Electronic – is it possible to load a transversal wave with a longitudinal wave

What I usually do is I try to ensure that the controller doesn't send commands faster than the robot can process. Sending instructions consistently faster than can be processed by the robot will always eventually result in a loss of information with either a FIFO or a LIFO buffer. As a backup to intermittent lag on the robot I would use a small FIFO buffer. The exact size depends on what the trade-off between lost commands vs. responsiveness.

a LIFO buffer really doesn't make much sense in any case because you'll end up with an out of order operation in case the robot responds to commands slowly. consider the following:

1. Send drive forward command
2. Send Activate servo 1
3. Send drive back command
4. Send Activate servo 2

With a LIFO structure, say all the commands get sent before the robot gets time to process any commands. The commands are now going to be executed in reverse order! The robot will activate servo 2, drive back, activate servo 1, then drive forward. Most likely this is never what you want.

If you're only ever processing the latest instruction, then no additional buffer would be needed at all.

Tannenbaum is alluding to secondary effects, such as intersymbol interference, that reduce the effective signal-to-noise ratio.

Intersymbol interference is created by nonlinearities in the phase/frequency response of the channel. These irregularities are generally proportional to the carrier frequency — for example, if a channel centered at 1 MHz has a quality factor (Q) of 50, it will have a 3-dB bandwidth of 20 kHz. But a similar channel centered at 100 MHz will have a bandwidth of 2 MHz.

If you need a bandwidth of 20 kHz for your signal, the 100-MHz channel will have a flatter response over any 20 kHz segment than the 1-MHz channel, reducing the phase distortion.

This is just one way of thinking about it. In reality, there are many factors that affect the flatness of any given communication channel — and the analog circuitry used to interface to it. It's just that in general, it's easier to keep distortions of this type low if the bandwidth is a smaller fraction of the carrier frequency.