CN105515929B - Computing method for data transmission reliability lower limit of FlexRay bus network - Google Patents

Computing method for data transmission reliability lower limit of FlexRay bus network Download PDF

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Publication number
CN105515929B
CN105515929B CN201510867007.8A CN201510867007A CN105515929B CN 105515929 B CN105515929 B CN 105515929B CN 201510867007 A CN201510867007 A CN 201510867007A CN 105515929 B CN105515929 B CN 105515929B
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message
bus network
delay
flexray
determining
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CN105515929A (en
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王刚
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University of Electronic Science and Technology of China
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University of Electronic Science and Technology of China
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/40006—Architecture of a communication node

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)

Abstract

The invention discloses a method for calculating a lower limit of data message transmission reliability in a FlexRay bus network under the condition of incomplete information, which comprises the following steps of 1) determining a change interval and a reference probability distribution f T of a sum T b + T f + T s of three delay variables T b, T f and T s according to a blocking time T b and a sending delay T f of a data message in a source node and a measurement result of processing delay T s by a software system, 3) calculating a maximum cross entropy R max of the T b + T f + T s and the corresponding reference probability distribution in an uncertain interval of the mean value T b, T f and T s of the three delay variables T b and T s, 4) determining a communication deadline W m according to the real-time requirement of the message in the FlexRay network, further determining a transmission message reliability function, 4) providing a communication reliability control system for the FlexRay bus network based on the invention, and providing a reliable communication control method for the FlexRaexRay bus network.

Description

Computing method for data transmission reliability lower limit of FlexRay bus network
Technical Field
The invention relates to the technical field of data transmission reliability of a field bus network, in particular to a computing method for the lower limit of the data communication reliability of a FlexRay network.
Background
As is well known, the real-time performance of data packets in many fieldbus networks is a key factor for the stable operation of the entire network system. If the transmission delay of some data messages exceeds the specified deadline, i.e. does not meet the real-time requirement, the system may generate unpredictable errors. In this sense, the transmission reliability of each data packet in a bus network can be characterized by its probability of meeting the real-time requirements. That is, the higher the probability that a data packet meets the real-time requirement, the higher the transmission reliability, and vice versa. Because of the important significance of the data message transmission reliability, the data message transmission reliability is always an important parameter in the field bus network system design stage. Accurate evaluation and calculation of this parameter is critical to the success or failure of a bus network design.
Currently, existing evaluation and calculation methods are performed based on fully knowing statistical information of various random variables (such as software processing time, transmission time, blocking time, and the like of various network nodes) affecting data transmission reliability in a bus network. I.e. to be able to obtain accurate values of the mean and variance of the above-mentioned random variables. From a more practical point of view, this is obviously not easy to do. Since the above statistical information such as the mean and variance of the random variables is generally obtained by means of multiple measurements, it is not feasible to accurately estimate the exact values of the mean and variance of each random variable. It is more reasonable to find the variation intervals (confidence intervals) of the mean and variance of these random variables by means of measurements. Under the condition that the information is incomplete, the transmission reliability of each data message under the worst condition, namely the lower limit of the data transmission reliability, is accurately calculated, and becomes an important target to be realized in the bus network design process.
In recent years, the FlexRay technology has been greatly developed. Due to the excellent performances in the aspects of instantaneity, bandwidth, fault tolerance and the like, the technology has wide application prospects in the fields of automobiles, aviation, aerospace and the like. In the design process of the FlexRay bus network, accurate calculation of the lower limit of the data transmission reliability is still an important problem to be solved. Unfortunately, currently there is no fully feasible computational method to do this.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a method for accurately calculating the lower limit of the transmission reliability of the data message of the FlexRay bus network under the condition of incomplete information by using the correlation theory of cross entropy among probability distributions.
In order to accurately calculate the lower limit of the transmission reliability of the data message in the FlexRay bus network, the calculation method provided by the invention comprises the following steps:
1) According to the blocking time T of a data message in the source nodebSending delay TfAnd software system processing delay TsThe measurement result of (2) isDetermining the variation interval corresponding to the mean and variance of the three variables and
2) Determining three delay variables Tb、TfAnd TsSum of T ═ Tb+Tf+TsReference probability distribution fT；
3) Calculating T ═ Tb+Tf+TsAt three delay variables Tb、TfAnd TsMaximum cross entropy R of the uncertainty interval of the mean and variance with a corresponding reference probability distributionmax；
4) Determining a communication deadline W according to the real-time requirements of the message in the FlexRay networkmFurther, calculating the message transmission reliability function;
5) calculating the lower limit P of the message transmission reliability according to the reliability functionl。
It should be noted that, in the present invention, only the random variable affecting the reliability of the packet transmission only includes the blocking time, the sending delay and the processing delay of the software system, and all follow the normal distribution. At the same time, these random variables are independent of each other. For a FlexRay network node, these conditions are generally fulfilled.
Compared with the prior art, the calculation method provided by the invention can effectively solve the important problem in FlexRay network design and provides accurate and scientific basis for network designers.
Drawings
FIG. 1 is a block flow diagram of the calculation method of the present invention.
Detailed Description
Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the preferred embodiment, a node in the FlexRay network has a data packet M, and the blocking time, the sending delay and the software system processing delay of the data packet M are respectively Tb、TfAnd Ts. According to the method of the present invention, the transmission reliability of the message M can be calculated according to the following procedureLower limit Pl M。
Step 1, determining three random variables T influencing a message M according to a measurement resultb、TfAnd TsThe mean and variance of (1) are respectivelyAnd
Step 2, determining T-T according to the measurement result of the FlexRay networkb+Tf+TsReference probability distribution density function fr。
wherein mubr、μfrAnd musrAre each Tb、TfAnd TsMean, σ, in the reference distributionbr、σfrAnd σsrAre each Tb、TfAnd TsThe variance in the reference distribution.
step 3, at Tb、Tfand TsThe mean value and the variance of the six parameters in respective change intervalAnd By calculating all possible probability distributions and a reference probability distribution fT(t) cross entropy R, taking its maximum value Rmax。
Wherein
Step 4, determining a communication deadline W according to the real-time requirement of the message M in the FlexRay networkmFurther, the message transmission reliability function A is calculatedm(T)
Step 5, according to the reliability function Am(T) calculating the lower limit P of the message transmission reliability according to the following methodl. Defining an optimization function B (x)
Where x ∈ [0, ∞). The univariate optimization function B (x) is optimized by Newton method in the interval [0, ∞ ] to obtain its maximum value Bmax. Thus, the lower limit P of the transmission reliability of the message M can be obtainedlIs composed of
Pl＝min(0,Bmax) (5)
The calculation method provided by the invention has simple and clear flow and is easy to realize, and provides a more convenient basis for the application and development of the future FlexRay network technology.

