用于油画鉴别的自适应MPSoC中NoC仿真平台研究

实时光谱图像技术的应用是数据和通信的密集型算法的综合。因为片上系统(SoC)具有较大的灵活性及良好的性能,并可以直接采用IP核,基于片上网络(NoC)的SoC架构是实现这种实时系统最合适的解决方案。针对不同的应用算法,调整基于SoC的NoC架构是较为复杂的工作,因为设计空间探索和实验需要大量的时间。针对这些问题,提出了一种探索和评估SoC架构性能的仿真平台。该仿真平台基于NoC和参数化的评估模块,在FPGA上对SoC的通信结构进行仿真,并将时间性能和模拟结果进行对比。基于该仿真平台的系统评估主要用来考察用于油画鉴别应用的MPSoC的性能。     

基于虚拟通道非均匀分布的路由算法

随着片上系统(systems on chip,SoC)集成度的提高,IP核之间的通信成为SoC急需解决的问题。近年来提出的片上网络(network on chip,NoC)是解决SoC通信问题的一种有效方法。虚拟通道和路由算法是NoC设计中的关键技术,对NoC的延时、吞吐量等性能有重要的影响。根据NoC负载分布特点,提出一种新的虚拟通道非均匀分布技术VCND。该技术在Mesh内部使用虚拟通道,在边界上使用非虚拟通道,从而减少缓冲单元的数量。同时提出一种改进的无死锁路由算法CXY(combination XY)。仿真结果表明,与XY路由算法和XY-YX路由算法相比,CXY路由算法提高了网络吞吐量,并降低了网络平均延时;相比虚拟通道均匀分布技术,VCND技术能够以较小的吞吐量和网络延时损失获得可观的缓冲单元利用率提升,并减少了路由器的面积。     

二次改进遗传算法与3D NoC低功耗映射

随着集成电路技术的迅速发展,芯片的集成度不断提高,片上众多处理单元间的高效互连成为关键问题,因而相继出现了片上系统(system-on-chip,SoC)和二维片上网络(two-dimensional network-on-chip,2D NoC).当二维片上网络在多方面达到瓶颈时,三维片上网络(three-dimensional network-on-chip,3D NoC)应运而生.三维片上网络已引起学术界和产业界的高度重视,三维片上网络低功耗映射是其中的1个关键问题.之前的研究曾提出过一种基于改进遗传算法的3D NoC低功耗映射算法,并收到了良好的仿真效果.但当问题规模变大时,计算量随之增大、运行效率明显降低.针对这一问题,对3D NoC中面向功耗优化的二次改进遗传算法任务映射机制进行研究,提出了一种新的3D NoC低功耗映射算法,并对该映射算法进行了仿真实验.实验结果表明,在种群规模较大的条件下,该算法不仅能够继续降低功耗,而且能够大幅度地减少映射算法的运行时间.     

Arteris:片上"互联网"时代

随着半导体工艺进入纳米阶段,IC设计的复杂度不断提高,IP核数量急剧上升,传统的技术已不能满足日益增长的设计需求,SoC(片上系统)设计不可避免地遭遇瓶颈:延迟限制、带宽限制、功耗限制等.在片上互联方面,传统的共享总线技术同样受到挑战.一种全新的集成网络互联体系-片上网络(Network on a Chip,NoC)被提出,NoC取代共享总线成为趋势.     

SoC片上通信结构的研究综述

由于系统芯片中IP核数目的逐渐增大,片上通信结构逐渐成了整个SoC的性能瓶颈,基于共享总线的SoC通信结构具有无法克服的局限性,这就对传统的共享总线片上通信系统提出了严峻的挑战。文中全面综述了近些年片上通信系统方面的研究,分析了共享总线,交叉开关,点到点,片上网络NoC(Network on Chip),混合互连五种片上通信结构的优缺点,以及对整个系统芯片性能的影响.最后指出片上通信研究的方向。     

NoC关键问题

片上网络(NOC)作为复杂SoC通信的一种解决方案,受到了工业界和学术界的广泛重视.NoC设计涉及了从物理层到应用层诸多方面的问题,本文对NoC研究中的关键问题做简单的介绍.     

改进量子算法的片上网络映射研究

片上网络（NoC）是解决片上系统（SoC）之间各个IP核通信的主要方法。其中NoC的映射是整个NoC设计过程中最为关键的步骤之一。采用一种改进的方法解决NoC映射问题,该方法基于量子进化算法,并在算法中采用一种改进的更新方法,之后引入精英策略,让所有中间过程的解都参与到迭代中,选择其中最好的解作为每次迭代的NoC映射最终解。使用该方法建立在延时约束下的NoC映射功耗数学模型,实验表明,该方法在NoC映射中能达到降低通信功耗的目的。     

基于一种新网络拓扑结构的低功耗研究

随着芯片集成度的提高,片上网络(Network on Chip,NoC)是片上系统(System on Chip,SoC)发展的必然趋势,其中功耗成为限制性能提高的瓶颈.为了降低NoC的功耗,提出一种新的拓扑结构HMesh(Hexagon Mesh)及适用于该拓扑结构的HM路由算法,并对Mesh、Torus和HMesh结构的功耗进行了仿真实验.实验结果表明,在网络不发生拥塞时,HMesh结构的平均功耗比Mesh结构和Torus结构分别降低了12.9％和11.24％,更适合片上网络的构造.     

