Single Antenna. Of Lte Downlink Papr Suppression And Snr Estimation Technology Research

As an optional project of next generation wireless and personal mobile communication system, long term evolution (LTE) adopts many new technologies, such as OFDM and AMC etc. Orthogonal frequency division multiplexing (OFDM) has recently been applied widely for its robustness to multi-path delay and easy equalization. OFDM has high peak-to-average power ratio (PAPR) problem for the adding of multicarriers.Adaptive modulation and coding (AMC) is a high bandwidth efficient technology by adaptively changing the transmit power, modulation pattern and coding rate according to the channel state. But signal to noise ratio (SNR) estimation is needed because the SNR was demanded for the adaptive modulation and coding. Hence, in this paper, we present some research work in PAPR reduction and SNR estimation for LTE downlink transmission with one antenna port.Five typies simulation scenes were derived by analyzing the frame structure of LTE downlink transmission for PAPR reduction. An EVM sorting clipping algorithm with error vector magnitude (EVM) constraints was proposed. Then improved EVM sorting clipping algorithms, iterative EVM sorting algorithm and EVM sorting RCF algorithm were developed.For LTE downlink transmission with 20M transmission bandwidth: For OFDM symbols only with QPSK modulation sheme, the simultaneous PAPR can be reduced to 6.14 dB while the complementary cumulative distribution function (CCDF) value is 10?4 ; For OFDM symbols with QPSK, 16QAM, 64QAM (with proportion 1/2, 1/4, 1/4)and reference signals, the simultaneous PAPR can be reduced to 7.26 dB, while the system requirement is 7.5dB; The improved algorithms were smooth in every simulation scenes, so there is no possibility to increase abruptly, which is good for amplifier's protection; PAPR reduction gain was proportional to the EVM lossness. For LTE downlink transmission, the SNR estimation was transformed to channel and noise power estimation according to requirement for channel and noise power estimation in LTE downlink transmission. Then the SNR estimation method was got by correcting signal and noise power.Simulation shows that for the proposed SNR estimation method while the true SNR is bigger than 2 dB over 80% statistical points whose difference between true SNR and estimate SNR was within 2 dB, over 90% statistical points whose difference between true SNR and estimate SNR was within 3 dB; The proposed method was robust to Doppler frequency which means that the difference between SNR estimation with different Doppler frequency was within 10%.The research results of PAPR reduction and SNR estimation for LTE downlink transmission with one antenna port can be applied in multi-antenna ports'case, and other systems which adopt OFDM and AMC technology(for example, WiMAX system). So the research result are of great theoretical importance and economic value.