ell edge is 2 and 8 Mbps, respectively. LTE1800 is the higher priority layer with 20 MHz system bandwidth. LTE Small Cell Optimization Exit point Entry point Higher priority LTE layer Hysteresis LTE entry point Lower priority LTE layer LTE exit point Hysteresis Lowest priority layer (2G or 3G) Loss of network service Figure 15.12 Network for the inter-layer mobility design example Minimum requirement for LTE uplink/downlink throughput at LTE800 cell edge is 1 and 4 Mbps, respectively. LTE800 is the lower priority LTE layer with 10 MHz system band- width. Downlink reference signal transmit power is 15 dBm per antenna branch on both layers. The thresholds are designed for the case when neighbour cells' average PDSCH PRB utilization is 20% in uplink and downlink. System supports RSRP- and RSRQ-based inter-frequency and inter-RAT measure- ment events in connected mode. In idle mode Release 9 RSRQ-based reselection is supported. Based on the above minimal set of assumptions, the task is to set the layer exit and entry points for idle and connected mode mobility. SINR Requirements for the Throughput Target Based on the minimum LTE throughput requirement, the SINR requirements are obtained by using a figure similar to Figure 15.7. From purely PUSCH throughput point of view SNR = -7 dB would still satisfy the throughput requirement with 90 PRBs transmission bandwidth. On the other hand as already discussed it should be kept in mind that the values much below SNR -3 dB should be avoided, unless eNodeB receiver performance curves indicate that the uplink control channels can be reliably detected at lower SINR. The downlink SINR requirement can be obtained similarly from Figure 15.7. The result is summarized in Table 15.10 for PUSCH and PDSCH. Layer RSRP Exit Point for Thermal Noise Limited Case It is instructive to first consider performance under thermal noise only, since this gives the best possible performance that cannot be exceeded in realistic interference conditions. If there is Inter-layer Mobility Optimization Tab