Software Defined Radio Development Research Articles

Wireless Signal Representation Techniques for Automatic Modulation Classification

In this paper, we present a comprehensive survey and detailed comparison of techniques that have been applied to the problem of identifying the type of modulation contained within received wireless signals. Known as automatic modulation classification (AMC), the problem has been studied for many decades. AMC plays a significant role in both military and civilian scenarios and is the main step in smart receivers. Especially with the development of software-defined radios and automatic communication systems, IoT technology and the spread of 5G technology bring the number of spectrum-using equipment explosion, making the problem of scarce spectrum resources more prominent. Although AMC techniques can be optimized from the classifier’s point of view, signal pre-processing also plays a critical role. Relevant data representation approaches include time-frequency analysis, cyclostationary transforms, and hybrid techniques.We provide a taxonomy of common approaches based on order and dimensionality along with an overall analysis of signal pre-processing algorithms for AMC. Furthermore, we reproduce the major existing schemes under uniform conditions, allowing an objective comparison among different methodologies. Finally, we create an open-source Python library to simulate these techniques so the results in this paper are reproducible for future research.

A Primer on Software Defined Radios

The commercial success of cellular phone systems during the late 1980s and early 1990 years heralded the wireless revolution that became apparent at the turn of the 21st century and has led the modern society to a highly interconnected world where ubiquitous connectivity and mobility are enabled by powerful wireless terminals. Software defined radio (SDR) technology has played a major role in accelerating the pace at which wireless capabilities have advanced, in particular over the past 15 years, and SDRs are now at the core of modern wireless communication systems. In this paper we give an overview of SDRs that includes a discussion of drivers and technologies that have contributed to their continuous advancement, and presents the theory needed to understand the architecture and operation of current SDRs. We also review the choices for SDR platforms and the programming options that are currently available for SDR research, development, and teaching, and present case studies illustrating SDR use. Our hope is that the paper will be useful as a reference to wireless researchers and developers working in the industry or in academic settings on further advancing and refining the capabilities of wireless systems.

Index Modulation Based Frequency Hopping: Anti-Jamming Design and Analysis

Reactive symbol-level jammer has attracted attention due to its low energy cost and high jamming efficiency. With the development of software-defined radio (SDR), the implementation of reactive symbol-level jamming has become more practical and efficient. To combat the reactive jammer, this paper proposes an index modulation based frequency hopping spread spectrum (IM-FHSS) scheme. Specifically, the current available frequencies are determined by multiple orthogonal frequency hopping (FH) patterns, and bit information is transmitted through the index of the active FH pattern. At the receiving side, we design an energy detector to distinguish the active and idle frequencies. With such implementation, IM-FHSS can obtain the improved resistance of reactive symbol-level jammer. Subsequently, we propose the alternative spectral efficiency (SE) mode of IM-FHSS in order to meet the high SE and low-power jamming scenarios. Furthermore, we analyze the BER of this scheme for the reactive symbol-level jamming under the cases of energy correlation, jamming rate, and phase offset. Theoretical analysis and simulation results show that IM-FHSS exhibits enhanced resistance to reactive symbol-level jamming than traditional FH scheme.

Dynamic Spectrum Anti-Jamming Communications: Challenges and Opportunities

Due to the openness of the transmission medium, it is necessary for radio systems to have anti-jamming abilities. Traditional anti-jamming methods such as sequence-based frequency hopping and direct sequence spread spectrum have shortcomings of low spectral efficiency and fixed communication patterns. With the development of software-defined radio, jamming devices are increasingly advanced and efficient. In this article, we propose a new paradigm for anti-jamming called DSAJ. With the help of cognitive radio and machine learning, the aim of DSAJ is to learn the dynamic and complex spectrum environment and obtain an optimal communication strategy. We first introduce the basic concept of anti-jamming communications and provide a brief summary of anti-jamming methods. Then, through a case study, mathematical modeling and applications of DSAJ are discussed for both single-user and multi-user systems. A real-life DSAJ testbed is described, and some potential research directions are discussed.

New Approach of Automatic Modulation Classification based on in Phase-Quadrature Diagram Combined with Artificial Neural Network

Automatic Modulation Classification (AMC) with intelligent system is an attracting area of research due to the development of SDR (Software Defined Radio). This paper proposes a new algorithm based on a combination of k-means clustering and Artificial Neural Network (ANN). We use constellation diagram I-Q (In phase, Quadrature) as basic information. K-means algorithm is used to normalize data transmitted and pollute by the Additive White Gaussian Noise (AWGN), then the new diagram obtained is considered as an image and coded in pixel before entering in MLP (Multi-Layer Perceptron) Neural Network. Simulation results show an improvement of recognition rate under low SNR (Signal Noise Rate) compare to some results obtained in the literature.

