s, packet errors, and real channel estimation (as opposed to ideal channel estimation) effects and re-transmission of erroneous packets; 15. Realistic modeling of the overhead channels, i.e., the overhead due to feedback and control channels. For each drop, the system-level simulations were conducted and the process was repeated with the users dropped at new random geographical locations within the network. A large number drops were simulated to ensure convergence in the system performance metrics and the width of confidence intervals of the user, and system performance metrics were calculated and reported. The confidence interval and the associated confidence level indicate the reliability of the esti- mated parameter value [7]. The confidence level is the probability that the true parameter value is within the confidence interval, such that the higher the confidence level, the larger the confidence interval. All cells in the network were simulated assuming dynamic channel models and the use of a 19-cell wrap-around scheme to model the inter-cell interference, except for the indoor environment. This section describes the link-level and system-level evaluation of the IEEE 802.16m and 3GPP LTE-Advanced against the ITU-R requirements for IMT-Advanced systems using the methodology specified by the ITU-R [4,5,6]. The theoretical background, including the definition of performance metrics, channel models, physical layer abstraction schemes, and traffic models are provided to ensure in-depth understanding of the evaluation process and the results. 12.1 DEFINITION OF THE PERFORMANCE METRICS The link budget is a commonly used metric to evaluate the coverage of a cellular system in the downlink or uplink. In order to calculate the link budget, one must account for all the gains and losses from the transmitter to the receiver over the air interface. It accounts for the attenuation of the transmitted signal due to propagation, as well as the antenna gains, cable and implementation loss, and other miscellaneous losses. The t