This was introduced in release 10 and is part of the heterogeneous network (HetNet) approach, where macro cells are complemented with pico cells inside their coverage area (hotspots in shopping centers, at airports, etc.). While the macro cells emit long range high power signals, the pico cells only emit a low power signal over short distances. To mitigate interference between a macro cell and several pico cells in its coverage area, eICIC coordinates the blanking of subframes in the time domain in the macro cell. In other words, there is no interference in those subframes from the macro cell so data transmissions can be much faster. When several pico cells are used in the coverage area of a single macro cell overall system capacity is increased as each pico cells can use the empty subframes without interference from the other pico cells. The downside is of course that the macro cell capacity is diminished as it can't use all subframes. Therefore, methods have to be put in place to quickly increase or decrease the number of subframes that are assigned for exclusive use of in pico areas when traffic patterns change.
