Licensed Assisted Access (LAA) is one of the option to use LTE technology over unlicensed spectrum. There are various methods exist to use LTE and WiFi together. In case of LAA, eNodeB will use WiFi as another channel for carrier aggregation. Usually in carrier aggregation, channels from the licensed spectrum are aggregated to create fatter pipe of radio interface with UE to increase throughput. LAA is also another form of carrier aggregation, in which some channels would be from unlicensed bands.
Since unlicensed band can be used any other user in the proximity of LTE cell, LAA method uses dynamic channel selection (to find the least used sub-band) and Listen before talk (to avoid trampling of other uses).
To enable this technology, hardware changes are required at eNodeB and UE both side assuming eNodeB and UE both supports carrier aggregation.