% Total circuit switched traffic in the Iub interface = (315.9 + 1889.2) + 10 ° % Iub signalling = 2429.69 kbps Step 4. Calculate the busy hour usage per user for packet switched traffic on the Iub interface. Packet switched data traffic = 600 MB/month/user 600 1024 X 1024 X 8 (bits / byte) X 10% BH usage per user = .66kbps 30 x 3600 Step 5. Calculate the total packet switched traffic on the Iub interface. Assumptions: Retransmissions: 25 % - This is just given here as a value for this example. Estimating retransmissions is a network- specific task. Soft handover = 40% ATM overhead = 30% Packet switched data services do not have any delay requirements but are best effort Traffic/user = 4.66 + 40% + 25% = 8.155 kbps/user Traffic/BTS = 8.15 kbps/user X 1000 users = 8155 kbps With ATM overheads Traffic/BTS = 8155 + 30% = 10 601.5 kbps/BTS With assumed Iub Signalling = 10% Total packet switched traffic in Iub/BTS = 10 601.5 kbps + 10° % Iub signalling = 11 661.65 kbps Step 6. Calculate the I-cs traffic. Inputs: Circuit switched data service channel in I-cs = 78.7 kbps (64 kbps + 23 % ATM overhead) Assume I signalling traffic = 1% Assume I-cs blocking = 0.1% Assume 50 3G BTS/RNC Total voice traffic = 1000 subscribers X 12 mErl/subscriber X 50 BTS = 6000 Erl Total voice service user connections based on Erlang B = 549 Total Circuit switched data traffic = 1000 subscribers X 10 mErl/subscriber X 50 BTS = 500 Erl Transmission Network Planning and Optimisation Figure 3.60 Point-to-point topology Total Circuit switched data service user connections based on Erlang B = 458 Total I-cs capacity = [11.7 kbps X 549 + (78.7 X 458)] X 1.01 = 42.89 Mbps Step 7. Calculate Iu-ps traffic. Inputs: Assume again I signalling = 1% Total protocol overheads = 24.2% Total packet switched user traffic/BTS = 4.66 kbps/subscriber X 1000 subscribers/BTS = 4660 kbps/BTS Total packet switched user traffic/RNC = 50 BTS X 4660 kbps/BTS = 233 Mbps Total PS traffic between RNC and SGSN = 233 + % + 24.29 % = 292.28 Mbps Step 8. Calculate the Iur traff