ps per voice channel over lub, for AMR 12.2 voice coding and 50% voice activity factor, including frame overhead UP/AAL2/ATM. There exists also 43% OH, i.e. 8.91 kbps per voice channel over Iu and CN for AMR 12.2 voice coding with 50% activity factor, including frame overhead UP/AAL2/ATM. The CS and PS may have 20-25% OH on CS over the Iub. This includes TCP/IP header compression and UP/AAL2/ATM. For PS, the average packet length is 125 bytes. The signalling OH amounts to 10% on top of framed user data, and 2% O&M OH on top of the framed user data on lub, both with a minimum of 64 kbps per link. In addi- tion, there is 25% frame overhead on signalling and O&M traffic. 7.9.1.4 Analysis Assumptions Grade-of-service (GoS) applies to the calculation for delay sensitive traffic, and delay varying services, i.e. voice and LCD services, where calculations estimate the required bandwidth to obtain a specific GoS. For ATM links carrying multiple services, the nar- row band Erlang formula applies while considering different amounts of multiple rate traffic. For regular TDM links carrying one single service, i.e. voice between BSCs and MSCs, e.g. the narrow band Erlang formula applies. We assume a load factor for ATM and IP links, i.e. 90% for ATM and 75% for IP links, which describe the maximum allowed theoretical loading on the links. However, we do not assume a load factor for TDM links. Thus, for links carrying both real-time and background type of traffic, the real-time bandwidth results from GoS calculations, and the average packet data originates from the load factor. On lub and Iur interfaces both voice, LCD and LDD data require the same quality. Thus, we include GoS calculations for LDD data. For all practical purposes, we assume that packet data terminates in a ISP, or 3rd party network at the local switch site in nodes A, B, or C; this means that no packet data transfer occurs between switch sites. We also assume that 30% of voice and CS data generated in the BSS and UTRAN connected to one switch site, terminates