In this paper, Extreme Value Theory (EVT) is presented to analyze wireless network traffic. The role of EVT is to allow the development of procedures that are scientifically and statistically rational to estimate the extreme behavior of random processes. There are two primary methods for studying extremes: the Block Maximum (BM) method and the Points Over Threshold (POT) method. By taking limited traffic data that is greater than the threshold value, our experiment and analysis show the wireless network traffic model obtained with the EVT fits well with that of empirical distribution of traffic, thus illustrating that EVT has a good application foreground in the analysis of wireless network traffic.
Reconfigurable Optical Add/Drop Multiplexers (ROADMs) are going to change the landscape for future metro optical networks. In this paper, we present the detailed design layouts for next generation metro optical network equipped with the most advanced 3rd generation ROADM modules. Mathematical equations have been developed to design complex network architecture based on traffic demand and the characteristics of network equipments. Our proposed design layout for next generation network alleviates some conventional design concepts that will ultimately reduce the capital- and operational-expenditure for the overall network.
The single-hop star-based network is proposed as a feasible topology to fit the rapidly-increasing bandwidth requirement in the AAPN research project. This paper investigates the node architecture to implement all-optical operations in such a network using available technologies. Based on the node placement in the network, two architectures are designed, one is placed in the edge and another one is used in the core. The edge node is a multi-stage electronic/optic switch, which aggregates legacy traffics and transmits them to the core node, or accepts optical messages from the core node and sends them to legacy networks. Each stage uses either electronic or optical components to implement signal storage, conversion or transmission. The core node is an all-optical switch which switches optical signals in different wavelength planes, while the controlling part works in electronic domain. A separate control plane is designed to manipulate the operation of different component devices. This system provides a common platform for the overlaid-star network. By introducing synchronization or not, we can employ reservation-based optical time-division-multiplexing (OTDM) or contention-based optical burst switching (OBS) in the designed architecture. No wavelength conversion or optical buffering is necessary by agilely scheduling the messages in both mechanisms. Our research is an efficient and feasible solution which satisfies the transmission requirement by taking into account of technological availability. Our design is supported by the performance evaluation of OTDM and OBS methods, and their comparisons under different scenarios.
The Routing and Wavelength Assignment (RWA) problem has attracted lots of attention in the research field for the past decade. Most of the existing works are the classic static RWA problem, which assumes every time for the reconfiguration, all the existing connections will be reconfigured. In a real operating network, the reconfiguration has to take the existing connections into consideration and any reconfiguration of the existing connection results in the disruption of the upper level traffic. The algorithms that are slow or do not consider the existing connections in the network cannot be used in the real-time reconfigurable network. In this paper, we propose the semi-dynamic/static network optimization problem that takes into consideration existing connections from the previous reconfiguration session. The objective function in the formulation is penalty-based, i.e., there are penalties for the reconfiguration of a connection, for the rejection of a connection demand and for the most congested link. Rules on the existing capacity and new demand in the new session are proposed. We have successfully used the Lagrange Relaxation (LR) and Subgradient Method to successfully solve this network optimization problem. This state-of-art frame work allows us to evaluate systematically some sample networks in terms of various network performances and behaviors. At the same time, excellent algorithm performance and efficient computation complexity are demonstrated.
All-Optical networks with the DWDM technology provide huge bandwidth and are the sole approach for transporting huge network traffic. However, this bandwidth is too coarse to be used by a single user and this is why the Optical Time Division Multiplexing (O-TDM) has been deployed in the optical networks to provide finer granularity and improve bandwidth usage. In contention-based slotted-optical networks, because there is no collaboration among the ingress switches, the data slots on the same wavelength and time-slot destined to the same destination may collide. In this paper, we detail contention avoidance schemes in two software and hardware categories and show that edge switches can have an important role in reducing loss rate in optical networks by transmitting traffic to each destination with equal probability (symmetric traffic transmission) and balancing traffic load on the wavelength channels. We also show that edge switches can have an important role in the loss rate reduction issue in optical networks by reducing traffic load and using more wavelengths/fibers to carry the same traffic.
The Agile All-photonic Backbone Network (AAPN) architecture has been proposed by the telecommunication industry as a potential candidate for the ultra high speed Next Generation Optical Network (NGON) architecture. AAPN network structure is composed of adaptive optical core switches and edge routers in an overlaid star physical topology. The AAPN employs fast packet switching architecture for the network traffic, and the packet scheduling is the main part of the AAPN. The objective is to forward the packets to their destination with the lowest drop rate and delay, the bandwidth allocation can be either located at the core node or the edge switch. Two types of scheduling are considered in the AAPN architecture, namely the centralized and the distributed schemes. In the centralized scheme all decisions are made at the core node while in the distributed scheme, they are made at the edge nodes. In this paper, we want to compare both scheduling schemes. We would also like to propose a promising integrated TDM architecture that combines the good attributes of both centralized and distributed scheduling schemes. We shall characterize such architecture by various measures such as delay and loss probabilities.
