Inter-Code Interference Canceller for Control Signals Using Cyclic Shift CDMA in LTE Uplink

This paper proposes an inter-code interference canceller (ICIC) for control signals carried by the Physical Uplink Control Channel (PUCCH) in the Long-Term Evolution (LTE) uplink using Discrete Fourier Transform (DFT)-precoded Orthogonal Frequency Division Multiple Access (OFDMA). In the proposed ICIC, a soft interference replica of another cyclic-shifted code channel for data symbols is generated from the log-likelihood ratio (LLR) of a posteriori probability (APP) in Max-Log-MAP and a complex fading envelope estimated using reference signals (RSs), and subtracted from the received signal iteratively. We also propose RS multiplexing employing a combination of block spread (BS) and cyclic shift (CS) for two RS symbols within a slot to achieve accurate channel estimation. Computer simulation results show that the proposed ICIC associated with RS multiplexing using a combination of BS and CS is effective in reducing the required average received signal-to-noise power ratio (SNR) even for 12 PUCCH multiplexing in frequency-selective fading channel with long delay spread.