Baseband Digital Signal Processing Research Articles

A DSP-Purposed REconfigurable Acceleration Machine (DREAM) for High Energy Efficiency MIMO Signal Processing

The wireless baseband processing algorithms are still developing and show a great diversity. The development of ASIC implementations cannot quickly adapt to the evolution of algorithms and standards. Meanwhile, the general-purpose processors cannot meet the real-time requirements in some scenarios. This paper proposes a DSP-purposed REconfigurable Acceleration Machine (DREAM) core for wireless baseband digital signal processing, which has a good trade-off between flexibility and performance. First, we abstract a set of shared operators with a moderate granularity from a variety of wireless MIMO signal processing algorithms. Then, we propose a two-step configuration process to reduce the size of the required reconfiguration bits. Besides, we design a conflict-free address generator to transfer data between the on-chip scratchpad memory and reconfiguration processing elements with high efficiency and high throughput. Finally, the prototype DREAM core has been implemented in TSMC CMOS 28 nm, and its area and power consumption have been analyzed. The chip has great flexibility in supporting a variety of wireless MIMO processing algorithms and a wide range of MIMO scales. The proposed DREAM core can achieve the normalized area efficiency and the normalized energy efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.67~Gbps/MGE$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15.05~Gbps/W$ </tex-math></inline-formula> , which are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.56\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4.18\times $ </tex-math></inline-formula> those of state-of-the-art reconfigurable implementations when running the WeJi-based MIMO detection algorithm.

О ПРИМЕНИМОСТИ МЕТОДА БЫСТРОГО ЦИФРОВОГО ФОРМИРОВАНИЯ ХАРАКТЕРИСТИК НАПРАВЛЕННОСТИ В СИСТЕМАХ ЛОКАЦИИ СО СЛОЖНЫМИ СИГНАЛАМИ

This work belongs to the field of hydroacoustics, namely to the problem of digitalbeamforming based on spatial fast Fourier transform (FFT) in a multibeam echo sounder(MLS) with baseband digital signal processing. The applicability of FFT-based beamformingwhen using relatively broadband signals is considered. The main attention is paid to the MLSwith a static beam pattern, at the same time, obtained results are also applicable to rangingsystems that provide dynamic beam control. The aim of the study is to establish the relatio nshipbetween the relative width of the signal spectrum and signal level in the spatial channelof the MLS with a given maximum beam steering. A qualitative condition for the applicabilityof FFT-based spatial beamforming for a probing signal with a given relative bandwidth isdetermined. An analytical expression linking the signal attenuation coefficient in the spatialchannel with the following signal and receiver characteristics was obtained: the number ofelements of the linear equidistant antenna array, the distance between array elements, beamsteering, the correlation function of the complex envelope of the signal, the window functionfor weighting the matched filter response in spectral domain. Presented results can be usefulin designing multibeam echo sounders, providing high resolution both in range and in angularcoordinates.

Physical Education Attendance Based on Wireless and Passive RFID Technology

Attendance information is an important data resource for physical education management in colleges and universities. Based on wireless and passive RFID technology theory, this paper designs a UHF passive RFID radio frequency identification physical education attendance model. The device includes three parts: carrier leakage canceller, radio frequency transceiver, and digital baseband signal processing. In the model hierarchy, the client sends a Web request to the server, and the request information is organized by the RFID document, including information such as the range, scale, and display attributes of the requested map. The Web server modifies the predefined map definition file by parsing the information. In the simulation process, the frequency domain model and baseband complex envelope time domain system of the RF front-end of the reader based on carrier leakage cancellation were built in ADS software and Matlab/Simulink, respectively. The reader front-end and digital baseband signal processing are comprehensively simulated, and the result verifies the function of the whole system. After testing and debugging, it has been proven that the median synchronization number of the signal is 12, the point synchronization number is 29, the input IDB compression point measured by a single tone is 9.6 dB smaller than that of IIP3, and the input IDB compression point measured by two tones is smaller than 14.4 dB, which can promote the informatization process of physical education management in colleges and universities.

