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In this technical report we have documented the work that was accomplished by RAN4 as part of the feasibility study on interference rejection receiver for LTE UE. 

Receiver methodologies and structures based on UE interference Rejection (IRC) were defined for interference-aware receivers. This type of receiver attempts to cancel the interference that arises from users operating outside the serving cell, which is also referred to as other-cell interference.

Interference models/profiles were developed for this other-cell interference in terms of the number of interfering cell to consider, and their powers relative to the total other cell interference power, the latter ratios referred to as Dominant Interferer Proportion (DIP) ratios.

For the purposes of this study it was determined that two interfering cells should be taken into account in the interference models. DIP ratios were defined based on two criteria; median values of the corresponding cumulative density functions, weighted average throughput gain.Of these criteria, the one based on the ‘weighted average’ was felt to offer a compromise between the conservative, median value criteria. Throughput estimates were then developed using link level simulations, which included the other-cell interference models plus OCNS models for the serving and interfering cells based on the results of interference modelling. Link level results were developed for a wide range of operating conditions including such factors as transport format, network scenario, modulation, and channel model. 

From the simulation results based on conditional median DIP, approximately 11 -24 % gain for CRS based transmission (serving cell: TM6) and 11-20 % gain for DM-RS based transmission (Serving cell: TM9 single layer) can be obtained by RS-based co-variance matrix estimation scheme in synchronous NW. Lower gain was observed for asynchronous NW from 3 simulations, but no conclusion could be made due to limited inputs. From the simulation results based on weighted DIP, approximately 20-33 % gain for CRS based transmission (serving cell: TM6) and 16-28 % gain for DM-RS based transmission (serving cell: TM9 single layer) could be observed. In addition, a system level study was conducted that indicated that MMSE-IRC receiver provided gains for cell edge user throughput from 5-25%.

With regards to implementation issues, it was felt that MMSE-IRC receiver is based upon known and mature signal processing techniques, and thus, the complexity is minimized. Given all of the above, RAN4 has concluded that throughput gain can be obtained by MMSE-IRC receiver in interference limited system/ condition for LTE/ LTE-Advanced.