Suggestions of efficient self-similar generators

It is generally accepted that self-similar (or fractal) processes may provide better models for teletraffic in modern computer networks than Poisson processes. If this is not taken into account, it can lead to inaccurate conclusions about performance of computer networks. Thus, an important requirement for conducting simulation studies of telecommunication networks is the ability to generate long synthetic stochastic self-similar sequences. A generator of pseudo-random self-similar sequences, based on the SRA method [5], is implemented and analysed in this report. Properties of this generator were experimentally studied in the sense of its statistical accuracy and the time required to produce sequences of a given (long) length. This generator shows acceptable level of accuracy of the output data (in the sense of relative accuracy of the Hurst parameter) and is fast. The theoretical algorithmic complexity is O(n) [20].

Modern communication networks are expected to have hundreds or thousands of network nodes to which thousands of users are connected. Neural networks can contribute to this emerging new telecommunication infrastructure by providing fast, flexible, adaptive, and intelligent control. This article discusses the neural networks used for solving various control problems in high-speed communication networks.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Interference is a critical problem in the wireless communication networks, and interference performance assessment is of great sensibility necessity. This paper proposes a new comprehensive interference assessment method, AHP-GRAP (Analytic Hierarchy Process - Grey Relational Analysis Process, AHP-GRAP) method. And the AHP-GRAP is applied to a real case to resolve the interference assessment problem in the high-speed railway wireless communication networks in this paper. In the proposed AHP-GRAP method, the relative weights of QoS (Quality of Service, QoS) criteria in the high-speed railway wireless communication networks are determined by AHP, and then these weights are used as coefficients of GRAP model. Based on the optimal value of the QoS in the high-speed railway wireless communication networks, GRAP is then used to perform the evaluation of interference. The results show that AHP-GRAP is a more comprehensive method to reflect the interference state of the systems than existing single criteria interference assessment algorithms.

Compound TCP is widely deployed in the Windows operating system, and the Drop-Tail queue policy is commonly used in Internet routers. We study models for Compound and Drop-Tail in the limiting regime of small router buffers, with smooth and with bursty traffic. We conduct a systematic local stability and local Hopf bifurcation analysis of the underlying non-linear, time-delayed, fluid models. The stability analysis allows us to capture relationships between protocol and network parameters to ensure stability in high bandwidth-delay environments. In particular, we exhibit that even minor variations in router buffer sizes, in a small buffer regime, can lead to Hopf induced limit cycles in the queue size. Limit cycles in the queue size may hurt end-to-end network performance and should, if possible, be avoided. Applying Poincare normal forms and the center manifold analysis, we explicitly show that the Hopf bifurcation is supercritical. Thus loss of local stability would give rise to limit cycles, which are also proved to be asymptotically orbitally stable. The analytical results are corroborated by packet-level simulations which are conducted in a network simulator. Some design guidelines to ensure the stability of, and low-latency in, highspeed communication networks are also provided.

High-speed railway (HSR) wireless communication network has won a great development in recent years. However, due to its unique characteristics, such as high speed, fixed mobility track, special traffic, frequent handover and bandwidth constraints, it is quite a challenge to carry out the performance analysis on HSR. In this paper, we derive the backlog and delay bounds for HSR communication network by using stochastic network calculus (SNC) with moment generating functions (MGFs). SNC is a highly useful tool in packet switched network performance analysis since 1990s. Different from the previous studies about SNC which mostly concentrate on general low-speed, traditional public communication network, we take the varying small-scale fading and large-scale fading into consideration by means of a novel multi-dimension finite-state Markov channel (FSMC) model. We elaborate the differences in packet-level channel model, traffic model of train control information and performance metrics in HSR communication network. Particularly, the backlog and delay bounds of HSR with different packet arrival rates and violation probabilities are derived when train travels from the cell center to the cell edge. What is more, the numerical results can help to provide a guideline for designing the proper violation probabilities and arrival rates to different types of traffic in HSR communication network.

As a ubiquitous phenomenon in communication networks, the self-similar nature of network traffic has recently received great interests and been extensively studied. In this paper, assuming the buffering capability of the source node, through combining the traffic properties and channel characteristics, we analyze the queuing behaviors of self-similar traffic which is characterized by Fractional Brownian Motion (FBM) model, and derive the asymptotic closed-form expressions for the tail distribution of the stable queue length, traffic characteristics and transmission rate in three-node cooperative relay wireless networks. We further analyze the effects of different degrees of self-similarity for long-range dependence (LRD) traffic on the queue length, and compare the queuing performance by adopting different relay cooperative strategies including amply-and-forward (AF) protocol and decode-and-forward (DF) protocol. Finally, simulation results validate the accuracy of the theoretical analysis, and further, some useful conclusions are obtained, such as, effects of long-range dependent traffic on network performance are different under small and large buffer sizes and there exists a buffer turning point; queuing behaviors for AF and DF cooperative transmission protocols also perform opposite trends at low signal-to-noise ratios and high signal-to-noise ratios, etc.

