17996623
Fault tolerant scheduling for fixed-priority tasks with preemption threshold
Fixed-priority with preemption threshold (FPPT) is an important form of real-time scheduling algorithm, which fills the gap between fixed-priority preemptive (FPP) and fixed-priority non-preemptive (FPNP). However, this scheduling scheme together with the requirements of fault tolerance makes the prediction of a real-time system's behaviors more difficult than traditional scheduling scheme. The major contribution of this work is twofold. First, we present an appropriate schedulability analysis, based on response time analysis, for supporting fault-tolerant FPPT scheduling in hard real-time systems. The error-recovery techniques are considered to be used to carry out fault tolerance. Second, we propose the optimal priority assignment algorithm which can be used, together with the schedulability analysis, to improve system fault resilience.
206594316
An OSEK COM Compliant Communication Model for Smart Vehicle Environment
Smart Vehicle Environment (SVE) is an important application of the idea of smart spaces. This paper presents Smart Vehicle Multi-Agent System (SVMAS) to achieve the goal of SVE and put forwards a commutation model for SVMAS based on SmartOSEK COM [1] to support data exchange. The paper also presents an approach to encapsulate the message to transport by CAN bus, and bring forward a simulator model for SVMAS. Finally the paper gives an example of the communication model which implements a dialogue between two agents and analyzes the performance. The contribution of our work is threefold. First, we adopt Knowledge Query and Manipulation Language (KQML) to describe the communication in vehicles. Second, we develop SmartOSEK COM to implement communication in vehicles. Third, we define the ACLcan protocol to transform the message from SmartOSEK COM to CAN frame.
11645102
Active Shape-from-Shadows with Controlled Illuminant Trajectories
We present an active vision algorithm for computing the orientation and position of a locally planar object, onto which is cast a shadow of the edge of a half-plane at an unknown location. This algorithm utilises active position control of a point light source, and employs a Kalman filter to perform temporal integration of measurements. The light source position is adjusted after each measurement so as to reduce the trace of the expected state estimate error covariance matrix for the next measurement. We demonstrate the active shape-from-shadows algorithm using a real robotic system.
95638
MU-MAQAS: A P2P based Model Updatable Mobile Automatic Q/A System
Along with the development of wireless technology and especially 3Gpsilas throw into commercial, the mobile value-added services gradually popular used, such as mobile automatic question and answer (Q/A) system. But the current mobile Q/A system mainly based on FAQ database, the question and answer can not be validated and updated by itself. So this paper attempts to implement a p2p based model updatable automatic Q/A system named MU-MAQAS for mobile phones using SMS interface. MU-MAQAS mainly includes: question & answer information collecting module and model manage & use module. It can automatically collect Q/A information from internet and update the Q/A model in time. A simulated Q/A system is also coded to validate the design. Results of simulation proved that under ideal conditions the systempsilas average responding time is less than 64 ms and precision is above 60% when there are no more than 3000 simultaneous asking queries, and so the completeness and feasibility of the systempsilas design is proved.
29355074
Joint Multiuser Precoding and Scheduling with Imperfect Channel State Information at the Transmitter
This paper addresses the joint design of multiuser precoding and scheduling for downlink multiuser (MU-) multiple-input-multiple-output (MIMO) systems with imperfect channel state information at the transmitter (CSIT). The major issue is to control the increased co-channel-interference (CCI) caused by CSIT error among users sharing the same time-frequency resource. We propose an advanced joint multiuser precoding and scheduling technique, which uses the statistical information of the CSIT error to predict the relationship among CCI, precoding matrixes and scheduling results, and utilizes such information to improve the precoding and scheduling algorithms for better CCI control. Simulation results have shown that considerable capacity improvement can be achieved by the proposed technique in the case of imperfect CSIT.
18692029
A CCI-Feedback-Aided Scheduling Technique for MU-MIMO
Imperfect channel state information (CSI) at the transmitter is one of the major challenges that the downlink multiuser multiple-input-multiple-output (MU-MIMO) technology faces in real applications. It will lead to increased co- channel interference (CCI) among users and deteriorate the capacity of MU-MIMO seriously, especially at high signal-to- noise-ratios (SNRs). In this paper, we propose an advanced MU-MIMO scheduling technique to improve the capacity of MU-MIMO in the case of imperfect CSI at the transmitter (CSIT). The rational behind the proposed scheme is the observation that the CCI level increases with the number of users simultaneously supported in MU-MIMO transmission. Thus, decreasing the number of simultaneous users can reduce CCI and sometimes even increase the sum capacity. Motivated by this observation, we design a CCI-feedback-aided scheduling technique, which adaptively adjusts the number of simultaneous users based on the CCI measurement at the user side. Simulation results have shown that considerable capacity gain can be achieved by the proposed scheduling technique at the cost of only one bit additional feedback per user and marginal complexity increase at both the transmitter and user side.
14894173
Gingko: correlating causal paths in distributed systems
Many large-scale systems are distributed systems of multiple communicating components. Finding causal paths of message traces between components throughout these systems is important to uncover runtime behaviors and identify the root cause of failures, but this "art" often hides in the heads of developers or domain experts. Our goal is to design tools and algorithms to help developers record this art into logs and help the modestly-skilled users and system administrators master it to make better use and management of distributed systems. In this paper, we present a methodology that automatically builds the causal paths of message traces by 1) an agreement with programmers on the style and content of logs produced by operational distributed systems they develop and 2) a correlation algorithm to build message causal paths with the clues from these logs. To validate this mechanism, we have implemented Gingko, a prototype providing a tool chain for users to gain better comprehensions of distributed systems and to debug them efficiently when errors happen.