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## Two-way Radio Breakthrough To Double Wi-Fi Speeds244

An anonymous reader writes "Scientists at Stanford University have built a radio that can transmit and receive at the same time on the same frequency. The breakthrough could lead to a twofold increase in performance for home wireless networks and end that annoying habit of pilots finishing every sentence with 'over.'" But you can still do it if you like. I'm not judging.
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## Two-way Radio Breakthrough To Double Wi-Fi Speeds

• #### he! (Score:5, Funny)

on Tuesday February 15, 2011 @01:07PM (#35212406) Homepage

First post, Over.

• #### Re: (Score:3, Funny)

by Anonymous Coward

Roger that. Over.

• #### Re: (Score:2, Funny)

We have clearance, Clarence.

Roger, Roger. What's our vector, Victor?

----------------------

Looks like I picked the wrong week to quit sniffing glue!

• #### Innovative (Score:5, Informative)

on Tuesday February 15, 2011 @01:07PM (#35212418) Homepage

Doing this On the same frequency is remarkable. but the gains they are claiming can be had right now by using TWO frequencies. Transmit on channel 1 receive on channel 12.. the other end does the opposite. the thing is, 90% of Ethernet traffic is not bi directional. it's packetized so their claims of DOUBLE will not be realized. when you set up a network connection from half duplex to full duplex you do not see a double in speed, just a double in capacity.

• #### Re: (Score:3, Interesting)

Doing this On the same frequency is remarkable. but the gains they are claiming can be had right now by using TWO frequencies. Transmit on channel 1 receive on channel 12.. t

This might be problem if you want mesh network with many (n>2) nodes. They (mostly) want to hear each other.

Anyhow, with 100 dB (10 000 000 000) times stronger transmit signal I somehow doubt if geometry of antennas can be accurate
enough to keep it working with changing temperature, humidity etc. over MHz of bandwith.
Maybe with heavy DSP processing and continuos monitoring?
Compensating for scattering of own signal, and all reflections from surounding objects?

On top of it, we normally use MIMO: so you hav

• #### Re: (Score:2)

While I find this interesting, there's still some lack of information.
For example, they claim they will do it by using two transmitters. This of course requires more hardware only to generate destructive interference at the receiver and improve the SNR. However, these two transmitters will generate most likely deep nulls at certain distances from them. The question is, does this really solve the problem, or anyone moving at certain speed is under the risk of hitting all the nulls and not listening to anyth
• #### Re: (Score:3, Informative)

Hey, it's just a news article. Here's the more technical stuff: http://sing.stanford.edu/fullduplex/ [stanford.edu] Short answer is the fact that the two transmit antennas are at different distances means they need a power difference in order to match amplitude at the receive antenna. This in turn limits the depths of nulls at distance.
• #### Re: (Score:2)

So if I send twice as much in the same amount of time it seems to me that that equals a doubling of speed or use of less resources in the case of sending and receiving on one frequency instead of tying up two frequencies. In the case of fiber optics where different colors are used to pump data that would enable twice the delivery totals for one cable in the same amount of time. Sounds good to me.

• #### Re: (Score:2)

Uh, this technology lets you SEND and RECEIVE on the same frequency at the same time. So, if the bandwidth of the link is 1Mbps, you can now send and receive 1Mbps at the same time. You can't send 2Mbps over the link, or receive as much.

So, other than your ACK packets getting out faster, this isn't going to speed up downloads much.

As far as fiber optic and different colors on the same cable goes - color is just another way of saying frequency. Using two colors at the same time is just another way of sayi

• #### Re: (Score:2)

when you set up a network connection from half duplex to full duplex you do not see a double in speed, just a double in capacity.

So a car analogy would be if you took a one way road and doubled the lane count with opposite flowing lanes, the cars don't move twice as fast, but twice as many.

Did you really need to be explained to anyone?

