Base Station MIMO Detector Algorithm Implementations

Despite the popularity of C-based High-Level Synthesis (HLS) tools, their generic input programming languages make it challenging for the designer to find the expression that will result in adequate hardware quality and performance. Moreover, the syntactic variance of the input description often causes the inability of the HLS tool to fully identify and benefit from the properties of the computations. In this work, we propose extending standard C-based HLS tools with the concept of computational patterns. In particular, we present a template-based hardware generation strategy which enables complete exploitation of the pattern properties to produce high-quality hardware modules. The parametric templates allow us to automatically scale the implementation to the resource and data-bandwidth constraints of the target device, independent from the analysis abilities of the HLS tool. To demonstrate the benefits of our approach, we generated hardware implementations for six applications which we composed using a set of computational patterns (i.e. map, zip and reduce), achieving 1.3× to 2.8× speed-up over a state-of-the-art commercial HLS tool.

Despite significant performance and power advantages compared to microprocessors, widespread usage of FPGAs has been limited by increased design complexity. High-level synthesis (HLS) tools have reduced design complexity but provide limited support for verification, debugging, and timing analysis. Such tools generally rely on inaccurate software simulation or lengthy register-transfer-level simulations, which are unattractive to software developers. In this paper, we introduce HLS techniques that allow application designers to efficiently synthesize commonly used ANSI-C assertions into FPGA circuits, enabling verification and debugging of circuits generated from HLS tools, while executing in the actual FPGA environment. To verify that HLS-generated circuits meet execution timing constraints, we extend the in-circuit assertion support for testing of elapsed time for arbitrary regions of code. Furthermore, we generalize timing assertions to transparently provide hang detection that back annotates hang occurrences to source code. The presented techniques enable software developers to rapidly verify, debug, and analyze timing for FPGA applications, while reducing frequency by less than 3% and increasing FPGA resource utilization by 0.7% or less for several application case studies on the Altera Stratix-II EP2S180 and Stratix-III EP3SE260 using Impulse-C. The presented techniques reduced area overhead by as much as 3x and improved assertion performance by as much as 100% compared to unoptimized in-circuit assertions.

To offset the high engineering cost of digital circuit design, hardware engineers are looking increasingly toward high-level languages such as C and C++ to implement their designs. To do this, they employ High-Level Synthesis (HLS) tools that translate their high-level specifications down to a hardware description language such as Verilog. Unfortunately, HLS tools themselves employ sophisticated optimization passes that may have bugs that silently introduce errors in realized hardware. The cost of such errors is high, as hardware is costly or impossible to repair if software patching is not an option. In this work, we present a translation validation approach for verifying the correctness of the HLS translation process. Given an initial C program and the generated Verilog code, our approach establishes their equivalence without relying on any intermediate results or representations produced by the HLS tool. We implemented our approach in a tool called VTV that is able to validate a body of programs compiled by the Xilinx Vivado HLS compiler.

Interface Synthesis in High-Level Synthesis (HLS) tool is the process by which it creates hardware interfaces from the formal C++ arguments of the C++ function being synthesized. The synthesis step uses size information from the C++ types along with user constraints and the interface components available in the libraries in order to identify the resources that can meet the user's constraints. During scheduling, the appropriate quantity of interface resources will be allocated and inserted into the resulting RTL netlist generated by the HLS tool. Interface Synthesis components can be simple wires, basic protocol req/ack like, or more sophisticated bus-protocol (masters and/or slaves). This work describes the design and the integration of a custom 10 component implementing STMicroelectronics proprietary STBus Type 3 protocol. STBus is a set of protocols, interfaces, primitives and architectures specifying an interconnect subsystem, versatile in terms of performance, architecture and implementation. The STBus includes heavy-pipelined transactions and out- of-order management.

