Abstract
The receiver of OFDM with Index Modulation (OFDM-IM) usually adopts a Log Likelihood Ratio (LLR) detection algorithm based on the activation state of subcarriers. However, the LLR detection algorithm will cause detection errors in subcarrier activation pattern (SAP) or get illegal SAP. Consequently, further errors occur in demodulation, increasing the bit error rate (BER). To solve this problem, we propose the protection scheme of subcarrier index aided by LDPC coding, which reduces the SAP detection errors by encoding the index information bits. On the receiver, the LDPC Coding Aided (LA) detection algorithm is designed, and the formula of LLR of index information bits is derived in detail. Monte Carlo simulation is carried out over multi-path fading channel by MATLAB software. The results show that under the condition that the spectrum efficiency is not lower than the classical OFDM-IM scheme, the proposed protection scheme can obtain a gain of about 5~9 dB when the BER is 10-4, effectively improving the BER performance of OFDM-IM scheme.
Highlights
Eb / N0,T 条件下,相比于传统的 OFDM⁃IM 传输方案, LA⁃OFDM⁃IM 的频域符号信噪比 γF 有所降低,这会 引起 SAP 判决正确时符号解调误码增多。 但接收
Protection scheme of subcarrier index in OFDM with index modulation aided by LDPC coding
The receiver of OFDM with Index Modulation ( OFDM⁃IM ) usually adopts a Log Likelihood Ratio ( LLR) detection algorithm based on the activation state of subcarriers
Summary
Eb / N0,T 条件下,相比于传统的 OFDM⁃IM 传输方案, LA⁃OFDM⁃IM 的频域符号信噪比 γF 有所降低,这会 引起 SAP 判决正确时符号解调误码增多。 但接收 图 4 给出了在 k = 2,BPSK 调制时 LA⁃OFDM⁃IM 传输方案和传统 OFDM⁃IM 传输方案的 BER 性能仿 真结果。 LA⁃1 和 LA⁃2 分别表示前者的索引比特和 调制比特,LLR⁃1 和 LLR⁃2 分别表示后者的索引比 特和调制比特。 从图 4 可以看出,在 BER 为 10⁃4时, LA⁃OFDM⁃IM 相比 OFDM⁃IM 索引比特部分可取得 大约 19 dB 的增益。 虽然 LA⁃OFDM⁃IM 传输方案的 γF 有所降低,但是由于 SAP 判决正确率的显著提 升,调制比特部分仍取得 5 dB 的增益。 从整体的误 码率性能来看, LA⁃OFDM⁃IM 传输方案有着 10 dB 左右 的 增 益。 就频谱效率而言, LA⁃OFDM⁃IM 的 0.667 ( bits · s-1 ) / Hz 相 比 OFDM⁃IM 的频谱效率 0.75 ( bits·s-1) / Hz略有损失。
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