How about if we stacked bidirectional lanes on top of each other so one lane represented both directions, and double capacity in the same square footage? Oooohh, I see what I did, deeeeeeeensittttyyyyy.

Doing this On the same frequency is remarkable. but the gains they are claiming can be had right now by using TWO frequencies.

Then they could move twice as much again with TWO full duplex frequencies!!11

• #### Re: (Score:2)

Some wireless equipment is used in this same way; bridges, mesh, etc.

The other issue is latency. That's not at all important, is it.

• #### Re: (Score:2)

It's true that FDMA can potentially also roughly double the capacity, as well as something more sophisticated like CDMA, but I wonder about its inherent tradeoffs compared to this "full-duplex" system. For practical FDMA systems, the frequency spacing between channels must either be close (implying a lossy duplexing RF circuit) or the spacing must be large relative to the channel bandwidth (so that efficient resonant antennas may be designed). In the first case, there is more loss due to the RF circuitry, w

• #### Re: (Score:2)

"Doing this On the same frequency is remarkable."

Not really, Quadrature Amplitude Modulation has been around for a long time, its usually done with both signals going in the same direction, doing it with signals going in opposite directions is an improvement, but its not that great a leap.

I wonder why nobody thought of it before, now with al lthe patents they get it might become mainstream in 20 years.

http://en.wikipedia.org/wiki/QAM [wikipedia.org]

• #### Re: (Score:2)

QAM is merely a modulation technique; it doesn't specify anything about how the RF is transmitted and received. Dual signals on the same frequency are often transmitted from the same antenna with point-to-point microwave today, with each signal on a different polarity (vertical and horizontal). QAM is often used as the modulation technique, but that has nothing to do with the cross polarization technique. The two signals on the receive end are often "improved" by taking a sample of the signal of the oppo
• #### Re: (Score:2)

Doing this On the same frequency is remarkable. but the gains they are claiming can be had right now by using TWO frequencies. Transmit on channel 1 receive on channel 12.. the other end does the opposite.

That only works when the conversation contains exactly 2 nodes. Node A transmits at freq 1 and receives at freq 2, whereas node B transmits at freq 2 and receives at freq 1. That CANNOT extended to a third node... hence, aviation conversations all use one frequency and everyone must take turns.

With this new breakthrough, everyone can be on the same frequency AND can be talking and listening at the same time.

None of this applies to ethernet because ethernet hubs/switches are built so as to separate every

• #### Re: (Score:2)

How about copying a file from one computer to another? Or sending a big file in email while downloading another big file? Or webcam chat?
• #### "Over"? (Score:2)

I haven't flown anything in 10 years, and "Over" was considered quaint even then...
• #### Re: (Score:2)

I haven't flown anything in 10 years, and "Over" was considered quaint even then...

I was under the impression that "Over" helped in that it let the other person know when your transmission was...y'know complete, not just so the other guy knew when to start talking.

• #### Re: (Score:2)

The click when you release the mic switch, and the fact that you've shut up, seem to work well enough. :)

It might well be different out in Shanwick country on HF (sadly, I've never had the chance to get out there as pilot), but certainly on VHF I've never heard it from anyone but a couple of old-timers.

• #### Re: (Score:2)

How do you differentiate between the click as the mic switch is released and the pilot shuts up because he's finished his message, and the click because he's had a heart attack and died, or the click because the transmission ended because he hit the ground?

• #### Re: (Score:2)

Who cares? At least he's not boring you with how great he is any more :D
• #### Re:"Over"? (Score:5, Informative)

on Tuesday February 15, 2011 @02:17PM (#35213482) Journal

Because in any case, the pilot has finished his/her message when you hear the mic click. Surely you don't think the conversation is going to continue?

More importantly, the pilot and controller speak to each other in very precisely defined and very concise language. It's pretty obvious when one of them is done yakking, the mic click is a convenience, like the "over" used to be before all radios had mic clicks.

A typical initial approach might go something like this:

"Bangor approach, Cessna five-two-five-Lima-Charlie, 12 miles west, descending 5000 with information Sierra, full stop."

