Baseband Channel Research Articles

PSRDP: A Parallel Processing Method for Pulsar Baseband Data

To address the problem of real-time processing of ultra-wide bandwidth pulsar baseband data, we designed and implemented a pulsar baseband data processing algorithm (PSRDP) based on GPU parallel computing technology. PSRDP can perform operations such as baseband data unpacking, channel separation, coherent dedispersion, Stokes detection, phase and folding period prediction, and folding integration in GPU clusters. We tested the algorithm using the J0437-4715 pulsar baseband data generated by the CASPSR and Medusa backends of the Parkes, and the J0332+5434 pulsar baseband data generated by the self-developed backend of the NanShan Radio Telescope. We obtained the pulse profiles of each baseband data. Through experimental analysis, we have found that the pulse profiles generated by the PSRDP algorithm in this paper are essentially consistent with the processing results of Digital Signal Processing Software for Pulsar Astronomy (DSPSR), which verified the effectiveness of the PSRDP algorithm. Furthermore, using the same baseband data, we compared the processing speed of PSRDP with DSPSR, and the results showed that PSRDP was not slower than DSPSR in terms of speed. The theoretical and technical experience gained from the PSRDP algorithm research in this article lays a technical foundation for the real-time processing of QTT (Qi Tai radio Telescope) ultra-wide bandwidth pulsar baseband data.

A double sideband combined tracking method for Galileo E5 AltBOC signals

The Galileo navigation satellite system (Galileo) E5 Alternative Binary Offset Carrier (AltBOC) signal brings various challenges due to its complex modulation, wide bandwidth, and multi-peaked auto-correlation function. While wideband tracking needs to solve the ambiguity problem and design dedicated baseband channels, the single-sideband cannot have the outstanding performance of the AltBOC signal. We propose a new tracking method called “Double Sideband Combined Tracking” (DSCT), which can fully exploit the AltBOC signal’s code tracking accuracy without ambiguity and ensure compatibility with Binary Phase Shift Keying (BPSK) processing channels, easily implemented in hardware. The DSCT employs one phase locked loop and one delay locked loop to track the carrier and code, respectively. The double-sideband correlation results used by the two loops are recovered by coherently combining the single-sideband correlation results of the two BPSK channels. Meanwhile, the combined model, the loop discriminator, and the ambiguity detection of the DSCT are discussed. Furthermore, the code tracking error caused by thermal noise is modeled and analyzed. The test results based on real Galileo E5 signals show that the DSCT exhibits better or comparable code tracking accuracy to the AltBOC wideband tracking method. When the loop falsely locks onto a side-peak, the DSCT can quickly detect and re-lock on the main peak.

On off keying line coding based optical transmitter for various both optical fiber communication and OWC channels

Abstract This paper demonstrated the on off keying line based optical line transmitter for different fiber communication and wireless lighted channels. The max Q form and min BER values after PIN receiver based optical fiber base band channel, linear multi-mode fiber channel and OWC at optimum length is clarified. Lighted power variations after light fiber channel, linear multi-mode fiber channel and OWC versus spectral base band wavelength variations at optimum length is demonstrated. Lighted power form variations after lighted base band fiber channel, linear multi-mode fiber channel and OWC versus time variations at optimum length is indicated. Total lighted power after optical fiber base band channel, linear multi-mode fiber channel and OWC at optimum length is clarified. Total electrical power after PIN receiver based optical fiber channel, linear multi-mode fiber channel and OWC at optimum length.

