HARQ-IR combining of erroneous another user or when a user transmissions fails to detect its own transmission Rate or C/I feedback Misinterpretation of rate or Potential transmission errors channel C/I value Transmit sector indication, Misinterpretation of selected Transmission errors transfer of HARQ states, sector or misinterpretation of frames to be re-transmitted. The performance (i.e., detection error rate) of the downlink control channel can be estimated using the physical layer abstraction method that is used to perform system-level simulations (for the traffic channels) with proper modifications to reflect any difference in the transmission format of the control channels. For static overhead channels, the received SINR is calculated through system-level simu- lation in order to estimate the demodulation performance. For dynamic modeling of overhead channels with open-loop power control, the required downlink power or bandwidth for transmission of the overhead channel is taken into consideration during system-level simulation. The system-level simulations calculate the received SINR during the reception of overhead information. The feedback errors, e.g., power control, HARQ feedback, MIMO rate indication, CQI channel, etc., and measurements errors (e.g., C/I measurement) are modeled in system-level simulations. Table 12-3 shows some typical signaling errors and their sources, and their potential impact on system performance. 12.3 TRAFFIC MODELS 12.3.1 Statistical Model for Conversational Speech Voice-over-Internet Protocol (VoIP) refers to real-time delivery of coded voice packets across networks using Internet protocols. A VoIP session is defined as the entire user call time. Several robust voice codecs for encoding conversational speech have been developed, such as ITU-T G.729 (8 kbps) [14] and 3GPP Adaptive Multi-Rate (AMR) codec (4.75-12.2 kbps) [9,10]. A typical conversation is characterized by periods of active speech or talk spurts followed by silent periods. Figure 12-2 illustrates a two-state Mark