Multiplierless Filtered-OFDM Transmitter for Narrowband IoT Devices

In cyclic-prefix orthogonal frequency-division multiplexing (CP-OFDM)-based radio access, the coexistence of different technologies without precise time-frequency synchronization is limited due to high out-of-band (OOB) emissions. Therefore, the spectrum enhancement techniques play a key role in relaxing the synchronization and power control requirements. This allows a higher degree of opportunistic spectrum use with minimized interference. In addition, all the transmitting devices have to fulfill specific transmitted signal quality requirements, including the maximum OOB radiated signal power. With the orthogonal frequency-division multiplexing (OFDM)-based radio access, some additional signal processing for improved spectrum containment is commonly needed to achieve these requirements. The filtering and time-domain windowing are two fundamentally different approaches for spectrum enhancement. The filtered OFDM (F-OFDM) provides better spectrum localization than the time-windowing schemes [such as windowed overlap-add (WOLA)], with the cost of higher complexity. This article introduces low-complexity solutions for spectrally enhanced narrowband OFDM transmitters based on the use of lookup tables (LUTs). The proposed LUT approach, requiring only memory units and a low number of additions, allows to avoid all computationally expensive operations in online transmitter processing, as it builds the transmitted signal by summing the stored partial waveforms optimized offline. In certain cases, completely multiplication- and summation-free designs are possible. The transmitters of narrowband Internet of Things (NB-IoT) devices are natural applications for the proposed LUT approach, as they require additional digital baseband signal processing to reach the emission requirements. It is shown that the proposed LUT schemes can provide significant savings in real-time computations of NB-IoT devices, while fulfilling the 3GPP requirements.

Adaptive suppression of passive intermodulation in digital satellite transceivers

For the performance issues of satellite transceivers suffering passive intermodulation interference, a novel and effective digital suppression algorithm is presented in this paper. In contrast to analog approaches, digital passive intermodulation (PIM) suppression approaches can be easily reconfigured and therefore are highly attractive for future satellite communication systems. A simplified model of nonlinear distortion from passive microwave devices is established in consideration of the memory effect. The multiple high-order PIM products falling into the receiving band can be described as a bilinear predictor function. A suppression algorithm based on a bilinear polynomial decorrelated adaptive filter is proposed for baseband digital signal processing. In consideration of the time-varying characteristics of passive intermodulation, this algorithm can achieve the rapidness of online interference estimation and low complexity with less consumption of resources. Numerical simulation results show that the algorithm can effectively compensate the passive intermodulation interference, and achieve a high signal-to-interference ratio gain.

Low Power Gated-Clock Design for Multi-core DSP Based SDR Platform

With the rapid development of wireless communication systems, multi-core DSP with high computing performance is an important part of SDR (Software-Defined Radio) platform. Research has focused on low-power design in SDR platform since the SDR platform is sensitive to power consumption. Following the baseband digital signal processing features of SDR application, this paper proposes a data-driven and task-driven gated-clock architecture. The DSP cores in the multi-core DSP can be turned on and turned off with this architecture at the appropriate time. Experiments show that the proposed low power gated-clock architecture can provide effective low-power performance for multi-core DSP in SDR platforms.

A Fully Integrated IEEE 802.15.7 Visible Light Communication Transmitter With On-Chip 8-W 85% Efficiency Boost LED Driver

This paper presents an IEEE 802.15.7 Physical Layer I (PHY-I) standard compliant visible light communication (VLC) transmitter system-on-a-chip (SoC), enabling the use of ordinary white LED lights as beacons or broadcasters for location-based applications. The mixed-signal SoC integrates a baseband digital signal processing (DSP) unit, a VLC modulator, and a switching boost LED driver with an on-chip power MOSFET. The DSP unit supports various coding schemes as well as both the on-off keying (OOK) modulation and the variable pulse-position modulation specified in the aforementioned standard. The boost LED driver is designed to power a matrix of 4 × 5 LEDs using Li-ion batteries for portable applications. The SoC simultaneously supports VLC and LED illumination with nine dimming levels. Implemented in a 0.35-μm CMOS process with 20-V devices, the SoC achieves a measured VLC data rate of up to 266 kb/s at a package error rate (PER) < 10% using a 211 −1 PRBS (pseudo random binary sequence) input. The communication distance measured is more than 2 m using no optical lens with the link efficiency of 5 nJ/bit. From an input at 3–5 V, the boost converter generates an output at 6–20 V with a 92% peak efficiency and an 8-W rating.

The Research on Phantom-Bit Technology of Digital Phase Shifters for Satellite Tracking System of Phase Array

Phased array satellite platform self-tracking system is for the stability between the missiles and other high-speed movement of the platform and the relay satellite two-way information transmission needs to carry out the self-tracking technology research of onboard platform-dimensional active phased array satellite. The system uses a sub-array correlation method for accurate measurement of the angle of the satellite signal. Receiving array is divided into four 4 * 4 sub-array, each antenna signal combining unit 4 sub array for 4-way A / D to be converted, through down-conversion, filtering, extraction and other processes to get a digital baseband signal, the baseband digital signal processing is to extract the angle error information into digital beam orientation system for tracking filtering operation, thereby ensuring that the transceiver has been aligned with the satellite antenna beam direction. In this paper ,phantom-bit technology for satellite tracking system under the condition of minimum beam displacement is researched for satellite tracking system.

