nt/estimation imperfections, and these are compensated by the Outer Loop Link Adaptation (OLLA) algorithm, which uses HARQ ACK/NAK feedback from the past to maintain the average BLER at the target level. OLLA has been shown to provide a good mitigation mechanism for the LA errors caused by the imperfect CQI feedback information [31-33]. As described earlier, wideband CQI may be required for VoIP traffic in order to keep the UL control overhead at a reasonable level. This implies that frequency domain packet scheduling gains are lost: the eNodeB packet scheduling can no longer track the frequency selective fading and will have to rely on a transmission scheme that offers maximal frequency diversity. Or similarly, frequency diversity transmission should be favored if, due to the increased velocity, frequency depen- dent CQI information is unreliable ( velocity >25 km/h). Frequency diversity transmission can be achieved by one of the following methods [34]: (1) Using localized transmission where a user is scheduled on multiple PRBs that are scattered over the full system bandwidth to offer maximal fre- quency diversity; or (2) Using distributed transmission where a number of PRBs (scattered over the full system bandwidth) are shared by a set of users. Distributed transmission refers to the case where one PRB of 12 contiguous subcarriers is shared between multiple users on a subcarrier resolution. The distrib- uted transmission feature was adopted by 3GPP Release 8 with the restriction that © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology Table 10.3 Impact of Wideband CQI to Capacity Used Packet Scheduling Method Dynamic Semipersistent Relative loss in capacity a user scheduled with distributed transmission shall always be scheduled on groups of Nd X 12 subcarriers, where Nd is limited to two (2). Method (1) offers a high degree of frequency diversity for cases where there is sufficient data for a user to be scheduled on multiple PRBs, that is, at least 3-4 PRBs. Unfor