e other hand, the dynamic operation allows to ensure service quality with 1 ms resolution with the use of licensed spectrum should the unlicensed spectrum become unusable due to any reason, such as smaller coverage, interference from another systems or avoidance, for example, of a radar operating in the band. The use of carrier aggregation allows automated and extremely dynamic selection between licensed and unlicensed bands for data, thus allowing the network to always provide sufficient service quality for the end user. Based on the studies conducted, the LTE technology can meet the regulatory requirements for the unlicensed band and allow the coexistence with the other LTE systems as well as other technologies, such as Wi-Fi, operating on the same frequency band. 10.5 Key Requirements for 5 GHz Band Coexistence The requirement for LBT has clear impact on the necessary changes to adapt LTE to be used on the unlicensed band. These changes will not only facilitate coexistence with Wi-Fi but also allow coexistence with other LTE networks operating on the same band. The requirement for LBT means that the current principle in use for licensed band operation (from the eNodeB) of continuously transmitting every 1 ms cannot be applied. In line with the regulation there is the requirement to listen for the channel and if a channel is detected busy then not to transmit. Also if the channel is determined to be free (the detected energy LTE Unlicensed CCA detects channel is free Load-based operation Distance between regular short control signalling transmissions Continuosly monitor CCA operation the channel CCA detects channel Maximum channel occupancy time is busy CCA detects Frame-based operation channel is free Fixed frame period Idle period with CCA Channel occupancy time Figure 10.3 Load-based and frame-based operation principles level is below threshold) one cannot continue transmitting forever but there is a maximum channel occupancy time after which one has to listen. This can be done either with a frame- based ope