IF Modulation in the Millimeter-Wave Transmitter End

This article describes a method of IF modulation used in millimeter-wave transmitter, the method is AD9857 combined with FPGA, choose the EP1C6 as a FPGA chip, and use this FPGA chip complete the base-band digital signal processing, and implement the control to the AD9857. AD9857 is a kind of the orthogonal frequency converter based on DDS technology, complete the functions of base-band digital signal interpolation filter, orthogonal modulation, and D/A conversion in the digital domain and complete QDPSK modulation signal output of 70MHz IF carrier. This method can eliminate phase and gain imbalances and distortion which caused by analog modulation, also can simplify the system structure, reduce cost and improve the performance and reliability of the system.

Optical-wireless-optical full link for polarization multiplexing quadrature amplitude/phase modulation signal transmission

We propose and experimentally demonstrate an optical wireless integration system at the Q-band, in which up to 40 Gb/s polarization multiplexing multilevel quadrature amplitude/phase modulation (PM-QAM) signal can be first transmitted over 20 km single-mode fiber-28 (SMF-28), then delivered over a 2 m 2 × 2 multiple-input multiple-output wireless link, and finally transmitted over another 20 km SMF-28. The PM-QAM modulated wireless millimeter-wave (mm-wave) signal at 40 GHz is generated based on the remote heterodyning technique, and demodulated by the radio-frequency transparent photonic technique based on homodyne coherent detection and baseband digital signal processing. The classic constant modulus algorithm equalization is used at the receiver to realize polarization demultiplexing of the PM-QAM signal. For the first time, to the best of our knowledge, we realize the conversion of the PM-QAM modulated wireless mm-wave signal to the optical signal as well as 20 km fiber transmission of the converted optical signal.

100-GHz Wireless-Over-Fiber Links With Up to 16-Gb/s QPSK Modulation Using Optical Heterodyne Generation and Digital Coherent Detection

In this letter, a novel technique for direct conversion of an optical baseband quadrature phase-shift keying (QPSK) signal to a millimeter-wave wireless signal and subsequent signal demodulation is reported. Optical heterodyne mixing of the optical baseband QPSK signal with a free-running unmodulated laser for the wireless signal generation is employed. To correct for the phase and frequency offset originating from the heterodyne mixing of the two free-running lasers, wireless signal demodulation based on optical coherent detection in combination with baseband digital signal processing is implemented. As a proof of concept, 5-Gb/s amplitude-shift keying and up to a 16-Gb/s QPSK wireless signal in the band of 75-110 GHz was generated and successfully demodulated. All-photonic millimeter-wave wireless signal generation and digital coherent detection at baud-rate are employed without complex optical phase-locked loop.

Radio-Frequency Transparent Demodulation for Broadband Hybrid Wireless-Optical Links

A novel demodulation technique which is transparent to radio-frequency (RF) carrier frequency is presented and experimentally demonstrated for multigigabit wireless signals. The presented demodulation technique employs optical single-sideband filtering, coherent detection, and baseband digital signal processing. Multigigabit wireless signal demodulation of 1.25-Gbaud quadrature phase-shift-keying modulated data at 40- and 35-GHz RF carrier frequency is experimentally demonstrated using the proposed demodulation scheme.

Power Amplifiers and Transmitters for Next Generation Mobile Handsets

As a wireless handset deals with multiple application standards concurrently, RF transmitters and power amplifiers are required to be more power efficient and reconfigurable. In this paper, we review the recent advances in the design of the power amplifiers and transmitters. Then, the systematic design approaches to improve the performance with the digital baseband signal processing are introduced for the next generation mobile handset.

Wireless Communications Transmitter Performance Enhancement Using Advanced Signal Processing Algorithms Running in a Hybrid DSP/FPGA Platform

This paper deals with digital base band signal processing algorithms, which are seen as enabling technologies for software-enabled radios, that are intended for the correction of the analog front end. In particular, this paper focuses on the design, optimization and testability of predistortion functions suitable for the linearization of narrowband and wideband transmitters developed with a hybrid DSP/FPGA platform. To select the best algorithm for the identification of the predistortion function, singular value decomposition, recursive least squares (RLS), and QR-RLS algorithms are implemented on the same digital signal processor; and, the computation complexity, time, accuracy and the required resources are studied. The hardware implementation of the predistortion function is then carefully performed, in order to meet the real time execution requirements.

