Performance of downlink control information signals using decision-feedback channel estimation for EPDCCH

In the Release (Rel.) 11 Long Term Evolution (LTE)-Advanced radio interface, the Enhanced Physical Downlink Control Channel (EPDCCH) is specified, which transmits downlink control information (DCI) signals. The EPDCCH is frequency-domain-multiplexed with data symbols and is used to transmit more DCI signals than the Physical Downlink Control Channel (PDCCH) for Rel. 8 LTE due to the application of multiuser multiple-input multiple-output (MIMO) and coordinated multi-point (CoMP) transmission and reception. This paper presents the effect of decision-feedback channel estimation (DFCE) using soft-symbol estimation of the DCI signals for the EPDCCH. We propose a DFCE method that improves the channel estimation accuracy by using soft-symbol estimation of the control signals based on the a posteriori log-likelihood ratio (LLR) at the soft output Viterbi algorithm (SOVA) for convolutional coding in addition to the demodulation reference signals (DM-RSs). Computer simulation results show that the DFCE is effective in decreasing the transmission power of the DM-RSs to approximately half compared to that for only conventional DM-RSs to achieve the same target block error rate from a low to high Doppler frequency region in a frequency-selective Rayleigh fading channel.