Q16 verification
--------------------------------------------------------------------------
floor ln2 = 0.693147180560   = -1.591745 dB
strictly decreasing in B on 1e3..1e12 Hz: True
strictly above ln2 for every finite B: True
log-log slope of (f - ln2) at B = 1 THz: -1.0000 (-> -1)

R = 1e+06 bit/s, table of bandwidths:
   B (MHz)  eta (bit/s/Hz)        Eb/N0         dB
      0.05        20.00000 52428.750000    47.1957
       0.1        10.00000   102.300000    20.0988
       0.2         5.00000     6.200000     7.9239
       0.5         2.00000     1.500000     1.7609
         1         1.00000     1.000000     0.0000
         2         0.50000     0.828427    -0.8175
         5         0.20000     0.743492    -1.2872
        10         0.10000     0.717735    -1.4404
        20         0.05000     0.705298    -1.5163
        50         0.02000     0.697974    -1.5616
       100         0.01000     0.695555    -1.5767

approach to the floor, f(eta) vs ln2*(1+eta*ln2/2):
     eta          exact    first order   rel diff
   1e-01    0.717734625    0.717169831   7.87e-04
   1e-02    0.695555006    0.695549446   7.99e-06
   1e-03    0.693387463    0.693387407   8.01e-08
   1e-04    0.693171204    0.693171203   8.01e-10
   1e-06    0.693147421    0.693147421   8.01e-14

with a per-hertz circuit cost alpha*B (W/Hz):
    alpha   B* (MHz)  B brute (MHz)      P* (W)
  1.0e-10      0.035          0.035  3.6334e-06
  1.0e-09      0.031          0.031  3.2586e-05
  1.0e-08      0.028          0.028  2.9527e-04
