Idawaty Ahmad

Two-Level Frames Aggregation with Enhanced A-MSDU for IEEE 802.11n WLANs

IEEE 802.11n defines two schemes of frames aggregation aimed at maximize utilizing WLAN PHY efficiency at MAC level, through sharing headers and timings overheads. Despite their efficiencies in enhancing the MAC throughput, the schemes are characterized with yet other overheads due to the aggregation. Moreover, none of the two schemes is optimal in every condition: Both should work together to achieve this. In this paper, in order to optimize channel’s bandwidth utilization, we proposed an enhanced A-MSDU with minimal headers overhead, and an efficient two-level aggregation scheme utilizing the enhanced A-MSDU. Results from the simulation show superiority of the proposed two-level aggregation in respect of throughput and overall channel utilization.

Improving utility accrual scheduling algorithm for adaptive real-time System

In this paper, we proposed a preemptive utility accrual scheduling (or PUAS) algorithm to further extend the functionalities of General Utility Scheduling (or GUS) algorithm proposed by Peng Li [1]. Both of these algorithms are developed for adaptive real-time system environment where untoward effects such as deadline misses and overloads are tolerable. The proposed algorithm focused on an independent task model, which works on deadline constraints that are specified by using step time/utility functions (or TUFs). The proposed algorithm improves the GUS algorithm by preempting the tasks that GUS abort due to its lower PUD, lowering abortion ratio which in turn increase accrued utility. This met the scheduling objective of maximizing utility, which are achieved thru completion of all tasks. Results from our simulations showed that the proposed algorithm PUAS achieved higher utility and lower abortion ration compared to GUS algorithm. This in effect, produced a much lower average response time, making PUAS more efficient in time-critical application domain.

Comparative Study of Packet Scheduling Algorithm in LTE Network

At present, Long-Term Evolution (LTE) is the most popular Internet access technology because of its robust wireless connectivity that can support data, voice, video and messaging traffic. This advantage has significantly increased the number of users availing themselves of these services through various devices. Such an increase in the number of users has also increased network traffic. Thus, scheduling algorithms are needed to prioritize and distribute available resources among users to improve system performance. Researchers have proposed several algorithms that focus on meeting the Quality of Service requirement for different applications. The current study evaluates the performance of four scheduling algorithms for LTE downlink transmission, namely, proportional fair, exponential PF, exponential rule and log-rule algorithms, in a certain scenario. The performance of these algorithms was evaluated using an LTE-Sim simulator. Simulation results show that the log-rule algorithm outperforms other packet scheduling algorithms in terms of delay, throughput and packet loss ratio when serving Voice-over-Internet Protocol packet data service on the LTE network.

Enhanced Preemptive Global Utility Accrual Real Time Scheduling Algorithms in Multicore Environment

This paper proposed an efficient real time scheduling algorithm using global scheduling paradigm running in multicore environment known as Global Preemptive Utility Accrual Scheduling (GPUAS) algorithm. The existing TUF/UA multiprocessor scheduling algorithms known as Greedy-Global Utility Accrual (G-GUA) and Non Greedy-Global Utility Accrual (NG-GUA) algorithms is seen to overlook the efficiency on its task scheduling algorithm. These algorithms have adapted the task migration attribute considering the load balancing problem in multi core platform. The existing PUAS uniprocessor scheduling algorithm is mapped into the multicore scheduling environment that consists of the global scheduling schemes considering the migration attribute of the executed tasks. The main principal of global scheduling is that it allows the executed tasks to migrate from one processor to the other processors whenever a scheduling event occurs in the system. The proposed GPUAS algorithm inherits the characteristics of PUAS in uniprocessor where it can preempt the highest PUD task at any event that occurs in the system. In this research, the proposed GPUAS algorithm enhanced the existing NG-GUA and G-GUA algorithms. The developed simulator has derived the set of parameter, events and performance metrics according to a detailed analysis of the base model. The proposed GPUAS algorithm achieved the highest accrued utility for the entire load range. The proposed GPUAS algorithm is more efficient than the existing algorithms, producing the highest accrued utility ratio and less abortion ratio making it more suitable and efficient for real time application domain.

A Discrete Event Simulation for Utility Accrual Scheduling in Uniprocessor Environment

This research has focused on the proposed and the development of an event based discrete event simulator for the existing General Utility Scheduling (GUS) to facilitate the reuse of the algorithm under a common simulation environment. GUS is one of the existing TUF/UA scheduling algorithms that consider the Time/Utility Function (TUF) of the executed tasks in its scheduling decision in a uniprocessor environment. The scheduling optimality criteria are based on maximizing accrued utility accumulated from execution of all tasks in the system. These criteria are named as Utility Accrual (UA). The TUF/ UA scheduling algorithms are design for adaptive real time system environment. The developed GUS simulator has derived the set of parameter, events, performance metrics and other unique TUF/UA scheduling element according to a detailed analysis of the base model.

Implementation of Backward Recovery Mechanism in Preemptive Utility Accrual Real Time Scheduling Algorithm

This paper proposed a robust algorithm named as Backward Recovery Preemptive Utility Accrual Scheduling (BRPUAS). The proposed algorithm solved the abortion problem in the existing TUF/UA scheduling paradigm known as ARPUAS that only considers the abortion recovery as their fault recovery solution. BRPUAS enables the re-execution of the affected tasks rather than abortion to reduce the number of aborted tasks. It ensures the correctness of the executed tasks in the best effort basis in such a way that the infeasible tasks are aborted and produced zero utility, while the feasible tasks are re-executed to produce positive utility and consequently maximizing the total accrued utility to the system. Simulation results revealed that the BRPUAS achieved higher accrued utility compared to the ARPUAS for the entire load range, making it more reliable and efficient for adaptive real time application domain.