Automatic Configurable Hardware Code Generation for Software-Defined Radios

The development of software-defined radio (SDR) systems using field-programmable gate arrays (FPGAs) compels designers to reuse pre-existing Intellectual Property (IP) cores in order to meet time-to-market and design efficiency requirements. However, the low-level development difficulties associated with FPGAs hinder productivity, even when the designer is experienced with hardware design. These low-level difficulties include non-standard interfacing methods, component communication and synchronization challenges, complicated timing constraints and processing blocks that need to be customized through time-consuming design tweaks. In this paper, we present a methodology for automated and behavioral integration of dedicated IP cores for rapid prototyping of SDR applications. To maintain high performance of the SDR designs, our methodology integrates IP cores using characteristics of the dataflow model of computation (MoC), namely the static dataflow with access patterns (SDF-AP). We show how the dataflow is mapped onto the low-level model of hardware by efficiently applying low-level based optimizations and using a formal analysis technique that guarantees the correctness of the generated solutions. Furthermore, we demonstrate the capability of our automated hardware design approach by developing eight SDR applications in VHDL. The results show that well-optimized designs are generated and that this can improve productivity while also conserving the hardware resources used.

Implementation of Multi-Hop Cognitive Radio Testbed using Raspberry Pi and USRP

The increased usage of wireless communication has created a wireless frequency shortage problem. Cognitive Radio (CR) has attracted public attention, as one of the solutions that can resolve this issue. In this paper, the authors built an actual CR system testbed using the SDR (Software Defined Radio) platform, USRP (Universal Software Radio Peripheral) board, the SDR development toolkit, GNU Radio, and Raspberry Pi3, which is a single board computer. They configured Secondary User (SU)s with Raspberry Pi3 for straightforward and portable test environment. The authors' testbed performs spectrum sensing based on energy detection and determines whether the channel is occupied or not. Experimental results not only show performance but also provide their testbed that works well in multi-hop environments.

Software-Defined Radio FPGA Cores: Building towards a Domain-Specific Language

This paper reports on the design and implementation of an open-source library of parameterizable and reusable Hardware Description Language (HDL) Intellectual Property (IP) cores designed for the development of Software-Defined Radio (SDR) applications that are deployed on FPGA-based reconfigurable computing platforms. The library comprises a set of cores that were chosen, together with their parameters and interfacing schemas, based on recommendations from industry and academic SDR experts. The operation of the SDR cores is first validated and then benchmarked against two other cores libraries of a similar type to show that our cores do not take much more logic elements than existing cores and that they support a comparable maximum clock speed. Finally, we propose our design for a Domain-Specific Language (DSL) and supporting tool-flow, which we are in the process of building using our SDR library and the Delite DSL framework. We intend to take this DSL and supporting framework further to provide a rapid prototyping system for SDR application development to programmers not experienced in HDL coding. We conclude with a summary of the main characteristics of our SDR library and reflect on how our DSL tool-flow could assist other developers working in SDR field.

Guest Editorial: Evolutionary Advancements in Wireless Software Defined Radio Systems

The field of wireless communications over the years has been constantly making significant advancements in the domain of Software Defined Radios (SDRs). These reconfigurable radios are also capable to learn from their environment like the spectrum and then undertake rapid decisions based on its selfdefined policies leading to the development of wider range of new applications. Thus, new topics and concepts are not only been investigated in the Digital Signal Processing domain but also in the Cognitive Radio domain for an effective and efficient use of the spectrum. Using such technologies with widely accepted international standards like the Software Communications Architecture (SCA) in military software defined radios also requires that they go through the testing and certification processes. Thus, in this Special Issue of the Springer Journal of Signal Processing Systems, all these topics leading towards the evolution of SDRs are discussed. This Special Issue comprises of three sets containing a total of nine articles. The first set of articles put focus on the various cognitive radio technologies like Dynamic Spectrum Access and Spectrum Sensing. The still existing inefficient use of the spectrum is discussed in various SDR research communities. New and innovative ideas are continuously investigated to use the spectrum in the most efficient way in order to meet the ever growing demands of high data throughput. Use of Cognitive Radios is one such way to achieve it. These radios are able to sense the radio environment in order to identify portions of the spectrum that are unused at a specific time or location and are able to reconfigure themselves. Various algorithms and techniques are being investigated to achieve such results in a dynamic environment. The second set of articles discusses several advanced Digital Signal Processing techniques. All these techniques aim at optimizing operationally relevant criteria. These criteria vary from achieving higher robustness, lower bit error rates, longer communication ranges, and minimal energy consumption to faster deployments. The proofs of the achievements are given either by simulation or by prototype implementation on off-the-shelf low cost hardware. The third set of articles illustrates the importance test and certification of Software Defined Radios in the military domain using internationally accepted standard like the SCA. Standards like the SCA allow waveforms to be ported easily across heterogeneous platforms. It also provides neatly defined interfaces and Application Program Interfaces (APIs) aimed to increase portability and interoperability of radios. In the final phase of the development of SDRs, efficient ways of testing and agencies providing the certification of standards play a significant role. * Marc Adrat marc.adrat@fkie.fraunhofer.de