The self-similar network traffic can have a detrimental impact on network performance, including amplified queuing delay, retransmission rate and packet loss rate. Modern network traffic consists of more bursts than Poisson models predict over many time scales. This difference has implications for performance. The video traffic research is important because self-similar nature of network traffic leads to a number of undesirable effects like high buffer overflow rates, large delays and persistent periods of congestion and the severity of these conditions is directly proportional to the degree of self-similarity. On the other hand, the long memory property of self-similar traffic is able to help to forecast traffic for the purpose of quality of service (QoS) provision. This work presents the results of the analysis of video traffic performed and study the structure of the video traffic to identify its characteristic features

A survey on the communication architectures in smart grid

The main challenge in the engineering of IP networks is the integration and support of a wide variety of applications and services combining voice, data, streaming, and VoD that have different traffic characteristics and require different levels of quality of service (QoS). The most important measures of QoS are the end-to-end delay, packet loss rate and delay variation or jitter. Any network design procedure must take them into account to insure that the real-time QoS requirements of real-time and interactive services can be met. However, the jitter has been extensively studied in relation to various scheduling and routing algorithms, but it has been rarely studied in the context of relationships between others parameters of quality of service. In this paper, we present a study under several scenarios in order to explore the behavior of jitter and delay and their impact on the network performance. We confirm that these two parameters behave differently in function of traffic load for Poisson and heavy-tailed traffic.

RATE-BASED CONGESTION CONTROLLERS FOR HIGH-SPEED COMPUTER NETWORKS

With the expansion of the scale of network system, the structure of high-speed railway train is more and more complex. The problems of real-time and reliability of network need to be solved. In this paper, aiming at the traditional train network communication mechanism, multi-objective particle swarm optimization algorithm is used to optimize the network design. The real-time performance of the network before and after optimization is simulated by OPNET. The experimental results show that the optimization algorithm in this paper can improve the real-time performance and reliability of the network.

Despite the fact that copyright infringers are being distributed in large quantities through the rapidly developed high-speed information and communications network in recent years, there is no system under the current legislation that allows copyright owners to directly request the online service provider (OSP) to disclose the infringer’s information. Even if the company voluntarily discloses user identity information, it may violate the Act on Promotion of Information and Communications Network Utilization and Information Protection (Information and Communications Network Act). The copyright holder can obtain effective remedy only when he uses OSP’s services to secure the identity information of the person who infringes his copyright. The purpose of the ‘Request System for Requesting Information on Replicators and Transmitters’ is to provide a procedure for the copyright holder to obtain the identity information of the infringer from the OSP within the scope necessary for litigation in order to obtain relief for copyright infringement. However, as requests for information provision are made indiscriminately even for minor copyright infringers, concerns about personal information infringement are increasing. This article examines the specific details of the information provision request system regarding the copy/transmitter, and furthermore, reviews the Information and Communications Network Act that stipulates the same system and foreign legal systems to solve the problem of abuse of information provision request.

Multicast is the ability to transmit information from a single source node to multiple selected destination nodes in a network. Current trends in networking applications indicate that there will be an increasing demand in future networks for multicast communication. Banyan networks have been proposed for use in ATM high-speed communications networks and have been used for the interconnection of processors in scalable parallel computers. This paper addresses the performance issues of supporting multicast communication in banyan networks. Previous work on the performance of banyan networks has been primarily for the networks which can support only one-to-one communication (i.e., unicast banyan networks). We present an analytical model for the performance of banyan networks which support multicast communication (i.e., multicast banyan networks). The performance of both unbuffered and buffered banyan multicast networks is analyzed. Our model yields a set of equations that can be solved for the throughput of the network. We show that the throughput of a multicast banyan network is generally higher than that of a unicast banyan network. In particular, we obtain that the throughput of an unbuffered multicast banyan network is /spl Theta/(N), where N is the size of the network, compared with /spl Theta/(N/log N) for an unbuffered unicast banyan network. In addition to the throughput, we also derive formulas for two other important performance metrics, average packet transfer time and packet loss probability, in the buffered multicast banyan networks.

Consumer broadband services are increasingly a mix of TCP-based and UDP-based applications, often with quite distinct requirements for interactivity and network performance. Consumers can experience degraded service when application traffic collides at a congestion point between home LANs, service provider edge networks and fractional-Mbit/sec `broadband' links. We illustrate two key issues that arise from the impact of TCP-based data transfers on real-time traffic (such as VoIP or online games) sharing a broadband link. First, well-intentioned modifications to traditional TCP congestion control can noticeably increase the latencies experienced by VoIP or online games. Second, superficially-similar packet dropping rules in broadband gateways can induce distinctly different packet loss rates in VoIP and online game traffic. Our observations provide cautionary guidance to researchers who model such traffic mixes, and to vendors implementing equipment at either end of consumer links.

The network planning is a key factor that directly affects the performance of the wireless networks. Distributed antenna system (DAS) is an effective strategy for the network planning. This paper investigates the antenna deployment in a DAS for the high-speed railway communication networks and formulates an optimization problem which is NP-hard for achieving the optimal deployment of the antennas in the DAS. To solve this problem, a scheme based on an improved cuckoo search based on dimension cells (ICSDC) algorithm is proposed. ICSDC introduces the dimension cell mechanism to avoid the internal dimension interferences in order to improve the performance of the algorithm. Simulation results show that the proposed ICSDC-based scheme obtains a lower network cost compared with the uniform network planning method. Moreover, ICSDC algorithm has better performance in terms of the convergence rate and accuracy compared with the conventional cuckoo search algorithm, the particle swarm optimization, and the firefly algorithm.