Networking

Wi-Fi: Breakthroughs in optical networking may make it obsolete

Promises of high throughput could mean your future in-home network may be using light instead of radio signals.

Wi-Fi has less than adequate throughput bandwidth; yet, users overlook that. Why? Because being able to roam is more important. Still, business-savvy research and development types see opportunity and are working hard to provide both mobility and bandwidth.

Optical Wireless (OW) networking may be one such solution. That's because OW networks overcome the following weaknesses inherent to Radio Frequency (RF) networks as pointed out in an article written by Dr. Mohsen Kavehrad:

Transmission speed
  • RF: Power levels that do not hurt indoor occupants (think microwave) limits the maximum data-transfer rate to several hundred megabits per second.
  • OW: Data transfer speeds equivalent to wired links. Experiments have shown speeds in excess of one gigabit per second are possible.
Bandwidth Limitations
  • RF: Full duplex is not possible; radio signals sent at the same time and frequency will interfere with one another.
  • OW: Photons do not interfere with one another. Usable bandwidth is limited only by the efficiency of the receiver's photodiodes.
Security
  • RF: Radio waves pass through walls, opening up chances for eavesdroppers.
  • OW: Light waves cannot pass through walls, preventing interception of the signal.
Multipath fading
  • RF: Due to the physical environment, variations of the same RF burst may reach the receiver at different times. If sufficiently out of phase, the receiver will not process the signals correctly.
  • OW: Destructive interference is impossible with light waves. A point of clarification on this portion of the report. I should have used the complete statement, which includes the following: The sensors on the active area of a photodiode absorb the waves separately and then average out the incoming energy, so no canceling can result. This means out-of-phase/out-of-time signals arriving at the same moment will not adversely affect the fly-eye receiver. (I apologize for the confusion, 26 Apr 2010)

Sounds good to me, yet I remember trying to line up the IR sensors on two computers so they would sync. That wasn't any fun.

New approach using OW

OW networks are not new. Using Free Space Optics (FSO), a form of OW is quite common. In fact, awhile ago a Ham radio friend and I set up a point to point system using laser-tag equipment (don't tell my son). It worked and was interesting, but not as cool as what Penn State researchers Dr. Mohsen Kavehrad and Dr. Jarir Fadlullah have accomplished.

They designed and built an experimental optical system that has high bandwidth, and it's not location sensitive. Somehow they overcame the need to directly point communicating sensors at each other.

Network configuration

The researchers created an experimental test bed to prove that Non-Line-of-Sight (NLoS) OW links are possible. The experimental equipment consists of an optical transmitter and receiver. I will let the research team explain the two main components:

Spot-diffusing transmitter: Utilizes multiple narrow light beams pointed in different directions, as a replacement for the conventional diffuse transmitter, which utilizes a single broad light beam aimed at an extended reflecting surface.

While the diffuse transmitter provides considerable immunity against beam blockage near the receiver, it yields a high path loss. The spot-diffusing transmitter is expected to reduce path loss, because the narrow beams experience little path loss traveling from the transmitter to the reflective surfaces.

Fly-eye receiver: Consists of a single imaging optical concentrator (e.g., a lens) that forms an image of the received light on a collection of photo-detectors, thereby separating signals that arrive from different directions. Implementation of an angle-diversity receiver using imaging optics offers two advantages over a non-imaging implementation.
  • All photo-detectors share a common concentrator, reducing size and cost.
  • The photo-detectors can be laid out in a single planar array, facilitating the use of a large number of receiving elements or pixels.

Basically, there is a transmitter with multiple light beams that are bounced off of a reflective surface, such as the ceiling. The receiver has the ability to process multiple light beams into usable information. The following slide shows the actual test setup:

The next slide lists the basic components and an interpretation of how the system works:

Potential applications

I realize this technology is not quite ready for production, but the professors are already looking at the potential uses for OW networking. Here are some examples:

  • Large facilities could easily have complete high-speed coverage with just a few devices, allowing many more non-interfering data streams than an RF network.
  • Airplane manufacturers with their concern over RF interference could incorporate OW networking into passenger lighting.
  • White LED lighting is the future of home lighting. A Japanese research team suggests using the same white LEDs as light sources for OW networks and Ethernet over Powerline technology as the back haul.
Final thoughts

Some say OW networking will have too many problems. Maybe, but lots of people feel that way about Wi-Fi and look how popular it is. Besides, there is no reason why multiple methods of wireless networking couldn't be incorporated into devices.