This tells the controller that:

1. You are intending to make an announcement to the controller at Bangor Center in charge of approaches (in case you fucked up your frequency, they can correct you quickly and get you on the right frequency).
2. You are a Cessna, US-registered, with tail number N525LC.
3. You are 12 miles to the west of the airport, at 5000 feet, and descending.
4. You have listened to their weather/conditions report recently, which is their update "S" (Sierra), and the letter is updated whenever the information is updated (usually once an hour). That means you already know the wind speed, altimeter settings, and preferred runway, and have adjusted all of your instrumentation and expectations appropriately.
5. You are requesting approach vectors for the currently-active runway (which you already know) and you intend to land there (full stop, as opposed to a touch-and-go or a practice approach but not a landing).

The controller will respond with something like this:

"Cessna Five-Lima-Charlie, Information Sierra current, enter 45 left downwind for runway one-eight-zero, report midfield"

This means:

1. The controller has acknowledged your presence, confirmed that you have the latest weather, and picked an abbreviation for your tail number that does not conflict with any other aircraft currently operating in his airspace. That will be your designation for the duration of your talk with this controller.
2. The controller wants you to enter the pattern at a 45-degree angle on the upwind side of the runway and call you again when you are properly established in a left downwind and abeam the middle of the runway.
3. There is no known traffic on that side of the field that will conflict with your entry, because the controller didn't mention any.

The conversation will proceed, with both the pilot and controller keeping radio use to the absolute minimum necessary to communicate what they need to say. If the frequency is really quiet, they might exchange a few jokes or snide remarks, but "over" is usually in the domain of CB radio, old timers who used to deal with really crappy radios, and bad movies.

Interruptions to what a pilot or controller is saying are obvious because of the way the language is constructed. This is done on purpose. If you say "Bangor approach, Cessna three-five..." then stop talking, you're going to hear a controller say something like "Unknown Cessna starting in three-five, please repeat, message not received." in just a very small handful of seconds.

• #### Re: (Score:2)

>pilot and controller speak to each other in very precisely defined and very concise language

Nice example, thanks!

Saying "over" is necessary when operating SSB on HF, you don't hear the mic clicks and sometimes not sure if person on other end has finished talking. Coast Guard uses "over" when operating on VHF marine channels which I assume for boat drivers steering outside or with a noisy engine or wind.

• #### Re: (Score:2)

HAM radio (in the "real" sense, where the H shands for HF) uses Over quite heavily, as the signal you're picking up is often coming from thousands of miles away and isn't really any higher than the ambient noise level. Even if there is a mic click, it's entirely possible that the other side can't hear it clearly. The communication is also usually much more conversational, and may include pauses while one party keeps the mic keyed briefly (or releases it but expect to pick it up again imminently).

• #### Re: (Score:2)

The click when you release the mic switch, and the fact that you've shut up, seem to work well enough.

ATC in the Southern Calfornia region appears to rely on patterns more than a click or silence, as they start talking the instant I've finished calling my tail number and a split second before I've released the mic switch. Then again, it does get pretty busy here: I've had to make six calls to SoCal Departure before I was acknowledged, and when I was, I was told to switch to another frequency because I'd al

• #### Re: (Score:2, Informative)

and the fact that you've shut up, seem to work well enough. :)

No it doesn't, I hope you don't fly anymore you're making a careless mistake about something that should have been taught to you before you took the ground exam.