面向测试优化的片上网络映射算法

针对复杂片上系统(SoC)芯片的片上网络(NoC）映射方案未考虑测试需求的问题,提出了一种面向测试优化的NoC映射算法,兼顾了可测性的提升和映射开销的最小化。该映射方案首先依据特定的测试结构,使用划分算法进行片上系统所有IP核的测试分组,其优化目标为测试时间最短;之后,再基于分组内IP核之间的通信量,应用遗传算法实现NoC映射,其优化目标是在测试优化的基础上实现映射开销最小。通过多个ITC'02测试基准电路进行的实验结果表明:应用该方案后,测试时间平均减少12.67%;与随机任务映射相比,映射代价平均减少24.5%。     

Mesh跳步容错路由算法

随着芯片集成度的提高,基于片上系统[1]（SoC）的片上网络（NoC）已成为芯片设计的重点。随着IP核的增多,节点和链路的故障率大大增加,这就使得运用容错以提高系统的可靠性成为NoC的设计重点。本文在对传统NoC容错技术的基础上,基于2D-Mesh拓扑结构,提出一种基于转弯模型（Turn Model）的跳步容错算法（Hop-Fault-Tolerant,HFT）,并在OPNET仿真平台对其进行仿真和性能分析。     

片上网络跨时钟域的高速数据通信接口设计

为了解决跨时钟域问题对基于片上网络的高速数据传输造成的功能误差,提出了一种新的片上网络跨时钟域高速数据通信接口电路.针对采用多电压频率岛分配方案的异步片上网络,将多路选择器模块和基于令牌环的环形异步FIFO相结合构成跨时钟域高速数据通信接口电路.实验结果表明,该算法及电路设计能够有效减小亚稳态的影响,增加片上网络系统数据传输的吞吐率,满足用于视频采集和处理系统的片上网络对大数据量和高速度数据码流进行实时传输的需求.     

A novel 3D NoC architecture based on De Bruijn graph

Networks on Chip (NoC) and 3-Dimensional Integrated Circuits (3D IC) have been proposed as the solutions to the ever-growing communication problem in System on Chip (SoC). Most of contemporary 3D architectures are based on Mesh topology, which fails to achieve small latency and power consumption due to its inherent large network diameter. Moreover, the conventional XY routing lacks the ability of fault tolerance. In this paper, we propose a new 3D NoC architecture, which adopts De Bruijn graph as the topology in physical horizontal planes by leveraging its advantage of small latency, simple routing, low power, and great scalability. We employ an enhanced pillar structure for vertical interconnection. We design two shifting based routing algorithms to meet separate performance requirements in latency and computing complexity. Also, we use fault tolerant routing to guarantee reliable data transmission. Our simulation results show that the proposed 3D NoC architecture achieves better network performance and power efficiency than 3D Mesh and XNoTs topologies.     

基于云自适应遗传算法的NoC映射研究

NoC映射是NoC设计中的重要步骤,映射结果的优劣对NoC的QoS约束和通信功耗有着很大的影响。提出一种采用云自适应遗传算法实现NoC映射的方案,该算法利用云模型对传统遗传算法加以改进,以此新方法自动调整遗传算法过程中的交叉概率和变异概率,从而达到优化遗传算法的目的。结合NoC映射中的具体问题,在功耗和延时约束的限制条件下,建立了延时约束下的NoC映射功耗数学模型。实验表明,该方法在NoC映射中取得了良好的效果,降低了通信功耗。     

一种片上网络的低延迟容错算法

为解决片上网络容错问题,利用端到端模式设计一种低延迟可靠传输算法。该算法利用发送端主动发送冗余数据包获得较小的延迟,将数据分成包集以提高链路利用率,进一步降低延迟。发送端只在收到接收端对当前包集的确认后才发送下一个包集的数据,由此保证高可靠性。通过不断发送数据包及端到端的反馈保证传输的正确性。NS-2仿真实验结果证明,该算法延迟低,片上通信可靠性高,可以有效处理传输过程中的瞬时错误。     

Stochastic communication for application-specific Networks-on-Chip

In this paper, we have developed analytical stochastic communication technique for inter and intra-Networks-on-Chip (NoC) communication. It not only separates the computation and communication in Networks-in-Package (NiP) but also predicts the communication performance. Moreover, it will help in tracking of the lost data packets and their exact location during the communication. Further, the proposed technique helps in building the Closed Donor Controlled Based Compartmental Model, which helps in building Stochastic Model of NoC and NiP. This model helps in computing the transition probabilities, latency, and data flow from one IP to other IP in a NoC and among NoCs in NiP. From the simulation results, it is observed that the transient and steady state response of transition probabilities give state of data flow latencies among the different IPs in NoC and among the compartments of NoCs in NiP. Furthermore, the proposed technique produces low latency as compared to the latencies being produced by the existing topologies.     