It's a good thing to step outside the box. Otherwise, we may miss opportunities such as the research being done by Dr. Mohsen Kavehrad and Dr. Jarir Fadlullah. I also want to thank both of them for allowing me to use excerpts from their paper.

About

Information is my field...Writing is my passion...Coupling the two is my mission.

92 comments
rsimkins
rsimkins

Nice article Mike. I think that this will be a niche technology, and as such not built into most mainstream devices - things like phones may not choose to host the power requirements of yet another connectivity technology. .11n Wi-Fi can produce throughput for a number of HD streams per AP, somewhere around 20-30 if planned properly. So i'm struggling to see many scenarios where Gigabit bandwidth is needed to make this OW technology preferable to Wi-Fi? A lot of 'better' technologies are lost by the wayside due to their inability to coexist, so I'm interested to see how this one does, but I'm assuming we're 5 to 10 years away from finding out.. Overall, I think it may catch on somewhere down the line in modern buildings built to technological requirements - particularly if the WLAN and building management systems can share infrastructure/power components like lighting and PIR activation.

The 'G-Man.'
The 'G-Man.'

than their WI-FI speed if all they use it for is general web work.

cliff
cliff

As far as roaming is concerned, it seems to me that OW won't offer the same sense of freedom that RF offers. That being said, RF has a lot of problems and I'm looking forward to seeing what can be done on the optical front.

Ron K.
Ron K.

I want to see broadband down this road. All there is is talk.

d_g_l_s
d_g_l_s

Where is the information about how the "signal" goes from room to room and through the house/building. I ask this because it was pointed out that the signal does not pass through walls. So this is very good for security compared to RF signals, but what does this do for the signal going around the house/building? Would it require expensive and/or multiple retransmitters? Just have to ask since I may have missed it somewhere in the article and responses. I'm going to answer my own question a bit as an exploration. There has to be a way as we will always find it! Some ways might include sending signals through fiber optics like through existing lighting routes. Another option might be to simply connect to all rooms through fiber optics in the walls with simple "diffusers" wherever needed/wanted.

waynesreed
waynesreed

"Wi-Fi has less than adequate throughput bandwidth; yet, users overlook that." With my cheap WiFi device at home I connect at 54mbps. This is significantly faster than the 5mbps (ish) I get from my ISP. It seems to me that connection to backbone is usually the bigger limitation and that WiFi offers plenty of bandwidth for anything I am likely to do on it. My home isn't the place where the problem currently exists.

joel
joel

Public Wireless at gigabit speeds sounds good to me. I say do it.

clay_bradshaw
clay_bradshaw

I think there more uses to this than mentioned. Secure areas can now use wireless networks with reduced concern for interception. Aircraft usage would allow systems to monitor structural stress (additional circuits to receivers as well as reducing the weight of the aircraft. The same could be used in builds to like skyscrapers and builds in hurricanes, earth quakes, etc..

Deadly Ernest
Deadly Ernest

in the larger corporate offices - especially government or hi-security ones. At present a lot of organisations have troubles making sure they have enough Ethernet cables available in open plan offices where they wish to maintain security. Where security is not so important, they now use wi-fi to save on the costs of putting in and shifting cables as they rearrange the office. I can see this working very well, if done right. Picture producing a working system of this, along with a plastic coating for windows. You coat the windows so the signal is interfered with and not usable once it goes through the coating. The individual computers and other devices are set up to bounce off the ceiling, and a number of the receivers are set up at suitable points to receive the signals and retransmit them down a fibre optic cable to other parts of the buildings - if required to leave the current office. Thus, all you need is a few good backbones to each floor, these receivers attached to the end of the cable, and they handle everything within that work area. All comms is kept within the area by the walls and the window coatings. You have the best of wi-fi convenience and security of cable.

Slayer_
Slayer_

If your within range of the beam, your probably within range of a cable... My internet modem, and thus my wireless router, is in my basement where the cable enters the house. With this system, I would need to be somewhere near by for this to work. I couldn't use my wireless upstairs. So I fail to see the point of this technology.

HAL 9000
HAL 9000

A couple of moves ago I could see the end of the Optical Fiber from my front door about 20 feet too far away. :( Col

Michael Kassner
Michael Kassner

I mentioned is Power over Ethernet. It could be used to get the digital traffic to the OW devices, since the lights need to be plugged into a power outlet.

zed.wagner
zed.wagner

Its for the simple reason that more than 90% of network traffic is conducted over Wired connections. 10 gigabit ethernet is becoming the new defacto standard. Faster 10 gigabit Ethernet standards have become available as the IEEE ratified a fiber-based standard in 2002, and a twisted pair standard in 2006. As of 2009[update] 10Gb Ethernet is replacing 1Gb as the backbone network and has just begun to migrate down to high-end server systems. 10 GBE devices are already old hat, as newer 40 GBE and 100 GBE standards are finalized this year. Frankly powerline based networking in the home makes greater sense. Seeing as desktops and laptops need an outlet for juice, and since your tethered to the outlet anyway... Also Powerline NICs & Routers have made enormous jumps in both speed and reliablity since thier first generation.

