Baseband System Research Articles

Power and Energy Efficiency of Multilevel Baseband Transmission Systems: Analysis, Optimization and Improvements

Power and energy consumption of communication net-works contribute to the resource demand and hence they impact the sustainability of the society. Transmission links form basic parts ofcommunication networks and thus they add to the overall communica-tio nnetworlks' resourcedemand. Therefore, it is important to optimize transmission links in order to support the energy-efficient design ot communication networks. In transmission systems the constellation size in general is a degnee of freedom when designing or adapting a transmission link. In this article, multilevel baseband transmission via additive white Gaussian noise (AWGN) channels and over copper cables is optimized with respect to minimum power and energy demand, respectively - for the relevant case of given throughput and fixed transmission quality of a transmission link. The results are two-fold: In the AWGN case the minimum power and energy is utilized at the smallest possible constellation size. In case of band- limited base band transmission over twisted-pair copper wires with linear equalization the optimum constellation size increases as the band limitation becomes stronger, ie, as the cable gets longer al fixed bit rate or as the bit rate is increased at fixed link length. The optimization of the constellation size enables significant power and energy savings per link in the range of 25 % to approximately 90 % compared to a conventional two-level baseband system.

A new scheme to enhance the performance of permutation index\u2013differential chaos shift keying communications system

In this paper, a new scheme based on permutation index–differential chaos shift keying is proposed, modeled, and evaluated in AWGN channel environment. Data is sent by frames, and each frame is headed by a single reference signal and followed by some information-bearing signals. Modulation is performed through permutations of a reference signal according to the mapped data. At the receiver, each incoming information-bearing signal undergoes all inverse permutation possibilities to perform a correlation with the delayed and stored version of the received reference signal. To decode the information bits, the detector selects the highest correlator outputs. The proposed scheme named single reference–permutation index–differential chaos shift keying is an enhanced version of PI-DCSK, and uses a single reference signal for multiple information-bearing ones. Hence, the energy requirement is saved by almost a half. The bit error performance is studied using the baseband system model and analytically tested using Gaussian approximation method. Results show the BER performance outperforms other standard and recently developed differentially coherent chaos systems, including Permutation Index–DCSK by an average of 2.25 dB. Moreover, the analytical form which is developed to predict the bit error rate (BER) is validated by simulation. Results demonstrate the performance in AWGN is closely matching with the simulation results, particularly at high SNR.

Optimum DCT type-I based transceiver model and effective channel estimation for uplink NB-IoT system

Single-tone and multi-tone transmissions in the narrowband Internet of Things (NB-IoT) uplink system can be accomplished by employing different orthogonal basis. In this paper, we develop an uplink NB-IoT baseband system model and derive the corresponding analytical signal model based on the discrete cosine transform type-I (DCT-I) domain. Basically, the circular convolution and channel matrix diagonalization issues for designing DCT-based systems are addressed without exploiting any redundancy (a prefix and a suffix sequences, and zero-padding (ZP)) into each transmitted data symbol blocks. In our proposed DCT-I based transceiver, we employ a standard cyclic prefix (CP) and apply discrete Fourier transform (DFT) and inverse DFT (IDFT) operations directly to make the channel matrix circulant and diagonal, resulting in the use of one-tap frequency-domain channel equalizer without incorporating extra front-end prefilter at the receiver. Furthermore, we propose novel least squares (LS) and linear minimum mean square error (LMMSE) channel estimators by considering the energy concentration and spectral compaction properties of DCT-I for the uplink NB-IoT system. The expressions for the DCT-I domain LS and LMMSE estimators are derived for channel frequency response estimation and mean square error computation. Finally, the viability of the proposed CP-DCT-I-NB-IoT uplink system, as well as the channel estimators, are tested compared with the standardized CP-DFT-NB-IoT and ZP-DCT type-2 even based single-carrier frequency-division multiple access (SC-FDMA) systems through rigorous computer simulations.

