r the other sta- tistics presented in this chapter as well. In Case 1, approximately 70% of the users use bundling (see Figure 10.9), SO approximately 70-80% more users can be fitted to the network without exceeding an outage, as is shown in Section 10.7. Due to the higher load compared to the nonbundling case, the average PDSCH utilization rate is approximately doubled with bundling. WO bundling W bundling Number of RBs scheduled per TTI[-] Figure 10.8 Cumulative distribution function for scheduled PRBs per TTI. © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3 GPP LTE Radio and Cellular Technology wo bundling W bundling Packets/TTl/user Figure 10.9 Probability distribution function for bundled packets TTI/user. 10.6.2.2 Semi-Persistent Resource Allocation In order to avoid control channel limitations for VoIP traffic in E-UTRAN, a concept of semi-persistent packet scheduling (PS) [8,19] was adopted in 3GPP for LTE. Semi-persistent PS can be seen as a combination of dynamic and persistent scheduling methods, where initial transmissions of VoIP traffic are scheduled with- out assigned L1/L2 control information by using persistently allocated time and frequency resources, whereas the possible HARQ retransmissions and SID trans- missions are scheduled dynamically. For VoIP traffic the used BLER target in DL is of the order 10-20%, and this together with SID transmissions implies that only 20-30% of the transmissions require L1/L2 control signaling in DL. As ini- tial transmissions are scheduled by using persistently allocated time and frequency resources, savings in control channel overhead are achieved with the cost of reduced time and frequency domain scheduling gains. The semi-persistent resource allocation method adopted in 3GPP LTE is talk spurt based persistent allocation, and in the DL direction the method works as fol- lows. At the beginning of a talk spurt, a persistent resource allocation is done for the user, and this dedicated time and frequency resource is used to transmit initial transmissi