J.J. Antonetti
J.J. Antonetti

I can see this as an avenue for better backhauls than from the ethernet over power that was mentioned in the article. I'm thinking this is great news! Hopefully it won't be as long in coming as WiMax has seemed to take!

Michael Kassner
Michael Kassner

What flavor of 802.11 are your using? 54 Mb/sec is best-situation bandwidth, not actual throughput for 802.11g. I agree with your contention that Internet access is more likely the bottleneck if you are the only user on that wireless network. If others are connected, the throughput bandwidth gets divided amongst the users. It also is dependent on the system's ability to prioritize time-sensitive traffic.

Michael Kassner
Michael Kassner

Forgive me, I get excited when I learn about cutting-edge research.

kevlar700
kevlar700

Most wifi runs at the resonance of water (1600 mhz microwaves) making it likely to be far more cancerous than mobile phone radiation, scientists have expressed concerns for wifi in schools. Whether it's enough to cause or contribute to cancer before you die naturally is the question. I'd rather put my head in a room with a light bulb than an open microwave without a safety cut off switch. It would also help protect from paedos listening in from outside.

Michael Kassner
Michael Kassner

I have read research, where they feel this will be a big deal in sensor technology.

rodmanbrowning
rodmanbrowning

You stated: "Thus, all you need is a few good 'BACKBONES' to each floor". Are these BACKBONES or BACKHAULS? I know this is probable nit-picking, but I'm trying to understand the concept in the scheme of things.

Michael Kassner
Michael Kassner

I see the simplest backbone as the power lines. Especially when you could use LED lighting as part of the transceiver.

The 'G-Man.'
The 'G-Man.'

Where RF is banned, say Planes or Hospitals

Michael Kassner
Michael Kassner

Every light in your house was a gigabit broadband transceiver? Would you think differently?

d_g_l_s
d_g_l_s

Hi Michael, Always appreciate the topics and relevancy. I've had experience with the current Ethernet over power and it really is not very good or reliable. But when we get it together why don't we just piggy-back the signal right on through the power cables into the PC and save ourselves another cable? :)

Michael Kassner
Michael Kassner

Why do you say that? I am interested in hearing your take on the situation. It seems like you may have some issues with Ethernet over Powerline. If so, I would love to learn about them.

rodmanbrowning
rodmanbrowning

Do you believe artificially generated light frequencies populated with data streams is any less detrimental than artificially generated radio frequencies. After all, a laser light will harm you as quick if not quicker than an open microwave

Michael Kassner
Michael Kassner

I have been involved with RF and mega-doses (1000 watts) since my 16th birthday. I am only now wondering about what that means. Your assumption has intrigued me to get up and do some research. Yet, your comment about 1600MHz confuses me. Wi-Fi does not run in that frequency range. I will say this; in my work, kitchen microwaves have scared me a great deal more than any communications device.

santeewelding
santeewelding

All males a transmitting node for dimensional changes broadcast over the network.

Deadly Ernest
Deadly Ernest

routers and switches on each floor, to the main router and the server room.

Deadly Ernest
Deadly Ernest

where you can cut it from the Internet - thus I see Ethernet still being in use for the corporate situation. I see the power line option as being more of a home usage version - or an Internet cafe type use.

brian
brian

but that is a very good application for it. I can also imagine hidden signals in advertising. Aim your cell phone at a billboard and run an app, and it calls the advertiser, sends you to their web page, plays a video, maybe downloads a digital business card. If the tech becomes ubiquitous throughout the target audience it could free advertisers to make more artistic billboards with less informational clutter from text and branding.

boomchuck1
boomchuck1

Interesting. Our local hospitals all have public wireless available to your room.

Michael Kassner
Michael Kassner

I quoted the professor as mentioning that in his report. He was especially interested in the airplane scenario.

edguyer@hotmail.com
edguyer@hotmail.com

There was an article in Scientific American several years ago about this very subject. They gave the scenario about each lamp in a house being a transmitter. Powerline Ethernet is already in use and combined with this technology it would allow for greater coverage. I have put in some campus wide wireless and could see where this would have been an advantage. Of course we will find out after it has been widely implemented that it somehow causes epileptic seizures.