Spectral-efficient hybrid precoding for multi-antenna multi-user mmWave massive MIMO systems with low complexity

Millimeter-wave (mmWave) massive multiple-input multiple-output (MIMO) systems allow for a data transmission rate of gigabits per second owing to the large bandwidth available in the mmWave spectrum and the antenna gains provided by the massive MIMO system. However, hybrid precoding with high complexity and low spectral efficiency cannot address the challenge of high cost and power consumption of RF chains of multi-user systems. In this paper, we propose a low-complexity hybrid precoding scheme for downlink multi-antenna multi-user mmWave massive MIMO systems, aiming to enhance the sum spectral efficiency (SSE) performance. We first extend the dimension of the analog precoding matrix into a square matrix and find the optimal analog combiner by selecting some of the discrete Fourier transform (DFT) bases, which enhances the equivalent baseband channel matrix gain. Then, we directly aggregate the channel gain through the equal gain transmission (EGT) method to ensure the frequency efficiency performance. Finally, we propose an improved BD scheme to design the digital precoder and combiner to reduce the inter-user interference. We consider both the mmWave channel and the Rayleigh channel to evaluate the performance of the proposed algorithm. The simulation results verify that the proposed scheme enjoys near-optimal achievable sum spectrum efficiency and BER performance in both the mmWave channel and Rayleigh channel and performs even better in Rayleigh channel than in the mmWave channel.

3-D Antenna Array Structures for Millimeter Wave Multi-User Massive MIMO Hybrid Precoder Design: A Performance Comparison

In this letter, we investigate the performance of various three-dimensional (3D) array structures in the design of hybrid precoder (HP) for millimeter wave (mmWave) multi-user massive multiple-input multiple-output (MU-mMIMO) systems. The proposed HP scheme involves two stages: (i) RF beamforming based on singular value decomposition (SVD) of channel matrix, and baseband MU precoding based on the instantaneous effective baseband channel to mitigate MU-interference by a regularized zero-forcing (RZF) technique. Illustrative results show that, in comparison to two-dimensional (2D) arrays, 3D array structures can provide high spectral and energy efficiencies as well as non-varying achievable rate independent from the user angular location.

Training-Based Hybrid Precoding Scheme for Multiuser Massive MIMO-OFDM

In this letter, we propose a training based hybrid precoding scheme for multiuser massive MIMO-OFDM time-division duplexing (TDD) systems, where we combine hybrid precoding design with channel estimation in a mixed-timescale structure. Firstly, we design a training based fully-digital precoder/combiner using the statistics of the transmitted and received signal under minimum mean square error (MMSE) criterion through an iterative process between downlink (DL) and uplink (UL), from which the radio frequency (RF) precoder/combiner is extracted using principal component analysis (PCA). Secondly, a low dimensional baseband (BB) channel is estimated and the BB precoder/combiner is designed by block diagonalization (BD) with the estimated BB channel. Thirdly, we discuss the transmission strategy for our proposed scheme in block-fading channels and limited feedback systems. Finally, we evaluate the sum spectral efficiency (SSE) and bit error rate (BER) performance of our proposed scheme and prove that our scheme has better performance compared to the existing schemes.

Constrained Tensor Decomposition-Based Hybrid Beamforming for Mmwave Massive MIMO-OFDM Communication Systems

Hybrid beamforming design for OFDM systems is hugely challenging since their analog precoders and combiners are shared among all subcarriers. This paper proposes a novel two-stage joint hybrid precoder and combiner design for maximizing the average achievable sum-rate of frequency-selective millimeter-wave massive MIMO-OFDM systems. In the proposed approach, the analog precoder and combiner design is formulated as a constrained Tucker2 tensor decomposition problem, which allows maximizing the sum of the effective baseband gains over every subcarrier while suppressing inter-user and intra-user interferences. The solution is obtained by a projected alternate least-square-based algorithm, which is suitable for both single-user (SU) and multiuser (MU) systems. The digital precoder and combiner for SU systems is obtained from the effective baseband channel' SVD. In contrast, for MU systems, it is obtained from the regularized channel diagonalization method, which balances multiuser interference and noise suppression. Numerical simulation results validate the effectiveness of the proposed method.

