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针对合成孔径雷达实时成像处理中数据量大、数据吞吐率高、成像算法实现复杂等特点,设计了适合于无人机载SAR实时信号处理系统的硬件平台和实时信号处理算法流程。该信号处理系统包括一块带有AD采集功能的接口板和两块以TS201为核心处理器的信号处理板。考虑到实时性要求和无人机平台的不稳定性,设计了一种结合惯导和回波数据进行运动补偿的改进型RD成像算法。在无人机平台上成功稳定地实现大面积连续实时成像,证明信号处理系统稳定可靠,实时信号处理算法可行。 相似文献
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提出了一种新的用于开放式系统的调度机制,即二维优先级实时调度,它不仅划分任务优先级,还划分调度策略优先级.任务的执行顺序由其调度策略优先级和任务优先级共同决定.它不仅可以解决传统优先级调度机制中机制与调度策略不能相分离的问题,还提高了效率.这种机制中引入的CPU带宽控制策略,可以根据需要实现硬实时、软实时、混合实时不同目标的实时系统,并简化了任务可调度性分析,且可以为不同权限或级别的用户提供不同QoS服务.这种调度架构不仅效率高,而且具有很强的开放性,适用广、易扩展. 相似文献
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In this paper, we present an approach to hardware-software partitioning for real-time embedded systems. Hardware and software components are modeled at the system level, so that cost and performance tradeoffs can be studied early in the design process and a large design space can be explored. Feasibility factor is introduced to measure the possibility of a real-time system being feasible, and is used as both a constraint and an attribute during the optimization process. An imprecise value function is employed to model the tradeoffs among multiple performance attributes. Optimal partitioning is achieved through the use of an existing computer-aided design tool. We demonstrate the application of our approach through the design of an example embedded system. 相似文献
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Time Petri nets (TPNs) have been widely used for the verification and validation of real-time systems during the software development process. Their quantitative analysis consists in applying enumerative techniques that suffer the well known state space explosion problem. To overcome this problem, several methods have been proposed in the literature, that either provide rules to obtain equivalent nets with a reduced state space or avoid the construction of the whole state space. In this paper, we propose a method that consists in computing performance bounds to predict the average operational behavior of TPNs by exploiting their structural properties and by applying operational laws. Performance bound computation was first proposed for timed (Timed PNs) and stochastic Petri nets (SPNs). We generalize the results obtained for Timed PNs and SPNs to make the technique applicable to TPNs and their extended stochastic versions: TPN with firing frequency intervals (TPNFs) and extended TPNs (XTPNs). Finally, we apply the proposed bounding techniques on the case study of a robot-control application taken from the literature. 相似文献
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《Communications, IEEE Transactions on》2006,54(10):1870-1877
In this paper, we consider wireless multicarrier communications systems applying different transmit-antenna diversity techniques. Whereas the transmitter has available multiple antennas, we assume a single antenna at the receiver. Thus, we consider multiple-input single-output multicarrier transmission systems which are of special interest for downlink mobile radio applications. For these systems, we investigate the matched-filter bounds (MFBs) which represent the performance in an environment free of any interference and, thus, are lower bounds on the achievable performance. Especially, we focus on the analytical determination of the MFBs for selection diversity (SD), since this transmit-antenna diversity technique requires the least amount of preprocessing at the transmitter. Based on the derived MFBs, SD is investigated in detail, and compared with other transmit-antenna diversity techniques which are based on the maximum-ratio and the equal-gain transmission principles, respectively. 相似文献
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This paper presents a method to reduce the energy consumption of multi-core systems characterized by processor cores and buses with discrete frequency levels under timing constraints. The proposed method takes the transformations of the original task graphs, which include dependent tasks located in different iterations, as inputs. The proposed method utilizes mapping selection as well as joint processor and communication frequency scaling to implement energy reduction. We conduct experiments on several random task graphs. Experimental results show that the proposed method can achieve substantial energy reduction compared with previous work under the same hard timing constraints. 相似文献
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This paper proposes a methodology for optimizing resource allocations within a real-time information system, given the availability constraints. In essence, the methodology reformulates the availability constraints into a state transition matrix. The state probabilities, computed from the transition matrix, form a portion of the input to the optimizing algorithm. This algorithm optimizes an arbitrary objective function of system resources, subject to the reformulated availability constraints. 相似文献
