VTC 2025 Spring Conference’s Shorts

Low Complexity Detection for Generalized Filter Bank Orthogonal Frequency Division Multipl...

The space-terrestrial integrated network (STIN) is one of the key development directions for future network architectures, offering global seamless connectivity, efficient resource utilization, and enhanced service reliability. Recently, the generalized filter bank orthogonal frequency division multiplexing (GFB-OFDM) has been proposed for the STIN system, which enables a flexible waveform mechanism for both terrestrial and non-terrestrial systems. However, research on GFB-OFDM detector remains scarce. In this paper, we model the symbol detection problem and introduce the linear detector and the non-linear detector into the GFB-OFDM system. Furthermore, based on the traditional expectation propagation (EP) algorithm, we propose a low-complexity eigenvalue approximation-based EP detector for the GFB-OFDM system, which achieves a lower complexity compared with the existing EP-like detector. Finally, the better error performance and the lower computational complexity of the proposed receiver are validated by the numerical results.Low Complexity Detection for Generalized Filter Bank Orthogonal Frequency Division MultiplexingYaxing Hao, Professor Fanggang Wang, Ziheng Xiao, Xin Nie, Beijing Jiaotong University; Yu Xin, Jian Hua, ZTE Corporation

A Novel GAMP-based Receiver for Nonlinearly Distorded Precoded OFDM Signals

We address the post-compensation of nonlinear distortion in precoded orthogonal frequency division multiplexing signals caused by power amplifier impairments. An iterative message-passing receiver is proposed, using generalized approximate message passing to perform OFDM demodulation and nonlinearity compensation, while deriving new messages towards the equalizer to establish a turbo-equalization scheme. Additionally, the complex integral required for GAMP is simplified, reducing it to a one-dimensional integral that can be computed numerically. The proposed receiver significantly outperforms previous GAMP-based distortion compensation techniques.A Novel GAMP-based Receiver for Nonlinearly Distorded Precoded OFDM SignalsHugo Parmentier, Centrale-Supelec; Frederic Lehmann, Telecom SudParis; BERTHET Antoine O., CentraleSupélec, Université Paris-Saclay

A New Delay-Doppler-Based Pilot Scheme for OFDM Systems

The orthogonal frequency division multiplexing (OFDM) waveform presents some limitations in time-varying channels, experienced e.g., in high-mobility environment. In this paper, we introduce a new channel estimation approach to enhance OFDM system performance in high-Doppler channels. This novel approach consists in inserting a pilot in the delay-Doppler domain, without puncturing the data in the frequency-time domain. Therefore, it avoids pilot overhead when the channel is very selective. Simulation results show that the proposed method outperforms the standard techniques by achieving a higher data throughput in high-mobility scenarios.A New Delay-Doppler-Based Pilot Scheme for OFDM SystemsYaya Bello, Vincent Corlay, Cristina Ciochina, Mitsubishi Electric R&D Centre Europe

RIS-Aided Integrated Sensing and Communication Waveform Design With Tunable PAPR

Low peak-to-average power ratio (PAPR) transmission is an important and favorable requirement prevalent in radar and communication systems, especially in transmission links integrated with high power amplifiers. Meanwhile, motivated by the advantages of reconfigurable intelligent surface (RIS) in mitigating multi-user interference (MUI) to enhance the communication rate, this paper investigates the design problem of joint waveform and passive beamforming with PAPR constraint for integrated sensing and communication (ISAC) systems, where RIS is deployed for downlink communication. We first construct a trade-off optimization problem for the MUI and beampattern similarity under PAPR constraint. Then, in order to solve this multivariate problem, an iterative optimization algorithm based on alternating direction method of multipliers (ADMM) and manifold optimization is proposed. Finally, the simulation results show that the designed waveforms can well satisfy the PAPR requirement of the ISAC systems and achieve a trade-off between radar and communication performance. Under high signal-to-noise ratio (SNR) conditions, compared to systems without RIS, RIS-aided ISAC systems have a performance improvement of about 50% in communication rate and at least 1 dB in beampatterning error.RIS-Aided Integrated Sensing and Communication Waveform Design With Tunable PAPRJinlong Wu, Lixin Li, Wensheng Lin, Wei Liang, Decan Zhao, Northwestern Polytechnical University; Zhu Han, University of Houston

Outage Probability Analysis for MF-RIS assisted AmBC Networks

This paper focuses on the performance analysis of multi-functional RIS (MF-RIS) assisted ambient backscatter communication (AmBC) networks. To be specific, we derive the closed-form and asymptotic expressions of outage probability for both data signal and backscatter signal with the consideration of imperfect and perfect successive interference cancellation (SIC) process. On this basis, the diversity orders, which are related to the number of MF-RIS elements and levels of imperfect SIC, are also derived. Numerical results indicate that the outage performance of MF-RIS-assisted AmBC networks outperforms that of passive and conventional relaying schemes.Outage Probability Analysis for MF-RIS assisted AmBC NetworksYapeng Guo, Yingjie Pei, Shixun Gong, Xiaofeng Tao, Beijing University of Posts and Telecommunications

Flat-Top Beamforming with Efficient Array-Fed RIS

Flat-top beam designs are essential for uniform power distribution over a wide angular sector for applications such as 5G/6G networks, beaconing, satellite communications, radar systems, etc. Low sidelobe levels with steep transitions allow negligible cross sector illumination. Active array designs requiring amplitude taper suffer from poor power amplifier utilization. Phase only designs, e.g., Zadoff-Chu or generalized step chirp polyphase sequence methods, often require large active antenna arrays which in turns increases the hardware complexity and reduces the energy efficiency. In our recently proposed novel array-fed reflective intelligent surface (RIS) architecture, the small (2×2) active array has uniform (principal eigenmode) amplitude weighting. We now present a pragmatic flat-top pattern design method for practical array (RIS) sizes, which outperforms current state-of-the-art in terms of design superiority, energy efficiency, and deployment feasibility. This novel design holds promise for advancing sustainable wireless technologies in next-generation communication systems, including applications such as beaconing, broadcast signaling, and hierarchical beamforming, while mitigating the environmental impact of high-energy antenna arrays.Flat-Top Beamforming with Efficient Array-Fed RISKrishan Kumar Tiwari, Giuseppe Caire, Technical University of Berlin

Creating An Interference-Free Environment Via Intelligent Reflecting Surface: A Blind Appr...

