g unavailable seconds at the near end. Near seconds end unavailability begins at the onset of 10 contiguous seconds which count severely errored IMA group seconds, including the first 10 seconds to enter the unavailable IMA group seconds condition, and ends at the onset of 10 contiguous seconds with no severely errored IMA group seconds, excluding the last 10 seconds to exit the unavailable IMA group seconds condition Conclusion This should conclude the discussion about what makes a difference in 3G transmission networks, what constitutes network quality and how revenues of the network operator can be maximised. The following tables give an example and insight into the kind of counters a regular 3G network should provide for monitoring the quality of transmission, as discussed above. Physical Layer, ATM Transmission Convergence Performance and Inverse Multiplexing ATM (IMA) Performance The counters in Table 3.16 are examples of what can be collected on the physical layer termination point (SET and PET). The physical performance indicators are the ESR, SESR and BBER, which have been defined before. The indicators using MML commands are shown in Figure 3.83. When the unit type is PET, the command is YMO: PET, 14; outputs. Based on the IMA counters given in Table 3.17, the following key performance indicators can be set to monitor IMA performance: IMALinkSeverelyErroredSeconds IMALink_SeverelyErroredSeconds = 100 (3.76) ns - IMALinkUnavailableSeconds where ns = number of seconds in the measurement period. ATM Adaptation Layer Performance The ratio of a successful AAL2 connection to the attempts made is very critical to measure the performance and the availability of the AAL2 user plane. Based on the results of the AAL2 KPI, if the target is not reached, a check of each counter permits identification of what is configured or set up wrongly. Some examples of AAL2 counters are given in Table 3.18. Transmission Network Planning and Optimisation PCM STATISTICS PERMANENT MEASUREMENT START TIME PET-14 2002-10-09 00:00 CRC 