The purpose of an End of Transmission marker is so that everyone listening has confirmation that they received ALL of your transmission as intended. So if for some reason my transmission is cut off and it seems like just silence you as a listener know it was cut off because you didn't h

• #### Re:"Over"? (Score:5, Insightful)

on Tuesday February 15, 2011 @02:36PM (#35213662)

It seems that in your rush to prove your superiority and brand me an idiot you missed the smiley, despite quoting it, possibly because it came after the End of Sentence marker and you'd stopped reading :P (There, did you get that one?) For the record, I haven't logged any flight time since summer 2000, so I'll grant you that my R/T is a little rusty, but I did know and use proper phraseology. I had to, or I'd get ritually humiliated by my colleagues in Air Traffic... Working at a commercial flight training centre, especially in one with "AREA OF INTENSE AERONAUTICAL ACTIVITY" plastered across it on the half-mill chart, you simply don't get away with sloppy R/T.

I love people who throw phrases like "idiots like you" around. Have to say I didn't especially enjoy sharing a cockpit with them, though, no matter how superior they thought they were. They tended to be precisely the sort of egotistical pillock that everyone but them knew was going to up in a smoking hole somewhere, and two I know of from flying elsewhere did just that. (Well, one in a smoking hole and one in a long line of aircraft parts across a mountain, since we're being pedantic.) A third disappeared behind the trees before recovering from his ill-advised attempt at aerobatics, I don't know how he survived.

I've flown as passenger and pilot with all sorts, from the late Mr. Cool to the chap who disabled the Bismarck (I saw the logbook entry) and a very quiet unassuming gentleman who turned out to have more types in his logbook than most of the instructors had hours. And I'll tell you this much: I'd far rather fly with the under-confident guy who's a bit mixed up on the R/T than the one who knows it all and thinks everyone else is an idiot. As my instructor said: The under-confident can learn, but the over-confident will. One way or another.

• #### Re: (Score:2)

Nope. You end the transmission with your tail number. It does double the work. Show's that your done and conveys information to the person receiving the transmission.

• #### Re: (Score:2)

I haven't flown anything in 10 years, and "Over" was considered quaint even then...

Even longer than that. I was a stuent pilot in 1981, and even then the convention was long obsolete.

• #### Re: (Score:2)

It's still used in military comms. Over is when you're done with your part of the conversation, and Out is when you're completely done. In the movies, that gets mangled to Over and Out.
• #### Re: (Score:2)

I still fly, and almost never hear this.

• #### Re: (Score:3)

Correct. I last flew about two years ago. We don't say "over". Ever. You sound like a trucker on a CB and you're only going to piss off the tower and the other pilots on the freq because you're wasting airtime, and sound like you don't know what you're doing. ATC comms can get super busy, and lives are (literally) at stake. If you listen to even a Class C approach frequency, it will sound like a nearly uninterrupted stream during busy times of the day. There isn't time for extraneous nonsense when Cess

• #### Re: (Score:2)

This directly contradicts with what I was taught and how the Class C I frequent operates. In the example below the Pilot should end with four seven whiskey. If not how does the tower know the correct plane is responding?

T: Four seven whiskey, turn right on alpha three and contact ground point eight
P: Right on alpha three, ground point eight. good day

• #### Re: (Score:2)

Technically, you're correct. I primarily dealt with class D airports with only one runway so it wasn't as big of a deal. I wouldn't call it a direct contradiction, but you're right - pilots should identify their aircraft in every transmission.

We say over or have a tone to signify when we are done speaking. There may be more than one person listening and its a cue for the next person not only that you are done talking, but your message came through. If you are listening and don't hear "over" or "beep" you say "come again" or "missed that last bit" or whatever jargon that the bands you are using requires. I'm not a pilot so all I know is terms i've used on CB over the years.
• #### Wow (Score:2)

Nice job. Though the problem off cross-talking has been solved for a long time using TDMA or CDMA.

• #### Re: (Score:2)

From the fine article, "Current phone networks allow users to talk and listen simultaneously but, the scientists said, they use a work-around that is expensive and requires careful planning."

• #### Re: (Score:2)

Current cell phone networks allow it too - but then frickin' idiot users go and buy push-to-talk cell phones.
• #### Re: (Score:2)

Well you don't even need to get that fancy. I though that this is what a Circulator [wikipedia.org] was for.
• #### Re: (Score:2)

Afaict on mobile phone networks TDMA and/or CDMA are used to seperate different users while FDMA is used to seperate uplink from downlink.

