What Interference Rejection Combining in LTE
The concept of Interference Rejection Combining (IRC) is to regenerate the transmitted signal based on the estimated data from the previous receptions, emulate the distortion occurring from the multi-path channels and, finally subtract all regenerated interfering signals from the uplink received signals to obtain more reliable estimation of original users’ data.
This feature utilizes the spatial separation and characteristics of inter-cell interference to determine the power of the interfering UE which belongs to another cell. Once the pattern and power level is determined, the victim cell can then remove the interferer from the received signals.
In comparison, Maximum ratio combining (MRC) do not make use of the spatial characteristics of the interference when calculating antenna weighting. So in cases where there are only a small number of dominating interfering sources, IRC can provide more improvement than MRC especially when there are a reasonable number of receive antennae for IRC to execute the compensation.
Conversely, if there are a large number of equal power signals arriving at the receive antennae, the gain of Interference Rejection Combining over Maximum ratio combining is not as significant.
Interference Rejection Combining is implemented in the baseband processing module of NodeB. It can reduce the interference impact of the neighboring users in the uplink. Therefore, Interference Rejection Combining can increase the uplink users’ throughput significantly and hence improves the users’ experience.
When Uplink Interference Rejection Combining is used, simulation has shown a maximum SINR gain of 7dB can be achieved over traditional MMSE interference reduction method. By outperforming Maximum Ratio Combining and MMSE receivers, Interference Rejection Combining can enhance network coverage and provide better QoS for cell edge users.