ell stream is maintained. Performance of the physical layer is another key issue. There are no objectives spec- ified for SES ATM or ATM availability (except in the definitions). SESATM is defined as a second when CLR > 1/1024 = 9.8 X 10-4 or SECBR > 1/32 = 3.1 x 10-2 as from ITU-T Recommendation I.357. Based on simulations, the equivalent worst-case BER for SESATM is 3.4 X 10-5 and the limiting parameter is SECBR. Performances and unavailability of ATM connections are related to this threshold value. Some examples are shown in Tables 8.2 and 8.3. Table 8.2 Access network performance objectives in ITU-T G.826 ITU-R Rec. F.1189-1: Performance Objectives for a National Access System; from G.828 Nearest Radio capacity container SES/month BERESR BERSES BERBBER PDH 2E1 VC-12 0.0034 0.00017 1.7E-05 1E-09 1.7E-04 2E-08 PDH 4E1 0.0043 0.00017 1.7E-05 7E-10 1E-04 5E-09 PDH 8E1/16E1 0.0064 0.00017 1.7E-05 8E-10 4E-05 3E-09 STM-1 0.0136 0.00017 1.7E-05 1E-10 2E-05 6E-10 Fixed block allocation C = 8.50% Access length L, rounded to nearest 500 km = 500 km 3G TRANSMISSION NETWORK PLANNING AND OPTIMISATION Table 8.3 Access network performances objectives as from ITU-T G.826 From 1.356 Equivalent Parameter Allowance 27 500 km Access network Scaling ref. 3.00E-07 7.20E-08 10.67 1.70E-11 9.50% 4.00E-06 3.80E-07 383.40 9.91E-10 SECBR 9.50% 1.00E-04 9.50E-06 SESATM 3.40E-05 8.7.5 Parameter Setting The inputs of the whole analysis process can be divided into three major categories. Di- mensioning parameters form the first inputs. The second inputs come from the actual im- plemented network, such as the capacity of the links and the media used, along with the synchronisation and network management settings. The third inputs are in the form of ATM parameters and radio network parameters (see Figure 8.15). General Data Radio & ATM Dimensioning (topology/Capacity/ Network Parameters Parameters Media/NMS etc) Network Analysis Optimised Parameters Figure 8.15 Process to study the impact of radio parameters on the transmission network The d