• #### Yaaawn (Score:2)

It's called a duplexer [wikipedia.org].

• #### Re: (Score:2)

A typical duplexer uses two frequencies in the same band that are usually close to each other. This is definitely an advance on that idea.

• #### Re: (Score:2)

I wonder if this work with radars. There is a minimum range with radars since the receiver is shut off while transmitting. If one has a 4 micro second transmit time than one has about 2,000 feet minimum range. It takes less than 4 micro seconds for the energy to travel to the target and return to the receiver when the target is less than 2,000 feet away from the transmitter.
• #### Re: (Score:2)

A duplexer allows the use of a single antenna for TX and RX, but the TX and RX must still happen on different frequencies, or in different time slots. This article would double the frequency spectrum capacity by allowing a two different two way conversations to exist in the spectrum used by a single duplex conversation today.
• #### Roger, Over (Score:5, Funny)

on Tuesday February 15, 2011 @01:17PM (#35212558) Homepage Journal
Roger Murdock: Flight 2-0-9'er, you are cleared for take-off.
Captain Oveur: Roger!
Roger Murdock: Huh?
Tower voice: L.A. departure frequency, 123 point 9'er.
Captain Oveur: Roger!
Roger Murdock: Huh?
Victor Basta: Request vector, over.
Captain Oveur: What?
Tower voice: Flight 2-0-9'er cleared for vector 324.
Roger Murdock: We have clearance, Clarence.
Captain Oveur: Roger, Roger. What's our vector, Victor?
Tower voice: Tower's radio clearance, over!
Captain Oveur: That's Clarence Oveur. Over.
Tower voice: Over.
Captain Oveur: Roger.
Roger Murdock: Huh?
Tower voice: Roger, over!
Roger Murdock: What?
Captain Oveur: Huh?
Victor Basta: Who?
• #### Actual information (Score:5, Informative)

<zurktech&gmail,com> on Tuesday February 15, 2011 @01:25PM (#35212698) Journal

How this actually works :
The Challenge in Achieving Full-Duplex

The problem that has historically prevented full-duplex is that, when a node transmits, its own signal is millions of times stronger than other signals it might hear: the node is trying to hear a whisper while shouting. The challenge is canceling the node's own transmitted signal (shout) from what it receives (whisper). Existing approaches, such as digital cancellation and noise cancellation circtuis, can cancel some of the transmitted signal, reducing its strength, but not enough to make a node able to receive.

Antenna Cancellation

Our design uses two transmit antennas one receive antenna per node. The transmit antennas send the same data and the receive antenna is placed such that there is destructive interference from the two transmit antennas, thus reducing self-interference. Offsetting the two transmit signals by half of the wavelength causes them to cancel each other, creating a null position where the transmitted signal is much, much weaker.

Combining antenna cancellation with cancellation through a noise cancellation circuit gives ~50dB reduction in self-interference before the RF signal is demodulated and sampled to the digital domain. Digital cancellation removes the residual interference.

http://sing.stanford.edu/fullduplex/ [stanford.edu]
The actual paper (PDF) :
http://sing.stanford.edu/pubs/mobicom10-duplex.pdf [stanford.edu]

• #### Re: (Score:3)

Have they tested this in non-laboratory conditions? The idea of transmitters being placed such that they perfectly cancel each other out sounds great, but what happens when you add in nearby objects that reflect RF?

• #### Re: (Score:2)

And have you seen that their first active component in the receive path is an intersil qhx220 that is a noise cancelling LNA. The IIP3 of this LNA is about -21dBm at 2.4GHz, so the P1dB will be about 10dB under that, and OFDM signals typically needing 5dB backoff from the P1Bb to get in the PER specs of 802.11x. So lets assume they are transmitting 15dBm from their transmit antennas (typical for a portable WiFi device) to avoid your LNA going non-linear you want to the cancellation of the transmit signals a

• #### Re: (Score:2)

It also limits the frequency range you can use, although depending on how good the digital concelation is this might still work for a relatively tight band. Oh, and there will be interference patterns beyond just the third antenna. If the receiver is in the wrong place, it will get the same massive cancelation.

