A New Modulation Method. Really?

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Introducing a new modulation method.

New modulation schemes don’t come along very often.  In fact, it has been years…decades really…. since any new modulation method has been invented.  Remember there are only three basic ways a carrier can be modulated:  by varying the amplitude, frequency or phase.  Or some combination of those.  Most of the useful combinations have already been discovered and either ignored or adopted.

Whether you know it or not, the most popular modulation scheme in use in the wireless world today is QAM or quadrature amplitude modulation.  It is a combination of both amplitude and phase modulation. Digital bit sequences are represented as unique amplitude-phase variants of the carrier.  For example, 64QAM uses 64 different amplitude-phase combinations to represent any 6-bit combination.

QAM is use everywhere because it is very spectrally efficient meaning that it can transmit more bits per Hz of bandwidth than almost any other modulation method.  It is used in HSPA and LTE OFDM cellular systems, Wi-Fi, cable TV, DSL modems and a wide range of microwave backhaul, and satellite systems.  It is hard to beat QAM despite the fact that it needs a better than average signal to noise ratio and linear power amplifiers for reliable communications. 

Anyway, along comes a new company MagnaCom with a new modulation method called WAve Modulation (WAM).  You won’t find it any textbook and the company won’t reveal any details on how it works.  MagnaCom’s goal is to challenge the dominance of QAM and ultimately replace it with WAM.  The company claims that it fully backwards compatible with QAM systems and does not require changing antennas or radio circuitry.  WAM is a purely digital modulation method that uses the same analog and RF circuits as QAM.

Even after a long briefing with the company, I still don’t know how it works.  One explanation said that I should view it as a multidimensional QAM.  Here is what MagnaCom’s release said about WAM: “WAM technology is a pure digital new modulation scheme, using spectral compression that improves spectral efficiency.  The spectral compression enables an increase in the signaling rate thereby affording the use of lower order alphabet, which reduces complexity.  It provides inherent diversity of time and frequency domains and uses nonlinear signal shaping.  The nonlinearities are handled digitally at the receiver side allowing a lower-cost and lower-power transmitter.”   

The discussion continues: “ WAM is a multi-dimensional signal construction operating in the Euclidean domain.  WAM is breaking the orthogonality of signal construction (zero ISI in a single carrier/zero ICI in OFDM) shown for the first time to increase capacity and provide an optimal handling of nonlinear distortion, ultimately resulting in significant improvements versus todays’ legacy QAM systems…”

That does not exactly explain it for me.  I keep wondering what a WAM signal looks like on a spectrum analyzer.  Can a constellation diagram be shown like with QAM?  In any case, I am sure that MagnaCom is just protecting its IP.  No doubt the whole thing takes place in a DSP or FPGA with some unique algorithms.  I would love to include mention in the 4th edition of my college textbook Principles of Electronic Communications Systems (McGraw Hill) as I am updating it.  But frankly I do not know what to say.

Despite the discomfort of not really knowing how WAM works, I am amazed at MagnaCom claims of amazing benefits.  These include, up to 10 dB system gain advantage, up to 50% lower power, up to 400% greater distance, up to 50% spectrum savings, better noise tolerance, major increase in speed, lower cost and easier design, and 100% backward compatibility.  Wow!

If these claims are real, MagnaCom will have a real success on their hands.  The above listed advantages are really needed and wanted especially in the wireless world that never has enough speed or bandwidth.  It will be interesting to see who adopts this, who makes chips and so on.  I wish MagnaCom great success.

Discuss this Blog Entry 28

on Feb 5, 2014

Wow, it just hit me. The author of this article is also the author of well-reputed standard communications books that electronics and communications engineering students study in universities (in the Philippines). Its Louis E. Frenzel. The book he mentioned above is great, got a chance to read it in the library. It certainly delves into the specifics of every modulation method (including the mathematics). I also have a personal copy of one of his books which I think is a must have for every beginner in telecommunications - "Communication Electronics" very simple, straight to the point explanations, one of the few texts that doesn't over-exaggerate every simple straightforward concept thus making it hard and time-consuming (readers of other communications literature will know, you go over the jargon and decrypt it and get frustrated of the verbosity).

Anyway, back to the article. 50% lower power! That would make the new Class A amplifier efficiency comparable to the Class B ones with transformer coupling (50%+25% = 75% with WAM compared with the 78.5% with QAM)! It also promises a gain 6 times greater or more, reaching 4 times the distance and consuming only half the bandwidth and so on (see above). WOW indeed!

