Sharif Digital Repository

By an increase in demands for multimedia services of mobile, wireless networks shall provide Quality of Service (QoS) requirements for users moving in cells. Multimedia services such as voice, data and image own different features and every QoS are different from the other due to delay and demand for bandwidth.
This thesis presents a new model of call admission control which consists of a few key elements for protecting the network in different conditions of workload in a manner that calls blocking /dropping are kept under desired level. This model consists of two traffic classes of voice and data in order to give apriority to handoff call over new call, the parameters in this model are... 

Achieving the required Quality of service (QoS) is a challenging task in the emerging next generation networked multimedia applications. Providing QoS guarantees becomes even more challenging when you add the complexities of wireless and mobile networks. An important aspect of wireless networks is their dynamic behavior. Especially when we need to transmit multimedia data over wireless networks, this problem becomes more significant. Live video with large end to end delay is meaningless and very low quality video is not satisfying. In recent years, a number of Protocols for providing guarantee of service are presented in the literature. These techniques include data link layer QoS schemes,... 

Multicasting has gained a lot of research attentions in facilitating group communications in wireless networks. Applying multicast mechanisms in Wireless Mesh Networks, brings a lot of benefits to these networks. In our research, we have introduced Cost-aware On-Demand Multicast Routing Protocol (C-ODMRP) as an extension of ODMRP that supports QoS provisioning for high quality applications in WMNs. In C-ODMRP, the nodes are prevented from applying the links that do not meet the QoS requirements. The multicast receivers are provided with resource-aware information to efficiently compute the cost of the routes when multiple routes from source to destination nodes are established. C-ODMRP takes... 

Next generation wireless networks support high data rates and QoS parameters of various users. OFMDA is a popular transmission technique to support high rate transmission, however in multi-access environments, it relies on careful resource allocation to guarantee the desired QoS parameters. While resource allocation in centralized scenarios such as cellular networks is relatively straightforward, the problem becomes quite complex in distributed scheduling of multiple access environments. One key resource is power assigned to each sub-channel which determines the overall transmission capacity.In this dissertation, firstly we introduce some cross layer QoS provisioning or power efficient QoS... 

In this thesis we have studied slotted and unslotted ALOHA random access optical CDMA packet switching networks with a chip-level receiver structure. We used generalized optical orthogonal codes (GOOC) and Overlapping PPM (OPPM) signaling technique to improve system performance. The impact of physical layer parameters such as GOOC code cross correlation value and OPPM overlapping index on key performance benchmarks such as network throughput and delay are analyzed. We have also studied the stability of the network based on the number of backlogged users, using expected state drift. It has been shown that using GOOC instead of strict OOC improves the network average delay and throughput.... 

Communications in organizations have been one of the most important issues. To run the business processes, the company needs communication between units and customers. We provide a tool which can be used as an aid for network designers by guiding them with a framework. The resulting QoS parameters help to provide more alignment between the network and business requirements. The framework contains values for delay, loss and availability as three QoS parameters of the network used in the business process. The organizations business processes are used as a basis for the method which used in the tool. We use UML as the tool to model the business processes in the organization and the process is... 

The efficient scheduling of independent and sequential tasks on distributed and heterogeneous computing resources within grid computing environments is an NP-complete problem. Therefore, using heuristic approaches to solve the scheduling problem is a very common and also acceptable method in these environments. In this thesis, a new task scheduling algorithm based on bee colony optimization approach is proposed. The algorithm uses artificial bees to appropriately schedule the submitted tasks to the grid resources. Applying the proposed algorithm to the grid computing environments, the maximum delay and finish times of the tasks are reduced.Furthermore, the total makespan of the environment... 

The rapid growth of broadband wireless access (BWA) has increased the demand of new  application  such  as  VoIP,  video  conferencing,  online  gaming  each  of  which  has  different requirement for quality of service. Due to limited bandwidth provided for these networks,  one  of  the  most  important  issues  is  how  effective  we  manage  bandwidth  in  order to support requests. The quality of service is an important indicator of the effective management  of  bandwidth.  Using  mechanisms  of  call  admission  control is  a  commonly  accepted method for balance between quality of service and increase of utilization resource  in  cellular  mobile  networks.  In  fact, ... 

Increasing demand for higher data rates and more reliable communications along with growing applications of multimedia networks in everyday life on one hand, and limited resources on the other, have given rise to researches investigating spectrum efficiency enhancement techniques, among which multiuser diversity has always been of considerable importance. This thesis is a study on utilization of multiuser diversity in wireless LANs via scheduling. Where throughput and Quality of Service (QoS) in communication networks are being investigated, it is mostly advantageous to describe the traffic behavior of resources by greedy or non-greedy models. So far, there are plenty of investigations on... 

Recently studies have shown that about 50% to 70% of voice calls and other traffics are used in indoors by users. Due to the growing need to increase the rate of communication networks and macrocells resource constraints in providing this need, the idea of using femtocells was proposed. These cells transmite traffics via IP network to the operator. This would reduce the load of macrocells and thereby increase the rate of network users. So the idea of using femtocells inside macrocells was introduced. In addition to increasing the rate of network, the other advantages of using femtocells are lower cost, lower power consumption and better user channel condition. The important challenge of... 