Background: In recent years, the rising demand for high-performance radar systems in aeronautics, astronautics, national defense, and civil communication has driven the widespread application of phased-array technology. The design of beam controllers, the core of phased-array systems, faces many challenges. Traditional implementation schemes are usually based on application-specific integrated circuits (ASIC) or discrete components, which have a long development cycle, poor flexibility, and limited adaptability. Field-programmable gate arrays (FPGA), with their high parallelism, reconfigurability, and powerful signal processing capabilities, offer a new way to implement phased-array control systems. But FPGA design has traditionally relied on register transfer level (RTL) description, which is inefficient and struggles to keep up with the rapid iteration of complex algorithms. With the development of high-level synthesis (HLS) technology, it has become possible to develop FPGAs using high-level languages such as C/C++. However, improving development efficiency while ensuring hardware performance remains a key issue in the design of phased-array beam controllers. Materials and Methods: This study employs an HLS - RTL co - design method to build a phased - array beam controller. This approach combines the strengths of HLS's efficient algorithm implementation and RTL's precise hardware interface control. The system architecture consists of three parts: the host - machine control layer, FPGA processing layer, and phase - control output layer. In the FPGA processing layer, the core beam - forming algorithm is implemented via HLS. Based on phased - array principles, this algorithm converts target angles to wave vectors and calculates phase - compensation values for each element in an 8×8 array. Pipelining and parallel processing techniques are used in the HLS design to optimize algorithm throughput and latency. The phase - control output layer, designed with RTL, repackages 64 calculated phase values and distributes them to 16 physical phase - shifter chips. Each phase - shifter manages four elements and receives control data through an SPI interface. Results: The proposed FPGA-based phased-array beam controller design in this paper has successfully achieved high - speed, high - precision beam control. By using the HLS - RTL co - design method, it has solved the problem of low algorithm implementation efficiency in traditional FPGA development and ensured the high performance and reliability of hardware interfaces. Experimental results indicate that the system meets or surpasses design targets on key performance indicators. Its end - to - end latency is kept within 130μs, it supports an angle update rate of over 5,000 times per second, and can satisfy the requirements for tracking highly dynamic targets in practical applications. Conclusion: The major contributions of this research are as follows: presenting an HLS - RTL co - design methodology for complex FPGA system development; designing an efficient phased - array beam - forming algorithm and its hardware implementation; and developing a flexible and scalable phased - array control system architecture that supports different array configurations. These findings are highly significant for beamforming technologies in phased - array radar and 5G communication systems, as well as for other FPGA applications requiring high - speed signal processing.

The potential of FPGAs as accelerators for high-performance computing applications is very large, but many factors are involved in their performance. The design for FPGAs and the selection of the proper optimizations when mapping computations to FPGAs lead to prohibitively long developing time. Alternatives are the high-level synthesis (HLS) tools, which promise a fast design space exploration due to design at high-level or analytical performance models which provide realistic performance expectations, potential impediments to performance, and optimization guidelines. In this paper we propose the combination of both, in order to construct a performance model for FPGAs which is able to visually condense all the helpful information for the designer. Our proposed model extends the roofline model, by considering the resource consumption and the parameters used in the HLS tools, to maximize the performance and the resource utilization within the area of the FPGA. The proposed model is applied to optimize the design exploration of a class of window-based image processing applications using two different HLS tools. The results show the accuracy of the model as well as its flexibility to be combined with any HLS tool.

Neural networks (NNs) are used in numerous applications such as audio–video processing and image classification. NNs can address the limitations of the traditional computer algorithms. Recently, the research utilizing field-programmable gate arrays (FPGAs) to implement NNs is on the rise due to low power dissipation, easy and fast reconfigurability offered by these platforms. This is due to the research and development efforts put into the design optimization to improve the throughput of FPGAs. The integration of appropriate hardware with advanced artificial intelligence (AI) software presents many challenges. This paper offers a generalized model of NNs on a FPGA device. In addition, it presents the design process for the high-level synthesis (HLS) tools to implement the project on FPGA. This paper shows the results of latency, timing, pre- and post-synthesis, implementation, and hardware utilization on Xilinx FPGA target device. In this paper, NN for XOR logic gate operation is performed and verified by using HLS tool, and FPGA implementation is proposed. The NN and backpropagation algorithm are developed in high-level programming languages like Python, Java, C, C++. The training part of the NN has been done by using open-source software Dev C++, and tuned weights are taken to Xilinx Vitis HLS. Simulation, synthesis, and implementation are performed by using Xilinx Vitis HLS and Vivado 2020.1 electronic design automation (EDA) tools. NN architecture with tuned weights is implemented on Xilinx ZYNQ FPGA target device. This paper shows that we were able to achieve latency in one clock cycle interval through pipeline and array partition.KeywordsHigh-level synthesis (HLS)Neural networks (NNs)Register transfer level (RTL)Field-programmable gate arrays (FPGAs)Systems on chip (SOC)Artificial intelligence (AI)Graphic processing units (GPUs)Generalized NNs (GNN)Recurrent neural network (RNN)Feed-forward neural networks (FFNNs)

