Turbo均衡中的符號(hào)方差反饋均衡器
doi: 10.11999/JEIT150825 cstr: 32379.14.JEIT150825
基金項(xiàng)目:
國(guó)家自然科學(xué)基金(61471351)，國(guó)家863計(jì)劃(2009AA 093301)
Symbol-variance Feedback Equalizer for Turbo Equalization
Funds:
The National Natural Science Foundation of China (61471351), The National 863 Program of China (2009AA 093301)
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摘要: 為了降低Turbo均衡中均衡器的復(fù)雜度，該文提出了符號(hào)方差反饋均衡算法(SVFE)。該算法是對(duì)精確的線性最小均方誤差估計(jì)值(LMMSE)進(jìn)行Taylor展開得到的。在該算法中，先利用時(shí)不變均衡器得到初步符號(hào)估計(jì)值，再根據(jù)先驗(yàn)符號(hào)方差對(duì)估計(jì)值加權(quán)，最后進(jìn)行時(shí)不變?yōu)V波得到更佳的符號(hào)估計(jì)值。由于用到了時(shí)變的先驗(yàn)符號(hào)方差信息，其性能更接近精確的LMMSE均衡器。將所提算法用于Proakis C信道下的Turbo均衡處理，和時(shí)不變均衡算法進(jìn)行仿真對(duì)比，所提算法將信噪比損失從0.83 dB降到了0.17 dB，并且仍可通過快速傅里葉變換降低為對(duì)數(shù)復(fù)雜度。
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關(guān)鍵詞:
- Turbo均衡 /
- 軟輸入軟輸出均衡 /
- 最小均方誤差線性均衡器
Abstract: A novel Symbol-Variance Feedback Equalizer (SVEF) algorithm is proposed to reduce the computational complexity of the equalizer in Turbo equalization. The derivation of the algorithm is based on the Taylor expansion of the Linear Minimum Mean Squared Error (LMMSE) estimation function. In the proposed scheme, the initial estimates are obtained from the time-invariant equalizer, then the estimates are weighted by the a priori symbol variances and finally filtered by a time-invariant filter to obtain better estimates. As the time-variant a priori symbol variances are utilized, the performance of the proposed equalizer is much closer to that of the exact MMSE linear equalizer. Simulation results show that the Signal-to-Noise Ratio (SNR) loss of the proposed scheme in Proakis C channel is reduced to 0.17 dB from 0.83 dB compared to the various time-invariant MMSE Turbo equalization, and its computational complexity can be reduced to logarithmical order by implementation based on the fast Fourier transform. -
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