Inter Cell Interference Coordination (ICIC/eICIC)

The term ICIC stands for Inter Cell Interference Coordination, it is a type of technology which is designed to reduce the interference created by two or more cells.

 

Under following situation a UE suffers more seriously from the interference,

  • Case 1: UE is in cell boundary of a cell. In this case, the signal from neighbour cell can act as interferer. In this case, signal strength from serving cell tends to be very weak and at the same time SNR would be very poor not only because of the weak serving cell signal but also because of the interference.

  • Case 2: UE is under coverage of a femto or pico cell. In this case, the Macro cells around those pico/femto cells or other pico/femto cell can act as interferer. In this case, the signal strength from serving cell may not be such a weak, but SNR tend to be poorer due to the interference.

  • Case 3: UE is located close to a CSG cell, but it is not the CSG member of that cell. In this case, the signal from the CSG cell act as very strong (sometimes stronger than the serving cell itself) and can be very problematic (This is why 3GPP take CSG as an important criteria for ICIC/eICIC implementation).

To overcome the above problems, ICIC has been introduced in 3GPP release 8.

ICIC (Inter Cell Interference Coordination)

  • This has been introduced in LTE 3GPP release 8.

  • ICIC is introduced to deal with interference issues at cell-edge.

  • ICIC reduces interference on traffic channels only.

  • ICIC uses power and frequency domain to mitigate cell-edge interference from neighbor cells.

  • In LTE ICIC, power of the few sub channels is lowered which results into their reception only near to the base station. Hence there would not be any interference to nearby base station transmissions.

  • X2 interface is used to share the information between the eNodeB’s.

eICIC (Enhanced Inter Cell Interference Coordination)

  • eICIC introduced in 3GPP release 10

  • eICIC introduced to deal interference issues in Heterogeneous Networks

  • eICIC reduces the severity of interference on traffic and control channels

  • eICIC uses power, frequency and time domain to mitigate intra-frequency interference in heterogeneous networks

  • eICIC introduces concept of "Almost blank sub-frame" (ABS) which do not send any traffic channels and are mostly control channel frames with very low power. If macro cell configure ABS sub-frames then UEs connected to pico/femto cells can send their data during such ABS frames and avoid interference from macro cell.

  • ABS configuration is shared via OAM or x2 interface. The configuration of blank subframe in LTE frame structure is transmitted over X2 interface by pico cell and using OAM by femto cell under closed subscriber group(CSG) environment.