A frame-based domain-specific language for rapid prototyping of FPGA-based software-defined radios

Abstract The field-programmable gate array (FPGA) technology is expected to play a key role in the development of software-defined radio (SDR) platforms. As this technology evolves, low-level designing methods for prototyping FPGA-based applications did not change throughout the decades. In the outstanding context of SDR, it is important to rapidly implement new waveforms to fulfill such a stringent flexibility paradigm. At the current time, different proposals have defined, through software-based approaches, some efficient methods to prototype SDR waveforms in a processor-based running environment. This paper describes a novel design flow for FPGA-based SDR applications. This flow relies upon high-level synthesis (HLS) principles and leverages the nascent HLS tools. Its entry point is a domain-specific language (DSL) which handles the complexity of programming an FPGA and integrates some SDR features so as to enable automatic waveform control generation from a data frame model. Two waveforms (IEEE 802.15.4 and IEEE 802.11a) have been designed and explored via this new methodology, and the results are highlighted in this paper.

Component-based waveform development: the Nucleus tool flow for efficient and portable software defined radio

With the advent of multi-processor systems on chip (MPSoCs) and due to the complexity and variety of modern wireless standards, academia and industry are moving towards software defined radio (SDR) solutions. It is the goal of the SDR approach to allow designers to describe a radio standard or waveform by means of a high level language. This allows faster waveform development cycles and makes it easier to migrate waveforms across different platforms. Out of many software paradigms, component-based software engineering (CBSE) is an attractive match for SDR, especially for baseband applications. It abstracts waveforms in the traditional way algorithm designers think of their applications and guarantees a high degree of portability. However, existing CBSE approaches for SDR have not been able to close the gap between specification and implementation so as to achieve the computational performance and the energy efficiency of handcrafted solutions. The main reason for this gap is that these flows rely on traditional compilers to lower the high level specification to the platform. The work presented in this paper builds on the Nucleus Concept (Ramakrishnan et al., IEEE Military Communications Conference (MILCOM 2009) [28]) in which computationally intensive kernels and their implementation characteristics on the target platform are known. This information allows a tool to close the performance gap, and thus enables efficient component-based SDR development. In this paper we present such a flow and its supporting environment, which includes state-of-the-art tools for system level design. The flow is demonstrated on a MIMO OFDM transceiver.

Analytical and Simulation-based Design Space Exploration of Software Defined Radios

The proposed idea of software defined radios (SDRs) offers the potential to cope with the complexity and flexibility demands of future wireless communication devices. Unfortunately, the tight interaction of software and hardware as well as the high computational requirements make development of SDRs to one of the most challenging tasks system architects are facing today. The main challenge is to select the optimal or a sub-optimal solution within the large design space spread by the many design options. This paper introduces a novel design space exploration framework for particular early development stages. The key contribution is a pre-simulation based mathematical analysis based on synchronous data flow (SDF) graphs in order to take the right software and hardware design decisions. This analysis can be utilized right from the start of the design cycle with only limited knowledge of the final implementation. In addition, the proposed technique seamlessly integrates into an electronic system level (ESL) based simulation framework. This allows for a smooth transition from pure mathematical analysis to the simulation of the final implementation. The practical usage of the framework and its capabilities are highlighted by a case study from a typical SDR design.

A seamless software defined radio development flow for waveform and prototype debugging

With the increasing number of wireless communication standards flexibility has gained more and more importance which has lead to the software defined radio (SDR) concept. However, SDR development has to face many challenges, among them are the questions how SDR systems can be designed to achieve flexibility, architectural efficiency, energy efficiency and portability at the same time. These requirements result in very elaborate architectures and a highly increased design complexity. To cope with such complexity, we proposed an SDR development flow. During the development of such SDR, debugging becomes more efficient on a prototype hardware implementation than on a simulation model. However, error analysis on a prototype suffers from strong limitations like a reduced state visibility. In this paper, an extension to the SDR development flow is presented and successfully applied to an example SDR. It allows for an efficient error analysis with the SDR simulation model by the feedback of stimulus data from the prototype.

COGNITIVE RADIOS FOR DYNAMIC SPECTRUM ACCESS - An Agile Radio for Wireless Innovation

We present the details of a portable, powerful, and flexible software-defined radio development platform called the Kansas University Agile Radio (KUAR). The primary purpose of the KUAR is to enable advanced research in the areas of wireless radio networks, dynamic spectrum access, and cognitive radios. We describe the KUAR hardware implementation and software architecture and present example application of the KUAR to modulation, spectrum measurement, channel estimation, and rapid configuration and adaptation. We outline research directions enabled by the KUAR