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In the era of Big Data, typical architecture of distributed real-time stream processing systems is the combination of Flume, Kafka, and Storm. As a kind of distributed message system, Kafka has the characteristics of horizontal scalability and high throughput, which is manly deployed in many areas in order to address the problem of speed mismatch between message producers and consumers. When using Kafka, we need to quickly receive data sent by producers. In addition, we need to send data to consumers quickly. Therefore, the performance of Kafka is of critical importance to the performance of the whole stream processing system. In this paper, we propose the improved design of real-time stream processing systems, and focus on improving the Kafka's data loading process. We use Kafka cat to transfer data from the source to Kafka topic directly, which can reduce the network transmission. We also utilize the memory file system to accelerate the process of data loading, which can address the bottleneck and performance problems caused by disk I/O. Extensive experiments are conducted to evaluate the performance, which show the superiority of our improved design. 相似文献
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《Vehicular Technology, IEEE Transactions on》2009,58(7):3347-3360
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In this paper new paging schemes are presented for locating mobile users in wireless networks. Paging costs and delay bounds are considered since paging costs are associated with bandwidth utilization and delay bounds influence call setup time. In general, location tracking schemes require intensive computation to search for a mobile terminal in current PCS networks. To reduce the paging costs, three new paging schemes, reverse, semi-reverse and uniform, are introduced to provide a simple way of partitioning the service areas and decrease the paging costs based on each mobile terminal's location probability distribution. Numerical results demonstrate that our approaches significantly reduce the paging costs for various probability distributions such as uniform, truncated discrete Gaussian, and irregular distributions. 相似文献
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Recently, there has been widespread interest in the extension of data networks to the wireless domain. However, scheduling results from the wireline domain do not carry over to wireless systems because wireless channels have unique characteristics not found in wireline channels, namely, limited bandwidth, bursty channel errors and location-dependent channel errors.In this paper, we study the problem of scheduling multiple real-time streams with deadlines, over a shared channel. We show that, in general, unlike the wireline case, the earliest due date (EDD) or shortest time to extinction (STE) policy is not always the optimal policy, even if the channel state is perfectly known and EDD is implemented only over channels in a Good state. Here, optimality is measured with respect to the number of packets lost due to deadline expiry. However, for most values of the channel parameters that are of practical interest, we show through analytical and numerical results that the EDD policy over Good channels is nearly optimal. Finally, through simulations, we also show that by combining this policy with fair scheduling mechanisms would result in scheduling algorithms that provide some degree of isolation between the sources as well as provide a natural way of compensating channels that see prolonged error bursts. 相似文献
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This paper presents a system level approach for the synthesis of hard real-time multitask application specific systems. The algorithm takes into account task precedence constraints among multiple hard real-time tasks and targets a multiprocessor system consisting of a set of heterogeneous off-the-shelf processors. The optimization goal is to select a minimal cost multi-subset of processors while satisfying all the required timing and precedence constraints. There are three design phases: resource allocation, assignment, and scheduling. Since the resource allocation is a search for a minimal cost multi-subset of processors, we adopted an A* search based technique for the first synthesis phase. A variation of the force-directed optimization technique is used to assign a task to an allocated processor. The final scheduling of a hard-real time task is done by the task level scheduler which is based on Earliest Deadline First (EDF) scheduling policy. Our task level scheduler incorporates force-directed scheduling methodology to address the situations where EDF is not optimal. The experimental results on a variety of examples show that the approach is highly effective and efficient. 相似文献
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动态电压调节是一种有效的节能技术.本文提出了多核处理器平台上的一种近似最优的动态电压调节算法.算法将电压调节问题转化为松弛时间分配问题,由任务集结构找到存在的松弛时间,针对不同类型的松弛时间,使用了并行补偿等分配方法.实验结果表明本文的算法能够有效的降低能量消耗且具有较低的时间复杂度. 相似文献
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建立了具有反馈型和非反馈型任务的物联网硬实时控制系统——混合控制任务系统(hybrid controlling task system,HCTS)的任务模型,以全面准确地描述系统中不同任务的结构、交互模式和运行特征,并提出了一种新的响应时间分析方法,用于验证系统是否满足实时性要求.实验结果表明,HCTS中的任务具有较小的平均最差情况下的响应时间,但是在反馈次数较多的情况下对任务的实时性具有不利影响,从而为HCTS的优化提供了支持. 相似文献