Sharif Digital Repository

In this paper, we present a decentralized algorithm to find minimum cost quality of service (QoS) flow subgraphs in network coded multicast schemes. The main objective is to find minimum cost subgraphs that also satisfy user-specified QoS constraints, specifically with respect to rate and delay demands. We consider networks with multiple multicast sessions. Although earlier network coding algorithms in this area have demonstrated performance improvements in terms of QoS parameters, the proposed QoS network coding approach provides a framework that guarantees QoS constraints are actually met over the network. Flow optimization, network coding, quality of service (QoS)  

In this paper, we consider the problem of optimum selection of quality-of-service (QoS) classes in underworking between the networks in a next-generation-network (NGN) environment. After introducing the delay-cost and loss-cost characteristics, we discuss the time-invariant (TI) and time-variant (TV) scenarios. For the TI case, we show that under nearly lossless transmission condition, each network can make its own optimization regardless of other networks. For the TV case, we present sufficient conditions under which the optimum QoS class of each network can be considered fixed with respect to time without considerable degradation in the optimization target. Therefore, under the conditions... 

In this paper, we present a novel multirate, differentiated quality of service (QoS) optical CDMA (OCDMA) system using multilevel signaling technique. The emphasis is on OCDMA systems employing multi-length variable-weight optical orthogonal codes (MLVW-OOC) as signature sequence. We begin by presenting a two-class variable-weight OCDMA system in which all users have the same energy level in one bit duration. As a consequence, high weight users transmit their corresponding optical pulses at a lower power while low weight users transmit their corresponding optical pulses at a higher power level. We show that using this multilevel signaling technique, while employing the well known optical AND... 

Many classes of applications require Quality of Service (QoS) guarantees from the system interconnect. In Networks-on-Chip (NoC) QoS guarantees usually translate into bandwidth and latency constraints for the traffic flows and require hardware support in the NoC fabric and its interfaces. In this article we present a novel NoC synthesis framework to automatically build networks that meet hard latency constraints of end-to-end traffic streams without requiring specialized hardware for the network components. The hard latency constraints are met by carefully designing the NoC topology and selecting the appropriate routes for flow using lean best-effort network components. We perform... 

In this paper, we analyze and obtain performance of a multilevel Optical Code Division Multiple Access (OCDMA) system with Variable-Weight Optical Orthogonal Codes (VW-OOCs) under the same-bit-energy assumption. The exact error-probability of this system is derived for the Generalized VW-OOCs (codes with arbitrary cross-correlation) which is necessary for the optimum design of multilevel OCDMA systems. We show that the bit power has an important role on determining the performance of codes with different weights. Furthermore, the results reveal that the performance of low-weight codes depends on the weight of the low-weight codes and the code-weight ratio of two classes. Moreover, our exact... 

One of the most important issues in cognitive radio networks is to guarantee quality of service (QoS) constraints for primary users. In this paper, a relay-based cognitive radio network is considered in which secondary users compete in a selfish manner to use a relay to improve their utility function, while maintaining interference at the primary receiver to be lower than a certain threshold level. This problem is modeled as a non-cooperative game and by using a proper pricing function in the definition of the utility function, it is shown that despite the selfish behavior of the users, Nash equilibrium (NE) with sub-optimum property is achieved. A distributed and novel algorithm to update... 

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 framework which can be used by network designers in an organization. The outcome of the framework is value for three QoS parameters: delay, loss and availability. The organizations business processes are used as a basis for the framework We used UML as the tool to model the business processes in the organization. First, the process is modeled with UML activity, sequence and class diagrams. Then, a three-step analysis has been conducted on the models to find the specifications of the business process. The analysis... 

The hierarchical coexistence of femtocells and macrocells is a promising approach for heterogeneous networks (HetNets), dealing mainly with indoor coverage issues and providing high data rates in cellular networks. As for any HetNet, mobility management with handoff issues on top, should be studied prior to hindering the successful deployment of these networks. The current study introduces a new handoff algorithm in hierarchical macro/femtocell HetNets based on the combination of quality of service metrics for efficient network selection including: received signal strength, co-channel interference level, and outage probability of each of femtocell and macrocell networks. The proposed... 

Recently, manufacturing firms and logistics service providers have been encouraged to deploy the most recent features of Information Technology (IT) to prevail in the competitive circumstances of manufacturing industries. Industry 4.0 and Cloud manufacturing (CMfg), accompanied by a service-oriented architecture model, have been regarded as renowned approaches to enable and facilitate the transition of conventional manufacturing business models into more efficient and productive ones. Furthermore, there is an aptness among the manufacturing and logistics businesses as service providers to synergize and cut down the investment and operational costs via sharing logistics fleet and production... 

