MIL-STD-187-721 Interoperability And Performance Standard For Advanced Adaptive Hf RadioThe purpose of this document is to describe the technical parameters for adaptive high frequency HF radio that are more advanced than those described in MIL-STD-188-141. The advanced technology contained in this standard will guide the planning of military adaptive HF radio network technology into the 21st century. To fully understand and utilize this document, it is necessary to refer to portions of MIL-STD-188-141.

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MIL-STD-187-721D

5.5.1.3  Spectral distortion.

a.  Spectral distortion shall be measured by comparing pairs of SINAD and PBER measurements of received ALE words to the theoretical modem performance curve (the dashed line labeled 'G'on figure 9).  Each (e.g., SINAD and PBER) measurement pair falls within one of the regions on figure 9; the number of that region is the spectral distortion measurement for that received ALE word.  Spectral distortion measurements shall be histogrammed in accordance with 4.5.3.

b.  Points along the lines that separate the regions shown on figure 9 are tabulated in table IX;

each column in the table is labeled with the corresponding curve number from the figure.

c.  The following simple algorithm, using the data from table X, may be used to quickly compute spectral distortion.

(1)  Measure SINAD and PBER for each word received.

(2)  Convert the measurements of each word to LQA codes (range 0-30) in accordance with MIL-STD-188-141.

SINAD (dB)

0   1   2   3   4   5   6   7   8   9  10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

1

0

Region 0

0.1

Region 1

1

0.01

Region 2

Gaussian

Channel

Region

Region 3

Rayleigh

Region

6

Region   4

5

(Flat Fading) Channel

2

0.001

G       6          5               4                                     3

FIGURE 9.  Spectral distortion partition of BER versus SINAD sample space.

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