In an earlier post I said
“There are, of course, standard ways to evaluate the performance of any digital communication system. The most basic one is to measure the bit-error-rate (BER) of the system for different signal to noise ratios at the receiver. The BER vs. SNR (or BER vs. Eb/N0) plots for conventional communication techniques, both measured and theoretical, appear in numerous books, papers and reports. Having an independent laboratory measure the BER vs. SNR plot for xMax would immediately establish its performance relative to existing techniques in a direct and convincing manner. This is a simple and completely routine test. It should be noted that this type of performance curve provides no information about the design or the internal workings of the communication system. Thus, concerns about revealing intellectual property related to the communication system are not a legitimate reason for avoiding publication of such results.”
I received a number of inquiries about this paragraph, so let me elaborate a bit.
Explanations of what is Eb/No can be found on Wikipedia and elsewhere on the web and of course in any standard text on digital communications. The useful aspect of Eb/N0 is that it allows a simple comparison of different modulation because it involved only the energy per bit (Eb) and the noise spectral density (N0) which is simply the noise power per Hz. In particular, Eb/N0 can be used to compare communication systems with different channel bandwidth and symbol rates.
An example of a BER vs. Eb/N0 curve is given by
The vertical axis shows the bit-error-rate and the horizontal axis the Eb/N0 (normalized SNR) values. The figure shows the BER curves for three conventional modulation techniques. This type of graph is the standard performance measure used to evaluate digital communication systems. You can find a very large number of examples of these curves for conventional communication systems. There is test equipment specifically designed to measure this curve, but it can also be measured by standard RF laboratory equipment.
The points I was trying to make related to xMax are:
(i) So far they did not publish this standard performance curve, which would establish immediately and conclusively the claimed performance advantage of xMax. If xMax has the claimed power efficiency its BER curve would be shifted significantly to the left of corresponding BER curves for conventional systems.
(ii) This type of curve reveals absolutely nothing about how the given communication system is designed. It is not possible to “reverse engineer” anything from this curve. Thus, concerns about revealing intellectual property can not be the reason for not publishing this type of curve.
Given the extraordinary nature of the xMax claims and the ease with which these claims can be verified or falsified (without revealing any technology secrets), it is puzzling, to say the least, that such a standard performance benchmark is not readily available.
Now it is possible that this information is available and I am simply unaware of it. I would appreciate if a reader aware of such information will point me to the source.