Recently, manufacturing firms and logistics service providers have been encouraged to deploy the most recent features of Information Technology (IT) to prevail in the competitive circumstances of manufacturing industries. Industry 4.0 and Cloud manufacturing (CMfg), accompanied by a service-oriented architecture model, have been regarded as renowned approaches to enable and facilitate the transition of conventional manufacturing business models into more efficient and productive ones. Furthermore, there is an aptness among the manufacturing and logistics businesses as service providers to synergize and cut down the investment and operational costs via sharing logistics fleet and production... 

In this article we present a new scheme to support multirate and multi-quality-of-service transmission in passive optical networks based on a hybrid wavelength-division multiplexing/optical code-division multiplexing scheme. The idea is to use multilength variable-weight optical orthogonal codes as signature sequences of a hybrid WDM/OCDM system. To provide the requested classes of service, the code weight and code length of MLVW-OOCs are designed based on the characteristics of the requested classes of service. In order to mitigate multiple access interference, we propose to utilize a multilevel signaling technique and interference remover structure based on advanced optical logic gate... 

All-optical multi-service path switching in optical code switched GMPLS core networks  

In this paper, we propose a new scheme to provide multiservice transmission on generalized multiprotocol label switching (GMPLS) networks using optical code-division multiplexing (OCDM) in each wavelength of a wavelength-division multiplexing system. To provide multiservice transmission in a typical GMPLS network, we propose to classify the fiber bandwidth into a number of waveband and consider the wavelengths of each waveband for a specific class-of-service such that the corresponding codes to be used are designed based on the characteristics of the class-of-service. The traffic behavior of the network is examined using Erlang's model, and the probability density functions (PDF) of the... 

The quality of service in Wireless Multimedia Sensor Networks (WMSN) is related to congestion in network. Recently different studies have been done on developing efficient protocols in the transport layer for controlling packet loss in WMSN. However, all of these protocols are independent of the characteristics of multimedia content. In this paper, a novel transport layer protocol, called Energy Efficient Congestion Avoidance (EECA), is proposed to minimize the packet loss ratio in WMSN by predicting congestion in network, and adjusting the source nodes output rate before congestion happening. EECA adjusts the output video quality in source nodes to adjust the source nodes video quality. The... 

In this paper, we investigate multi-quality of service (QoS) routing and spectrum assignment in elastic optical networks (EONs) by utilizing network state information in terms of bandwidth usage and holding time of established connections. Toward this aim, two types of traffic, namely big data traffic (BDT) requests, and fixed rate flow requests (FLRs) are considered, where BDTs can tolerate a pre-determined initial delay while FLRs must be served immediately without any delay. We assume that both frequency and time usage of optical bandwidth is slotted, and accordingly optical resources are defined in a two-dimensional (2D) time/frequency domain, where the smallest resource is specified... 

An enhanced media access control (MAC) layer protocol that uses the signaling method benefits of the physical layer in order to provide different levels of quality to different users in optical code-division multiple-access (OCDMA) packet networks is presented. In the proposed network architecture the users are categorized into two classes of service, one having a higher quality level and the other having a lower quality level. Users of each class transmit at the same power level and different from the other classes’ users. Also, the MAC of each user estimates the amount of interference on the channel and adjusts the packet transmission’s time to improve network performance. Through... 

By occurring failures in computer networks, routing protocols are triggered to update routing and forwarding tables. Because of invalid tables during update-time, transient loop may occur and packet-drop rate and end-to-end delay increase which means that the quality of service decreases. This paper studies the effect of routing-tables update-time on networks' performability, i.e. the ability of network to deliver services at predefined level. A sample network is studied and the simulation results show that faster updates of routing table, improve network's performability in the presence of failures. Since it may not worth or even be practical to accelerate all routers in the network, this... 

By occurring failures in computer networks, routing protocols are triggered to update routing and forwarding tables. Because of invalid tables during update-time, transient loop may occur and packet-drop rate and end-to-end delay increase which means that the quality of service decreases. This paper proposes a parallel architecture for a router to recalculate and update routing table. Simulation results show that with dual-processor architecture, this update time could be up to 40% improved, depending on the network topology and the size of tables. This paper also studies the effect of this speed-up on networks' performability, i.e. the ability to deliver services at predefined level. A... 

Resource allocation with quality of service constraints is one of the most challenging problems in elastic optical networks that is normally formulated as a mixed-integer nonlinear optimization program. In this paper, we focus on novel properties of geometric optimization and provide a heuristic approach for resource allocation that is much faster than its mixed-integer nonlinear counterpart. Our heuristic consists of two main parts for routing/traffic ordering and power/spectrum assignment. It aims at minimization of the transmit optical power and spectrum usage constrained to the quality of service and physical requirements. We consider three routing and three traffic ordering procedures...