Considering the advantages of optical communications and code division multiple access technique, Optical Code Division Multiple Access Networks (OCDMANs) was introduced. Thence, many researchers have suggested methods for creating Quality of Service (QoS) differentiated classes in OCDMANs. In this thesis, we have comprehensive review on the QoS assignment methods and enhance them by offering new techniques. In physical layer, we concentrate on variable chip rate OCDMANs and in MAC sub-layer, a new algorithm named Adaptive Level Control (ALC) is introduced. Then, we focus on the physical design of OCDMANs. Firstly, we solve the problem of one-class OCDMAN and introduce few simple and... 

Video communications over mobile ad hoc networks is increasingly deployable as these networks become deployed in various applications such as disaster recovery. Error-prone nature of the mobile ad hoc networks and the vulnerability of compressed video to packet losses have brought many challenges to realize video transmission over MANETs. In this thesis, it is tried to achieve a good quality of service by resilient video coding and multipath transmission over mobile ad hoc networks. To generate error resilient video, a hybrid method is used by combining scalable video coding and multiple description video coding techniques. First, the video sequence is coded to two layers and then each layer... 

In a data network, expressing an appropriate model for traffic and service is necessary for the guarantee of quality of service (QoS) parameters, e.g. delay and backlogged traffic. There are four main approaches for modeling the traffic and service. First approach is classic queuing theory. It is a useful tool for analyzing the networks with memory less input traffic. Second approach is deterministic network calculus. In this approach some deterministic bounds on delay and backlogged traffic can be derived. However, it is not accurate for analyzing the bursty traffic and wireless networks, because only trivial bounds can be derived in these scenarios. Third approach is effective bandwidth... 

The rapid growth in demand for computational resources driven by new applications and services had led to establishment of new cloud data centers. Such Data Centers consume enormous amount of electrical energy resulting in high costs and carbon emissions. Dynamic Consolidation of virtual machines and turning idle hosts off allow cloud providers to reduce energy consumption. But consolidation of virtual machines may leads to quality of service(QoS) degradation and Service level Agreement(SLA) violation. One of the most important reasons for QoS degradation is the migration overhead, therefore the number of VM migrations should be controlled. Over the last few years, VM consolidation problem... 

Wireless technology is growing rapidly. We have seen the evolution of these networks from first to fourth generation. Along with this growth, number of users needing wireless data services supporting real-time multimedia applications with high quality of service is growing annually. The challenge is to have the best connection anytime anywhere. Radio access technologies (RATs) consist of different types. Each RAT has its own technological characteristics. Operators constantly are seeking to increase their subscribers by providing high quality services so they can earn more profit. On the other hand users try to have a better experience from provided data services according to their... 

Results showed that 9 factors of “Brand Equity”, “Product Quality”, “Service Quality”, “Service Recovery”, “Perceived Value”, “Relationship”, “Employee Satisfaction”, “Physical Environment” and “Distribution Channel” are most effective factors by researchers that have effect on customer satisfaction. Thus, the Macromodel of this research was designed based on these factors. Due to limitations and context of the research, “Service Quality”, “Service Recovery” and “Relationship” were chosen in the final model. Results of questionnaire showed that the 5 parameters of “Service Recovery Speed”, “Reliability”, “Responsiveness”, “Empathy” and “Seller-focused antecedents” was the most important... 

In this work we have investigated the methods of providing quality of service in cognitive radio networks. At first, we have explained the various algorithms of providing BER quality of service in wireless networks. Especially we have explained those algorithms which are known as the distributed power control algorithms. Then we have introduced methods of using adaptive modulation and we have used this kind of modulation to provide delay quality of service in cognitive radio networks. We have done this by maximizing the sum of effective capacities of secondary links under the power constraints and also the interference constraints set by the primary receivers. Finally, we have introduced... 

Fiber optic networks are the most attractive technology to deal with the ever increasing demands for high rate transmission with guaranteed quality of service and affordable costs. Optical-to-electrical (O/E) and electrical-to-optical (E/O) conversion at intermediate routers are the restricting processes in current optical networks. There is a great interest to remove O/E and E/O conversion at intermediate routers to achieve an all-optical transmission between source and destination. Optical circuit switched (OCS) networks are the first generation of all-optical networks, which are restricted due to its limitation such as being connection oriented, low bandwidth utilization, and coarse... 

The availability of wireless sensor networks (WSN) and possibility of sense and transmission of multimedia data has fostered the development of wireless multimedia sensor networks (WMSN). Limitations of WSNs such as energy constraint and bandwidth alongside WMSNs quality of services requirements, causes challenges in routing of these networks. Many methods has been proposed to overcome routing challenges in WMSNs. Group of these methods transmit data to next hop by using geographical location of nodes. In order to meet QoS requirements of WMSNs as much as possible and reduce interference of routing paths, a new method is proposed. Proposed method is a location aware and nodes are aware of... 

Analysis of traditional spectrum allocation schemes shows underutilization of radio spectrum. This is main motivation behind deployment of cognitive radios and improving spectrum efficiency. One of the most important issues in cognitive radio networks is to guarantee quality of service (QoS) constraints for the primary users. Another problem which must be considered during network design is to design distributed algorithm with few amount of control messages. However, there is a tradeoff between to be distributed of algorithm and to be efficient. We have used game theory to analyze convergence, effectiveness and uniqueness of stable point of network.
This thesis is organized in two parts....