g out of network service completely. The level thresholds summarized in Table 15.11 could be considered relatively high, but it should be remembered that the design was based on throughput targets of 8 and 2 Mbps for 20 MHz downlink and uplink, respectively. One could allow lower thresholds to be used if the throughput target was reduced or the thresholds were instead designed for voice service with certain voice quality target. Alternatively it can be imagined that a certain target probability of call drop is used as the design criterion which would again result in different threshold settings. The connected mode parameters implement the same exit and entry points as in idle mode. The event reporting parameters (time to trigger, reporting interval, reporting amount, etc.) are omitted. Table 15.13 Connected mode inter-layer mobility thresholds for the LTE800 layer Idle mode parameter Value Comment A4Threshold -109 dBm LTE1800 entry point. The same as threshX,high,P LTE Small Cell Optimization Moving to a higher priority layer in connected mode corresponds to the A4 measurement event. With the LTE800, the problem is when to trigger measurement gaps. Since the path loss difference to LTE1800 based on frequency difference is about 7 dB - neglecting modifiers from differences in penetration loss, antenna system gains and SO on - there is a risk of having measurement gaps active for long periods of time without finding any suitable target cell on LTE1800. The A1 event could be used to trigger gaps if the level of the LTE800 serving cell is better than some threshold, indicating that the probability of finding a suitable target cell satisfying A4 is high. Utilizing 80-ms gaps minimizes throughput degradation at the expense of slowing down the measurement process. The measurement gap active time could also be limited by the system if the A4 event is not triggered within a certain time, to avoid having gaps active when there is no higher priority layer coverage available in the first place. 15.4.4 Inter-layer Mobility Ex