Baseband Algorithms Research Articles

A review of RIS-assisted wireless communication research

This paper presents a review of the research progress in Reconfigurable Intelligent Surface (RIS) assisted wireless communications. It begins by providing an overview of recent developments and trends in the field of wireless communications. The following sections introduce the fundamental principles of both RIS technology and wireless communication technology, providing a foundation for the subsequent comprehensive examination of the current research status of RIS-assisted wireless communication. This study then turns to an in-depth analysis of the advancements in RIS-assisted wireless communication research, encompassing hardware regulation, baseband algorithms, multi-access enhancement, and network design. Subsequently, this paper offers a concise examination of the opportunities and challenges associated with RIS in wireless communication. This paper closes with a summary of the field of RIS-assisted wireless communication, followed by an outlook on future directions.

Conflict-Free Parallel Data Access Technology for Matrix Calculation in Memory System of ASIP of 5G/6G Macro Base Stations

Among the physical layer baseband algorithms in macro base stations, the matrix processing has the dom-inant computing cost, large data access overhead and com-plicated addressing mode. The existing data access methods are not the best solution for memory system of ASIP (Ap-plication Specific Instruction Set Processor) in 5G/6G macro stations. We hence proposed a parallel conflict-free data access method for matrix. Moreover, we proposed a non-redundant access method for positive definite matrix that stores only trigonometric part, and the corresponding parallel addressing method with low storage overhead. Our method solves the problem of data conflict and minimizes the memory space of ASIP, and supports ASIP to approach the performance limit of architecture to the maximum ex-tent under the constraint of architecture and data parallel-ism. We implemented the proposed method as a static memory optimizer, which provides a tool for the design and optimization of memory system of ASIP in 5G/6G macro base stations with low overhead. Experimental results show that for 64W64 positive definite matrix inversion algorithm based on Cholesky decomposition, our addressing method can save 32% of the execution time, and the cost of memory space is reduced by half.

Measurement and Estimation Methodology for EMC and OTA Testing in the VIRC

In recent years, promising results have been reported with the vibrating intrinsic reverberation chamber (VIRC) combining performance and cost-efficiency for electromagnetic compatibility (EMC) measurements. This also makes it a potentially attractive solution for over-the-air (OTA) testing, which is yet to be investigated. Therefore, this article proposes the first systematic and thorough methodology to characterize the VIRC for use in EMC and OTA testing of wireless baseband algorithms of narrow-band single-input single-output channels. This methodology has been developed to measure and estimate the channel first- and second-order temporal and spectral characteristics taking into consideration the effect of different carrier frequencies, rotational speeds of VIRC motors, and loading conditions. It is then applied to a channel setup inside a VIRC for a preliminary investigation before the VIRC itself is fully characterized. It is shown that mounting an absorber in a specific location on the hatch significantly improves the rejection rate of the chi-squared goodness-of-fit test for Rician distribution without increasing the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$K$</tex-math></inline-formula> -factor above <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 10 dB over the frequency range 755–2740 MHz in the VIRC under investigation. However, the proposed methodology has been devised to be universal to any reverberation chamber, and the obtained results can be used to improve EMC testing due to the better understanding of the unique VIRC environment.

Register allocation compilation technique for ASIP in 5G micro base stations

The currently available compilation techniques are for general computing and are not optimized for physical layer computing in 5G micro base stations. In such cases, the foreseeable data sizes and small code size are application specific opportunities for baseband algorithm optimizations. Therefore, the special attention can be paid, for example, the specific register allocation algorithm has not been studied so far. The compilation for kernel sub-routines of baseband in 5G micro base stations is our focusing point. For applications of known and fixed data size, we proposed a compilation scheme of parallel data accessing, while operands can be mainly allocated and stored in registers. Based on a small register group (48×32b), the target of our compilation scheme is the optimization of baseband algorithms based on 4×4 or smaller matrices, maximizing the utilization of register files, and eliminating the extra register data exchanging. Meanwhile, when data is allocated into register files, we used VLIW (Very Long Instruction Word) machine to hide the time of data accessing and minimize the cost of data accessing, thus the total execution time is minimum. Experiments indicate that for algorithms with small data size, the cost of data accessing and extra addressing can be minimized.