On the performance of OFDM and single carrier communication over wideband HF channel: theory and practice

Using wideband High Frequency (WBHF) communication has not been a luxury now due to the urgent need for the transfer of large files over long distances without the need for sophisticated infrastructure. The channel model helps in evaluating the performance of communications systems without the need for a real transmission. The existing HF ITU-R(International Telecommunication Union Radio) channel models are valid only for narrowband channels of bandwidth 3KHz and are valid up to 12KHz. Another channel model for WBHF with bandwidth up to 1MHz was given by Vogler yet, the model was mathematically intractable and allow no further analysis to take place. Noting that, WBHF demands channel bandwidth greater than 12KHz (e.g:24KHz). In this paper, we present a WBHF channel model that is both accurate and mathematically tractable laying the foundation for an informative comparison between different communication systems. The accuracy of the proposed model is first to cross verified against Vogler’s wideband model in terms of the channel impulse response, frequency response and channel scattering characteristics. This comparison leaves our model qualified to evaluate a newly developed standard of HF wideband Waveforms presented to support high data rates and link reliability requirements. Further, we establish a detailed comparison between OFDM and single carrier signaling schemes over the considered WBHF proposed ionospheric channel, under many parameters that affect the performance of both systems. We investigate the justification of using both systems under different channel conditions, we also derive the necessary rate formulas for each signaling scheme and provide simulation environment of both systems on selected samples of the ITU-R channel models for the HF ionospheric channel representing most of the channel conditions. It is coming up that in quiet channel conditions the OFDM outperforms SCCP, while in disturbed conditions SCCP shows more robustness against channel conditions than OFDM. Simulation results are shown that support our analytical results. In addition, we present a Software Defined Radio Hardware implementation of an OFDM wideband HF Transceiver. The developed implementation has been evaluated using an equivalent baseband channel model based on the ITU-R HF channel model.

Hybrid Beamforming for Sum Rate Maximization in Wideband Multi-User MIMO Relay Systems

Hybrid precoding has a great potential to achieve near-optimal performance with few radio-frequency (RF) chains in comparison to the number of antennas. This paper proposes a novel hybrid beamforming solution for sum rate maximization in a wideband multi-user multi-input multi-output (MU-MIMO) relay system. The problem at hand is non-convex and hence mathematically intractable due to the constant modulus constraints associated with the analog beamforming design at communicating nodes shared by all sub-carriers. Furthermore, relaying in MU-MIMO systems under frequency-selective channels is also a challenging task as it requires complicated signal processing. To address this problem, source analog beamformer, relay RF combiner and phase-only processing component at each destination are obtained by deriving the common RF processing matrix which enables beamforming gain over all sub-carriers. This process involves reconstruction loss minimization for designing the required analog beamforming vectors having ability to maximize end-to-end signal-to-interference plus noise ratio (SINR). The relay analog precoder is designed by maximizing the received power at each destination through gain maximization of the equivalent baseband channel over the allocated frequency spectrum. To reduce the computational complexity of the iterative approach used to find the relay RF precoding matrix, the closed form expression is derived for achieving the desired objective. Finally, digital baseband processing components are obtained from the equivalent baseband channels by suppressing the interference among transmitted signals indirectly. Simulation results for different system configurations reveal that the proposed algorithm can achieve near-optimal performance.

Energy-Efficient MU-Massive-MIMO Hybrid Precoder Design: Low-Resolution Phase Shifters and Digital-to-Analog Converters for 2D Antenna Array Structures

This paper investigates a multi-user massive multiple-input multiple-output (MU-mMIMO) hybrid precoding (HP) scheme using low-resolution phase shifters (PSs) and digital-to-analog converters (DACs). The proposed HP approach involves two stages: RF beamforming based on the slowly time-varying channel second-order correlation matrix, and baseband MU precoding based on the instantaneous effective baseband channel to mitigate MU-interference by a regularized zero-forcing (RZF) technique. We consider three HP design architectures: (i) HP using full-resolution PSs and DACs, with a baseband transfer block for constant-modulus RF beamformer, (ii) HP using $b$ -bit PSs and full-resolution DACs, with an orthogonal matching pursuit (OMP) based algorithm that can approach the optimal unconstrained RF beamformer, and (iii) HP using $b$ -bit PSs and $q$ -bit DACs, taking into account also DAC quantization noise. Illustrative results show that the proposed HP schemes with low-resolution PSs can approach the sum-rate of full-resolution PSs by using only 2-bit PSs, while offering higher energy efficiency. Furthermore, a study of sum-rate results for various PS and DAC quantization levels reveals that HP can achieve near-optimal performance with only 2-bit PSs and 5-bit DACs. Moreover, a comparison of the different array configurations, namely, uniform linear array (ULA), uniform circular array (UCA), uniform rectangular array (URA), and concentric circular array (CCA), indicates that URA and CCA outperform UCA and ULA in terms of spectral and energy efficiencies.