Validation of a software‐defined baseband system for satellite telemetry and telecommand

SummaryThis paper presents the validation of a software‐defined baseband (SDB) system for satellite telemetry and telecommand (TM/TC). The baseband system was developed using the open‐source GNU Radio development kit. It runs on a personal computer connected to a commercial‐off‐the‐shelf (CoTS) RF frontend. The validation process was performed by the use of a mission‐qualified satellite emulator, a state‐of‐the‐art baseband unit, and orbiting satellites. The baseband is designed to offer multimission support. Hence, it includes a suite of modulation schemes, line codes, matched filters, and Consultative Committee for Space Data Systems (CCSDS) forward error correction codes (convolutional, Reed–Solomon, concatenated, and low‐density parity‐check [LDPC]) typically employed in TM/TC missions. The figures of merit used for the validation of the TM receiver are bit error rate (BER) and frame error rate (FER). For the TC transmitter, the validated features are modulation index, power spectrum, and the physical layer operations procedures (PLOP).Graphical Abstract We present the validation of a software‐defined baseband system for satellite ground operations. Based on low‐cost software‐defined radios, the baseband show minimal performance degradation in a laboratory environement. Infield tests shows that the baseband is capable of supporting ground operations for orbiting satellites.

Complex vector fitting toolbox: a software package for the modelling and simulation of general linear and passive baseband systems

Complex vector fitting (CVF) is a robust method to efficiently and accurately model general linear and passive baseband systems. Such models are important for the analysis and design of modern electronic and optical communication systems. This letter introduces an efficient toolbox implementation of the CVF algorithm. The effectiveness of the code is illustrated on a suitable application example.

An Analysis Pipeline for CHIME/FRB Full-array Baseband Data

Abstract The Canadian Hydrogen Intensity Mapping Experiment (CHIME) has become a leading facility for detecting fast radio bursts (FRBs) through the CHIME/FRB backend. CHIME/FRB searches for fast transients in polarization-summed intensity data streams that have 24 kHz spectral and 1 ms temporal resolution. The intensity beams are pointed to predetermined locations in the sky. A triggered baseband system records the coherent electric field measured by each antenna in the CHIME array at the time of FRB detections. Here we describe the analysis techniques and automated pipeline developed to process these full-array baseband data recordings. Whereas the real-time FRB detection pipeline has a localization limit of several arcminutes, offline analysis of baseband data yields source localizations with subarcminute precision, as characterized by using a sample of pulsars and one repeating FRB with known positions. The baseband pipeline also enables resolving temporal substructure on a microsecond scale and the study of polarization including detections of Faraday rotation.

Design and implementation of enhanced permutation index differential chaos shift keying system

In standard PI-DCSK, information is transmitted by sending reference chaotic signal followed by information bearing signal, which is simply a permutated version of the reference signal. Permutation is performed based on a specific data map. In this paper, a developed version of (PI-DCSK) is presented and tested in AWGN and multipath Rayleigh fading channels environment. Information bearing signal is generated by mapping first set of information bits to the reference bit while the second set is mapped to the permutated-time reversed version of same reference signal. Both versions is added together on the same time slot. At the receiver, each incoming signal undergoes two operations; permutation and time reversal followed by permutation to detect the two different sets of information. This arrangement offers high data rate and reduce the energy requirement utilizing the low cross correlation between the chaotic signal and its time reversed version. The bit error performance is studied using baseband system model and analytically tested using Gaussian Approximation (GA) method. System performance is evaluated analytically to predict the Bit Error Rate (BER) using computer simulations. Results show that system performance is outperform the recent developed one by an average of at 2.25 dB while outperform the other standard chaos based scheme by an average of at same Eb∕N0. Moreover, the analytical form which are developed to predict the BER is validated by simulation.

Analysis of Intersymbol Interference Characterized by the Large Array Antennas Adopted in a 60-GHz-Band Gigabit Compact-Range Wireless Access System

A compact-range wireless access system in the 60-GHz band has been proposed for multi-Gb/s data transfer. A prototype Gigabit Access Transponder Equipment (GATE) was built to evaluate the system performance in terms of received signal strength, signal-to-noise ratio (SNR), and bit error rate (BER). The proposed system operates in the near-field regions of large array antennas adopted in the transmitter (Tx). The time delays due to the signals transmitted from different array elements to the receiver (Rx), or/and those due to the multiple reflections between Tx and Rx antennas become comparable with the symbol lengths in our gigabit wireless access system. In that sense, this system would be susceptible to intersymbol interference (ISI). In this study, the concept of ISI is introduced in the antenna field for the first time. An equivalent baseband communication system is newly proposed to evaluate the wireless channel, including Tx and Rx antennas. The analysis procedures and equations are provided for the calculation of ISI. The ISIs due to three potential contributions are analyzed in detail. It is verified that our proposed ISI analysis has succeeded in relating the antenna characteristic to the system performance observed in the baseband.

