OFDM傳輸中的子帶自適應(yīng)Turbo編碼調(diào)制
Subband Adaptation Employing Turbo Coded Modulation for OFDM Transmissions
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摘要: 為了在無(wú)線數(shù)據(jù)傳輸中獲得更高的頻譜利用率，提出了一種用于正交頻分復(fù)用(OFDM)的基于容量估計(jì)的子帶自適應(yīng)Turbo編碼調(diào)制方法。其目標(biāo)是在恒定發(fā)送功率和目標(biāo)誤碼率(BER)限制下優(yōu)化系統(tǒng)吞吐。仿真表明，在發(fā)端完全信道估計(jì)下，此自適應(yīng)OFDM方法比基于固定門(mén)限的自適應(yīng)Turbo編碼調(diào)制有2.5-5 dB的信噪比(SNR)增益。然而，時(shí)變信道中反饋信息的延時(shí)會(huì)帶來(lái)自適應(yīng)性能的惡化。文中接著通過(guò)研究表明，在子帶自適應(yīng)編碼調(diào)制中，減少選取子帶的個(gè)數(shù)，充分利用OFDM頻域上的分集特性是一種可以降低信道時(shí)變帶來(lái)性能惡化的有效途徑。
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關(guān)鍵詞:
- 自適應(yīng)OFDM; Turbo編碼調(diào)制; 子帶
Abstract: To improve the spectral efficiency for wireless data transmissions, a subband-by-subband adaptive turbo coded modulation scheme based on capacity evaluation is proposed for Orthogonal Frequency Division Multiplexing (OFDM). The target is to optimize the overall throughput under constant transmit power and target Bit-Error-Rate (BER). Sim-ulation results show that the adaptive OFDM scheme exhibits a 2.5~5 dB Signal to Noise Ratio (SNR) gain relative to fixed threshold adaptive turbo coded modulation when the transmitter knows the perfect channel information. However, the adaptation performance is degraded due to the feedback delay in time-varying channels. Then, the investigation indicates that decreasing the amounts of subbands, and utilizing the diversity characteristic adequately in frequency domain of OFDM is an effective approach to reduce the performance degradation. -
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