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Real-Time Operating Systems
Published in Leanna Rierson, Developing Safety-Critical Software, 2017
Round-robin. The name of the algorithm comes from the round-robin principle, where each person has an equal share of something. I once made it to the 4-H showmanship round-robin competition. Each competitor was given an equal time to show a horse, a steer, a pig, and a lamb. You’ll be pleased to know that I earned the Reserved Grand Champion trophy. The round-robin scheduling algorithm is one of the simplest scheduling algorithms for sharing time on a processor. A minor time slice is defined by the system, and all processes are kept in a circular queue. The scheduler goes around the queue, allocating processor resources to each process for a time slice interval. As new processes arrive, they are added to the tail of the queue. The scheduler functions by selecting the first process from the queue, setting a timer to interrupt after one time slice, and then dispatching the process. If the process is not finished at the end of the time slice, it is preempted and added to the tail of the queue. If the process does finish before the end of the time slice, it releases the processor. A context switch occurs every time a process is granted access to the processor. The context switching adds overhead to the process execution time [9].
Computers
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
A.M. MacLeod, P.F. Martin, W.A. Gillespie
Instrumentation systems are real-time environments, i.e., their operation requires that tasks be carried out within specified time intervals; for example, the capture of data must occur at specified moments. Operating systems adopt a range of strategies for determining the scheduling of software tasks. Round-robin scheduling, for example, provides each task with execution time on a rota basis, with the amount of time being determined by the priority of the task. Operating systems which support preemptive scheduling allow high-priority tasks to become active if a specified event such as trigger signal occurs. The speed at which an operating system can switch from one task to another (i.e., context switch) is an important metric for real-time systems.
A channel-aware downlink scheduling scheme for real-time services in long-term evolution systems
Published in Artde D.K.T. Lam, Stephen D. Prior, Siu-Tsen Shen, Sheng-Joue Young, Liang-Wen Ji, Engineering Innovation and Design, 2019
Han-Sheng Chuang, Shang-Lin Hsieh, Chen-Feng Wu
Round Robin scheduling is a non-aware scheduling scheme that lets users take turns in using the shared resources (time/RBs), without taking the instantaneous channel conditions into account. Therefore, it offers great fairness among the users in radio resource assignment, but degrades the system throughput (Habaebi, et al., 2013). The algorithm selects the users without considering channel condition. If all the users have been served, the scheduler will start again with the same queue. The major advantage of this kind of algorithm is its simplicity. The major disadvantage of the RR algorithm is that this algorithm does not consider users’ CQI feedback, which leads to low and unequal throughput.
Integrated scheduling and link adaptation for heterogeneous networks: design and performance analysis
Published in International Journal of Electronics, 2020
Mehrdad Taki, Mohammad Bagher Nezafati
As a simple scheme, Round-Robin scheduling assigns time slices to each link in equal proportions. The basic scheme does not consider the different requirements of the users. To enhance the basic scheme, we consider another channel unaware scheme which allocates divisions of the time to each link with considering user requirements. We define as the division of time that is assigned to the link , irrespective of its channel state. The link adaptation is performed in the user section. This scheme is referred as the requirement-based separate scheduling and link adaptation (RSSLA). The average transmission rate of link with continuous rate adaptation and constant transmission power is computed as