High Speed Downlink Packet Access (HSDPA) is the extension to the Universal Mobile Telecommunication System (UMTS). HSDPA allows for higher data rates due to new adaptive Modulation and Coding (AMC) techniques, Hybrid Automatic Repeat reQuest (H-ARQ) and fast scheduling algorithm. One of the key features of HSDPA technology is to handle UMTS traffic classes with different Quality of Service (QoS) requirements. In order to provide QoS several scheduling algorithms, QoS control constraints, and different other schemes have been proposed in literature. In the thesis, a simple matlab based model for HSDPA is presented in order to simulate various algorithms. The QoS controls in terms of guaranteed bit rate (GBR) have been implemented by means of barrier functions which perform barrier around the feasible region. The results illustrate the trade-off between the cell throughput and the minimum guaranteed bit rate. Traffic classes are prioritized by means of QoS parameters. The priority is given to RT traffic streams over interactive services. Real-Time (RT) algorithms have been simulated to prioritize traffic classes based on delays. / QoS is the ability to provide resources and prioritize different applications. As mentioned before, the 3GPP standard defines four categories of service (Conversation, streaming, interactive and background) for UMTS. Strategies in traffic management, priority GBR allowances and bandwidth are important strategies for traffic differentiation and quality of service (QoS). Providing QoS over HSDPA is one of the challenging tasks for researchers. The significant results and findings of our thesis are as follows • In this thesis various algorithms were implemented with their duties barrier to provide guarantees of quality, in terms of speed guaranteed (GBR). The emphasis was to ensure the flow and priority categories of traffic. First the performance of algorithms were studied alone and then along with the barrier functions. It is concluded that barrier functions play an important role by means of providing QoS guarantee in HSDPA, considering channel conditions. Traffic classes were prioritized on QoS parameters defined for barrier functions. It was found that minimum bit rates were maintained by barrier functions but the cell throughput decreases with their barrier functions depending upon QoS parameters. The streaming aware scheduler has been evaluated by means of simulations in mixed scenarios and it is concluded that this algorithm protects streaming QoS in high overload conditions. It is therefore concluded that barrier functions and streaming aware schedulers are the best option for QoS control. These schedulers are very simple and consider diversity gains as well.

Thesis (Ph. D.)--University of Oregon, 2004. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 189-198). Also available for download via the World Wide Web; free to University of Oregon users.

Real-time systems are those whose correctness depends not only on logical results of computations, but also on the time at which the results are produced. This thesis provides a formal definition for real-time systems and includes the following original contributions on real-time scheduling algorithms. The first topic studied in the thesis is minimizing the total penalty to be paid in scheduling a set of soft real-time tasks. The problem is NP-hard. We prove the properties of any optimal scheduling algorithm. We also derive a number of heuristic algorithms which satisfy the properties obtained. Moreover, we obtain a tight upper bound for the optimal solution to the problem. Numerical results that compare the upper bound with the optimal solution and the heuristic algorithms are provided. In the second part of this thesis, we study the problem of minimizing the number of processors required for scheduling a set of periodic preemptive independent hard real-time tasks. We use a partitioning strategy with an EDF scheduling algorithm on each processor. The problem is NP-hard. We derive lower and upper bounds for the number of processors required to satisfy the constraints of the problem. We also compare a number of heuristic algorithms with each other and with the bounds derived in this research. Numerical results demonstrate that our lower bound is very tight. In the third part of the thesis, we study the problem of uplink scheduling in telecommunication systems with two dimensional resources. Our goal is to maximize the total value of the packets sent in uplink subframe such that system constraints and requirements are satisfied. The packets have various QoS requirements and have either soft or hard deadlines. We take two approaches, namely 0-1 and fractional approaches, to model the problem. Considering the properties of the application, we derive globally optimal solutions in polynomial time for the models. We also present a method to fine-tune the models. Numerical results are provided to compare the performance of the various optimal algorithms each corresponding to a model. / Thesis (Ph.D, Computing) -- Queen's University, 2009-04-24 08:22:04.238

Wireless scheduling is a fundamental problem in wireless networks that involves scheduling transmissions of multiple users in order to support data flows with as high rates as possible. This problem was first addressed by Tassuilas and Ephremides, resulting in the celebrated Back-Pressure network scheduling algorithm. This algorithm schedules network links to maximize throughput in an opportunistic fashion using instantaneous network state information (NSI), i.e., queue and channel state knowledge across the entire network. However, the Back-Pressure (BP) algorithm suffers from various drawbacks - (a) it requires knowledge of instantaneous NSI from the whole network, i.e. feedback about time-varying channel and queue states from all links of the network, (b) the algorithm requires solving a global optimization problem at each time to determine the schedule, making it highly centralized. Further, Back-pressure algorithm was originally designed for wireless networks where interference is modeled using protocol interference model. As recent break-throughs in full-duplex communications and interference cancelation techniques provide greatly increased capacity and scheduling flexibility, it is not clear how BP algorithm can be modified to improve the data rates and reduce the delay. In this thesis, we address the drawbacks of Back-Pressure algorithm to some extent. In particular, our first work provides a new scheduling algorithm (similar to BP) that allows users to make individual decisions (distributed) based on heterogeneously delayed network state information (NSI). Regarding the complexity issue, in our second work, we analyze the performance of the greedy version of BP algorithm, known as Greedy Maximal Scheduling (GMS) and understand the effect of channel variations on the performance of GMS. In particular, we characterize the efficiency ratio of GMS in wireless networks with fading. In our third and fourth work, we propose and analyze new scheduling algorithms that can benefit from new advancements in interference cancelation techniques. / text

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph.D.)--University of Melbourne, Dept. of Mechanical Engineering, School of Engineering, 2009. / Typescript. Includes bibliographical references (p. 177-184)

Thesis (Ph. D.)--University of Hong Kong, 2003. / Includes bibliographical references. Also available in print.

In this thesis, we propose a number of distributed schemes for wireless communications in the cross layer design context, considering an uplink random access network in which multiple users communicate with a common base station. In addition, we perform a comprehensive study on a splitting based multiuser selection algorithm which is simple, effective, and scales with the network size. First, we investigate a reservation-type protocol in a channel aware ALOHA system. Various Markovian models are used to describe the system and to capture the temporal correlation of the channel evolution. The average throughput of the system is obtained using the Markov Analysis technique and we show that the reservation protocol can achieve better performance than the original channel-aware ALOHA by reducing the collision probability. Second, for better resource utilization in the Opportunistic Multichannel ALOHA scheme, we propose a simple extension to the transmission policy that exploits the idle channels. Performance analysis shows that, theoretically, the maximum system throughput can be improved by up to 63% in the asymptotic case. Through numerical results, it can be seen that a significant gain is achieved even when the system consists of a small number of users. Third, we consider a splitting based multiuser selection algorithm in a probabilistic view. Asymptotic analysis leads to a functional equation, similar to that encountered in the analysis of the collision resolution algorithm. Subject to some conditions, the solution of the functional equation can be obtained, which provides the approximations for the expected number of slots and the expected number of transmissions required by the algorithm in a large system. These results shed light on open design problems in choosing parameters for the algorithm when considering the delay and the overhead jointly. A typical example is to optimize the parameters that minimize the weighted sum of these measures of interest.

The primary purpose of this work is to propose a new scheduling approach of multimedia data streams in real-time communication and also to study and analyze the various existing scheduling approaches.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 70-72) Also available in print.