An improved blind selected mapping with decoding complexity reduction for orthogonal frequency division multiplexing system

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Date
2019-05-01
Authors
Adnan Haider Yusef Sa’d
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SLM is a well-known peak-to-average power ratio (PAPR) reduction technique that is capable of effectively reducing the system’s PAPR without distorting the signal. However, SLM causes a data rate loss issue due to the necessity for sending the selected iteration index to the receiver as side-information. To solve this issue, many blind SLM (BSLM) methods have been proposed in the literature. Such BSLM methods embed side-information in either pilot or data signals using phase or energy disparity forms. Hence, the receiver can blindly decode the signals using a maximum likelihood (ML) decoder. In this research, different data-based BSLM schemes with very low decoding complexity are proposed for both QAM and PSK modulation. The proposed BSLM schemes are broken down into three main stages for different system parameters (𝑞, 𝑁, and 𝑈). The first stage is addressed by introducing the concept of the maximum likelihood with prior knowledge (MLPK). Then, new optimized property based MLPK decoders are derived for PSK and QAM modulations where the BSLM decoding complexity is reduced by (𝑞−1)/𝑞 |∙|2 operations. The next proposed approaches (SNR-independent and SNR-dependent methods) address the problem concerning the large number of subcarriers for two scenarios of SNR information availability of the received signal. The performance of the decoding complexity reduction ratio (DCRR) is fixed for the SNR-independent method. However, it varies based on the SNR information for the SNR-dependent method, and hence, the SNR-dependent method can achieve the maximum DCRR of (𝑁−𝐿)/𝑁 AN IMPROVED BLIND SELECTED MAPPING WITH DECODING COMPLEXITY REDUCTION FOR ORTHOGONAL FREQUENCY DIVISION MULTIPLEXING SYSTEM at high SNR values. The complexity of the last stage is addressed using a biorthogonal-hybrid SI estimation process. All proposed complexity reduction methods pertaining to either 𝑞 or 𝑁 system parameter reduce the BSLM decoding complexity significantly. However, the final BSLM designs using a combination of all proposed methods achieve a very significant DCRR over the conventional BSLM. The joint implementation of the SNR-dependent method with the enhanced property-based MLPK decoder, for instance, achieved a DCRR of 99.6% over the conventional BSLM at SNR per bit of 11 dB(AWGN) and 22 dB(Rayleigh) for 𝑁=512, 𝑞=4, and 𝑈=16. Finally, a new simple binary-based phase de-rotation process is proposed to eliminate the symbol demodulation process that is due after the SI decoding process. Hence, the proposed BSLM receiver designs have lower complexity even compared to the conventional SLM at high SNR values.
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