activity Figure 10.6 Noise rise as a function of the inactive UE number and the DPCCH activity factor. (Source: Tao Chen et al., "Uplink DPCCH gating of inactive UEs in continuous packet connectivity mode for HSUPA," IEEE WCNC, March 2007. With permission.) 0.65 for the typical 3-sector macro cell scenario and the required DPCCH E/INo is about - -18 dB for the inactive UE [18]. Obviously, up to 30 inactive users with the continuous DPCCH transmission in this case can eat up all reserved radio resources, that is, a 6 dB noise rise target. However, the less the DPCCH activity or the less inactive the UEs, the less interference is experienced in UL. With VoIP over E-DCH, the UL transmission of voice is not continuous as the CS voice over Dedicated Channel (DCH). One voice frame is transmitted every 20 ms, or two voice frames every 40 ms if bundling of two voice packets is allowed. With VoIP, the continuous transmission of the UL control channel DPCCH would consume the scarce radio resources and become inefficient. Overhead from HS-DPCCH carrying CQI report Except for the DPCCH channel, there are certain other control channels such as HS-DPCCH which may consume the UL radio resource. HS-DPCCH, carrying CQI information for DL channel sensitive schedulers and adaptive modulation scheme selections, may be transmitted periodically according to a CQI reporting period controlled by RRC. Correspondingly, the effect of the CQI reporting period © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology can be studied according to the earlier-stated equations as well. Reducing CQI activity (i.e., increasing the CQI reporting period) from once per 10 ms to once per 20 ms increases the VoIP capacity by about 10% and going down to one CQI transmission per 80 ms increases the VoIP capacity by 20% (from CQI once per 10 ms). On the other hand, the larger transmission interval of CQI may worsen the downlink performance due to less reliability of CQI. Therefore, the CQI reporting period should be