MTTRSMean Time to Restore Service
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Under the asymmetric model with N potentially available channels, MTTR upper bound is (N -1) T, where T is the sequence period in which channel replacement procedure is used and T = 2N -1.
In the absence of the incumbents' activity, ETTR and MTTR are smaller than the number of the available channels i.e.
The MTTR of S-CHS and A-CHS are 2N - 1 and 3N + 1, respectively.
MTTR means the maximum time for two CH sequences to rendezvous when all licensed channels are available and maximum conditional time to rendezvous (MCTTR) means maximum time for two CH sequences to rendezvous when all channels are not surely available for all CR nodes.
Rendezvous algorithms should have a bounded and small MTTR, which is the maximum time for two CH sequences to achieve rendezvous.
Most of the papers in the literature are concerned with MTTR, average TTR (ATTR) or expected TTR (ETTR).
MTTR of MtQS-DSrdv equals 86 slots (using Map(1), but 57 slots with Map(2)), which happens in two shifts only.
Therefore, we also check the MTTR statistics while both CRs apply 8 channel maps, but they can meet only on 2 common channels because only these two are available for one of the CRs.
The MTTR of DSMMAC is slightly lower (25 slots) than that of MtQS-DSrdv (29 slots, see Table 3).
This map construction gave us the worst possible map cases, since the mean MTTR is always equal to the MTTR and is constant as shown in the table; that is, there are no differences between MTTR, Y (minimum of MTTR maxima), and [[mu].sup.MTTR].
As mentioned above, the table shows the worst cases of MTTR. If we select other sequences we can improve the MTTR, for example, with 5 available channels and the sender adopting the following sequence: {0,1,2,3,4, 1,2,0,4, 3, 2,3,4, 0,1, 3,4,1,2, 0, 4,0,3,1,2}, and the receiver with the sequence: {4,0,1,2,3, 4,0,1,2,3, 4,0,1,2,3, 4,0,1,2,3, 4,0,1,2,3}, we can improve [[mu].sup.MTTR] to 15 with [[sigma].sup.MTTR] = 5.4 and Y = 8.
For instance, if the [[kappa] = 5, but r = 8, then the MTTR of A-MOCH equals 60 (occurring 32 times), with p = 58.5, which is automatically worse than MtQSDSrdv with the combination of maps with 5 and 8 channels (5-8 in Table 3).