Compilation of Parallel Data Access for Vector Processor in Radio Base Stations

The data size and data feature under the cur-rent mainstream compilation schemes can be diversified, formal methods are thus mandatory. However, in a micro base station, as an embedded system, the typical feature or opportunity of baseband algorithms is its predictable small code and data sizes. The research is thus needed and there is so far no dedicated research on the related register alloca-tion algorithms. In this letter, we focus on compilation re-search for baseband kernel subroutines of 5G micro base stations. We proposed a parallel data access compilation scheme for applications with fixed and known data size, while operation data can be mostly stored and allocated in register file. The goal of the compilation scheme is to opti-mize algorithms based on 4x4 or smaller matrices, to reach the maximum register file utility, and eliminate the extra register data swapping. At the same time, we hide the data access time when allocating data into register file, and minimize the data access cost by using VLIW machine, so that the overall running time is minimum. Based on a small register group (48x32b) and the proposed compilation method, this letter implemented frequently used baseband subroutines (kernels) of 4x4 matrix with complex variables of 16b+16b and reached minimized run time. Results show that the extra addressing and data accessing cost is mini-mized for algorithms with small data size.

Improved Real Time GPS RF Data Capturing for GNSS SDR Applications

Global Navigation Satellite System (GNSS) software-defined radio (SDR) is a programmable software receiver, primarily used to receive satellite data and provide user position. It is flexible and cost-effective compared to conventional satellite receivers. In GNSS SDR, recording the live raw data in real-time is a challenging task as large data are sent by the satellites at a very high speed. These data are further processed by the baseband algorithms which provide the user location. The accuracy of the tracked location depends on the precision of the data captured. Among the available hardware receivers, USRP RF front end kit provides flexibility. This paper proposes an efficient approach to capture the real-time GPS data by using the USRP N210 kit. If the receiver is not tuned with the exact parameters, the problems of data overflow and underflow occur. A novel data controlling queue thread method is introduced to overcome this problem. It is evident that the results obtained from our method are very close to those of Ublox GPS.

SOFTWARE DEFINED ANTENNA TESTING

Microstrip patch directional antennas are an attractive solution for modern wireless systems due to their high gain and directivity. Being an attractive solution creates the need to design such devices for various application scenarios. We have addressed that need by designing, simulating, and testing a rectangular microstrip patch directional antenna at 5GHz. Antenna patch and ground plane were designed with the well-known guided wavelength equation. The antenna performance, in terms of return loss at -10dB, gain, bandwidth, and the radiation pattern was analyzed with a simulation model. The proposed antenna achieved an impedance bandwidth of 77.8MHz (from 4.9662GHz to 5.0440GHz) and a gain of 6.26dBi at 5GHz. The antenna performance was verified with a software defined radio platform. We found that the software radio measurements confirmed the key simulation results. Furthermore, the extensive use of simulation enabled us to develop both antenna and digital baseband algorithms in parallel.

Phase Retrieval Motivated Nonlinear MIMO Communication With Magnitude Measurements

This paper proposes a multiuser magnitude-only (MO-)MIMO, whose base station acquires quantized magnitudes of the complex baseband signals through envelop detectors and low-resolution ADCs. Consequently, MO-MIMO enjoys much lower circuit power and cost in comparison with the conventional MIMO. Because the phase information is unavailable, all the existing MIMO baseband algorithms cannot be applied into MO-MIMO. Therefore, two types of channel estimators and multiuser detectors are constructed by first categorizing the channel estimation and multiuser detection problems as a quantized phase retrieval (PR) problem, and then solving the latter by developing two methods under the framework of generalized approximate message passing (GAMP). The first method directly applies GAMP to solve the quantized PR problem by exploiting the probability relationships between the quantized magnitude measurements and unknown complex signals. The second method iterates between the missing phase estimation and signal recovery, where the latter calls for GAMP to handle a linear mixing problem with quantized observations. The developed estimators and detectors call for matrix-vector multiplications and nonlinear function calculations as the most complex operations, handle the nonlinear quantization loss specially, and exploit the signal prior probability distributions. Finally, their effectiveness is validated experimentally.

Baseband design for 5G UDN base stations: Methods and implementation

Baseband design and implementation for micro/pico base stations (mBS) in 5G ultra-dense network (UDN) is studied. Low cost is an essential requirement for mBS baseband in UDN. Digital baseband cost of ASIC/ASIP (Application Specific Integrated Circuit / Instruction-set processor) is of the most uncertainty in mBS system. However, the actual costs and hardware feasibility of the baseband are yet unknown to network deployers and researchers. In this paper, we studied the baseband hardware system design and implementation for low-cost mBS. We analyzed popular baseband algorithms and architectures for both full-digital and hybrid beamforming (BF) for UDN. We then proposed feasible chip-level solutions for the baseband with up to 128-antenna BS system, and estimated their implementation cost. Results show that among full-digital BF algorithms, zero-forcing is a choice of high performance and low cost; for hybrid BF, 4×32 architecture (32 RF chains) provides good reduction in baseband cost with acceptable performance loss, thus it can be a preferable solution under low cost consideration. The proposed system planning method can also be used for the design of other related systems.

