lculated assuming the use of the 3GPPAMR 12.2 kbps codec with a 50% speech activity factor such that the percentage of users in outage is less than 2%, where a user is defined to have expe- rienced outage if less than 98% of the VoIP packets have been delivered successfully to the user within a one-way radio access delay bound of 50 ms. The assumptions and configuration parameters used in the system-level simulations for VoIP are as described in Table 12-4 and Table 12-5. Note that the downlink to uplink ratio is 4:4, i.e., four downlink subframes and four uplink subframes, for the TDD mode for all VoIP simulations. Furthermore, the cyclic prefix of 1/16 is used for all VoIP capacity calculations. In the downlink, a combination of DRU and mini-band CRU subchannelization schemes is used in the simulations. Since the control channels are always allocated in the distributed resources, a fixed division is assumed in each subframe between the DRU and mini-band CRU resources. The SFBC mode with a 2 antenna configuration and non-adaptive precoding is used when DRU subchannelization is utilized, whereas with mini-band CRU, rank-1 transmission with wideband CHAPTER 12 Performance of IEEE 802. 16m and 3GPP LTE-Advanced beamforming is employed. The MMSE receiver is modeled in the MS for channel estimation and data detection. The chase combining HARQ with a maximum re-transmission delay of four frames and up to four re-transmissions are used. A fixed overhead is assumed for non-user-specific and HARQ Feedback A-MAPs. The Assignment A-MAP overhead is explicitly modeled based on the scheduled allocations in each subframe in the downlink and uplink. It is assumed that two OFDM symbols per frame are consumed for the preambles and midamble, and the midamble estimation errors are taken into consideration in the results. The superframe headers consume 20 LRUs in the first subframe of every superframe and signaling errors are explicitly modeled in the VoIP simulations. Persistent scheduling for individual VoIP connections is used to