• #### Re: (Score:2)

Thank you for the links. I was hoping someone would post them.

The PDF is pretty good. The idea is brilliant in its simplicity and damn, it works. Good for these folks, this is remarkable work.

• #### Re: (Score:2)

Wouldn't the range be reduced if "the transmitted signal is much, much weaker"?
• #### rock in water... (Score:2)

The transmitted signal is much, much weaker in the area of destructive interfierance.

Think of a pool of still water. If you throw a rock into it, you see waves propagate out from the impact.

If you throw two rocks in (or to be more accurate, 180 degrees out of phase, so one rock in and one rock out) at the exact same time, each rock will create the same waves as the single rock, but in one very tiny area directly between the two rocks the waves will cancel eachother out and the water will remain perfectly st

• #### Re: (Score:2)

Except that from my days working with ADCs and coherent demodulation I know that 1deg of phase error between the two transmit signals will reduce the isolation between the two transmitted signal to 40dB. That 1deg of phase difference is 0.3mm at 2.4GHz

The authors say they need 50dB of isolation, whereas as my guess they need more like 60dB for a reasonable transmit power. There is a need to precisely place three antennas probably about 10cm apart with a positioning error of a very very small fraction of a m

• #### Re: (Score:2)

I guess it would help with spectrum conservation or something, but I just don't see how that would help in practice - after all, this method requires three antennas! With that, you could be broadcasting and receiving (though not at the same time) on three different channels all at once [wikipedia.org]!

Actually, now that I think about it, this could work well from a security perspective. Imagine you've got two stations, A and B, transmitting data at the same time using this method. Now someone stucks an antenna somewhere in

• #### Re: (Score:2)

Offsetting the two transmit signals by half of the wavelength...

Wait, does is this over-the-air "same frequency", which would imply that they are merely trading off bandwidth to achieve full-duplex?

Two transmitters (transceivers) on the "same" frequency normally implies two transmitters / transceivers using the same frequency and the same bandwidth (and modulation), otherwise you are merely doubling the signal bandwidth used as this seems to suggest.

I can imagine that it could mean that is merely an offset (or delay) used for filtering, not over the air, but this is not

• #### Re: (Score:2)

Considering the two transmitter one reciever idea, doesn't multipath eliminate the gains, or at least make the cancellation not reliably predictable, significantly reducing the cancellation in a non-ideal environment?
• #### *KSSCHK* (Score:5, Funny)

on Tuesday February 15, 2011 @01:27PM (#35212732)

I end all my sentences with *ksschk* so it sounds like I'm in space.

• #### FYI - Pilots don't use "over." (Score:2)

Pilots don't use over. Pilots end a transmission with their tail number.

• #### There is another way (Score:3)

on Tuesday February 15, 2011 @01:42PM (#35212966) Homepage

It's called time domain multiplexing. If you chop the transmitter on and off at a rate much faster than the data rate you can hear bits in between your chopped up transmissions. Sorta like fast break-in amateur CW where you can hear between the dots and dashes. This would require synching the two stations chop rate. Since the 'chopping' is done above the nyquist sample rate, no data is lost, and you get true full duplex speed.

• #### Limitations (Score:5, Informative)

on Tuesday February 15, 2011 @01:46PM (#35213010)

The signals will only perfectly cancel when they are separated by a distance that is exactly one half the wavelength. Assuming you separate the two transmit antennas by this distance at the carrier frequency, then there will be a limitation on the available bandwidth. This is because the further you get away from center frequency, and away from the ideal antenna spacing, the less destructive interference you will have (and the more your transmit signal will leak into your receive signal). So you will double your capacity for only narrowband channels.

