- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Soft-Output Detection Methods for Sparse Millimeter Wave MIMO Systems with Low-Precision ADCs
摘要： In this paper, we propose computationally-efficient yet near-optimal soft-output detection methods for coded millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems with low-precision analog-to-digital converters (ADCs). The underlying idea of the proposed methods is to construct an extremely sparse inter-symbol-interference (ISI) channel model by jointly exploiting the delay-domain sparsity in mmWave channels and a high quantization noise caused by low-precision ADCs. Then we harness this sparse channel model to create a trellis diagram with a reduced number of states and a factor graph with very sparse edge connections, which are used for computationally-efficient soft-output detection methods. Using the reduced trellis diagram, we present a soft-output detection method that computes the log-likelihood ratios (LLRs) of coded bits by optimally combining the quantized received signals obtained from multiple receive antennas using a forward-and-backward algorithm. To reduce the computational complexity further, we also present a low-complexity detection method using the sparse factor graph to compute the LLRs in an iterative fashion based on a belief propagation algorithm. Simulations results demonstrate that the proposed soft-output detection methods provide significant frame-error-rates gains compared to the existing frequency-domain equalization techniques in a coded mmWave MIMO system using one or two bit ADCs.
关键词： soft-output detection,time-domain equalization,low-precision analog-to-digital converter (ADC),multiple-input-multiple-output (MIMO),Millimeter wave communications
更新于2025-09-23 15:22:29
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Optical Fiber Communications (Principles and Applications) || Radio over Fiber
摘要： Radio over Fiber (RoF) technology can integrate advantages of both wireless networks and optical fiber networks. Recently RoF technology has found numerous applications in broadband wireless access communication networks, radio astronomy, RADAR and millimeter-wave communications, antenna array beam-forming, establishment of up- and down-converting links using photonic signals, spectroscopy, imaging, and electronic warfare.
关键词： wireless networks,RoF,radio astronomy,optical fiber networks,millimeter-wave communications,antenna array beam-forming,photonic signals,broadband wireless access,electronic warfare,Radio over Fiber,spectroscopy,RADAR,imaging
更新于2025-09-12 10:27:22
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Compressed Sensing-Aided Index Modulation Improves Space-Time Shift Keying Assisted Millimeter-Wave Communications
摘要： In this treatise, we present the concept of Compressed-Sensing (CS)-aided Space-Time Shift Keying Index Modulation (STSK-IM), where a virtual domain Orthogonal Frequency Division Multiplexing (OFDM) symbol is divided into Na-sized blocks, which carry K STSK codewords over a specific combination of virtual-domain sub-carriers and then converted to the frequency domain with the aid of a CS matrix. We design the system for operation in the Milli-meter Wave (mmWave) frequency band. Furthermore, we amalgamate our soft-decision-aided scheme both with the concept of Coordinate-Interleaving (CI) as well as a Discrete Fourier Transform (DFT)-aided codebook design conceived for analogue beamforming, which is vitally important for mmWave systems. In the proposed system, the number of implicit bits conveyed by the activated sub-carrier Frequency Index (FI) is determined by the number of the available K to Na sub-carrier permutations. Hence, we propose two FI allocation techniques, namely the Distinct FI (DFI) and the Shared FI (SFI) based schemes, which strike a trade-off between the attainable sparsity level and the achievable capacity limit. We then introduce a reduced-complexity detection technique in order to mitigate the detection complexity to order of the optimum detector from O(Nc · (Q · L)K) to O(?Nc · (Q · L)K), where ?Nc ≤ Nc. We also formulate the Discrete-Input Continuous-Output Memoryless Channel (DCMC) capacity and invoke EXtrinsic Information Transfer (EXIT) charts for characterizing the achievable performance limit of the reduced-complexity aided detector. Finally, we analyze the BER performance of both the uncoded and of our coded CS-aided STSK-IM systems associated with both the optimum and the reduced-complexity detectors.
关键词： Spatial Modulation,Compressed Sensing,mmWave,Reduced Complexity detection,Millimeter-wave communications,Space-Time Shift Keying,channel coding,PSK,QAM,MIMO,Coordinate Interleave,Spatial modulation,5G,OFDM,Index modulation,wideband channel
更新于2025-09-11 14:15:04
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Atmospheric turbulence mitigation using spatial mode multiplexing and modified pulse position modulation in hybrid RF/FSO orbital-angular-momentum multiplexed based on MIMO wireless communications system
摘要： In this paper, the capacity of a free-space optical (FSO) communication over radio frequency (RF) could potentially be increased by the simultaneous transmission of multiple orbital angular momentum (OAM) based on spatial mode multiplexing (SMM) as an additional effective degree of freedom (EDOF) and quadrature amplitude modulation (QAM). This paper describes using hybrid RF/FSO-OAM based on multiple-input multiple-output (MIMO)/SMM using M-ary modified pulse position modulation (MPPM) and spatial PPM (SPPM) for potentially enhancing capacity in wireless communication systems. We present an analytical system design concerning OAM multiplexing and MIMO/SMM processing in free space communications channel under atmospheric turbulence (AT). Here, we assume a new architecture that closes the gap in speeds between millimeter-wave (mm-wave) wireless and optical links. In this study, we highlight recent advances in the use of OAM multiplexing for high-capacity FSO and mm-wave communications. We have developed the MPPM in FSO communication over RF using the source Gaussian model and SMM by proposing a new version of hybrid SPPM and MPPM. The novelty approach presents performance enhancement of the acquisition, pointing, tracking position and AT mitigation of link. We propose to use SMM combined with OAM-QAM based MIMO communications system to mitigate both weak and strong turbulence distortions. Simulation results show that the capacity of OAM-based MIMO system outperforms the capacity of the conventional MIMO system when the propagation distance is larger than a specific threshold. The use of transmitter lenses could enhance the OAM beams with a larger mode spacing (MS) of 2 (OAM l +1, l +3, l +5, l +7 transmitted) shows a lower power penalty (PP) when the inter-channel crosstalk overwhelms a larger lateral displacement of about 2 mm. Using the lenses at the transmitter to focus OAM beams could reduce power loss and PP in OAM-based FSO links and that this improvement might be more significant for higher-order OAM beams and provide high power-efficiency. With a larger of the transmitter and receiver 8 cm, 10 cm aperture size respectively, the system with mode spacing of 2 (OAM l +1, l +3, l +5, l +7 transmitted) and mode spacing of 3 (OAM l +1, l +4, l +7, l +10 transmitted) of OAM beams based on MIMO should fulfill lower-power penalty of 2.2 dB, 3.4 dB, as respectively and could enhance system robustness under angular error but degrade tolerance of lateral displacement. The proposed system provides an excellent signal-to-noise ratio (SNR) for the capacity in the regime of strong atmospheric turbulence. In this way, the maximization of FSO communication and RF wide, the data capacity enhancement, and it is considered a massive solution in the bandwidth provision for future access networks. This work could be beneficial to the practical implementation of OAM-MIMO/SMM multiplexed RF/FSO links.
关键词： Multiple-input multiple-output,Spatial mode multiplexing,Orbital angular momentum,Free space optical communications,Millimeter-wave communications,Modified pulse position modulation
更新于2025-09-04 15:30:14