High-level synthesis (HLS), which automatically synthesizes a register-transfer level (RTL) circuit from a behavioral description written in a high-level programming language such as C/C++, is becoming a more popular technique for improving design productivity. In general, HLS tools often generate a circuit with a larger area than those of hand-designed ones. One reason for this issue is that HLS tools often generate multiple instances of the same module from a function. To eliminate such a redundancy in circuit area in HLS, HLS tools are capable of sharing modules. Function-level module sharing at a behavioral description written in a high-level programming language may promote function reuse to increase effectiveness and reduce circuit area. In this paper, we present two HLS techniques for module sharing at the function level.

The rapidly increasing complexities of hardware designs are forcing design methodologies and tools to move to the Electronic System Level (ESL), a higher abstraction level with better productivity than the state-of-the-art Register Transfer Level (RTL). Behavioral synthesis, which automatically synthesizes ESL behavioral specifications to RTL implementations, plays a central role in this transition. However, since behavioral synthesis is a complex and error-prone translation process, the lack of designers' confidence in its correctness becomes a major barrier to its wide adoption. Therefore, techniques for establishing equivalence between an ESL specification and its synthesized RTL implementation are critical to bring behavioral synthesis into practice. The major research challenge to equivalence checking for behavioral synthesis is the significant semantic gap between ESL and RTL. The semantics of ESL involve untimed, sequential execution; however, the semantics of RTL involve timed, concurrent execution. We propose a sequential equivalence checking (SEC) framework for certifying a behavioral synthesis flow, which exploits information on successive intermediate design representations produced by the synthesis flow to bridge the semantic gap. In particular, the intermediate design representation after scheduling and pipelining transformations permits effective correspondence of internal operations between this design representation and the synthesized RTL implementation, enabling scalable, compositional equivalence checking. Certifications of loop and function pipelining transformations are possible by a combination of theorem proving and SEC through exploiting pipeline generation information from the synthesis flow (e.g., the iteration interval of a generated pipeline). The complexity brought by bubbles in function pipelines is creatively reduced by symbolically encoding all possible bubble insertions in one pipelined design representation. The result of this dissertation is a robust, practical, and scalable framework for certifying RTL designs synthesized from ESL specifications. We have validated the robustness, practicality, and scalability of our approach on industrial-scale ESL designs that result in tens of thousands of lines of RTL implementations.

Multiple access techniques like single carrier frequency division multiple access (SC-FDMA) requires orthogonal subcarriers to be distributed among various active users by the base station (BS). Intelligent scheduling of available subcarriers can significantly improve the quality of service (QoS) by employing SC-FDMA for uplink mobile communication. The BS scheduler must efficiently utilize the available frequency and multi-user diversity with limited side information exchange. In this regard, a simplified mathematical approach is first discussed for symbol error rate (SER) analysis of SC-FDMA system over a generalized multipath channel utilizing the statistical characterization of effective noise after equalization. The derived expressions of SER are generalized and simplified as it only depends on the equalizer amplification factor (EAF). The analysis is then used as a quick and accurate method to compare performance over various available subbands (SB's) for subcarrier distribution by BS scheduler with less side information to be exchanged. Since the error rate is directly dependent on EAF, we have used EAF for channel-dependent scheduling (CDS) performed by the base station (BS) for SC-FDMA.