Claims (1)

1. Blocking time T of data message at source nodebSending delay TfAnd software system processing delay TsThe method for ensuring the transmission reliability of the data message in the FlexRay bus network design is characterized by comprising the following steps of:
Step 1, according to T of a data messageb、TfAnd TsDetermining the variation interval corresponding to the mean and variance of the three variablesAnd
Step 2, determining three delay variables Tb、TfAnd TsSum of T ═ Tb+Tf+TsReference probability distribution ofWherein mubr、μfrAnd musrAre each Tb、TfAnd TsMean, σ, in the reference distributionbr、σfrAnd σsrare each Tb、TfAnd TsVariance in the reference distribution;
Step 3, calculating T ═ Tb+Tf+TsAt three delay variables Tb、TfAnd Tsmaximum value R of cross entropy of uncertain interval of mean and variance and corresponding reference probability distributionmaxCross entropy ofWherein
Step 4, according to the real time of the message in the FlexRay networkRequesting, determining the communication deadline W of the messagemFurther, the message transmission reliability function is calculated
step 5, defining an optimization function according to the message transmission reliability functionx ∈ [0, ∞), and the maximum value B of the optimization function B (x) is obtained by Newton methodmaxIf the lower limit of the communication reliability of the message is Pl＝min(0,Bmax)；
Lower limit P of the communication reliabilitylThe method is applied to FlexRay bus network design so that the data message transmission meets the real-time requirement.
CN201510867007.8A 2015-12-01 2015-12-01 Computing method for data transmission reliability lower limit of FlexRay bus network Expired - Fee Related CN105515929B (en)

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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102148762A (en) * 2011-04-28 2011-08-10 合肥工业大学 Hybrid scheduling method for control area network (CAN)-FlexRay gateway
KR20140064646A (en) * 2012-11-19 2014-05-28 로베르트 보쉬 게엠베하 Method for testing of receiving a message in a terminal

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102148762A (en) * 2011-04-28 2011-08-10 合肥工业大学 Hybrid scheduling method for control area network (CAN)-FlexRay gateway
KR20140064646A (en) * 2012-11-19 2014-05-28 로베르트 보쉬 게엠베하 Method for testing of receiving a message in a terminal

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
《FlexRay总线网络调度算法研究》;卯昊龙等;《自动化与仪器仪表》;20150725;全文 *
《基于FlexRay的汽车通信网络设计流程与方法》;吴泽民;《2013中国汽车工程学会年会论文集》;20131126;全文 *

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