VTC 2025 Spring Conference’s Shorts

Circularly Shifted Block QAM-FBMC System With Two-Stage Detector

A block quadrature amplitude modulation based filter bank multi-carrier (QAM-FBMC) system with circularly shifted prototype filters is proposed. Since the circularly shifted prototype filters do not satisfy the complex orthogonality, the intrinsic interference occurs in the block QAM-FBMC system. Additionally, the inter-block interference (IBI) and inter-carrier interference (ICI) occur in the multipath fading channels since the circularly shifted prototype filters degrade the localization in the time domain. In order to reduce the intrinsic interference, we adopt a frequency domain minimum mean-squared error receiver which is derived from an effective channel matrix which is represented by the transceiver structure and channels. Then, the two-stage detector is applied to reduce IBI from the preceding block and suppress ICI which occurs from the loss of signal in the current block. Numerical results show that the proposed block QAM-FBMC system achieves low out-of-band emission similar to the conventional offset QAM-FBMC (OQAM-FBMC) system and almost the same bit error rate performances as the orthogonal frequency division multiplexing with a cyclic prefix (CP-OFDM) in the multipath fading channels. Also, the block QAM-FBMC system obtains higher spectral efficiency by eliminating the transition time compared to the QAM-FBMC and OQAM-FBMC systems.Circularly Shifted Block QAM-FBMC System With Two-Stage DetectorJoonhyeok Sung, Sooyong Choi, Yonsei University

An Efficient Blind Carrier Frequency Offset Estimation Algorithm for QAM

This paper presents a method for blind carrier frequency offset (CFO) estimation for quadrature amplitude modulation (QAM). Our proposed algorithm has three major steps, including two-stage full modulation removal, symbol aggregation, and iterative parabolic interpolation. In the first step, a preliminary CFO estimate will be evaluated using the QPSK sub-constellations. The modulation values of the remaining constellation points are partially removed based on the preliminary CFO estimate, and the residual modulation values are quantized to achieve the full modulation removal. In the second step, modulation-removed symbols are paired and weighted based on their reliability levels. This symbol aggregation step improves the estimation accuracy and reduces the FFT size of the following FFT-based CFO estimation. A trade-off between performance and complexity can be achieved by adjusting the aggregation length. In the final step, an iterative parabolic interpolation technique is introduced to mitigate the estimation bias. Performance evaluation shows that the proposed method provides better mean square error (MSE) performance and comparable complexity compared to the existing CFO methods for QAM.An Efficient Blind Carrier Frequency Offset Estimation Algorithm for QAMHuang-Chang Lee, National Taiwan Ocean University; Yi-Wei Lu, Hong-Yu You, Yeong-Luh Ueng, National Tsing Hua University

3D-Continuous Fluid Antenna System-Enabled Index Modulation

This paper propose a novel three-dimensional continuous fluid antenna system-enabled index modulation (3D-CFAS-IM) scheme, where the fluid antenna can move continuously within a 3D region to fully exploit spatial resources. The optimal positions of the fluid antenna are determined by maximizing the minimum Euclidean distance between different receive patterns, and their indices are used to implement IM. The achievable rate, bit error rate (BER) performance, and computational complexity of the proposed scheme are analyzed. Simulation results demonstrate that the proposed scheme achieves better BER performance and a higher achievable rate compared to existing schemes, with acceptable complexity. Additionally, the impact of channel estimation errors on system performance is investigated.3D-Continuous Fluid Antenna System-Enabled Index ModulationBo An, Liang Wu, Zaichen Zhang, Southeast University

Joint Optimization of Channel Reuse and Power Allocation in Shared D2D Communication Mode

Spectral efficiency in mobile networks can be increased by allowing devices communicating directly with each other in a form of device-to-device (D2D) communication to reuse channels assigned to cellular devices, i.e., devices communicating via base station. However, the resources reuse leads to additional interference between the cellular and D2D devices. This interference can be suppressed by a smart selection of channels to be reused and allocation of transmission power to all devices at the reused channels. Since this problem is NP-hard, we propose a solution based on deep deterministic policy gradient (DDPG) for cellular channel reuse decisions combined with deep neural network (DNN) for transmission power allocation to all devices. Both machine learning models (DDPG and DNN) are naturally sub-optimal. Thus, we further extend the work towards coordinated learning of both DDPG and DNN so that a potential performance degradation due to sub-optimal outputs of DNN and DDPG is suppressed via a mutual interaction between DDPG and DNN. Simulation results show that proposed solution boosts sum capacity by up to 63% compared to the best-performing state-of-the-art work.Joint Optimization of Channel Reuse and Power Allocation in Shared D2D Communication ModeIshtiaq Ahmad, Zdenek Becvar, Pavel Mach, Czech Technical University in Prague

Strength of Augmented Responses in Linear Overloaded MIMO Detection

In this paper, the appropriate strength of augmented responses is investigated in linear multi-input multi-output (MIMO) detection. The augmented responses is used to generate a square channel matrix for applying linear MIMO detection schemes in overloaded MIMO systems. It is originally proven that the strength of augmented responses should be as small as possible. If gradient descent direction random walk MIMO detection is applied, the augmented responses limits the step size of the gradient descent algorithm. Thus, the strength of the augmented responses effect on the convergence rate of the gradient descent algorithm and bit error performance. Numerical results obtained through computer simulation show that the optimum values of the augmented responses exists.Strength of Augmented Responses in Linear Overloaded MIMO DetectionYukitoshi Sanada, Keio University

Secrecy Performance of a Keyhole-based Multi-user System with Multiple Eavesdroppers

