A study item for further improved minimum performance requirements for UMTS/HSDPA UE (FDD) was approved at the 3GPP RAN #30 meeting [1]. This technical report summarizes the work that RAN4 has accomplished in this study item to assess the feasibility of both one-branch and two-branch interference cancellation/mitigation UE receivers. These receivers attempt to cancel the interference that arises from users operating outside the serving cell. This type of interference is also referred to as 'other-cell' interference. In past link level evaluations, this type of interference has been modelled as AWGN, and as such can not be cancelled. The study item has developed models for this interference in terms of the number of interfering Node Bs to consider, and their powers relative to the total other cell interference power, the latter ratios referred to as Dominant Interferer Proportion (DIP) ratios. DIP ratios have been defined based on three criteria; median values of the corresponding cumulative density functions, weighted average throughput gain, and field data. In addition, two network scenarios are defined, one based solely on HSDPA traffic (HSDPA-only), and the other based on a mixture of HSDPA and Rel. 99 voice traffic (HSDPA+R99). Interference aware receivers, referred to as type 2i and type 3i, were defined as extensions of the existing type 2 and type 3 receivers, respectively. The basic receiver structure is that of an LMMSE sub-chip level equalizer which takes into account not only the channel response matrix of the serving cell, but also the channel response matrices of the most significant interfering cells. HSDPA throughput estimates are developed using link level simulations, which include the other-cell interference model plus OCNS models for the serving and interfering cells based on the two network scenarios considered. In addition, system level performance is assessed to determine the gains that interference cancellation/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 one-branch and two-branch Interference Cancellation (IC) receivers. The reference receivers for the type 2i and type 3i are defined, both of which are based on LMMSE sub-chip level equalizers with interference-aware capabilities. Clause 5 describes the two 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 IC receivers. The DIP ratio is defined as a key statistical measure, which forms the basis of the three types of interference profiles considered. Clause 7 defines the code and power characteristics of the signals transmitted by the serving and interfering cells for the two network scenarios defined in clause 5. These latter definitions essentially define the signal characteristics of the desired user, the common channels and the OCNS for both serving and interfering cells. Clause 8 summarizes the link level simulation results based on the assumptions developed in clause 6 and clause 7, while clause 9 summarizes the system level performance characterization. Clause 10 discusses the possible receiver implementation losses for a two-branch, sub-chip based LMMSE equalizer with interference aware capabilities. Finally, clause 11 provides the relevant conclusions that can be taken from this study.

The objective of this study is to evaluate the feasibility and potential performance improvements of interference cancellation/mitigation techniques for UTRA FDD UE receivers, based on realistic network scenarios. Scope of the work includes:

• Determine realistic network scenarios.
• Determine suitable interference models for 'other cell' interference.
• Evaluate the feasibility of two-branch interference cancellation receivers through link and system level analysis and simulations.
• Evaluate feasibility of one-branch interference cancellation receivers through link and system level analysis and simulations.