Hardware Implementation for Belief Propagation Flip Decoding of Polar Codes

Belief propagation (BP) decoding has natural advantages in throughput for polar codes to meet high-speed and low-latency requirements. The soft outputs of BP decoding can be utilized further for joint detection and decoding in the baseband communication system. However, its error-correction performance is not comparable with the successive cancellation list (SCL) decoding. Belief propagation flip (BPF) decoding is recently proposed to improve the error-correction performance of BP decoding and indicates the potential to compete with SCL decoding. In this paper, we propose an advanced BPF (A-BPF) scheme that reduces the decoding latency with the help of one critical bit and improves the error-correction performance by the proposed joint detection criterion. To improve area efficiency in the hardware level, an optimized sorting network is proposed and applied for the A-BPF decoder. The decoder is implemented on 65 nm CMOS technology for length-1024 and rate-1/2 polar codes, and the results show that the proposed decoder can achieve a close frame error rate performance to the SCL decoder with four lists and deliver a throughput of 5.17 Gb/s at $E_{b}/N_{0}=4.0$ dB.

THz wireless communication system based on wavelet transform

SummaryWith a very wide frequency band not allocated at present, THz waves have many optimal characteristics such as high transmission rate, large capacity, and high security. The research of THz communication technology has become a hotspot in wireless communication. For THz wireless communications, it is crucial to study advanced electrical signal processing techniques. In this paper, in view of the shortcomings of traditional orthogonal frequency division multiplexing (OFDM) technology, we propose wavelet transform orthogonal multicarrier modulation method in THz system. In addition, we study THz channel coding technology to ensure that the THz wireless communication baseband system has better bit error rate (BER) performance and low computational complexity. Based on above, a THz wireless communication baseband system is conceived.

A 75-Gb/s/mm2 and Energy-Efficient LDPC Decoder Based on a Reduced Complexity Second Minimum Approximation Min-Sum Algorithm

This article presents a high-throughput and low-routing complexity low-density parity check (LDPC) decoder design based on a novel second minimum approximation min-sum (SAMS) algorithm. The routing congestion is mitigated by reducing the required interconnections in the critical path of the routing network. The implementation and postlayout results with 28-nm 1P9M CMOS process show that the proposed design can achieve a throughput of 10.5 Gb/s for a millimeter-wave 60-GHz baseband system while satisfying the low bit error rate (BER) requirements (10−7). The proposed design reduces the wiring in the routing network by 21% and improves the area by 12% compared to the conventional min-sum (MS) and normalized MS (NMS) algorithm. Additional hardware optimizations are obtained by considering the internal message passing resolution based on the BER and signal-to-noise ratio (SNR) requirements for a practical baseband system. The power consumption is efficiently reduced by the employment of a shared address generator that exploits the degree of parallelism to reduce the switching activity on a group of memory elements. The LDPC decoder is implemented with a core area of 0.14 mm2, power consumption of 81 mW at 312.5 MHz, and the area and power efficiency of 75 Gb/s/mm2 and 10.2 pJ/bit, respectively.

