The number of subscribers is growing rapidly, creating new demands for higher capacity. Several techniques are commonly used, such as cell splitting, and heterogeneous network deployment, etc. However, there are 2 factors that would limit the capacity that can be achieved by these techniques. Firstly, a lot of new cell edges would be created. Strong co-channel interference from the neighbour cells would degrade the downlink performance of cell edges UEs significantly. Secondly, many lightly loaded cells, or even unused cells, would be created. Because it is impractical to accurately deploy every cell right at the hotspot centre, some cells will inevitably be lightly loaded, while some will be heavily loaded. The potential of IC capable UE has been observed during the heterogeneous network work item. Pre-decoding IC, post-decoding IC, and MMSE based IS (type3i) UE have been studied. According to link simulation results, significant gain of an IC capable UE over non-IC UE can be observed near the cell edge, especially when the UE suffers strong co-channel interference. However, it is also observed that although UE can perform IC alone without network involvement, the CSI reporting is unstable due to the interference variation. In addition, it is not clear how the network would identify the UE with IC capability so that the network can be further benefited from the IC capable UEs. Furthermore, there may be potential solutions that can improve UE's IC performance, or reduce UE's IC implementation complexity. As a result, further study is necessary to explore the potential of the IC capable UEs with network assistance. This study item is to investigate how network involvement can assist the performance of ICS capable UE, as well as system capacity. Both intra-Node B and inter-Node B are to be considered, assuming ideal backhaul and non-ideal backhaul. With enhanced network signalling, better cell edge UE's performance should be achieved. With enhanced cell offloading techniques for ICS capable UE, the originally lightly loaded cells would be able to serve more UEs, increasing the overall system capacity.

The study on network-assisted interference cancellation and suppression for UMTS has as a target to investigate the potential solutions in the areas of mechanisms for offloading, CQI mismatch issue, and signaling of parameters for UEs with NAICS capability and enhanced techniques , including considerations to minimize the impact on physical layer and legacy terminals and networks. [2].

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

• References are either specific (identified by date of publication, edition number, version number, etc.) or non specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.

The objectives of the study item are the following:

• Identify the scenarios of interest and simulation assumptions for network assisted interference cancellation and suppression (NAICS). Both homogeneous and heterogeneous networks should be considered (RAN1):
  • The scenarios of interest should consider co-channel intra-Node B and inter-Node B interference conditions.
  • Both non-MIMO interference and MIMO interference should be considered.
• Identify the UE receiver types with interference awareness that can be beneficial in the identified scenarios. Both interference cancellation (IC) receiver and interference suppression (IS) receivers, e.g., type 3i receiver, should be considered (RAN1).
• Investigate the potential NAICS solutions to benefit the receivers with interference awareness:
  • Identify the parameters to support UE with NAICS capability, for example semi-static/dynamic, cell-specific/UE-specific parameters. The trade-off between gains, and additional overhead and implementation complexity, should be studied (RAN1, RAN2).
  • Study mechanisms for offloading UEs with NAICS capability (RAN1, RAN2).
  • Study solutions to resolve the CSI mismatch issue for UEs with NAICS capability, e.g., enhanced UE feedback reporting techniques (RAN1).

The study shall include considerations to minimize the impact on physical layer and legacy terminals and networks.