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Scheduling Real-Time Programs with Static Compiler Transformations
Seongsoo Hong 한국정보과학회 1996 Journal of Electrical Engineering and Information Vol.1 No.3
This paper presents a compiler-based approach to tuning real-time programs under fixed priority scheduling. It has two interrelated components, a static code transformation algorithm and a modified rate-monotonic scheduling method. The code transformation tool decomposes an unschedulable task into two subtasks, one that is time critical and the other that is unobservable. This is made possible by an event-based semantics in that a program's external behavior is determined soly by externally observable events. The tranformation tool glues back the decomposed subtasks such that the time critical subtask finishes before the unobservable one. The new taks substitues the original one in the input task set. For scheduling analysis, the rate-monotonic scheduling approach is used. However, the transformed task is not consistent with rate-monotonic task model in the sense that it has a deadline which constrains only the time critical portion of its exection. To address this problem, we propose a dynamic modification of rate-monotonic scheduling method based on priority exchange. It allows programmers to directly use the simple rate-monotonic schedulability analysis. The code tranformation tool can help real-time programmers in reducing effort at the final stage of development, when fully implemented.
Building Light Weight CORBA Based Middleware for the CAN Bus Systems
Hong, Seongsoo Institute of Control 2001 Transaction on control, automation and systems eng Vol.3 No.3
The software components of embedded control systems get extremely complex as they are designed into distributed systems get extremely complex as they are designed into distributed systems consisting of a large number of inexpensive microcontrollers interconnected by low-bandwidth real-time networks such as the controller area network (CAN). While recently emerging middleware technologies such as CORBA and DCOM address the complexity of distributed programming, they cannot be directly applied to distributed control system design due to their excessive resource demand and inadequate communication models. In this paper, we propose a CORBA-based middleware design for CAN-based distributed embedded control systems. Our design goal is to minimize its resource need and make it support group communication without losing the IDL (interface definition language) level compliance to the OMG standards. To achieve this, we develop a transport protocol on the CAN and a group communication scheme based on the well-known publisher/subscriber model. The protocol effectively realizes subject-based addressing and supports anonymous publisher/subscriber communication. We also customize the method invocation and message passing protocol, referred to as the general inter-ORB protocol (GIOP), of CORBA so that CORBA method invocations are efficiently serviced on a low-bandwidth network such as the CAN. This customization includes packed data encoding and variable-length integer encoding for compact representation of IDL data types. We have implemented our CORBA-based middleware on the mArx real-time operating system we have developed at Seoul National University. Our experiments clearly demonstrate that it is feasible to use CORBA in developing distributed embedded control systems possessing severe resource limitations. Our design clearly demonstrates that it is feasible to use a CORBA-based middleware in developing distributed embedded systems on real-time networks possessing severe resource limitations.
Intelligence Transportation Safety Information System
Hong, YouSik,Park, Chun Kwan,Cho, Seongsoo,Hong, Suck-Joo The Institute of Internet 2014 International Journal of Internet, Broadcasting an Vol.6 No.2
These days the large-scale car accidents have often been occurred by overspeeding in disregard of sharp curve, foggy and freezing regions. This paper has proposed the algorithm to calculate the safety speed in real time that can protect the car accidents under these weather and road conditions using Fuzzy reasoning theory. Under raining and snowing, drivers have to slow down the traffic safety speed by 1/3 of the traffic safety speed indicated on the existing speed sign plate based on their decision. So it is difficult to calculate and then observe the safety speed. This paper has performed the simulation that provides the deivers with the optimal safety speed considering the road and weather conditions in real time to improve these problems. We have proved this method can improve more 25% than the existing one.
SenOS : 동적 센서 노드 재구성을 위한 상태 기반 운영 체제 구조
홍성수(Seongsoo Hong),김태형(Tae-Hyung Kim),한승현(Seung-Hyun Han),박선희(Sunheui Park) 한국정보과학회 2003 한국정보과학회 학술발표논문집 Vol.30 No.2Ⅰ
무선 센서 네트웍은 동작 환경과 구조가 매우 특이하게 개발자들은 센서 네트웍의 노드를 디자인할 때 많은 제약 조건들과 요구 조건들을 고려해야 한다. 먼저 무선 센서 네트웍 상의 각 센서 노드에는 극도로 제한된 하드웨어 자원 조건 하에서도 무선 통신 기능뿐만 아니라 동시에 여러 이벤트를 재빠르게 처리할 수 있는 기능이 포함되어야 한다. 또한 환경과 응용 프로그램의 변화에 잘 대처하기 위해 런타임(runtime)에 각 센서 노드들을 동적으로 재구성할 수 있는 기능이 제공되어야 한다. 이러한 디자인 요구 조건들과 제약 조건들을 얼핏 서로 상반된 것처럼 보이는데, 무선 센서 노드들을 위한 실행 환경을 디자인할 때는 이러한 조건들을 모두 만족시킬 수 있는 운영 체제가 반드시 필요하다. 본 논문에서는 우리는 무선 센서 노드들을 위한 매우 효율적이고 효과적인 유한 상태 머신(finite state machine) 기반의 운영체제, SenOS를 제안한다. 또한, 새로운 운영 체제인 SenOS가 극도의 제한적인 자원에서도 동시성과 반응성, 재구성성의 요구 조건을 모두 만족시키면서 동작할 수 있다는 것을 보일 것이다.