Signal Processing in Massive MIMO With IQ Imbalances and Low-Resolution ADCs

This paper proposes a massive multiple-input multiple-output (MIMO) with low-precision in-phase quadrature-phase (IQ) (de-)modulators and low-resolution analog-to-digital convertors, and develops uplink baseband algorithms for the proposed MIMO system. The IQ imbalance parameters are recovered by a two-stage method. At the first stage, the base station (BS) antennas acquire phase-shifted versions of their imbalance parameters after receiving some predefined training sequence emitted by a specific transceiver that is near to the BS and shares flat-fading channels between itself and the BS. At the second stage, the phase shifts from the first stage are estimated by the specific transceiver through receiving a common sequence transmitted by the BS antennas alternatively. In order to jointly handle the IQ imbalance and nonlinear quantization loss, the IQ-imbalanced multiuser (MU)-MIMO with single-antenna users is first converted into an IQ-balanced MU-MIMO with dual-antenna users. Then, two kinds of channel estimator and multiuser detectors are constructed for the equivalent IQ-balanced system based on the spectral projected gradient method and vectorized message passing de-quantization algorithm. Our numerical results validate the effectiveness of the above baseband algorithms, and show that the proposed massive MIMO is more energy-efficient than the conventional one when the channel coherence time is long enough.

Multilevel power modeling of base station and its ICs

A new power estimation method is proposed for base station (BS) in this paper. Based on this method, a software platform for power estimation is developed. The proposed method models power consumption on different abstraction levels by splitting a typical base station into several basic components at different levels in the view of embedded system design. In particular, our focus is on baseband IC (Integrate Circuit) due to it’s the dominant power consumer in small cells. Baseband power model is based on arithmetic computing costs of selected algorithms. All computing and storage costs are calibrated using algorithm complexity, hardware architecture, activity ratio, silicon technology, and overheads on all hierarchies. Micro architecture and IC technology are considered. The model enables power comparison of different types of base stations configured with different baseband algorithms, micro architectures, and ICs. The model also supports cellular operators in power estimation of different deployment strategies and transmission schemes. The model is verified by comparing power consumption with a real LTE base station. By exposing more configuration freedoms, the platform can be used for power estimation of current and future base stations.

An open access 4×4 MIMO testbed and its validation with an IEEE 802.11n WLAN system

Multiple-Input Multiple-Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) have been widely accepted as key techniques of the current and future wireless communication systems. In this paper, an open access MIMO testbed is presented, on which the researchers can demonstrate and evaluate their baseband algorithms over the real wireless channel, without knowing much details about the hardware of the testbed. Moreover, an IEEE 802.11n transmission scheme is implemented as a design example to validate this testbed as well as demonstrate the transmission characteristics of MIMO-OFDM.

Physical Layer Development Framework for OsmocomBB

The open source GSM protocol stack of the OsmocomBB project offers a versatile development environment regarding the data link and network layer. There is no solution available for developing physical layer baseband algorithms in combination with the data link and network layer. In this paper, a baseband development framework architecture with a suitable interface to the protocol stack of OsmocomBB is presented. With the proposed framework, a complete GSM protocol stack can be run and baseband algorithms can be evaluated in a closed system. It closes the gap between physical layer signal processing implementations in Matlab and the upper layers of the OsmocomBB GSM protocol stack. An embedded version of the system has been realized with FPGA and PowerPC to enable real-time operation. The functionality of the system has been verified with a testbed comprising an OpenBTS base-station emulator, a receiver board with RF transceiver and our developed physical layer signal processing system.

GRANULARITY OF EFFICIENT ENERGY SAVING IN WIRELESS SENSOR NETWORKS

Most existing techniques for reconfigurable processors focus on the computation model. This paper focuses on increasing the granularity of Efficient Energy Saving units without compromising flexibility. This is carried out by matching the granularity to the degree-of-freedom processing in most wireless Networks. A design flow that accelerates the exploration of tradeoffs among various architectures for the configurable unit is discussed in this paper. In this Paper we mentioned in detailed way of evaluates various baseband algorithms and presents the granularity of configurable units, describes the architecture of each configurable unit and presents the methodology used in the architectural tradeoff analyses as well as the tradeoff results.

MAC and baseband processors for RF-MIMO WLAN

The article describes hardware solutions for the IEEE 802.11 medium access control (MAC) layer and IEEE 802.11a digital baseband in an RF-MIMO WLAN transceiver that performs the signal combining in the analogue domain. Architecture and implementation details of the MAC processor including a hardware accelerator and a 16-bit MAC-physical layer (PHY) interface are presented. The proposed hardware solution is tested and verified using a PHY link emulator. Architecture, design, implementation, and test of a reconfigurable digital baseband processor are described too. Description includes the baseband algorithms (the main blocks being MIMO channel estimation and Tx-Rx analogue beamforming), their FPGA-based implementation, baseband printed-circuit-board, and real-time tests.

