A study item for minimum performance requirements for interference Mitigation of Cell-specific Reference signals
(CRS-IM) for LTE/LTE-Advanced (FDD/ TDD) homogeneous network was approved at the 3GPP RAN #59 meeting.
This technical report summarizes the work that RAN4 has accomplished in this study item to assess the feasibility
of CRS-IM UE receivers for Homogenous deployment. These receivers attempt to mitigate the CRS interference that
arises from users operating outside the serving cell. CRS-IM has been studied in the Rel-11 Work Item on FeICIC. Due
to its benefits under the condition where interference from CRS dominates but is negligible from data assuming data RE
muting, the CRS-IM has been standardized under the above operation conditions for heterogeneous deployments and
the corresponding requirements were specified in Release 11. At the same time, the enhanced performance requirement
in homogeneous network deployment for MMSE interference rejection combining (MMSE-IRC) receiver were
extensively studied and specified in Release 11.
The MMSE-IRC receiver can suppress both data and CRS interference
without the need to differentiate them. However, the UE performance in homogenous deployment may be further
improved by using the same CRS-IM capability as defined for FeICIC, especially when similar interference conditions
arise under low traffic loading of neighbouring cells and under similar scope as in FeICIC i.e. synchronous network
operation and UE reference receiver assuming single FFT processing. In past link level evaluations, this type of
interference has been modelled as almost blank subframe, as defined in FeICIC WI, or full traffic, as defined in
MMSE-IRC receiver. The study item has developed models for this interference in terms of their powers relative to the total
other cell interference power, and their resource allocation according to traffic loading levels. Some of these previously
identified scenarios studied in Release 11 for specifying MMSE-IRC receiver performance requirements and the
corresponding link/system parameters are reused.
The baseline detector structure is that of an MMSE-IRC detector as defined in 3GPP TR 36.829 combined with a CRS-IM receiver.
The same CRS-IM receiver defined for FeICIC is reused here. LTE throughput estimates are developed using link level
simulations. In addition, system level performance is assessed to determine the gains that interference mitigation
receiver might provide in throughput and coverage. Complexity issues associated with implementing these types of
receivers are also discussed. The content of each specific clause of the report is briefly described as follows.
Clause 1 of this document defines the scope and objectives of this feasibility study.
Clause 4 describes the receiver methods that can be applied to CRS-IM receivers.
Clause 5 describes the network scenarios that were defined and used to generate the interference statistics, which were
then used to develop the interference models described in clause 6.
Clause 6 defines the interference models/profiles that were developed in order to assess the link level performance of