".....Ah BOB Stargate, why do you even have separate accounts if you're going to be so easily recognised? ...."
Because I am NOT Bombastic Bob! I am StargateSG7, a user based in Vancouver, Canada. Bombastic Bob, I think is based in Southeast England. We for SOME REASON have the same writing style using that OPPOSING caps style. I also think we probably came from the same pressure-cooker background of 1980'era MiniComputer/Mainframe computing and Large Data Systems management which probably EXPLAINS WHY we are so hyperactive and well.....BOMBASTIC....!!!!
I do machine vision systems and video processing research for various entities of which I have a stake in. Bombastic Bob I believe is a SysOps/DevOps person.
I AM NOT BOMBASTIC BOB !!!! Ya Got The Wrong Guy!
Now back to the main subject at hand!
QAM bandwidth is governed by the number of symbols which are in fact a series of radio waves of a specific amplitude and phase that are SUPPOSED to appear in a Specific Quadrant when those signals are displayed on a Vectorscope (which is a type of Oscilloscope -- i.e. do note the word Quadrature!).
When you divide up a vectorscope into quadrants and place TARGET-points within those qradrants, ANY incoming signal of a specific frequency that has it's amplitude HITTING those target points is considered a signal that signifies the digital signal symbol that represents that target point (i.e. example the binary digit 15 or 1111 in bitwise notation for any RF signal that say....hits the quadrature target at XY-Point X:200, Y:-200 +/- 0.2% of graph size)
Signals that DO NOT hit those target points on the scope are rejected as NOT being part of any symbol set.
Now the problem is that RF signals have multipathing and reflect, diffract, refract and otherwise mis-time themselves. If only one or two waveforms do that, then we can easily have circuitry that REJECTS those signals as NOT being part of a QAM modulation schema.
BUT if MORE THAN ONE set of waveforms has the same general amount of multipath and distortion behaviour, then the circuits MUST ASSUME that it is the SIGNAL ENVIRONMENT itself that is causing the problems and thus attempt to recover those distorted signals by creating a PLUS/MINUS DIFFERENCE-based error correction scheme that ACCOUNTS for those distortions.
So the circuits look for IDEAL SIGNAL ECC/Correction-specific RF Frames or Packets every few seconds or even microseconds that are of a format that are considered IDEAL signals. When the RECEIVED IDEAL signals are compared against the internal-to-phone's or wireless router's IDEAL SIGNAL reference waveform, then we can figure out how much time and phase distortion is occurring and then apply THAT distortion difference calculation to ALL OTHER incoming signals so we can determine if the incoming digital RF signals hit the QAM signal quadrature placement points which indicates they are a VALID QAM symbol!
Today, it's usually QAM-64 (16 points per quadrature) or QAM-256 (64 points per quadrature) that represents up to 64 symbols or 256 symbols per modulation set. NOW as of 2018 QAM-1024 and QAM-4096 are coming out within specialty systems (usually video and mobile voice phone oriented) because a few "dropped" symbols doesn't mean all that much to understanding a voice of video stream. You would hear static or see macro-blocks. That is NOT too big of a deal for the average user/consumer!
BUT with DIGITAL DATA where every bit counts, we still use OLDER QAM because we can more reliably recover digital data from an RF signal. However, the data rate is much LOWER!
Soooooo, with much more precise clocks, we can BETTER place the QAM symbols with the QAM quadratures so they can be recovered more effectively within even a heavily distorted, time-delayed and out-of-phase RF signals environment.
The MORE IDEAL reference signals are sent closer together, the more accurately I can MEASURE time and phase distortions to BETTER recover actual digital data! Ergo, i get MUCH HIGHER bandwidth into the Terabits-per-Second range!
And with QAM-128-Kilo or QAM-ONE-Mega we can have 128 Thousand or One Million symbols per RF digital modulation signal set which means ENORMOUS full-duplex download AND upload bandwidth per user!
which equals Tottenham Football Match Watch-on-the-London-Tube Heaven! (or here in Canada, it means I can watch the Vancouver Canucks hockey team PROBABLY actually make it to the playoffs AND maybe even WIN the Stanley Cup in the 2019 playoffs all the WHILE watching from my tablet whilst seated lazily on my boat anchored in English Bay listening to the Seagulls float by and having two pints at a time!)
Is THAT not a good enough reason to get QAM-ONE-Mega up and running sooner rather than later?