were summed
together, except one of them went through an inversion, so the output was the
DIFFERENCE SIGNAL. When receiving from OAM Parabolic, the output of this
"Interferometer" was the OAM Signal. A parallel, Yagi Antenna link was
transmitting at the same time on the same frequency. Transmit power was
adjusted so that the received signal level matched the interferometer output,
thereby adjusting for the much higher Gain in the Parabolic than the Yagi and
overcoming whatever losses were in the Interferometer. I THINK that the
interferometer had to be reconfigured to switch between the Yagi signal (l=0)
and the Helicoidal Parabolic signal (l=1)....or maybe they used another Yagi
at the receiver????

They had to carefully move the receive interferometer around until they found the fairly
small "sweet spot" where the OAM signal could be detected.

I would like to see how much "leverage" the OAM signal has versus conventional,
since it appears to be a minor "tweak" to the primary signal, so I would expect the
sensitivity would be much less....and how much loss was there in the interferometer....

And I don't know what they had in mind when they claimed an additional 5X increase
in capacity using "multiplexing" techniques.....

Current OAM antennas are clearly limited to point-to-point links, vice broadcast.


==========================================================
I followed several references....below are a "must read".

Fabrizio Tamburini et.al. - Encoding Many Channels in Same Freq thru Radio Vorticity -
First Experimental Test - 1107.2348 - 17pgs 1Mar2012.pdf
http://arxiv.org/ftp/arxiv/papers/1107/1107.2348.pdf [Better Quality Graphics]

Bo Thide + Fibrizio Tamburini et.al. - Radio Beam Vorticity and Orbital Angular Momentum -
1101.6015 - 3pgs 31Jan2011.pdf
http://arxiv.org/pdf/1101.6015.pdf [A bit more info re Venice Experiment.]

H Then + B Thide et.al. - Detecting Orbital Angular Momentum in Radio Signals - 0805.2735 -
5pgs 18May2008.pdf [THEORY, Tripole & Multi-Element Arrays]
http://arxiv.org/pdf/0805.2735.pdf

B Thide et.al. - Utilization of Photon Orbital Angular Momentum in Low-Freq Radio Domain -
0705.1208 - 4pgs 1May2009.pdf
http://arxiv.org/pdf/0705.1208.pdf [Multi-Element Antenna Array]

Bo Thide - Nonlinear Physics of the Ionosphere and LOIS/LOFAR - 0707.4506 - 6pgs 31Jul2007.pdf
http://arxiv.org/pdf/0707.4506.pdf [Multi-Element Antenna Array]

These were conveniently found via Columbia Univ's Archive Search Engine:

arXiv.org Search for Downloads - Tamburini_F
http://arxiv.org/find/physics/1/au:+.../0/1/0/all/0/1

arXiv.org Search for Downloads - Thide_B
http://arxiv.org/find/astro-ph/1/au:.../0/1/0/all/0/1

Some additional references:

R. Compton, Jr - "The tripole antenna: An adaptive array with full polarization flexibility"
[IEEE is a subscription service....or visit a well equipped Univ. Library]
http://ieeexplore.ieee.org/Xplore/lo...hDecision=-203

H.T. Hayvaci et.al., Univ. of Chicago, Presentation: Tripole antennas for Wi-Fi:
http://signal.ese.wustl.edu/MURI/pub...07_Hayvaci.pdf
holl_ands is online now  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Canadian TV, Computing and Home Theatre Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome