e observation interval. However, during this observation interval, there would have been other TE values that were not considered in the TIE calculation. Taking the example as shown in Figure 5-18, there were k time error values (k also being the obser- vation interval). These time error values were denoted as x(n), x(n+1), X (n+2) X(n+k)- The TIE calculation only considered x(n) and x(n+k) because the observation interval was k cycles starting at cycle N. It could be that these two values do not capture the maximum or minimum time error values. To determine the maximum variation during this time, one needs to find the maximum TE ( x(max)) and minimum TE (x(min)) during the same observation interval. Time delay ((max) X(n+k) P(min) Observation interval (k) Figure 5-18 TIE and MTIE Example This maximum variation of the TIE within an observation interval is known as the maximum time interval error (MTIE). The MTIE is defined in ITU-T G.810 as "the maximum peak-to-peak delay variation of a given timing signal" for a given observation interval. As this essentially represents the variation in the clock, it is also referred to as the maximum peak-to-peak clock variation. The peak-to-peak delay variation captures the two inverse peaks (low peak and high peak) during an observation interval. This is calculated as the difference between the maximum TE (at one peak) and minimum TE (another peak) for a certain observation interval. Figure 5-18 shows an example of TIE and of MTIE for the same observation interval, illustrating the maximum peak-to-peak delay variation. The example in Figure 5-18 clearly shows that during an observation interval k, while the TIE cal- culation is done based on the interval between x (n) and x(n+k), there are peaks during this interval that are the basis for the MTIE calculations. These peaks are denoted by P(max) and P(min) in the figure. Note also that as the MTIE is the maximum value of delay variation, it is recorded as a real max- imum value; not only for one observation interval but for al