Wave modulation, the term seems to be intuitively misleading, like the carrier is a WAVE that is undergoing MODULATION. The term doesn't imply anything revealing to its nature.
Maybe we can derive the nature of this WAM scheme from the benefits it gives or from some of the descriptions. They mentioned a "multi-dimensional signal construction operating in the Euclidean domain". Euclidean, hmmm, 2 coordinate system, 2 coordinates x and y, multi-dimensional... 3 coordinates? 3D constellation diagram? Could the "wave" being described be the 3rd axis? Almost all improvements mentioned are multiples of 1/2 (i.e. 50% BW and power). Could it mean that with WAM there are 8 points on the 3D constellation diagram, compared with the 4 points of ordinary QAM ? I never really know. Which makes this affair all the more exciting. CAN'T WAIT FOR THE TECHNICAL PAPER :)

on Feb 6, 2014

I think you are on the right path. The third axes is time. If you change the constellation in a known way over time you can change the wave that comes out. Each point on the constellation will represent a different symbol at a different time.

on Feb 10, 2014

Just read the patent. It looks like the Euclidean space they were referring to was the distance between the vectors used as error metrics. What I had in mind was a contrast to hyperbolic geometry and such. haha... took the words too literally.

It also looks like the change is in the DSP/coding level. The same QAM is still being used "...an inter-symbol correlated (ISC) signal that carries information bits and that passed through a non-linear circuit; said information bits are MAPPED INTO N-QAM SYMBOLS and N is an integer..." No wonder it would be backward compatible with QAM.

Anyway, the thought of a 3D constellation diagram drew quite some enthusiasm from me.

on Feb 10, 2014

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=...

Oh yeah, the link to the said patent by Magnacom filed on November 12, 2013.

on Feb 19, 2014

New modulation schemes are 'discovered' every couple of years it seems.. very few of these pan out and many of them remain under a cloak and dagger lockout of information that is supposedly to protect the innocent from theft of new technology.

About 15 years ago when the set of technologies that would go into '4G', NGMN, Next Generation Mobile Networks was being hashed around in the various standards groups (mainly IEEE 802.16/20/11, 3GPP), I evaluated a few such modulation schemes and had discussions with leading companies and researchers. As it has turned out, those methods that were properly vetted through peer review technical papers and filing of patents that made sense to me at the time are the only ones I know of that have moved forward as part of the overall modulation and signal processing methods.

I will remain skeptical of any company that holds out dramatic improvements but is not willing to say how it can be accomplished.

One way to test new approaches for circuits is the 'black box' method: A new signal processing, modulation scheme, RF circuit, smart antenna sub-system or set if algorithms can be tested by setting up a test that clearly shows a test setup for measurable inputs and outputs of the black box that remains undisclosed. For example, signal gains and bits/hertz rates for current 3G-4G CDMA and OFDM modulation schemes are well documented such that what is considered achievable under a know test setup will fit into a range. The new technology, in this case one that is supposed to work with the existing technology, should be able to be shown to contribute to performance as claimed. If a company is not willing to do what amounts to as a black box proof of principle of operation, what they offer should be held with extreme suspicion.
Its up to the engineering community to tell companies or individual inventors "exceptional claims requires exceptional proof". Even if they refuse to provide clear technical explanation of how the supposed revolution in technology works, all should be able to provide a suitable 'black box' test that shows that it works based on reasonable observation.

-robert

on Feb 5, 2014

WAM bam thank you ma'am. Sounds like a load of hype to me. Much like the crossed field antenna.
Lou, aren't frequency and phase modulation basically the same thing? I was taught that there are only two kinds of modulation: linear (which includes AM) plus angle (which includes both FM and PM. Perhaps just a matter of semantics...

on Feb 5, 2014

It would certainly give MagnaCom bad publicity if it were all hype.

(I'd also like to speak for Lou)
Yes, there are essentially only 2 kinds of modulation, and all other modulation schemes stem from a unique combination of both. QAM is changing both amplitude and phase to create a unique symbol, which can be plotted as a phasor in a 2D plane (constellation diagram).

on Feb 5, 2014

They apparently have quite a few patents on it (at least doing a quick search at the PTO looking at MagnaCom as licensee):

They are all claiming various of the communications benefits in the article. I have not had the time to digest them yet, but they are there for the looking.

You can do a quick search at USPTO.gov:

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=...

on Feb 5, 2014

Talking about patents, could this one turn into a standard essential one (SEP) if the claims were true?

on Feb 5, 2014

It seems intuitive to me.