Low-Complexity Multistage Optimal Detection for SVD-Based Hybrid Millimeter Wave MIMO Systems

The singular value decomposition (SVD) based hybrid processing for millimeter wave (mmWave) multiple-input multiple-output (MIMO) systems attempts to eliminate mutual interference between data streams by processing the original channel matrix to an approximate diagonal matrix. However, the non-zero off-diagonal entries will result in performance loss. To improve the performance with low-complexity, we propose a multistage optimal detection algorithm for SVD-based hybrid mmWave MIMO systems. At the first stage, a decision criterion is proposed by effectively exploiting the characteristic that the magnitudes of off-diagonal entries of the baseband channel matrix are relatively small. Through this decision criterion, some elements of global optimal solution can be determined. The ratio of the determined elements to all elements is analyzed to reveal the advantage of proposed decision criterion. At the second stage, we further propose a decision feedback algorithm to detect more elements of global optimal solution. If all elements are determined, the detection is complete, otherwise it enters the third stage. In the case of third stage, we apply the maximum likelihood (ML) detection algorithm to solve the residual small-scale optimization problem containing only few undetermined elements. Numerical experiments show that the number of elements required to be determined by ML detection is relatively very small or zero, in most situations, that is why the algorithm has a significantly lower complexity.

A 84.48-Gb/s 64-QAM CMOS D-Band Channel-Bonding Tx Front-End With Integrated Multi-LO Frequency Generation

In this letter, an ultra-broadband D-band wireless front-end transmitter (TX) in 45-nm CMOS SOI is proposed. Based on channel bonding and 64-QAM modulation, it achieves 84.8-Gb/s data rate by combining $8\times 2.16$ GHz baseband channels. The eight baseband channels are aggregated at intermediate frequency (IF) in two sets of four channels and then upconverted to two adjacent sub-bands at D-band. The required millimeter-wave local oscillators (LOs) are generated on-chip. The IF band is 57.96 to 66.66 GHz, and the considered transmission band is from 140.895 to 158.265 GHz. The presented TX integrates two upconverter mixers, two power amplifiers, and an on-chip power combiner in addition to the two LO genertors with a total dc power consumption of 420 mW from a 1-V voltage supply, and occupies a compact active area of 2.98 mm2.

Bridging the Gap Between MMSE-DFE and Optimal Detection of MIMO Systems

In this paper, we propose a novel low-complexity, near-optimal soft-input soft-output detector for $\text {N}\times \text {M}$ multiple-input multiple-output (MIMO) systems. Our algorithm is based on the combination of minimum mean square error decision feedback equalization (MMSE-DFE) and conditional optimization. In a round-robin fashion, one symbol is detected using exhaustive search in such a way that all $\text {N}\times (\text {M}-1)$ submatrices of the baseband channel matrix are considered and the one with the best metric is chosen. This search over all columns of the channel matrix, which can be performed in parallel, has the advantages of improving the performance of the hard-output version of the detector, and refining the list of candidates for efficient implementation of the soft-output detector for MIMO systems with error correcting codes. In particular, it is shown that the error performance of the soft-output system is comparable to that of the list sphere decoder (LSD) but with much smaller list size, and hence smaller complexity than the latter. We also analyze the performance and complexity of the proposed algorithm and discuss different techniques to further reduce its complexity without affecting the performance. Finally, the obtained theoretical results are validated via simulations.