The performance of an optical burst switching network is determined by the comprehensive effect of various parameters. This paper presents analysis results of an all-optical burst switching network which consists of edge nodes, which are responsible for traffic aggregation and distribution, and core nodes, which transmit payload data burst in the optical domain. Some essential parameters are compared on their effects on implementing switching operation, contention resolution and routing functions. We have examined the interrelationship of these parameters. Typical performance criteria are investigated in a sample OBS network.
The Agile All-photonic Backbone Network (AAPN) architecture has been proposed by the telecommunication industry as a potential candidate for the ultra high speed Next Generation Optical Network (NGON) architecture. AAPN network structure is composed of adaptive optical core switches and edge routers in an overlaid star physical topology. In this paper, we examine various optimization issues for AAPN architectures. The optimization procedure is based on a Lagrangean relaxation and subgradient method. Based on the optimization methodology provided in the previous research, we propose a modified algorithm to optimize AAPN networks, with respect to the assumptions used in AAPN. The results for different network configurations are studied and the influence of network resources is also studied. Our algorithm is shown to be very computational effective on the AAPN networks, and the bounds generated are mostly within 1% of the final objective value.
In this work we examine various survivability schemes for an agile all-photonic backbone network (AAPN). The AAPN architecture has been proposed by the telecommunication industry as a possible candidate for the ultra high speed Next Generation Optical Network (NGON) architecture, and implements an adaptive optical core and edge routers or switches in a star formation. In this paper we study the issue of network survivability in AAPN architecture. We examine different choices for edge-switch traffic restoration, including 1+1 path protection, cycle-based approaches and protection trees, and their pros and cons. We have also analyzed and compared the performance of the proposed schemes.
This work presents the performance analysis of ring resonator-based tuneable optical filters, namely the influence of the design parameters such as coupling coefficient (k), coupler loss coefficient (a) and operating temperature (t) on the optical performance of the filter. Computed results have shown that a and k dramatically influences the performance of the add-drop filter, the operating temperature can effectively be used as a mechanism of selecting the desired frequencies within the dynamic range of the filter, and special attention should be paid to the operating temperature range of the filter in order to avoid a decrease of its free spectral range below the value of the desired pass bandwidth. Preliminary sensitivity analysis has also revealed that the single ring add-drop filter design is almost insensitive to the relative position of the two optical couplers onto the ring, and therefore very versatile for integration into a photonic chip.
TCP congestion control mechanism has been widely investigated and deployed on Internet in preventing congestion collapse. We would like to employ modern control theory to specify quantitatively the control performance of the TCP communication system. In this paper, we make use of a commonly used performance index called the Integral of the Square of the Error (ISE), which is a quantitative measure to gauge the performance of a control system. By applying the ISE performance index into the Proportional-plus-Integral controller based on Pole Placement (PI_PP controller) for active queue management (AQM) in IP routers, we can further tune the parameters for the controller to achieve an optimum control minimizing control errors. We have analyzed the dynamic model of the TCP congestion control under this ISE, and used OPNET simulation tool to verify the derived optimized parameters of the controllers.
An understanding of the traffic characteristics and accurate traffic models are necessary for the improvement of the capability of wireless networks. In this paper we have analyzed the non-linear dynamical behavour of several real traffic traces collected from wireless testbeds. We have found strong evidence that the wireless traffic is chaotic from our observations. That is we found from the traffic correlation dimension, largest Lyapunov exponent and the principal components analysis, which are typical indicators of chaotic traffic. This gives us the good theoretical basis for the analysis and modeling of wireless traffic using Chaos Theory.
KEYWORDS: Head, Internet, Analytical research, Device simulation, Computer simulations, Systems modeling, Information technology, Detection and tracking algorithms, Signal detection, Linear filtering
In this paper, we investigate the application of the head dropping policy as a partial solution to the problem of queue oscillation encountered by RED and its variants. With this method, instead of the tail dropping, which is currently used by RED and many other AQM schemes, the TCP source can be informed of the congestion occurring in the bottleneck router a time period earlier. Specifically, that is a time period of the queuing delay. We have compared DH-RED (drop head RED) and DH-BLUE (drop head BLUE) with the current RED and BLUE in a variety of situations and found that the performances such as the queue size stability as well as packet drop rate can be greatly improved.
We study the dynamic allocation of bandwidth for video traffic in wireless networks. Our approach consists of two stages. In the first stage, we apply the FARIMA (Fractional Autoregressive Integrated Moving Average) models to forecast traffic based on online traffic measurements. In the second stage, we use the forecast results to allocate bandwidth dynamically. We evaluate our FARIMA-based scheme by comparing it with the ARIMA-based and the static schemes in terms of packet loss probability, queue length and bandwidth utilization. Through the experiments with real traffic traces, we demonstrate our approach works well for highly fluctuating traffic in WiFi.