PARALLEL PIPELINED MULTI RADIX VARIABLE LENGTH FAST FOURIER TRANSFORM ARCHITECTURE

There is an enormous demand for high speed data communication or high speed internet using Long Term Evolution (LTE) or LTE-Advanced communication methods. To achieve the high speed data rate in the receiver side, it is necessary to achieve high throughput in the Fast Fourier transform (FFT) architecture. Hence there is demand to improve the throughput of the FFT architectures used for high speed data communication. The FFT architecture is designed and optimized for LTE-A applications. However, the high throughput has been achieved by sacrificing hardware resources of the Field Programmable Gate Array (FPGA). Many fixed and variable length FFT processors are proposed by the researchers with improved performance focusing either on algorithmic modifications, novel architectural optimizations or radix selection. Among these FFT processors, the goal and main objectives of this paper are: 1. To design and implement a pipelined FFT architecture to give high throughput for LTE-A MIMO applications 2. To develop an intellectual property (IP) core for FFT computation with variable FFT size 3. To propose a parallel implementation to increase the performance of LTE-A baseband processing system. In an Orthogonal Frequency Division Multiplexing (OFDM) baseband communication system, FFT operation is one of the highest computationally serious tasks which directly influence the communication system performance factor. The baseband hardware has to be capable as well as efficient enough to calculate FFT in specific timing restrictions. Thus, the parallel pipelined multi radix Variable Length FFT architectures for LTE-A Multiple-Input-Multiple-Output (MIMO) applications have been designed. The proposed FFT architecture delivers a throughput of 550 MSPS at the maximum clock rate of 550 MHz. The proposed FFT support the FFT length of 64, 128, 256, 512, 1024 and 2048 for LTE-Advanced MIMO standard. The proposed FFT architecture has been implemented in Xilinx Artix-7 FPGA device and the performance metrics have been analysed. Even though the proposed FFT architecture consumes additional Block-RAMs (BRAM) and quite an amount of Xilinx-Xtreme Digital Signal Processor (DSP)/ DSP48 resources, the Power Delay Product (PDP) of the proposed FFT is excellent compared to the existing FFT architectures. The proposed multi radix mixed 2/3/5 parallel pipelined 2048 point FFT architectures exhibits very less latency of 11.382 µs at 550 MHz clock frequency compared to the existing system with the latency of 56.88 µs at 200 MHz clock frequency. Moreover, the designed FFT architecture utilizes 96 Xilinx Xtreme DSP blocks 25040 clock cycles to complete the FFT operation with an excellent throughput of 2200 MSPS with FFT computation time of 45.528 µs at the clock frequency of 550 MHz for the 4x4 MIMO- OFDM architecture. Therefore, the designed FFT provides high throughput rate in order to meet the modern wireless standard specifications. The proposed FFT architecture outperforms well in terms high throughput, low latency and better PDP with extra hardware as trade-off for both for Single FFT and for MIMO technology.

Concurrent development and verification of an all‐software baseband for satellite ground operations

SummaryCommunication systems are adopting all‐software architectures, because of their scalability, extensibility, flexibility, and cost‐effectiveness. This paper introduces a concurrent approach to the development and verification of baseband systems for satellite ground operations based on the behaviour‐driven development methodology. The open‐source GNU Radio development kit is used for developing the software‐defined radio baseband signal processing, as well as simulating the satellite and realistic channel impairments. The system performance at the end shows deviations of less than 1 dB with respect to the ideal performance and the Green Book standards specified by the Consultative Committee for Space Data Systems.

Modeling and Analysis of Signal Integrity of High-Speed Interconnected Channel With Degraded Contact Surface

High-speed interconnected channels, including printed circuit boards (PCBs) and high-speed connectors, are widely used in digital baseband communication systems. Connector degradation may lead to deterioration of the integrity of digital signals and is one of the major causes of low communication quality. In this work, the effect of electrical contact degradation on signal integrity was investigated using model analysis and experimental testing. A 3-D electromagnetic field model of a high-speed channel with a degraded contact surface was developed to evaluate transmission loss, signal reflection, and crosstalk. Using multiconductor transmission line theory and contact physics, a distributed parameter circuit model of a high-speed channel with a degraded contact surface was also developed. The electromagnetic field model results are in good agreement with those obtained from the distributed parameter circuit model. Both the electromagnetic field model and the circuit model results are validated using experimental tests. The results of this investigation provide a better understanding of the characteristics of signal transmission through a degraded contact surface in a high-speed channel and theoretical support for identifying failure features in fault diagnosis.

A novel Technique for Linearizing Digital Pre-distortion in Power Amplifiers for OFDM Applications

In this paper, a novel technique is proposed for linearizing digital pre-distortion in power amplifiers for OFDM systems. For this purpose, a hybrid technique comprising search table method and polynomial method is employed such that as few as hardware are utilize in implementation in order to not only decreases computational complexity but also leads to a fast response capability. Furthermore, least mean square (LMS), as a competitive method, was employed in the proposed technique. Coefficients of look-up table are estimated by LMS method as a forward program with the least error amount in order to estimate modulator output of OFDM. In addition, designing of several RF power amplifiers and their linearization unit in ADS software results in elimination of non-linear distortions of these amplifiers by linearizing unit, and yet various realistic involved phenomena in base-band pre-distortion system design, including memory effect, antenna mismatch, and etc., are studied. Measures such as ACPR were adopted for the purpose of linearization measurement and comparison. High The peak-to-average power ratio (PAPR) is one of the biggest problems in OFDM systems that by combining these techniques, we improve it. The obtained results of the proposed technique are presented both by look-up table and frequency spectrum of output signal. The results also indicate appropriate performance of the proposed technique. Simulations were carried out on ADS software, while final signal output was extracted by MATLAB.