Instead of orthogonal Amplitude and Phase constellation of baud symbols in QAM, the Euclidean geometry relies on some integer radius values and phase or Polar geometry

The state table of baud symbols defines the transition bandwidth used or minimum symbol interval, such if the lowest common denominator of all possible combinations are used as an integer for each state change and some bandwidth hungry state transitions are eliminated, it results in more efficient used of Baud / Hz of bandwidth. maybe...

I think the compression tricks comes from nonlinear pre-compensation and post-compensation for ISI with variable time response filtering based on patterns from previous symbols received. Not too much different from pre-comp used by HDD's for RLL codes.

6dB improved compression is impressive for AWGN ..

Whats the catch? Worse BER under Ricean Fading?

Rice Fading is when echos off walls cancel with the orignal signal to make a dead spot. Most common connection failure mode in WiFi when surround by conductive walls. Move Lappy 1cm or 1 degree .. is all it takes to get out of a RICEAN deadspot.

My opinions are just a guess.

on Feb 10, 2014

"Ricean Fading" applies to all kinds of transmission so it couldn't be a unique catch for WAM.
Additive White Gaussian Noise AWGN isn't a deterministic factor of spectral efficiency in the modulation level.
And how did Intersymbol Interference ISI get into the picture of spectral compression? I didn't know ISI was also a problem with HDDs.

on Feb 5, 2014

Patent 8582637 seems to be the overaching one. It describes a predistortion method of introducing inter-symbol interfierrence and an adaptive equalizer on the receive and to recover the orginal. It seems to be based on nearest neighbor type error minimization. Most of the other patents are details of generating and correcting the signal, including carrier/clock recovery, forward error correction, etc.

The only thing that appears fundamentally new here is the non-linear pre-distortion and recovery technology.

The whole thing almost reminds me of a patent troll trying to wrap the obvious in some new twist in hopes of wraping a net around a lot more stuff than they actually contributed.

on Feb 5, 2014

Perhaps the information to wave translation is memory driven from tables similar to 64QAM that have been tweaked to optimize performance. It would take a lot of memory to store the waveforms for all the combinations, but memory is cheap now and bandwidth is limited.

on Feb 5, 2014

Two points: 1) The claims being made might be true INDIVIDUALLY but not simultaneously. 2) How close are existing QAM systems to the Shannon limit? That will give the upper bound on how much better WAM might be overall.

lrs
on Feb 6, 2014

A point to ponder! If this WAM technique really ensures better Spectrum usage, can the Cellular Telephones converted from Simplex to Duplex like land line telephony?

on Feb 6, 2014

Non linear transition shift compensation is a common trick used in high density magnetic recording for many years. But it won't improve signal density by 200%. And how can they patent it if its old stuff?

on Feb 6, 2014

I wonder if it has anything to do with the two dimensional structure of the transmitted wave front (kind of like orthogonal wave transmission doubles bandwidth).

Perhaps they employ multiple sources, spatially separated, and employ beam shaped reception to separate the individual data streams at the various angles to the receiver. This would minimize the changes required against existing technology, only modifying new receivers to include beam forming and multiple Transmit/Receive channels. This would work best with line-of-sight frequencies.

The only limits to bandwidth increase would be the ability to discriminate multiple transmit/receive channel angles. At light wave frequencies, the possibilities would be google-like (the number, not the internet people), as each visual pixel around you could be a transmit/receive channel.

Of course for this to work for a large population, all transmitters and receivers must have beam shaping capabilities. Nothing is free!

on Feb 6, 2014

Precomp in hard drives is to compensate for the non-linearity of the write process to correct timing and location of the highest density bits recorded to the media. The benefit only amounts to 1-2% of linear density improvement.

I agree with Halc, that a measure of the code should be against the Shannon limit. Claims of 10 dB gain are likely against some form of limitation in the receiving under some noise or distortion condition.

on Feb 11, 2014

Does this have anything to do with Wavelet Modulation?
I suspect not due to the QAM compatibility.

on Feb 18, 2014

Lou, you say that QAM is the prime modulation, but my experience with microwave links has been that QPR rules. QPR reduces the bandwidth (less noise). One of the Japanese radios used 511QPR in one polarization and 1023QPR in the other. These units send a line of sight signal to the next mountain/hilltop/tower in the chain. I suspect NASA's deep space network uses a smaller constellation and a lower BAUD than microwave. But QPR has S/N advantages.
Bill

on Feb 18, 2014

I would guess at a new version of FSK Diversity, sort of like TV vector mod remember analog TV?...now you could have 12 pairs of tones at 15 degrees around the circle and the receiver does the work of sorting it out. I can see that done easier with DSP power than the old fashioned resonator filters!

on Feb 20, 2014

Whoh! very impressive! Sounds like the Rockwell Retro Encabulor!

http://www.youtube.com/watch?v=RXJKdh1KZ0w

If you add up the claims it gets rather silly... less bandwidth, faster throughput, less power.