This paper investigates the secrecy performance of a keyhole-aided multi-user communication network in the presence of multiple eavesdroppers. The communication happens through the same keyhole for legitimate users and eavesdroppers. In this context, the secrecy performance is evaluated for a user scheduling technique by obtaining the exact closed-form expression of secrecy outage probability (SOP). Further, a simplified asymptotic SOP expression is derived assuming high signal-to-noise ratio (SNR) scenario for a better understanding of the impact of system parameters. The effect of the keyhole parameters, number of users, number of eavesdroppers, and threshold secrecy rate on the SOP performance are also investigated for the considered system model. In the high-SNR regime, the asymptotic SOP saturates to a constant value and does not depend on the keyhole parameter and the channel parameter of the source-to-keyhole channel.Secrecy Performance of a Keyhole-based Multi-user System with Multiple EavesdroppersParwez Alam, Ankit Dubey, Indian Institute of Technology Jammu; Jules M. Moualeu, University of the Witwatersrand; Telex M. N. Ngatched, McMaster University; Chinmoy Kundu, Tyndall National Institute

Robust Phase Difference-based Spectrum Sensing Under Impulsive Noise and Noise Uncertaint...

In this work, we delve into the performance of the recently proposed cosine feature recognition detection (CRD) spectrum sensing technique, which leverages the phase difference distribution of the received signal. The analysis takes into account impulsive noise (IN) and noise uncertainty (NU), both of which are well-known factors that degrade communication system performance. The conventional energy detector (ED) approach serves as a benchmark for comparison. The simulation results indicate that the CRD technique achieves near-perfect robustness in the presence of IN and excellent performance under NU, whereas the performance of ED is drastically degraded under these harsh conditions. These findings provide valuable insights into the trade-offs between detection complexity and robustness, contributing to the design of more reliable spectrum sensing systems for cognitive radio networks.Robust Phase Difference-based Spectrum Sensing Under Impulsive Noise and Noise UncertaintyAndré Antônio dos Anjos, LuÃ

Predictive Configured Grant Scheduling for Deterministic Wireless Communications

Future wireless networks must enhance their capacity to sustain deterministic service levels and support emerging time-sensitive services in key verticals. The ability to guarantee bounded latencies heavily depends on efficient radio resource management. Configured Grant (CG) scheduling can reduce latency by pre-allocating resources, but its effectiveness and efficiency decrease under variable traffic patterns. This study presents a novel predictive CG scheduling scheme that pre-allocates resources based on traffic predictions while accounting for prediction inaccuracies. By considering these inaccuracies, the scheme significantly improves the ability to meet bounded latency requirements, which are essential for supporting deterministic service levels. Our evaluations show that the proposed scheme significantly enhances the capacity to support deterministic service levels while improving resource utilization, even in scenarios with variable and mixed traffic flows with diverse requirements.Predictive Configured Grant Scheduling for Deterministic Wireless CommunicationsSyed Morsleen Riaz, Universidad Miguel Hernández de Elche; Mª Carmen Lucas Estañ, Universidad Miguel Hernandez de Elche (UMH); Baldomero Coll-Perales, Universidad Miguel Hernandez de Elche; Javier Gozálvez, Universidad Miguel Hernandez de Elche (UMH)

Experimental Outdoor Performance Evaluation of TVWS Narrowband Data Communication Using SD...

Large-scale deployment of Internet of Things (IoT) networks in the industrial, scientific, and medical (ISM) band leads to spectrum congestion and requires multiple gateways to cover wide areas. This will increase cost, complexity, and energy consumption. TV White Spaces (TVWS) provides an abundant spectrum sufficient for low-data-rate IoT applications. This low-frequency band offers coverage over larger areas due to the ability of wireless signals to penetrate obstacles and terrain. In this paper, we examine the performance of narrowband data communications in TVWS through an outdoor experiment in a suburban area with non-line-of-sight (NLOS) propagation scenarios. We implement a software-defined radio (SDR) testbed and develop a new benchmark module in GNU Radio to perform outdoor experiments for TVWS narrowband data communication between a gateway and wireless nodes at various locations. The results reveal that the system can achieve a throughput of up to 97 Kbps with a packet error rate (PER) and packet loss rate (PLR) under 1% over NLOS paths, making it suitable for low-data rate applications. This work offers valuable insights for designing the physical layer of narrowband white space devices (WSDs). The developed benchmark tool will also greatly assist other researchers in evaluating the performance of SDR-based communication systems.Experimental Outdoor Performance Evaluation of TVWS Narrowband Data Communication Using SDR PlatformMUNEER ALZUBI, King Abdullah University of Science and Technology (KAUST); Mohamed-Slim Alouini, King Abdulah University of Sience and Technology (KAUST)

Post-Disaster-Aware Proactive Deployment of Aerial Base Stations for Resilient Cellular Ne...

This paper proposes a novel proactive deployment framework for multiple aerial base stations (ABSs) to enhance the resilience of cellular networks against post-disaster disruptions. Unlike conventional approaches that optimize the ABS deployment separately for pre and post-disaster conditions, our proposed framework jointly optimizes the ABS deployment providing high-quality services continuously from pre-disaster to post-disaster environments. By formulating the joint optimization problem, our strategy maximizes the minimum user satisfaction before disasters and the user coverage after disasters. Our simulation results demonstrated that our strategy significantly outperformed the existing strategies by achieving the pre and post-disaster network performance while requiring only a marginal increase in the number of ABSs.Post-Disaster-Aware Proactive Deployment of Aerial Base Stations for Resilient Cellular NetworksTakeshi Hirai, Osaka University; Wonjae Shin, Korea University; Naoki Wakamiya, Osaka University