With the wider usage of mobile applications like social networking and point-to-point video/file sharing, uplink traffic load is becoming much heavier, and LTE uplink spectral efficiency improvement tends to be an essential and practical requirement for operators. In typical LTE homogenous network, frequency reuse factor of one is utilized, and inter-cell interference has a substantial impact on uplink performance. For heterogeneous network with co-channel deployment of macro and low power base stations (BSs), the interference is even stronger due to a large number of low power BSs deployed. In both cases, BS MMSE-IRC (Minimum mean square error - interference rejection combining) receiver is considered as a promising approach for spatial domain interference handling. The MMSE-IRC receiver can suppress inter-cell interference as well as intra-cell interference, and thus achieve cell-edge and cell-average spectral efficiency gain over MMSE receiver. Moreover, the implementation complexity increase is moderate, since this kind of baseband processing technique is relatively mature nowadays. To verify BS receiver's ability of inter-cell interference suppression, a new work item on "Performance requirements of MMSE-IRC receiver for LTE BS" was approved at RAN #66 [2], and the present document summarizes the work done under this work item.

The present document should fulfil the following objectives:

• Phase I:
  • Identify target deployment scenarios and agree on relevant network parameters. Both homogeneous deployment (macro cell only) and heterogeneous deployment (co-channel between macro cell and low power node) should be considered.
  • Conduct system-level simulation to determine the inter-cell interference modelling methodology and other side conditions needed for link-level simulation, and link-level simulation to evaluate gain of MMSE-IRC over baseline receiver (MMSE receiver)
• Phase II:
  • LTE BS MMSE-IRC receiver is assumed as the reference receiver structure for specifying the requirements.
    • Demodulation RS based MMSE-IRC receiver can be considered as baseline, and practical and realizable implementation should be taken into account.
  • Specify the enhanced demodulation performance requirements for verification of BS receiver's ability on inter-cell interference suppression.
    • For PUSCH, specify enhanced demodulation performance requirements based on the reference receiver.
    • For PUCCH, with lower priority, determine whether to specify enhanced demodulation performance requirements based on the reference receiver.
  • Specify the enhanced conformance test requirements.