1. Problem Description Primary receiver Secondary receiver eNodeB Aim: Reception of MIMO signals by a secondary receiver Parameterize design of secondary receiver with transmission optimized for primary receiver Detect unknown precoder CLSM relaying (also: act as relay node)

2. Precoder Matrix Detection Goal: Design of receivers for MIMO-OFDM without PMI information at secondary user Approaches + Hypothesis testing Framework Simple ML detection Cluster variance ─ Blind equalization

3. Precoder Detection – Simple ML detector

4. Precoder Detection – Cluster variance

5. BLER vs. SNR – Simple ML vs Cluster variance Carrier frequency = 2110 MHz 1000 subframes, 12 RBs scheduled, MMSE channel estimator, SSD receiver

6. Precoder Detection Summary Simple ML within 2dB of BLER performance vs. known PMI case Simple ML typically outperforms cluster variance, in 2x2 MIMO Performance gap reduced in 4x4 MIMO Additional diversity as each codeword is sent on 2 antennas Computational requirement less than SSD receiver (linear in M, # precoders, constellation size)

7. Ongoing Work Comparing MATLAB LTE System Toolbox with TU Vienna LTE-A simulator MATLAB LTE System Toolbox +Compliant with 3GPP Release 8, 9, 10 +Modular structure, well documented +End-to-end link level simulations, decode over-the-air LTE signals* +Downlink and Uplink channels modelled +User Feedback block implemented ─No inbuilt schedulers for MU-MIMO, no inbuilt Multi-cell scenario 1 ─No SSD receiver Baseband, user mobility modelled only through Doppler shift, etc. TU Vienna (LTE-A) Simulator 2 +Built in MU-MIMO & Multi-cell scenarios +User Feedback implemented +End-to-end link level simulations +Inbuilt schedulers, SSD receiver ─Poor documentation, no working Uplink ?Standard Compliance, accuracy/completeness of existent blocks? * Not real-time 1 Can be coded using the blocks 2 Based on documentation

8. Future Work Consider more elaborate simulations Simulate both Primary and secondary user simultaneously Test the relaying scenario proposed  Vary channel conditions and relative position of receivers Interference from neighboring cells Impact of scheduling multiple users Design improved precoder detectors utilize information from previous subframes