 are modeled: processing delay over the air interface and the channel condition of each UE. The processing delay is modeled as a constant delay. The user channel condition only models the experienced bit error rate (BER), which is binomially distributed with a mean of 5% per user. With this assumption, there is no differentiation of good and bad users, as all have same loss probability in the air interface. When BER is greater than zero, there is frame loss over the air interface. This will cause RLC retransmissions, which result in the increase of the end-to-end application delay. Modeling of Radio Network Layer (RNL) Protocols The RNL include RLC, MAC and FP protocol layers. Their specifications have been introduced in section 3.3.1. The modeling of the RLC considers both transparent mode (TM) and acknowledged mode (AM). The RLC AM is only used for the packet-switched traffic. For simplification of the simulation model, the basic RLC functions, i.e. segmentation and reassembly, padding, in-sequence delivery of the upper layer PDUs, and Automatic Repeat Request (ARQ) were modeled, but other functions such as flow control, window mechanisms, etc., were not implemented in the model. The modeling of the ARQ function was simplified. Instead of implementing the complex procedure including polling, generating status reports, managing the retransmission buffer, etc., the retransmissions of the RLC PDUs were modeled by delaying the PDUs with certain retransmission delay (either taking empirical values or from a statistical distribution). For the MAC layer, the transport channels like DCH, RACH and FACH were modeled where the user data is mapped onto them. For each transport channel, the forming of the Transport Block Set (TBS) and the corresponding Transmission Time Interval (TTI) were implemented depending on the assigned data rate. The FP layer conveys the data to the lub transport network layer. In the simulation model, the FP PDU delay, i.e. the delay of transmitting one FP PDU from the RNC to the Node B, is measure