Wireless network modeling and simulation tools for designers and developers - [Modeling and simulation: a practical guide for network designers and developers]

Modeling and simulation methods are employed by scientists and engineers to gain insight into system behavior that can lead to faster product time-to-market and more robust designs. These advantages come at the cost of model development time and the potential for questionable results because the model represents limited attributes of the actual system. M & S techniques are used to characterize complex interactions and performance at various layers of the protocol stack. This article provides a discussion of M & S for wireless network designers and developers, with particular attention paid to the architectural issues, as well as a discussion of the various communication M & S tools available today. The topics presented span the protocol stack, including radio-frequency-propagation M & S tools, physical-layer and waveform M & S, network-layer M & S, and distributed simulation, as well as waveform generation for test and evaluation.     

Modeling and simulation: a practical guide for network designers and developers - [Guest editorial]

Modeling and simulation (M&S) is a critical element in the design, development, and test and evaluation (T&E) of any network product or solution. This feature topic features seven articles that present practical information such as current best practices, tools, and techniques.     

Simulation tools for multilayer fault restoration - [Modeling and simulation: a practical guide for network designers and developers]

The complexity of networks today makes it difficult to handle fault restoration by means of human intervention. Future network architectures are expected to be self-protecting and, more generally, self-organizing. In this article we describe the modeling methods and simulation tools we have used for the analysis of a new integrated restoration scheme operating at multiple layers/networks. The networks over which we have performed the analysis are ATM and SDH, but the methodology could be applied to other multilayer architectures too. A network model has been created that consists of both ATM and SDH layers. Using this network model, we have seen how the new scheme explores the free bandwidth over both layers. The multilayer bandwidth exploration was modeled using Microsoft Visual C++. Using OPNET Modeler, a node model was created to analyze the restoration message processing within it and the interaction with other nodes for the purpose of simulating the restoration delay. The article emphasizes the simulation methodology rather than the results of the simulation. Among others, we describe which additional functionalities a simulation tool is necessary to have in order to simulate multilayer networks. A comparison of OPNET and Microsoft Visual C++ is made, describing their advantages and the reasons we found it necessary to use both.     

Design validation of service delivery platform using modeling and simulation - [Modeling and simulation: a practical guide for network designers and developers]

The value of models as tools to design and plan networks, aid the decision-making process, and as methods to conceptualize abstract ideas is well known. Models play a key role in evaluating varied design options and assist in discovering design issues that likely will impact performance. In the service delivery platform, spreadsheet models can be applied to learn about strategic traffic volume, estimate end-to-end latencies and box capacities, whereas more complex simulation models can help to clarify an understanding of the dynamic aspects and trade-offs that influence the end-user experience. This article discusses how modeling and simulation effectively help validate the design of various components constituting the service delivery platform.     

Service-oriented broadband wireless network architecture - [Guest editorial]

In the past few years, broadband wireless networks have been very attractive as a key technology for providing Internet access because of quick and cost-effective deployments. In addition to the features of high data rate and large coverage, broadband wireless networks also promise to rapidly provide access to locations in the world?s rural and developing areas where broadband is currently unavailable, as well as compete for urban market shares. Till now, most existing efforts have been focused on basic access capability. However, to successfully operate broadband wireless networks, a crucial issue must be addressed: how to support a variety of services and applications within the broadband wireless networks? As an example, there is an increasing need to efficiently support applications such as voice over IP (VoIP), video streaming, music downloading, IP TV, and many others.     

Downlink scheduling for multimedia multicast/broadcast over mobile wimax: connection-oriented multistate adaptation - [Service-oriented broadband wireless network architecture]

With its comprehensive QoS support and ubiquitous coverage, the mobile WiMAX network offers promising opportunities for unwiring the last mile connectivity to Internet. However, stringent QoS demands of multimedia applications entail studies on service-oriented radio resource management. This article systematically examines the design issues and the state of the art of multimedia downlink scheduling in the multicast/broadcast-based WiMAX system. We propose a viable end-to-end framework, connection-oriented multistate adaptation, by considering cross-layer adaptations in source coding, queue prioritization, flow queuing, and scheduling. Its performance is confirmed by simulations on important metrics, showing that the framework can effectively accommodate heterogeneity in link variations, queue fluctuations, and reception diversities.     

Modeling and performance evaluation of a cellular mobile network

An analytic model of cellular mobile communications networks with instantaneous movement is investigated in this paper. This cellular mobile network is showed to be equivalent to a queueing network and furthermore the equilibrium distribution of this cellular mobile network is proved to have a product form. The explicit expressions for handoff rates of calls from one cell to another, the blocking probability of new calls and handoff calls are then obtained. Actual call connection time (ACCT) of a call in this cellular mobile network is characterized in detail, which is the total time a mobile user engages in communications over the network during a call connection and can be used to design appropriate charging schemes. The average ACCT for both complete call and incomplete call, as well as the probability for a call to be incomplete or complete, are derived. Our numerical results show how the above measures depend on the new call arrival process for some specific reserved channels numbers in each cell. The results presented in this paper are expected to be useful for the cost analysis for updating location and paging in cellular mobile network.     