This is a really low grade form of marketing BS. The claims " up to 10 dB system gain advantage, up to 50% lower power, up to 400% greater distance, up to 50% spectrum savings, better noise tolerance, major increase in speed" violate Shannon's Limit. 400% greater distance means I could lower the power by 12 dB for the same distance. If I can also lower power by 50% then I have a 12+3 =15 dB improvement in energy per bit compared to the noise (Eb/No).
Not remotely possible. He also claims to get more bits (i.e higher speed) in half the spectrum while lowering the modulation order (alphabet). Nuts.
He is claiming all this is possible by "compressing the spectrum".

What he doesn't say is how much spectrum it takes to contain 99% of his transmitted power. This is the ultimate and defining parameter to look for in any modulation. Each "bit" of user data requires a certain quantity of ergs of energy to be differentiated from the noise of the RF channel it is transmitted in, regardless of the modulation type.
A lot of quack-pseudo engineers have claimed a new modulation that puts lots of bits through a seemingly narrow channel but when it is examined, the skirts of the modulation are many channels wide, which lets in many channels of unwanted noise power and thus the range is shortened or the power required rises dramatically. Ultimately it all comes down to Eb/No.
These claims are fraudulent marketing nonsense.

on Feb 25, 2014

“ WAM is a multi-dimensional signal construction operating in the Euclidean domain. WAM is breaking the orthogonality of signal construction (zero ISI in a single carrier/zero ICI in OFDM) shown for the first time to increase capacity and provide an optimal handling of nonlinear distortion, ultimately resulting in significant improvements versus todays’ legacy QAM systems…”

After reading this I first thought it was way too early for the April edition, but better brains than mine seem to have weighed in with a better understanding of the arcane jargon.

MEGO!

on Feb 26, 2014

It sounds like the description of this modulation technique was written in such a way as to obscure rather than describe how it works. It sounds as though it was written by a clever patent lawyer. My feeling is that if it can use the same hardware as a QAM signal, the differences must be in software and that it is actually a software compression scheme of some sort intended to increase the throughput while still using the same QAM hardware. If this were a clever data compression scheme, it might work to increrase the effective data rate while still using lower level QAM modulation. "Non-linear pre-distortion" and "fully digital" add up to digital compression in my mind.

As to the benefits, I suspect that they should properly be read as "up to 10 dB system gain advantage OR up to 50% lower power OR up to 400% greater distance OR up to 50% spectrum savings OR better noise tolerance OR a major increase in speed",

on Feb 26, 2014

This sounds like trellis coded modulation (TCM) using QAM as the base waveform. That has been used for decades (V.32, V.34) to gain a better symbol error rate without increasing the power or bandwidth.

These claims also sound like some of the claims for Walker's VPSK modulation. They're not the same, but the claims sound similar.

on Feb 26, 2014

Wonderful and enlightening discussion. However may I interject some key elements which I have discovered during my career starting in 1973: The descriptions and news releases provide essential engineering data which most seem to overlook. That being the artistic presentation which is meant to impress investors and stockholders, an action which ensures the success of the technology's acceptance and profitability.

on Feb 26, 2014

Wrong as usual. But of course our technology is crippled by the FCC narrow thinking: everything has to have a center frequency and a narrow bandwidth.
Our Military uses SPREAD SPECTRUM, invented in ancient times by Hedy Lamar. This could be implemented using low power (<50mW) but FCC refuses because "interference to other services". But because of the wider banwidth (allows more data) it minimizes interference with narrow band services and becomes a small amount of random noise. Since noise across across widely different frequencies is not coherent the transmission distance is improved. unlike CDMA, the frequencies are pseudo random which makes it impossible to listen in (in real time) (why do you think we upgraded Iraq's infrastructure with GSM?). Again the FCC's preoccupation with communication being "in a band" as well as the Military/NSA objections have worked against this useful modulation option.

on Feb 26, 2014

I seem to remember an article in Popular Electronics about using "Solitons" since they would not be subject to the limitations of wave based electronic signals e.g. RF.

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Lou Frenzel is the Communications Technology Editor for Electronic Design Magazine where he writes articles, columns, blogs, technology reports, and online material on the wireless, communications...
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