We study the problem of interference cancelation with the aid of an intelligent reflecting surface (IRS), where the objective is to determine the reflection coefficients at the IRS such that the interference signals are canceled at the receiver. Specifically, we are interested in a “blind” scenario where the channel state information (CSI) between the interference sources and the receiver is unknown. To tackle this challenging problem, we propose a sample-efficient blind approach which utilizes a small number of average received signal power measurements to automatically identify a reflection coefficient vector that is orthogonal to the cascaded interference channels and thus nullifies the interference signals at the receiver. Simulation results show that the proposed method can effectively cancel the interference signals and enhance the signal-to-interference-plus-noise ratio (SINR).Creating An Interference-Free Environment Via Intelligent Reflecting Surface: A Blind Approach Without Knowledge of CSIPeilan Wang, university of electronic science technology of China; Binyao Ma, University of electronic science technology of China; Jun Fang, University of Electronic Science and Technology of China; Bin Wang, National University of Defense Technology; Hongbin Li, Stevens Institute of Technology

Adaptive Modulation and Coding for OTFS-based LEO Satellite-Terrestrial Communications

In satellite-terrestrial links, the high-speed movement of low earth orbit (LEO) satellites induces significant doppler effects. By employing orthogonal time frequency space (OTFS) modulation technology, information symbols are effectively mapped into the delay-doppler domain, significantly mitigating the adverse impacts of doppler effects on transmissions. Furthermore, the short packet is introduced into satellite-terrestrial communications to meet diverse latency requirements. Due to the limited channel coding capacity of short packets, adjusting the channel coding rate and symbol modulation order according to the channel conditions is crucial in satellite communications. However, real-time channel state information feedback is precluded by the rapid variations in satellite-terrestrial channels, the large feedback latency, and the limited resources for frequent feedback. Therefore, implementing a feedback-free transmission approach is particularly essential. In this paper, we design a feedback-free OTFS-based adaptive modulation and coding (AMC) scheme to accommodate varying communication requirements and conditions. Extensive simulations with different orbital altitudes, carrier frequencies, and packet lengths have shown that the proposed approach can be effectively adapted to LEO satellite channels, enabling a feedback-free AMC in the LEO satellite-terrestrial communications.Adaptive Modulation and Coding for OTFS-based LEO Satellite-Terrestrial CommunicationsJiaxin Li, Jianzhe Xue, Zhanxi Ma, Xin Zhang, Zeyu Sun, Haibo Zhou, Nanjing University

Energy Efficiency of Non-Diagonal RIS-Aided Wireless Communication Systems

Reconfigurable Intelligent Surfaces (RIS) have emerged as a promising technology for enhancing wireless communication by dynamically controlling the propagation environment. Recently, a non-diagonal RIS architecture has been proposed, enabling more advanced signal manipulation by allowing signals impinging on one element to be reflected from another element after appropriate phase-shift adjustment. This paper analyzes the energy efficiency of non-diagonal RIS-assisted wireless communication systems in high- and low-signal-to-noise-ratio (SNR) regime. We derive closed form expressions of the spectral and energy efficiency for both the non-diagonal and its diagonal counterpart, which is used as a benchmark for comparison. Simulation results reveal that non-diagonal RIS systems are the preferred choice for communication systems that prioritize spectral efficiency. Interestingly, for energy efficiency, the selection between diagonal and non-diagonal RIS architectures depends on the received SNR conditions, with diagonal RIS systems excelling at high SNR and non-diagonal RIS systems performing better at low SNR scenarios.Energy Efficiency of Non-Diagonal RIS-Aided Wireless Communication SystemsMostafa Samy, University of Luxembourg; Hayder Al-Hraishawi, University of South Florida; Abuzar B. M. Adam, SnT, University of Luxembourg; Madyan Alsenwi, University of Luxembourg; Symeon Chatzinotas, SnT, University of Luxembourg; Bjorn Ottersten, University of Luxembourg

Efficient Stochastic Polar Decoder With Correlated Stochastic Computing

Polar codes have gained significant attention in channel coding for their ability to approach the capacity of binary input discrete memoryless channels (B-DMCs), thanks to their reliability and efficiency in transmission. However, existing decoders often struggle to balance hardware area and performance. Stochastic computing offers a way to simplify circuits, and previous work has implemented decoding using this approach. A common issue with these methods is performance degradation caused by the introduction of correlation. This paper presents an Efficient Correlated Stochastic Polar Decoder (ECS-PD) that fundamentally addresses the issue of the ‘hold-state’, preventing it from increasing as correlation computation progresses. We propose two optimization strategies aimed at reducing iteration latency, increasing throughput, and simplifying the circuit to improve hardware efficiency. The optimization can reduce the number of iterations by 25.2% at Eb/N0 = 3 dB. Compared to other efficient designs, the proposed ECS-PD achieves higher throughput and is 2.7 times more hardware-efficient than the min-sum decoder.Efficient Stochastic Polar Decoder With Correlated Stochastic ComputingJiaxing Li, Shuwen Zhang, Zhisong Bie, Beijing University of Posts and Telecommunications