Turbo Modulation Identification Algorithm for OFDM Software-Defined Radios
Turbo Modulation Identification Algorithm for OFDM Software-Defined Radios
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DOI：
10.1109/lcomm.2021.3054590
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发表时间：
2021-05-01
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影响因子：
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通讯作者：
Mostafa, Hala
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文献类型：
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作者：
Marey, Mohamed;Mostafa, Hala
自动调制识别（AMI）问题是正交频分复用（OFDM）软件定义无线电（SDR）系统面临的主要挑战之一。先前报道的这方面的研究仅限于无编码传输；然而，实际系统通常采用纠错码。在这项工作中，我们利用无线通信系统中广泛使用的比特交织编码调制迭代解码 (BICM-ID) 方案的特性，为 OFDM-SDR 系统开发一种新颖的 AMI 算法。由于精确的最大似然（ML）解决方案在实践中很难处理，因此我们采用期望最大化（EM）过程作为统计分析工具。所提出的识别算法以迭代方式工作，其中BICM-ID方案的信道解码器提供的软信息被用作所提出的标识符的先验信息。结果表明，该算法的识别性能通过迭代得到了显着的提高，优于传统的未编码算法。这些有利的结果是通过减少处理时间和对传输损伤（例如时钟定时偏移、频率偏移、多普勒频移和相位噪声）可接受的敏感性来实现的。
The problem of automatic modulation identification (AMI) is one of the main challenges that faces orthogonal frequency division multiplexing (OFDM) software-defined radio (SDR) systems. The previously reported studies of this aspect have limited to uncoded transmission; however, practical systems typically employ error-correcting codes. In this work, we exploit the properties of bit-interleaved coded modulation iterative decoding (BICM-ID) schemes, which are widely used in wireless communications systems, to develop a novel AMI algorithm for OFDM-SDR systems. Since the exact maximum-likelihood (ML) solution is intractable in practice, we resort to an expectation-maximization (EM) procedure as a statistical analysis tool. The proposed identification algorithm works in an iterative fashion, in which the soft information provided by the channel decoder of BICM-ID scheme is utilized as a priori information to the proposed identifier. The results indicate that the identification performance of the proposed algorithm achieves a significant improvement with iterations and outperforms that of the conventional uncoded algorithms. These favorable results are achieved with reduced processing time and acceptable sensitivity to transmission impairments, such as clock timing offset, frequency offset, Doppler shift, and phase noise.