Efficient Design of OFDMA-Based Programmable Wireless Radios

With the increasing demand for efficient spectrum management, programmable wireless radios can potentially play a key role in shaping our future spectrum use. In this paper, we consider the design of low-power programmable wireless radios based on orthogonal frequency division multiple access (OFDMA). To meet the demands of higher data rate communications, we split OFDMA symbols carrying multiuser data across several noncontiguous bands of available spectrum. To relax power consumption in analog-to-digital and digital-to-analog converters, we use a programmable narrowband RF front end comprising of programmable synthesizers and fixed low-pass filters. To perform digital baseband signal processing in an energy efficient manner, we propose efficient designs for the fast Fourier transform (FFT) and inverse FFT (IFFT) modules. Our designs of the FFT/IFFT modules reduce power consumption and chip area, and are capable of handling the dynamic nature of spectrum in programmable radios. To recover data that falls within the transition band of the filters, we propose a combiner similar to maximal ratio combiner. We also present the complete design of programmable wireless radios in accordance with the IEEE 802.22 (draft) standard.

Development of MIMO-SDR Platform and Its Application to Real-Time Channel Measurements

A multiple-input multiple-output software defined radio (MIMO-SDR) platform was developed for implementation of MIMO transmission and propagation measurement systems. This platform consists of multiple functional boards for baseband (BB) digital signal processing and frequency conversion of 5 GHz-band radio frequency (RF) signals. The BB boards have capability of arbitrary system implementation by rewriting software on reconfigurable devices such as field programmable gate arrays (FPGAs) and digital signal processors (DSPs). The MIMO-SDR platform employs hybrid implementation architecture by taking advantages of FPGA, DSP, and CPU, where functional blocks with the needs for real-time processing are implemented on the FPGAs/DSPs, and other blocks are processed off-line on the CPU. In order to realize the hybrid implementation, driver software was developed as an application program interface (API) of the MIMO-SDR platform. In this paper, hardware architecture of the developed MIMO-SDR platform and its software implementation architecture are explained. As an application example, implementation of a real-time MIMO channel measurement system and initial measurement results are presented.

A new adaptive delay method for wideband wireless Kahn's RF power amplifiers

This paper presents an adaptive delay control method used in wideband Kahn's envelope elimination and restoration (EER) RF power amplifiers (PAs). Besides control circuits, envelope and phase signals are also implemented by baseband digital signal processing (DSP) technique. It avoids using not only nonlinear limiter and envelope detector, but also difficult RF delay module or complicated feedback loop, each of which is necessary in conventional EER PA's structure. With the help of applying phase detector, counter, and latch register, the delay varies adaptively with circuit parameters, and then the new PA maintains performance at all times. With the application of this method we can realize a PA applicable to IEEE 802.11b standard with 11 MHz signal bandwidth, of which adjacent channel power ratio (ACPR) is better than -40 dBc at the first side lobe

A 900 MHz CMOS RF transceiver including digital baseband and hardware‐MAC for IEEE 802.15.4/ZigBeeTM applications

AbstractThis paper presents a fully‐integrated RF transceiver operating from 860 to 930 MHz. The device parameters are compliant to the IEEE 802.15.4 standard. The analogue portion of the chip contains a direct‐conversion receiver, a fractional‐N PLL, a direct‐conversion transmitter and a TR‐switch. Digital baseband signal processing as well as MAC support are also implemented on the same chip. Only minimal external components are needed to form a complete wireless network application two low‐cost crystals, the PLL loop filter, an antenna and a low‐cost 8 bit microcontroller. Therefore, this chip is one of the most integrated 802.15.4 transceiver ICs presented to date. The receiver input sensitivity is −98 dBm. The chip is fabricated in a 0.25 μm CMOS technology with MIM‐capacitors, deep n‐well and a thick top metal layer. Copyright © 2005 AEIT.

Advanced methods for I/Q imbalance compensation in communication receivers

I/Q signal processing is widely utilized in today's communication receivers. However, all I/Q processing receiver structures, such as the low-IF receiver, face a common problem of matching the amplitudes and phases of the I and Q branches. In practice, imbalances are unavoidable in the analog front-end, which results in finite and usually insufficient rejection of the image frequency band. This causes the image signal to appear as interference on top of the desired signal. We carry out general signal analysis of an imbalanced I/Q processing receiver and propose novel methods for I/Q imbalance compensation using baseband digital signal processing. A simple structure for compensation is derived, based on a traditional adaptive interference canceller. Improved image rejection can also be obtained by using more advanced blind source separation techniques. Theoretical analysis of the performance of the proposed imbalance compensation structures is presented. In addition, some simulation results are provided in order to further evaluate the performance of the proposed methods. The results indicate that the I/Q imbalance can be effectively compensated during the normal operation of the receiver even in the rapidly changing case, as long as a linear system model for the imbalance is valid.

Design Methodology of a Low-Energy Reconfigurable Single-Chip DSP System

In this paper, we first present a reconfigurable architecture template for low-power digital signal processing, and then an energy conscious design methodology to bridge the algorithm to architecture gap. The energy efficiency of such an architecture and the effectiveness of the methodology are demonstrated in case study implementations targeting baseband voice processing and digital signal processing.