A Low-Power and Flexible Energy Detection IR-UWB Receiver for RFID and Wireless Sensor Networks

This paper presents an energy detection Impulse Radio Ultra-Wideband (IR-UWB) receiver for Radio Frequency Identification (RFID) and Wireless Sensor Networks (WSN) applications. An Application-Specific Integrated Circuit (ASIC) consisting of a 3-5 GHz analog front-end, a timing circuit and a high speed baseband controller is implemented in a 90 nm standard CMOS technology. A Field-Programmable Gate Array (FPGA) is employed as a reconfigurable back-end, enabling adaptive baseband algorithms and ranging estimations. The proposed architecture is featured by high flexibility that adopts a wide range of pulse rate (512 kHz-33 MHz), processing gain (0-18 dB), correlation schemes, synchronization algorithms, and modulation schemes (PPM/OOK). The receiver prototype was fabricated and measured. The power consumption of the ASIC is 16.3 mW at 1 V power supply, which promises a minimal energy consumption of 0.5 nJ/bit. The whole link is evaluated together with a UWB RFID tag. Bit error rate (BER) measurement displays a sensitivity of -79 dBm at 10 Mb/s with 10-3 BER achieved by the proposed receiver, corresponding to an operation distance over 10 meters under the FCC regulation.

Implementation of a [formula omitted] MIMO-OFDM receiver on an application specific processor

This paper describes the implementation of the hard computational kernels required for the baseband (BB) processing of a 2×2 multiple-input multiple-output (MIMO)-OFDM receiver on a design-framework for application specific processors. The employed low-complexity BB algorithms are described and their computational complexity is derived. The receiver is split into two parts which are mapped onto two application specific processors, each tailored to the computational needs of the associated digital signal processing kernels. The first processor performs the per stream MIMO-OFDM processing. The second processor handles the MIMO detection. Finally, the 0.18μm 1P/6M CMOS technology layout of both fabricated application specific processors is presented. Real-time BB processing is possible on these engines running at a clock frequency of 250MHz.

Novel Methodology for Functional Modeling and Simulation of Wireless Embedded Systems

A novel methodology is presented for the modeling and the simulation of wireless embedded systems. Tight interaction between the analog and the digital functionality makes the design and verification of such systems a real challenge. The applied methodology brings together the functional models of the baseband algorithms written in C language with the circuit descriptions at behavioral level in Verilog or Verilog-AMS for the system simulations in a single kernel environment. The physical layer of an ultrawideband system has been successfully modeled and simulated. The results confirm that this methodology provides a standardized framework in order to efficiently and accurately simulate complex mixed signal applications for embedded systems.

Software-defined-radio-assisted adaptive broadband frequency hopping multicarrier DS-CDMA

Against the backdrop of the explosive expansion of the Internet and the continued dramatic increase in demand for high-speed multimedia wireless services, there is an urgent demand for flexible, bandwidth-efficient transceivers. Multistandard operation is also an important requirement for the future generations of wireless systems. This article presents a versatile broadband multiple access scheme, combining frequency hopping with multicarrier DS-CDMA (FH/MC DS-CDMA). In the short term, the proposed FH/MC DS-CDMA scheme could be employed in the existing second- and third-generation CDMA system bands. Hence, it has the potential of supporting compatibility with these existing systems. This article also shows that FH/MC DS-CDMA exhibits a high grade of flexibility in the context of system design and parameter reconfiguration. Therefore, in the long term, the proposed FH/MC DS-CDMA scheme is capable of meeting the requirements of future broadband mobile wireless systems, with the aid of introducing more advanced techniques facilitated by the employment of software-defined radios (SDR) and with the advent of efficient adaptive baseband algorithms.

Discrete Estimation of Continuous Angle-Modulated Signals Over Multipath Channels for Aeronautical Communication

The multipath channel for communication between an aerospace vehicle and a ground terminal is modeled by a multiplicative first-order Markov process. The multiplicative process is treated as a component of the message model and the discrete-time demodulation algorithms using the extended Kalman nonlinear estimation technique are developed for continuous-time angle-modulated signals. The equivalent baseband form of the demodulator structure is derived. Two examples of the message process are discussed for an FM system. The simulation results are presented for various values of the bandwidth expansion ratio and the additive SNR. The performance of the baseband algorithms is discussed.