This paper presents a distributed scheme for link failure recovery in mesh optical networks, based on the use of network hierarchical spanning trees. The scheme intends to maximize restorability in a network with known working and spare capacities. The hierarchical protection tree (p-tree) provides the hierarchical layering of the network. The straddling links that are not located on the tree are protected through tree branches to the higher layer Parent nodes. The links on the tree are protected by links to backup parent nodes. We study the problem of finding the most optimized network tree to achieve maximum restorability, and present heuristics for finding the best tree. Our algorithm includes two steps: Selection of the best root node for the tree, and construction of the tree based on distribution of tree ID labels among the nodes. Each node selects a primary parent node and a backup parent node, and constructs pre-determined protection paths accordingly. In case of failure, all connections on a link are switched quickly to the protection path as a bundle. We perform restorability analysis for several real and arbitrary long-haul networks and show that our scheme provides excellent network restorability along with exceptional scalability and maintainability.
We construct a multi-stage optical switch model with multilayer Kautz graphs. The switching path is built up by using the routing principle in the regular graph. A 3-stage switch is demonstrated. The modeling study shows pretty good statistics in terms of latency, packet loss and capacity. Implementation of this architecture with star couplers and other optical components is also discussed.
This work proposes and analyses a sparse reconfigurable optical add/drop multiplexer consisting of eight tuneable ring resonator-based optical filters, and two eight channel arrayed waveguide routers. The design features a 0.25 add-drop factor, 32 channels in a four-skip-one architecture at 0.8 nm channel spacing, covers the conventional band, and takes advantage of the main limitation of single ring resonator-based optical filters, namely the rather limited free spectral range. Coupled mode theory and its transfer matrix formalism have been used to design the tuneable add-drop filters, while classical theory of signal spectral analysis have been used for determining its performance characteristics. The computed results for a sparse tuneable optical add-drop multiplexer equipped with single-ring add-drop filters were add/drop insertion loss 0.77 dB, through adjacent insertion loss 2.7dB, worst add/drop adjacent cross talk -43dB, add/drop bandwidth at full width half maximum 0.221 nm, and group delays between 0.05 ps and 2 ps for add/drop and through optical channels. The proposed tuneable OADM exhibits a very good magnitude response and properly adds, drops, removes and/or lets through the selected channel without disturbing the other channels.
This work presents the analysis of ring resonator based tuneable optical filters and their proposed application in wavelength division multiplexing transmission systems. Using coupled mode theory and its transfer matrix formalism it has been shown that single-ring resonator add-drop filters with coupling coefficients k can provide similar or better performance than double ring resonator add-drop filters with coupling coefficients k/2, while benefiting from simple and more robust designs, simplified tuning control, and easier manufacturing. Further analysis of the their dynamic range showed that thermally tuneable single-ring add-drop filters can easily cover four optical channels at 0.8nm spacing. Their proposed application is a sparse reconfigurable optical add-drop multiplexer with 0.25 add-drop factor and 32 channels at 0.8nm channel spacing that can be utilized in linear, ring, and mesh all-optical WDM networks/transmission systems.
This paper introduced the Extreme Value Theory (EVT) for analysis of network traffic. The role of EVT is to allow the development of procedures that are scientifically and statistically rational to estimate the extreme behavior of random processes. In this paper, we propose an EVT_based procedure to fit a model to the traffic trace. We have performed some simulation experiments on real-traffic traces such as video data to study the feasibility of our proposed method. Our experiments showed that the EVT method can be applied to statistical analysis of real traffic. Furthermore, since only the data greater than the threshold are processed, the computation overhead is reduced greatly. It indicates that EVT method could be applied to real time network control.
KEYWORDS: Atrial fibrillation, Network architectures, Internet, Computer simulations, Process control, Linear filtering, Computer science, Electronics engineering, Information technology, Control systems
In this paper, we propose a new active queue management mechanism called the RIO-SD (RED IN and OUT with Selective Dropping) to control ill-behaved flows in DiffServ networks. Under this scheme, core routers are not required to maintain per-flow state, and the ill-behaved flows can be identified based on the drop history of the "OUT-profile" virtual queue. Control is effected by placing two pre-filters in front of the "IN-profile" and "OUT-profile" virtual queues respectively. Simulation results indicate that our approach can also improve the performance of other normal flows. Our work demonstrates that our algorithm is robust and simple to use.
Switching and scheduling are the two key elements to enable QoS awareness in IP routers. This paper extends our previous research work in ATM networks and introduces per-flow switching and per-flow scheduling in the design of QoS- capable IP routers. We switch IP packets on a per-flow basis and essentially create a virtual pipe from source to destination for every IP flow. We present a per-flow scheduling discipline to enable elasticity from every virtual pipe. We evaluate several key QoS parameters: delay, delay jitter, throughput, and packet loss ratio, to gauge the performance of our proposed switching and scheduling schemes.
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