Inter-cell interference is the most interesting aspect in the LTE radio interface regarding radio quality and throughput of specific connections between the UE and network.
As in 3G UMTS, neighbor cells in LTE operate on the same frequency in UL and DL. So, the DL signals of all cells received at a certain geographic position interfere with each other in 3G UMTS, while on the UL each UE is an interferer to all other mobiles within a certain geographic
area. This is a limitation of CDMA techniques that cannot be challenged in general.
In LTE, thanks to Frequency Division Multiple Access, techniques are now being introduced that provide mechanisms to avoid inter-cell interference. Simply explained, in LTE the base station (eNB) with very high periodicity collects information about the current interference
situation in each cell.
Knowing which particular subcarriers of the available range are currently impacted by interference, the scheduler can assign only interference-free subcarriers to active connections .
A rescheduling of assigned resources is executed with a periodicity of 1ms. In other words, within 1 second the subcarriers used for a particular connection can change up to 1000 times.