Frequency Interleaving IF Transmitter and Receiver for 240-GHz Communication in SiGe:C BiCMOS

This article presents a fully integrated modular wideband frequency interleaving (FI) transmitter and receiver for high data rate communication applications. At the transmitter side, three independent in-phase and quadrature-phase (IQ) baseband channels are upconverted to different intermediate frequencies (IFs) and then interleaved. At the receiver side, the interleaved signals are downconverted and separated back to each independent channel. Single-ended inputs and outputs are utilized to reduce the pin count, for a more practical realization and higher potential toward future system scaling. Special design techniques are followed to minimize crosstalk and intermodulation products between the channels. All circuits are manufactured and measured in a 130-nm SiGe:C BiCMOS technology with $f_{\textbf {T}}/f_{\textbf {max}}$ =300/500 GHz. The FI transmitter achieves a channel bandwidth of 2.5 GHz with less than 3-dB difference across different channels until 15-GHz IF. It consumes 560 mW from 2.5 and 3.3 V supplies and occupies a silicon area of 1.9 mm2. The FI receiver achieves a baseband channel bandwidth of 2.5 GHz with a 1-dB difference between the channels until the same IF. It consumes 860 mW from 2.5 and 3.3 V supplies and has a chip area of 1.55 mm2. The circuits are deployed in a communication experiment; first, in a back-to-back test with a direct cable connection, demonstrating a data rate of 15.6 Gb/s across the three IQ channels with a 16-QAM modulation scheme and a worst case transmitter-to-receiver error vector magnitude (EVM) of −18.6 dB. Then, a wireless experiment is performed with a 240-GHz front end with on-chip antenna, demonstrating a data rate of 7.8 Gb/s with QPSK modulation and a worst case EVM of −8.3 dB, across a wireless link of 15 cm. To the best of our knowledge, this is the first article that demonstrates a wireless transmission at sub-terahertz (sub-THz) carrier frequencies utilizing FI architectures.

SWIPT Signaling Over Frequency-Selective Channels With a Nonlinear Energy Harvester: Non-Zero Mean and Asymmetric Inputs

Simultaneous wireless information and power transmission (SWIPT) over a point-to-point frequency-selective channel is studied. Leveraging a small-signal model for a nonlinear energy harvester, a general form of the delivered power in terms of system baseband parameters is derived, which demonstrates the dependency of the delivered power on higher moments of the baseband channel input. The optimization problem of maximizing rate-power (RP) region is studied. Assuming that the channel state information (CSI) is available at both the receiver and the transmitter, and constraining to the non-zero mean Gaussian input distributions, an optimization algorithm for power allocation among different subchannels is studied. As a special case, optimality conditions for zero mean Gaussian inputs are derived. Results obtained from the numerical optimization demonstrate the superiority of the non-zero mean Gaussian inputs (with asymmetric power allocation in each complex subchannel) in yielding a larger RP region compared to their zero mean and non-zero mean (with symmetric power allocation in each complex subchannel) counterparts. The results motivate the design of new modulation for SWIPT and contrast with the SWIPT design under linear energy harvesting, for which the circularly symmetric Gaussian inputs with water-filling power allocation are optimal.

Secure Hybrid Beamformers Design in mmWave MIMO Wiretap Systems

Millimeter wave (mmWave) communications have been considered as a key technology to enable very high data rate in the fifth-generation applications. Multiple-input–multiple-output (MIMO) systems with hardware efficient analog/digital hybrid beamformer architecture have been widely considered to overcome the severe propagation loss of the mmWave channels. However, physical layer security in the mmWave wiretap MIMO systems and secure hybrid beamformer design have not been well investigated. In this paper, we consider the problem of the hybrid beamformer design for the secure transmission in mmWave wiretap MIMO systems in order to protect the legitimate transmission from eavesdropping. We aim to develop efficient secure hybrid beamformer design algorithms for both codebook-free and codebook-based analog beamformer schemes with either high-resolution or low-resolution phase shifters. Particularly, when eavesdropper's channel state information (CSI) is known, we first propose a joint analog precoder and combiner design algorithm that can prevent the information leakage to the eavesdropper. Then, the digital precoder and combiner are computed based on the obtained effective baseband channel to further maximize the secrecy rate. If prior knowledge of the eavesdropper's CSI is unavailable, we develop an artificial-noise-based hybrid beamforming approach, which can disrupt eavesdropper's reception while maintaining the quality-of-service of the intended receiver at a prespecified level. Extensive simulation results validate the effectiveness of the proposed secure hybrid beamformer designs under different availabilities of eavesdroppers CSI.