.Martin.
.Martin.

if it was to work through the home/ office lighting system. If not, it will be a bust. who will be able to justify a repeater in every room?

Michael Kassner
Michael Kassner

give Ethernet over Powerlines another chance. Like most technology it has grown up. Second, OW introduces mobility plus bandwidth. Almost the best of both worlds.

J.J. Antonetti
J.J. Antonetti

Ethernet over power is good technology, but I believe that this would allow for faster transmission rates. A mesh network with this type of backhaul would be ideal. I can't see the validity (unless I missed something) of it in the workplace or at home due to nlos limitations. Yes laser has been used in the past but the need for precision alignments made it very hard to get good signals. I'm thinking this might be a better solution.

Michael Kassner
Michael Kassner

Laser and microwave RF are really different in how they affect humans. In order to debate that, you would need to define the conditions.

kevlar700
kevlar700

Sorry got my devices mixed up, most wifi especially older hardware runs at around 2500 mhz which is within the microwave band, the middle of which is 2400 mhz. And I would rather be burnt by a laser (not in my eye) which isn't going to happen than receive radiation resonating my cells. Whiskey causes throat cancer because it irritates cells increasing the chances of mutation. If engineers can cause a bridge to collapse through underestimating resonance, I think they can underestimate or ignore microwaves causes of cancer?

santeewelding
santeewelding

The various emanations fuse synaptic connections where, before, there were none. This enables you to "see" what others do not. This is evident in your case.

Michael Kassner
Michael Kassner

I think we were just unclear as to definitions. I should have provided a better description.

Michael Kassner
Michael Kassner

I know that Ethernet over Powerline digital traffic will not get past a transformer. I don't know if BPL is the same or not. I wonder if that is why some SmartGrid networks use WiMAX as well.

Deadly Ernest
Deadly Ernest

will ensure some countries and regions won't be able to use it for many decades, if at all. Also, have you seen if it works at a reasonable rate if the signal has to go through a sub-generator; nothing I've read says that the signal will continue down the line past the sub-generator, but I'm not current on the Internet over power lines tech.

Michael Kassner
Michael Kassner

I have the sneaking feeling it is going to be very pervasive.

Michael Kassner
Michael Kassner

But, with the Smart Grid coming everything may be shoved down the power line; phone, Internet, and so on.

Michael Kassner
Michael Kassner

And called geo-locational advertising. I think billboards may go away, the adverts will pop up on your phone.

Michael Kassner
Michael Kassner

I should start a series about down the road technology. OW is a few years away and we need to view it that way. Who knows what may happen with RF technology.

brian
brian

as a precautionary measure against some crack-headed lawyer "suing-to-settle" for the theoretical tissue damage or increased risk of cancer associated with exposure to microwave. Whether that's reasonable or would even eliminate the presence of microwave RF in the hospital is highly questionable, but the horrible legal climate in medicine could easily lead to precautions like that.

Michael Kassner
Michael Kassner

Completely separate from the hospital's network? I suspect so.

HAL 9000
HAL 9000

Works for me. :^0 But I wanted to use EOM in the Subject line. :_| Col 0:-)

kama410
kama410

Seriously, the security implications of this idea are a bit nightmarish. You really want your private information passed along the power circuits in your house... and out to the power company? I suppose a filter on your power line would prevent that. I really don't know anything about the 'mechanical' aspects of that. I am glad you know what NT means. I don't assume that everyone does. Courtesy in communications. And: You can't please everyone all the time. Had I not put that in the body, someone else would be annoyed because they didn't know what NT meant and there wasn't a real message there, right? The real determinant factor as to putting a short explanation of what NT means in the body of the message is the fact that, while most of the people on these forums could reasonably be expected to know what NT means, something is required in the body portion and it requires only seven more keystrokes to provide a sufficient explanation for anyone who does not know what NT means. Presumably, anyone who already knows what NT means will simply ignore the explanation and, in fact, except under special circumstances (such as your own) will not even see the explanation in the body portion of the message. Maybe I could use the black windows to heat water to generate electricity to power LED lighting to light my home since there isn't any light coming in the windows...

HAL 9000
HAL 9000

That way you'll be able to use your Windows for other things that may be useful. :D OH and I know what NT means but I still had to open your message so I could reply to it. :^0

Michael Kassner
Michael Kassner

I will have to ask if that was taken into consideration.

Michael Kassner
Michael Kassner

It would depend on the type of transceiver built into the computer as well. It is my understanding that they could be quite small.

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