The Research Of Weakly Hard Real-Time System Based Improved Constraint And Its Algorithms

With fast development and popularization of computer's technology,real-time system has been indispensable part of people's production and life.The real-time system has characters such as response in time,high dependability,dedication and less artificial interference,which is widely applied in the industrial control,military defense,information communication,network delivering and multimedia processing.However,new requirements and challenges arise from some new network applications' appearance,especially such as multimedia video and audio for loss tolerant.Then the concept of weakly hard real-time is presented,which not only enriches and extends the classical theory of real-time system,but also meets new requirements and challenges.So related issues on weakly hard real-time are becoming hot point of research nowadays.The content of the thesis will focus on constraint specification of weakly hard real-time,scheduling algorithms based on weakly hard real-time and related experiments.The theory of weakly hard real-time can uniformly describe different kinds of real-time system.Both hard real-time and soft real-time system are the typical weakly hard real-time systems.In this thesis,a new specification of weakly hard real-time is proposed,and the scheduling algorithm based this constraint is devised. The main detail research works in the thesis can be described as follows:1)Review four classical weakly hard real-time constraint specifications proposed by Bernat.Depending on their characters,put forward three deductions and two new theorems for relationship between constraints. Then analyse shortages of constraints(m,k)-firm and <(?>-firm and propose a new constraint((?),m,k)to make up their shortages.Besides, discuss the strict relationship between the new constraint((?),m,k)and classical constraints with variety of three parameters.2)Research static and dynamic scheduling algorithms of weakly hard real-time system,especially DBP and E-DBP dynamic scheduling algorithms,and discuss their methods of priority assignment.Then basing on the new constraint((?),m,k),anew dual priority dynamic scheduling algorithm was devised.Detailedly analyse algorithm of dual priority and relationship between priority and dynamic invalidation state after task finished or missed.3)Compile program by VC to experiment.Comparing DBP scheduling algorithms,evaluate weakly hard real-time QoS for new scheduling algorithm from aspect of main standard of QoS——dynamic invalidation rate.