Topology control for service-oriented wireless mesh networks - [Service-oriented broadband wireless network architecture]

Topology control is one of the most critical design issues in multihop wireless networks. Topology control has been investigated extensively in the literature. Nevertheless, it is noted that most existing studies do not consider the requirements on upper layer applications or services. In this article we address the topology control issues on service-oriented wireless mesh networks. In particular, we provide a comprehensive survey of existing works on topology control from a service- oriented perspective. We then propose a general framework for topology control in service- oriented WMNs. To demonstrate the effectiveness of the framework, we conduct a case study in which the main objective is to maximize the overall throughput in a network with random unicast traffic. The performance of this topology control scheme is evaluated by numerical results. In addition, it is illustrated that the generated topology can support advanced technologies, including network coding and physical-layer network coding, which can significantly improve the throughput capacity of a network.     

Security in service-oriented vehicular networks - [Service-oriented broadband wireless network architecture]

Service-oriented vehicular networks support diverse infrastructure-based commercial services including Internet access, real-time traffic concerns, video streaming, and content distribution. The success of service delivery in vehicular networks depends on the underlying communication system to enable the user devices to connect to a large number of communicating peers and even to the Internet. This poses many new research challenges, especially in the aspects of security, user privacy, and billing. In this article we first identify the key requirements of authentication, privacy preservation, and billing for service delivery in vehicular networks. We then review the existing industrial and academic efforts on service- oriented vehicular networks. We also point out two security challenges, minimizing vehicleto- infrastructure authentication latency and distributed public key revocation, which are considered among the most challenging design objectives in service-oriented vehicular networks. A novel fast vehicle-to-infrastructure authentication based on a vehicle mobility prediction scheme and an infrastructure-based short-time certificate management scheme are then proposed to address these two challenges.     

The architecture and a business model for the open heterogeneous mobile network - [ITU-T kaleidoscope]

The mobile communications market has grown rapidly over the past ten years, but the market could reach saturation in the foreseeable future. More flexible mobile networks that can meet various user demands and create new market openings are required for further growth. Heterogeneous networks are more suitable than homogeneous networks for meeting a wide variety of user demands. There are two types of heterogeneous networks: a closed type, where network resources are deployed and operated by communication carriers, and an open type, where network resources can be deployed not only by existing operators, but also by companies, universities, and so on. It will be easy for newcomers to enter mobile businesses in an open heterogeneous mobile network so many innovative services are likely to be provided through cooperation between various companies or organizations. This article proposes a revised architecture for TISPAN-NGN, which corresponds to heterogeneous networks and open mobile markets, and presents a new business model.     

Dynamic composition of services for end-to-end information transport - [Service-oriented broadband wireless network architecture]

An increasing number of communication technologies in access and core segments of the network belonging to different providers and subject to different network design criteria are making networks complex and difficult to manage. In such networks it is also more difficult to guarantee requested levels of quality of service. Service oriented design can be the answer to problems facing the providers of services for information transport. In this article we propose an end-to-end service composition for information transport based on principles from service oriented architecture (i.e., dynamically composing transport services with characteristics matching the requirements of a given application). SOA principles are similar to those behind the division of labor, and therefore should give providers incentive to adopt them to make better use of resources and increase revenue. As we show, some SOA concepts are similar to concepts in the open systems interconnection reference model, with the key advantages of dynamism and flexibility. We discuss service oriented networks based on transport service composition across access and core segments, and describe access network selection for online gaming. In particular, we show how semantic technologies can be used for layer 2 queries and discuss the advantages of using knowledge bases over traditional approaches.     

Network-coding-based scheduling and routing schemes for service-oriented wireless mesh networks - [Service-oriented broadband wireless network architecture]

Service-oriented wireless mesh networks have recently been receiving intensive attention as a pivotal component to implement the concept of ubiquitous computing due to their easy and cost-effective deployment. To deliver a variety of services to subscriber stations, a large volume of traffic is exchanged via mesh routers in the mesh backbone network. One of the critical problems in service-oriented wireless mesh networks is to improve the network throughput. Wireless network coding is a key technology to improve network throughput in multihop wireless networks since it can exploit not only the broadcast nature of the wireless channel, but also the native physical-layer coding ability by mixing simultaneously arriving radio waves at relay nodes. We first analyze the throughput improvement obtained by wireless network coding schemes in wireless mesh networks. Then we develop a heuristic joint link scheduling, channel assignment, and routing algorithm that can improve the network throughput for service-oriented wireless mesh networks. Our extensive simulations show that wireless network coding schemes can improve network throughput by 34 percent.