Efficient security zones implementation through hierarchical group key management at NoC-based MPSoCs

Sensitive applications are split into the IP cores of the Multi-Processors System-on-Chip (MPSoCs). In order to isolate the sensitive communication among such IP cores, security zones based on conference keys agreement can be built. However, the flexibility and dynamic nature of MPSoCs force reshaping the security zones at runtime. It is still a challenge to achieve efficient computation and distribution of new conference keys in MPSoC environments. In order to solve this problem, in this work we propose the combination of two techniques: i) high performance NoC, able to efficiently communicate data and control packets in the system; and ii) hierarchical group-key management for efficient security zone modification. We implement three hierarchical protocols and we show that by decentralizing the security management of the rekeying process and using a two-level NoC, it is possible to achieve an improvement of the performance compared to the previous flat approaches.     

Congestion-aware ant colony based routing algorithms for efficient application execution on Network-on-Chip platform

Networks-on-Chip (NoC) is an interesting option in design of communication infrastructures for embedded systems. It provides a scalable structure and balanced communication between the cores. Parallel applications that take advantage of the NoC architectures, are usually are communication-intensive. Thus, a big deal of data packets is transmitted simultaneously through the network. In order to avoid congestion delays that deteriorate the execution time of the implemented applications, an efficient routing strategy must be thought of carefully. In this paper, the ant colony optimization paradigm is explored to find and optimize routes in a mesh-based NoC. The proposed routing algorithms are simple yet efficient. The routing optimization is driven by the minimization of total latency during packets transmission between the tasks that compose the application. The presented performance evaluation is threefold: first, the impact of well-known synthetic traffic patterns is assessed; second, randomly generated applications are mapped into the NoC infrastructure and some synthetic communication traffics, that follow known patterns, are used to simulate real situations; third, sixteen real-world applications of the E3S and one specific application for digital image processing are mapped and their execution time evaluated. In both cases, the obtained results are compared to those obtained with known general purpose algorithms for deadlock free routing. The comparison avers the effectiveness and superiority of the ant colony inspired routing.     

Application mapping to mesh NoCs using a Tabu-search based swarm optimization

A hybrid optimization scheme is presented that combines Tabu-search, communication volume based core swapping and Discrete Particle Swarm Optimization (DPSO) for NoC (Network-on-Chip) mapping. The main goal of the optimization is to map an application core-graph such that the overall communication latency of the NoC is minimal. It is assumed that the target NoC has a 2D-mesh topology. DPSO is used as the main optimization technique where each swarm particle move is influenced by the global and local best, previous visited search space locations, and a deterministic method to reduce communication volume of existing mapping. We employ a Tabu-list to discourage swarm particles to re-visit the explored search space and propose an alternative direction towards the intended movement direction. The methodology is tested for some multimedia applications as well as randomly generated large network of synthetic cores-graphs. For larger applications, our hybrid scheme generates high quality NoC mapping solutions as compared to DPSO based existing techniques.     

片上网络的星型簇结构通信能耗研究

相对于传统的平面结构,三维片上网络具有更好的集成度和性能。提出一种基于三维网格的星型簇结构的片上网络(3D SCBM-NoC),3D SCBM-NoC可以减少路由节点,降低处理节点间的通信代价。通过分析3DSCBM-NoC的拓扑结构,建立了针对星型簇结构的片上网络通信能耗模型,分别使用顺序方法和蚁群算法实现了片上网络映射。实验结果表明,相对于处理节点规模相同且数目为16的3D Mesh-NoC和2D Mesh-NoC,3DSCBM-NoC的通信能耗明显降低。     

基于拥塞控制的片上网络多播路由算法

为了满足片上网络日益丰富的应用要求,多播路由机制被应用到片上网络,以弥补传统单播通信方式的不足。以Mesh和Torus类的片上网络为例,分析了基于路径的3种多播路由算法(即XY路由、UpDown路由和SubPartition路由算法),并研究了相应的拥塞控制策略。通过模拟实验表明,多播较单播通信具有更小的平均传输延时和更高的网络吞吐量,且负载分配均匀;特别是SubPartition路由算法随着规模增大效果更加明显;提出的多播拥塞控制机制,能更有效地利用多播通信,提高片上网络的性能。