Transceiver Design With UCD-Based Hybrid Beamforming for Millimeter Wave Massive MIMO

Hybrid transceiver designs for millimeter wave massive multiple-input multiple-output systems are feasible candidates to reduce the volume of radio frequency (RF) chains, decomposing the signal processing into the analog and digital domains. The existing schemes heavily depend on the singular value decomposition to obtain subchannels with uneven power gains, causing bit error rate (BER) performance degradation. In this paper, we propose a hybrid transceiver design based on the uniform channel decomposition (UCD), yielding subchannels with identical gains to improve the BER performance. Inspired by the UCD concept, we derive an equivalent optimization problem and propose two schemes, namely, phase-extraction and iterative update, to determine the RF beamformers, yielding an effective baseband channel with the greatest possible geometric mean of singular values. We apply the UCD with a minimum mean squared error criterion to complete the baseband beamforming. Finally, we combine the hybrid UCD beamforming with the vertical-Bell Labs layered space-time and dirty paper coding, to eliminate the inter-subchannel interference. An asymptotic analysis of the scheme performance is also pursued. The simulation results show that the proposed hybrid scheme outperforms the conventional schemes on the transmission BER, which achieves a spectral efficiency close to that of the fully-digital counterpart.

Low-Complexity Multiuser Receiver for Massive Hybrid Array mmWave Communications

In this paper, we study the low complexity reception of multiuser signals in uplink millimeter wave (mmWave) communications using a partially connected hybrid antenna array. Exploiting the mmWave channel property, we propose a low-complexity user-directed multiuser receiver with three novel schemes for allocating subarrays to users. This receiver only requires the knowledge of angles-of-arrival (AoAs) for dominating paths and a small amount of equivalent channel information instead of perfect channel state information. For comparison, we also derive a successive interference cancellation-based solution as a performance benchmark. We design two types of reference signals with the channel estimation method to enable efficient and simple estimation for AoA and equivalent baseband channel. Also, we provide analytical results for the performance of the AoA estimation, using the lower bounds of mean square errors in line-of-sight dominated mmWave channels. The simulation results validate that the proposed channel estimation method is effective when employed in combination with a zero-forcing equalizer.

Over-Sampling Codebook-Based Hybrid Minimum Sum-Mean-Square-Error Precoding for Millimeter-Wave 3D-MIMO

Hybrid precoding design is challenging for millimeter-wave massive MIMO. Most prior hybrid precoding schemes are designed to maximize the sum spectral efficiency, while seldom investigating the bit-error-rate (BER). Therefore, this letter designs an over-sampling codebook (OSC)-based hybrid minimum sum-mean-square-error (min-SMSE) precoding to optimize the BER. Specifically, given the effective baseband channel consisting of the real channel and analog precoding, we first design the digital precoder/combiner based on min-SMSE criterion to optimize the BER. To further reduce the SMSE between the transmit and receive signals, we propose an OSC-based joint analog precoder/combiner design. Simulation results show that the proposed scheme can achieve the better performance than its conventional counterparts.

Iterative hybrid precoder and combiner design for mmWave MIMO-OFDM systems

This paper investigates the problem of hybrid precoder and combiner design for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems operating in millimeter-wave (mmWave) bands. We propose a novel iterative scheme to design the codebook-based analog precoder and combiner in forward and reverse channels. During each iteration, we apply compressive sensing technology to efficiently estimate the equivalent MIMO-OFDM mmWave channel. Then, based on the effective channel, we designed the analog precoder and combiner to alleviate the interference between different data streams as well as maximize the spectral efficiency. The digital precoder and combiner are finally obtained based on the effective baseband channel to further enhance the spectral efficiency. Simulation results demonstrate that the proposed iterative hybrid precoder and combiner algorithm has significant performance advantages.