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

considered approximately stationary, N1 = 15. This first epoch represents the most up-to- date channel quality measure available.

b. The second, third, and fourth time epochs shall consist of: 5 minute intervals up to 1 hour old (second epoch), hourly intervals from the current hour to 24 hours (third epoch), and cumulative results since start-up (fourth epoch). Epoch 2 employs t2 = 300 seconds and N2 =

12 so that five t1-length samples from epoch 1 are summarized in each t2-length sample (t2 =

5t1) in epoch 2. Similarly, epoch 3 consists of 24 1-hour samples: t3 = 3600 seconds and N3

= 24. Finally, epoch 4 contains counters that accumulate all samples.

4.5.3.3 Histogram generation.

a. For each channel quality measure or link performance measure X, where X is one of the channel quality measures or link performance measures listed in 4.5.3, sets of bins hX(i; j, k) shall be used to store exceedance histograms of the samples x of that measure as described below, for every channel to every reachable station. In the notation hX(i; j, k), the index k refers to an epoch (1 < k < 4), the index j refers to a particular exceedance histogram (set of bins) within that epoch (1 < j < Nk), and the index i refers to a particular bin within that histogram (see figure 2). In addition, for each epoch, a set of counters shall be used to accumulate current measurements to form the next set of histograms; these counters are labeled as j = 0 in the figure.

b. For the purpose of histogramming, the range of values for each measure shall be quantized into a number of subranges with lower thresholds, in accordance with table XVI, plus an additional (lowest) subrange with a threshold less than any valid sample. As each sample arrives, it shall be compared to the lower endpoint of each subrange. Each counter shall be incremented if the sample exceeds the lower endpoint of the subrange corresponding to that counter. Because the lower endpoint of the lowest subrange is always less than the smallest possible value, bin 1 in each exceedance histogram will contain a count of the total number of samples represented in that histogram. Because the same thresholds are used for each of the four epochs, only one quantizer is needed. Each epoch independently accumulates the samples as they arrive.

c. For each epoch, when an integrating period tk has elapsed, the histograms shall be shifted one position to the right; the counter contents shall become hX( ; 1, k), and the oldest histogram hX( ; Nk, k) shall be discarded. Epoch 4 is a special case; epoch 4 counters shall simply accumulate all samples, with no averaging over individual integrating periods.