Design Issues and Simulative Validation of Multiuser Turbo-SIC Receiver in LTE: Towards Real-Time Performance Measurements

Multiuser MIMO is a promising technique to increase the available spectrum in next generation 5G wireless networks, especially in enhanced Machine Type Communications (eMTC) for emerging Internet-of-Things (IoT) applications where the large number of users shares the limited band. Significant uplink capacity improvements can be achieved by assigning the same time-frequency resources to several users simultaneously. This requires advanced signal processing at the eNB, named multiuser detection (MUD), to reduce the mutual interference between users and appropriately decode the superposed signals. Turbo-SIC is a very efficient MUD scheme that applies Successive Interference Cancellation (SIC), based on soft outputs of Turbo decoder, prior to the Minimum Mean Square Error (MMSE) detection. However, Hybrid Automatic Repeat Request protocol (HARQ), a retransmission MAC protocol between eNB and UE, imposes the very strict timing requirements for the receiver's processing at the eNB. We use OpenAirInterface (OAI) both to experimentally examine the Turbo-SIC detection performance in LTE system and to evaluate processing requirements for real-time implementation on General Purpose Processor (GPP). We present some initial results and further discuss on design issues and timing requirements for real-time implementation.