Orthogonal frequency-division multiplexing (OFDM) has been selected as the basis for the fifth-generation new radio (5G-NR) waveform developments. However, effective signal processing tools are needed for enhancing the OFDM spectrum in various advanced transmission scenarios. In earlier work, we have shown that fast-convolution (FC) processing is a very flexible and efficient tool for filtered-OFDM signal generation and receiver-side subband filtering, e.g., for the mixed-numerology scenarios of the 5G-NR. FC filtering approximates linear convolution through effective fast Fourier transform (FFT)-based circular convolutions using partly overlapping processing blocks. However, with the continuous overlap-and-save and overlap-and-add processing models with fixed block-size and fixed overlap, the FC-processing blocks cannot be aligned with all OFDM symbols of a transmission frame. Furthermore, 5G-NR numerology does not allow to use transform lengths shorter than 128 because this would lead to non-integer cyclic prefix (CP) lengths. In this article, we present new FC-processing schemes which solve the mentioned limitations. These schemes are based on dynamically adjusting the overlap periods and extrapolating the CP samples, which make it possible to align the FC blocks with each OFDM symbol, even in case of variable CP lengths. This reduces complexity and latency, e.g., in mini-slot transmissions and, as an example, allows to use 16-point transforms in case of a 12-subcarrier-wide subband allocation, greatly reducing the implementation complexity. On the receiver side, the proposed scheme makes it possible to effectively combine cascaded inverse and forward FFT units in FC-filtered OFDM processing. Transform decomposition is used to simplify these computations. Very extensive set of numerical results is also provided, in terms of radio-link performance and associated processing complexity.
Secure OFDM Waveform Design for ISAC: Artificial Phase-Doppler Shifts Against Passive Sensing
Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；Nokia Bell Labs Stuttgart（诺基亚贝尔实验室斯图加特）；Hensoldt Sensors GmbH（亨索尔特传感器有限公司）；Technical University of Munich（慕尼黑工业大学）
DBU-OFDM: A Trainable Deep Block-Unitary OFDM Waveform for Integrated Sensing and Communication
State Key Laboratory of Novel Software Technology, Nanjing University（南京大学新型软件技术国家重点实验室）；School of Information and Communication Engineering, University of Electronic Science and Technology of China（电子科技大学信息与通信工程学院）；National Mobile Communications Research Laboratory, School of Information Science and Engineering, Southeast University（东南大学信息科学与工程学院移动通信国家重点实验室）；Purple Mountain Laboratories（紫金山实验室）
Movable-Antenna-Empowered ISAC: 3D Ambiguity Function Analysis, Waveform Design and Antenna Position Optimization
Beijing Institute of Technology（北京理工大学）；School of Information and Electronic Engineering, Beijing University of Posts and Telecommunications（北京邮电大学信息工程学院）
University of Southampton（南安普顿大学）；InterDigital；Indian Institute of Technology Jodhpur（印度理工学院乔德普尔分校）；Indian Institute of Technology, Kanpur（印度理工学院坎普尔分校）
PAPR-Aware Waveform Design for Energy-Efficient MIMO-OFDM SWIPT
National Key Laboratory of Wireless Communications, University of Electronic Science and Technology of China（电子科技大学无线通信国家重点实验室）；School of Information Science and Technology, Southwest Jiaotong University（西南交通大学信息科学与技术学院）；Department of Electronic and Electrical Engineering, University College London（伦敦大学学院电子电气工程系）；Department of Electronic Engineering, Kyung Hee University（庆熙大学电子工程系）
Mobile Communications Beyond 52.6 GHz: Waveforms, Numerology, and Phase Noise Challenge
在本文中，提供了5G新无线电（NR）物理层演进以支持超过52.6GHz通信的首要考虑因素。此外，基于OFDM和DFT-s-OFDM的网络的性能进行了评估，特别强调相位噪声（PN）引起的失真。结果表明，DFT-s-OFDM在5G NR Release 15假设下对PN更具鲁棒性，即关于支持的相位跟踪参考信号（PTRS）设计，因为它直接在时域中实现了更有效的PN缓解。为了进一步提高PN补偿能力，修改了用于DFT-s-OFDM的PTRS设计，而对于OFDM波形，引入了新的块PTRS结构，提供了与具有增强PTRS设计的DFT-s-OFDM相似的链路性能。我们证明，现有的5G NR Release 15解决方案可以扩展到支持具有增强PTRS结构的60 GHz载波频率的高效移动通信。此外，对于超过52.6GHz的通信，可以考虑用于用户数据的基于DFT-s-OFDM的下行链路，以利用更高阶的调制和编码方案来进一步提高系统功率效率和性能。最后，提供了网络链路预算和小区大小考虑，表明在具有特定发射功率调节的某些频带处，小区大小最终可以是下行链路受限的。
Delay-Doppler Domain Signal Processing Aided OFDM (DD-a-OFDM) for 6G and Beyond
Beijing Jiaotong University（北京交通大学）；University of New South Wales（新南威尔士大学）；Technical University of Berlin（柏林工业大学）；Queensland University of Technology（昆士兰科技大学）；Southern University of Science and Technology（南方科技大学）；Xi’an Jiaotong University（西安交通大学）；Southeast University（东南大学）