The pdf gives actual numbers. I just wanted to point out that there is a limitation on bandwidth.

You might also think, "If I know what I'm transmitting, why can't I just subtract it from what I receive?" This has to do with the dynamic range of the receiver, which is a function of the number of bits in your analog to digital converter. You must attenuate your received signal so that you don't saturate your converter. Have you ever turned the volume up so loud that you begin to hear distortion? It's the same thing.

So you are receiving this loud unwanted transmit signal, and this soft receive signal. You must lower the volume so that you are not distorting the highest signal. This lowers the volume on the desired signal as well. You can lower it so much that your analog to digital converter is not able to differentiate between a 1 and a 0 anymore.

I think if you could have an A2D with enough bits that you didn't care if you received the transmitted signal, then you could just carefully subtract out the unwanted transmit signal. Maybe I should patent that? Meh. I'm probably wrong.

• #### Re: (Score:2)

You're correct in identifying dynamic range as one of the major issues here. An A2D with an extremely high number of bits would help, as you could recognize both the faint and large signals simultaneously, and with prior knowledge of the large transmitted signal it could be removed from the data.

But there is another issue, which is the dynamic range of the RF hardware itself. Their experiments were conducted at 0dBm (1mW) transmit power, but that is not at all realistic if you want to get decent range, a

• #### when will we see this technology? (Score:2)

The researchers have not detailed when the technology might appear in hardware, but said they had applied for a patent and ...

So....never?

• #### General Honoré (Score:2)

I do wish someone would explain to Ret. General Honoré that when doing television interviews, ending sentences with "over" is not really necessary.
• #### Circular polarization (Score:2)

Theoretically there are still other ways to double data flow while keeping the same frequency. Using circular polarization one sender can emit clockwise rotating waves, the other sender the opposite. Linear polarization can be destroyed by wave reflections on obstacles, but afaik circular polarization is rather immune.

• #### Re: (Score:2)

My grandfather was an anternna engineer contracting work for various US agencies (Air Force, Navy, NASA, and some others) for decades. They're well aware of using circular polarization for stuff like this. However, it's not practical to do on the kind of scale discussed here, where you're looking for something that can be put in a cell phone without significantly enlarging the case.

• #### Not to be a nit pick (Score:2)

Seriously, pilots almost never say over. I'm not exactly sure when this stopped, but I never used over at the end of my transmissions.

Usually pilots start every request with who they're calling and their callsign, either full or short (on the West coast of the US you can usually get away with just your make and last three characters after your initial transmission to a controller. If they are getting instructions or information from a controller they usually end their acknowledgement with their callsign. Ex

• #### Ummmm ... (Score:2)

The breakthrough could lead to a twofold increase in performance for home wireless networks and end that annoying habit of pilots finishing every sentence with "over".

Ummm, yeah. Except for with voice, you can't have fully bi-directional communication.

It's not possible to listen to the other guy while you're talking. So, pilots and anybody who needs to have any actual radio discipline will still need to say "over".

Otherwise it would sound like a typical con-call when everybody is trying to talk at once.

• #### Re: (Score:2)

It's not possible to listen to the other guy while you're talking. So, pilots and anybody who needs to have any actual radio discipline will still need to say "over".

Point taken about guys. But women seem to do it all the time. Whether any actual communications go on I can't say.

Now excuse me while I prepare the sofa in the den as a place to sleep for the next few days.

• #### It's a clever twist (Score:2)

there seem to be several ways of achieving this in other scenarios
• near end echo cancellation; a wide dynamic range receiver that can subtract the station's own forward transmission from the mix of forward and reverse transmissions on the line, many modern 2-wire digital line systems (eg. DSL, V.90) work this way
• A variation of the above for satellite transmission that tracks the phase and frequency offsets in the satellite transponder to achieve a similar forward channel cancellation eg. PCMA [viasat.com]
• an iterative v