Hardware Trojans are a major concern for integrated circuits. All parts of the electronics supply chain are vulnerable to this threat. Trojans can be inserted directly by a rogue employee or through a compromised computer-aided design tool at each step of the design cycle, including an alteration of the design files in the early stages and the fabrication process in a third-party malicious foundry. While Trojan insertion during the latter stages has been largely investigated, we focus on high-level synthesis (HLS) tools as a likely attack vector. HLS tools are used to generate intellectual property blocks from high-level specifications. To demonstrate the threat, we compromised an open-source HLS tool to inject three examples of HLS-aided hardware Trojans with functional and nonfunctional effects. Our results show that a black-hat HLS tool can be successfully used to maliciously alter electronic circuits to add latency, drain energy, or undermine the security of cryptographic hardware cores. This threat is an important security concern to address.

In digital signal processing, digital down converters (DDCs) convert digitized, band-limited signals to lower frequency signals at a smaller sampling rate to simplify subsequent filtering stages. Software-defined radio (SDR) is a radio communication system in which components that are traditionally implemented in hardware are implemented in software on an embedded system. DDCs are widely used in modern communication systems, such as SDRs. Herein, we propose a low-power- and area-optimized implementation of a DDC for SDR applications. The DDC was designed using an innovative and novel high-level synthesis (HLS) design method based on application-specific bit widths for data nodes. The results achieved after a field programmable gate array (FPGA) implementation are superior to those obtained from hand-coded register transfer level (RTL) implementations in terms of area and power efficiency, with almost the same speed of operation. Our results were obtained using the MATLAB hardware description language (HDL) coder for HLS and Xilinx Vivado (a software for the synthesis and analysis of HDL designs) for synthesis. The DDC down-converts an input of 200 MHz signal to an output of 2 MHz signal. This implementation was conducted on a real FPGA hardware (Xilinx Kintex-7) and verified against the design specifications using an FPGA in the loop feature of HDL Verifier and MATLAB. In addition, we propose a generic methodology for improving the area, speed, and power for different application designs and HLS tools. The proposed methodology is also applicable to hand-coded RTL designs for any application.

Designs generated by high-level synthesis (HLS) tools typically achieve a lower frequency compared to manual RTL designs. In this work, we study the timing issues in a diverse set of realistic and complex FPGA HLS designs. (1) We observe that in almost all cases the frequency degradation is caused by the broadcast structures generated by the HLS compiler. (2) We classify three major types of broadcasts in HLS-generated designs, including high-fanout data signals, pipeline flow control signals and synchronization signals for concurrent modules. (3) We reveal a number of limitations of the current HLS tools that result in those broadcast-related timing issues. (4) We propose a set of effective yet easy-to-implement approaches, including broadcast-aware scheduling, synchronization pruning, and skid-buffer-based flow control. Our experimental results show that our methods can improve the maximum frequency of a set of nine representative HLS benchmarks by 53% on average. In some cases, the frequency gain is more than 100 MHz.

High-Level Synthesis (HLS) tools are aimed at enabling performant FPGA designs that are authored in a high-level language. While commercial HLS tools are available today, there is still a substantial performance gap between most designs developed via HLS relative to traditional, labor intensive approaches. We report on several cases where an anticipated performance improvement was either not realized or resulted in decreased performance. These include: programming paradigm choices between data parallel vs. pipelined designs; dataflow implementations; configuration parameter choices; and handling odd data set sizes. The results point to a number of improvements that are needed for HLS tool flows, including a strong need for performance modeling that can reliably guide the compilation optimization process.

A common use for Field-Programmable Gate Arrays (FPGAs) is the implementation of hardware accelerators. A way of doing so is to specify the internal logic of such accelerators by using Hardware Description Languages (HDLs). However, HDLs rely on the expertise of developers and their knowledge about hardware development with FPGAs. Regarding this, efforts have been focused on developing High-level Synthesis (HLS) tools in an attempt to increase the overall abstraction level required for using FPGAs. However, the solutions presented by such tools are commonly considered inefficient in comparison to the ones achieved by a specialized hardware designer. An alternative solution to program FPGAs is the use of Domain- Specific Languages (DSLs), as they can provide higher abstraction levels than HDLs still allowing the developers to deal with specific issues leading to more efficient designs and not always covered by HLS tools. In this paper we present our recent work on a DSL named LALP (Language for Aggressive Loop Pipelining), which has been developed focusing on the development of FPGAbased, aggressively pipelined, hardware accelerators. We present the recent LALP extensions and the challenges we are facing regarding to the compilation of LALP to FPGAs.