profile changes greatly during the mass event compared to a normal traffic condition and typically the uplink traffic volume exceeds the downlink traffic volume during the highest loaded time. Therefore, the uplink inter-cell interference control becomes crucial from end-user performance point of view. The downlink interference control is very important from the throughput per user point of view and due to the physical downlink control channel (PDCCH) capacity. High downlink LTE Small Cell Optimization: 3GPP Evolution to Release 13, First Edition. Edited by Harri Holma, Antti Toskala and Jussi Reunanen. © 2016 John Wiley & Sons, Ltd. Published 2016 by John Wiley & Sons, Ltd. LTE Small Cell Optimization Mass events are uplink limited also in LTE. DL interference impacts the PDCCH capacity as well Interference as DL throughput performance. Signalling Very high signalling capacity required. capacity Peak >250 actions second BTS. Control channel High RACH, PUCCH and PDCCH capacity and dimensioning efficient PDCCH link adaptation required. Inter-frequency load balancing algorithms must Load balancing minimize signalling while balancing the load. Figure 13.1 Main factors impacting the mass event performance interference reduces the PDCCH capacity and the spectral efficiency of the physical downlink shared channel (PDSCH). The decreased PDCCH capacity in turn reduces the number of UE that can be scheduled simultaneously per transmission time interval (TTI) for UL and DL further reducing the spectral efficiency (due to the reduced frequency-selective scheduling gain). The amount of signalling traffic per eNodeB in terms of call setups and releases, and incoming and outgoing handovers, can also limit the total traffic and therefore signalling peaks (amount per second) need to be carefully monitored. Control channel dimensioning and maximum number of supported radio resource control (RRC)-connected users are of great importance during the mass event. The capacity of all control channels needs to match or exceed the maximum