Functional Analysis of Software-Defined Radio Baseband for Satellite Ground Operations

This paper presents functional analysis and system specifications of a baseband system using software-defined radio (SDR) technology. The analysis is primarily based on the latest blue-book standards from the Consultative Committee for Space Data Systems (CCSDS). It covers telemetry, telecommand, and ranging, as well as some specifications of the associated physical layers. The SDR-based baseband system is envisioned to support ground operations in the form of a software-as-a-Service (SaaS) private cloud.

Analog Approximate-FFT 8/16-Beam Algorithms, Architectures and CMOS Circuits for 5G Beamforming MIMO Transceivers

Emerging millimeter-wave (mmW) wireless systems require beamforming and multiple-input multiple-output (MIMO) approaches in order to mitigate path loss, obstructions, and attenuation of the communication channel. Sharp mmW beams are essential for this purpose and must support baseband bandwidths of at least 1 GHz to facilitate higher system capacity. This paper explores a baseband multi-beamforming method based on the spatial Fourier transform. Approximate computing techniques are used to propose a low-complexity fast algorithm with sparse factorizations that neatly map to integer $W/L$ ratios in CMOS current mirrors. The resulting approximate fast Fourier transform (FFT) can thus be efficiently realized using CMOS analog integrated circuits to generate multiple, parallel mmW beams in both transmit and receive modes. The paper proposes both 8- and 16-point approximate-FFT algorithms together with circuit theory and design information for 65-nm CMOS implementations. Post-layout simulations of the 8-point circuit in Cadence Spectre provide well-defined mmW beam shapes, a baseband bandwidth of 2.7 GHz, a power consumption of 70 mW, and a dynamic range >42.2 dB. Preliminary experimental results confirm the basic functionality of the 8-beam circuit. Schematic-level analysis of the 16-beam I/Q version show worst-case and average side lobe levels of −10.2 dB and −12.2 dB at 1 GHz bandwidth, and −9.1 dB and −11.3 dB at 1.5 GHz bandwidth. The proposed multi-beam architectures have the potential to reduce circuit area and power requirements while meeting the bandwidth requirements of emerging 5G baseband systems.

Performance of Vector Fitting Algorithm Applied to Bandpass and Baseband Systems

This article presents the performance evaluation of Vector Fitting Algorithm (VFA) from a system identification perspective. In this paper, VFA has been first applied to known baseband and bandpass systems such as Butterworth lowpass and bandpass filters to analyze the algorithm’s pole-residue extraction ability for band-limited noisy data. The poles identified by the algorithm for different bandwidths and noise powers are compared with the actual system poles of the baseband and bandpass systems. It is concluded that the algorithm is capable of identifying the actual system poles even if the capture bandwidth is less than the 3 dB bandwidth, which is a significant observation of this paper. It is also seen that the system identification performance with noisy data is better for baseband systems when compared to bandpass systems. Further, a practical investigation has been done to evaluate VFA performance for modeling a microstrip coupled line filter in the presence of noise.

Guest Editorial Advanced Baseband Processing Circuits and Systems for 5G Communications

This special issue of the IEEE Journal on Emerging and Selected Topics in Circuits and Systems (JETCAS) aims at demonstrating the latest research progress on circuits and systems design for efficient baseband realization of 5G wireless.

Advanced Baseband Processing Algorithms, Circuits, and Implementations for 5G Communication

The rapid emergence of 5G communications technology and standardization has seen an accelerated transfer of theoretical concepts to advanced development and implementation. Not only are 5G baseband signal processing algorithms becoming more important, but also the co-design and implementation of corresponding circuits, architectures, and platforms are becoming necessary due to rapid standardization of 5G communications. This timely overview paper introduces circuits and systems (CAS) for key enabling technologies for the new 5G era: massive MIMO, mmWave baseband systems, NOMA schemes, advanced channel coding, and so on. The state-of-the-art research progress in these areas is summarized for interested readers to initiate discussion on limitations of existing solutions and open research problems that are looking for innovative solutions, especially in the CAS area. We hope this paper can bridge the gap between the theoretical investigation and application implementation for 5G communications.