Analysis And Research On The Network Performance And Data Integrity Of Distributed Ima

With the rapid development of micro-electronic technology,information technology,multimedia service and more complicated airspace environment,aircraft is highly dependent on the avionics system.In order to satisfy the growing demand of aircraft,the data transfer between subsystems of Distributed Integrated Modular Avionics(DIMA)has soared.Since the network bandwidth is limited,sharing conflicts between competitive links,which are generated by multi-tasking,will affect temporal determinacy of data transmission and decrease the stability and reaction capability of avionics.Meanwhile,with the extensive implementation of interactive entertainment system,data stored in the avionics network is no longer physically isolated.The illegal tampering and deletion will bring a great threat to avionics system.As a new generation structure of avionics system,DIMA puts forward a higher request for the real-time,low-latency of network data transmission and security of data storage.This thesis focuses on time uncertainty problem in data transmission and data integrity verification issues in data storing.This thesis presents several key techniques and research achievements,which will further improve the applicability of DIMA.The main research contents and innovative work of this thesis are as follows:1.This thesis proposes a Time-triggered AFDX(TTAFDX)network architecture,which combines time-triggered mechanism with traditional AFDX by comprehensive analysis and improvement.Refers to the SAE AS6802,this thesis proposes a compatible clock synchronization technique for TTAFDX.The virtual link is classified into two categories: time-triggered and rate-constrained virtual link.To solve the temporal uncertainty problem of time-critical message transmission in DIMA,system will select appropriate virtual link type for transmission task according to the real-time and temporal determinacy requirement.The hardware design of TTAFDX is the same as AFDX,which will shorten the development cycle and reduces the cost.2.This thesis proposes two scheduling strategies for both TTAFDX end system and switch system respectively.One of them is frame-length prior based scheduling and the other one is cycle-prior based scheduling.Cycle-prior based scheduling drops the bandwidth utilization when time-triggered virtual links' frame lengths differ a lot.Frame-length prior based scheduling is proposed to solve this problem.Using network calculus method,TTAFDX is compared with FIFO scheduling based AFDX and static priority scheduling based AFDX respectively in the aspect of real-time performance.The result shows that,the fixed delay is the main part of the time-triggered virtual link latency,and the deterministic of rate constraint virtual link is also improved.3.To further improve the performance of TTAFDX,this thesis proposes a Successive Minimal-Quantum Round Robin(SMQRR)scheduling algorithm for rate-constrained virtual link,which is fairness,efficient,and has a low latency bound.For each data flow,the data served in each round is corresponding to its weight.By refining the data amount to be served and round robin mode,SMQRR effectively overcomes the unfairness caused by different frame lengths and avoids the situation that the data flow may not be served for a long time.Theoretical derivation and simulation analysis shows that SMQRR has better latency and fairness than Weighted Elastic Round Robin(WERR)and Deficit Weighted Round Robin(DWRR).4.This thesis proposes a data integrity verification model and an algebraic signature based data integrity verification scheme.For new model civil aircraft using DIMA system,openness and interactivity brings unprecedented security threats to avionics data.The algebraic signature based static data integrity verification scheme can greatly reduce communication overhead,and check out the data error with high probability in the case of data destruction.Forward error correction coding is used to guarantee the integrity of avionics data.The safety analysis and experimental results reveal that the computation performance is effective,and bounded by disk I/O.5.Based on skip-list and Merkle Hash Tree(MHT)data structure,this thesis proposes two dynamic data integrity verification schemes respectively.Skip-list and MHT structures can support fully dynamic data operations.This scheme uses Bilinear Map to support privacy-preserving data integrity verification operations.The scheme allows unlimited times verification without the need for the verifier to compare against the original data,which reduces the communication and computation complexity dramatically and preserves the privacy of the data.Extensive security analysis and simulation show that the proposed scheme is highly provably secure.Some of research achivements and thoughts elaborated in this thesis have been implemented in some sub-topics of national basic research,civil aircraft research.The results show that temporal determinacy is improved for time-critical data transmission and data reliability and security is guaranteed for distributed data storage.The practicabilities of the research results are verified.