priority layer if RSRP is used to control cell reselection, resulting in ping-pong. Hence in practice it is easiest to resort to a single trigger quantity, either RSRP or RSRQ. Essentially this means that the mobility should by default be based either on downlink throughput (RSRQ) or uplink throughput (RSRP combined with assumed uplink noise rise), unless some vendor-specific algorithms are available. Threshold Settings Tables 15.11, 15.12 and 15.13 provide the parameter settings for the example. The example design can be summarized as Layer exit point is RSRP < -112 dBm. Layer entry point is RSRP > -109 dBm. Hysteresis values are 3 dB with ping-pong controlled by timers. Inter-layer Mobility Optimization Table 15.11 Idle mode mobility thresholds for LTE layers Idle mode parameter Value Comment qRxLevMin -120 dBm Both layers threshServingLow,P -112dBm LTE1800/LTE800 exit point in idle mode, broadcast on SIB3 threshX,low,P -109 dBm LTE800 entry point, broadcast on LTE1800 SIB5 threshX,high,P -109 dBm LTE1800 entry point, broadcast on LTE800 SIB5 Treselection 5 seconds Long inter-layer reselection timer to avoid ping-pong due to 3 dB hysteresis, intra-layer reselection timer can be shorter Table 15.12 Connected mode inter-layer mobility thresholds for the LTE1800 layer Idle mode parameter Value Comment A5Threshold1 -112 dBm Serving cell RSRP must be below this value. The same value as threshServingLow,P A5Threshold2 -109 dBm LTE800 entry point, minimum required level from LTE800 to trigger handover. The same value as threshX,low,P A2Threshold -112 dBm Serving cell RSRP to activate measurement gaps A1Threshold -109 dBm Serving cell RSRP to deactivate measurement gaps The values are based on uplink SINR target of -7 dB and 3 dB uplink noise rise which could be considered an optimistic assumption for a non-optimized network. A safety margin of 2-4 dB could be added. The UMTS900 settings in exit and entry direction have been omitted for brevity, but they should be based on minimal service requirements to avoid UE endin