Design and analysis of an IEEE 802.21-based mobility management architecture: a context-aware approach

Broadband wireless technologies will soon become an integral part of daily life. In this paper we present the design rationale of a context-aware mobility management architecture for seamless handover in heterogeneous networks. Our proposal is a new cross-layer and interactive approach to seamless handover of users and their services. We present a simple though effective analytical model in typical deployment scenarios in heterogeneous networks with the use of the IEEE Media Independent Handover services. Such analytical model is used to evaluate the resulting handover delay when deploying common mobility protocols in our architecture, such as Mobile IP, Hierarchical MIP, and Proxy MIP.     

A gateway approach to mobility integration of GPRS and wireless LANs

This article presents a gateway approach to the integration of GPRS and wireless LANs (WLANs). The proposed architecture leverages mobile IP as the mobility management protocol over WLANs. The interworking between GPRS and WLANs is achieved by a gateway that resides on the border of GPRS and WLAN systems. The design goal is to minimize the modifications in GPRS and WLANs as both systems are widely available in the market already. By deploying the gateway, users can seamlessly roam among the two systems. The proposed architecture and design principles have been implemented in a commercial GPRS network operated by the Taiwan Cellular Corporation. Empirical experiments with multimedia applications were conducted to analyze the performance in terms of handoff latency, packet delay, and throughput.     

A mobility toolbox architecture for all-IP networks: an ambient networks approach [architectures and protocols for mobility management in all-IP mobile networks]

The future Internet will need to cater to an increasing number of mobile devices and mobile networks, roaming across different access networks and trust domains. In addition, various limitations imposed by the end user, service provider, or network operator agreements and preferences will need to be considered. A plethora of mobility management protocols have been proposed to handle different and mostly limited sets of these mobility requirements. In this article we make the case for coexistence of mobility protocols in order to support the large range of mobility scenarios possible in future all-IP networks. This coexistence takes the form of a mobility toolbox that enables mobility handling mechanisms to be selected according to the context. We then present a design for the mobility toolbox as a component of the ambient networks architecture, including a simplified mobility tool interface toward protocol modules, and show how it meets the requirements of future all-IP networks. We further demonstrate the feasibility and performance gains of the mobility toolbox architecture with a prototype implementation based on network mobility.     

An overlay and distributed approach to node mobility in multi-access wireless networks

Nowadays many manufacturers are building mobile devices with multiple interfaces. Thus, users have access to different types of wireless access networks, which often, as for WLAN and cellular systems, coexists independently. The challenge is to make such multiple access networks to cooperate to have ubiquitous access and enhanced user quality of service. In this paper we present a scheme to allow inter-technology mobility by the introduction of an overlay network, which works on top of current (and future) networks. The proposed architecture controls all the aspect related to the mobility management: mobile node localization, handover decision and execution. The approach is distributed: it is the mobile node that decides which network to use, based on the offered service quality and the cost of the communication of the available networks, and triggers the handover execution directly to the corresponding host, using optimized SIP-based procedures. The overlay network copes with the mobile node localization. We implemented our solution in the laboratory to prove its validity and to test performance using real equipment. We also simulated the scheme using ns-3 to extend the evaluation to large scale deployments. In both test environments, our solution demonstrates high accurateness in selecting the network with the best quality as well as in supporting seamless vertical handover.     

User mobility profile prediction: An adaptive fuzzy inference approach

Predicting the probabilities that a mobile user will be active in other cells at future moments poses a significant technical challenge to network resource management in multimedia wireless communications. The probability information can be used to assist base stations to maintain a balance between guaranteeing quality of service (QoS) to mobile users and achieving maximum resource utilization. This paper proposes a novel adaptive fuzzy logic inference system to estimate and predict the probability information for direct sequence code division multiple access (DS/CDMA) wireless communications networks. The estimation is based on measured pilot signal strengths at the mobile user from a number of nearby base stations, and the prediction is obtained using the recursive least square (RLS) algorithm. Numerical results are presented to demonstrate the performance of the proposed technique under various path loss and channel shadowing conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Global versus distance-based local mobility tracking strategies: aunified approach

We have considered fixed location areas for personal communication systems with hysteresis effect in the location update process. Our scheme can be seen as a hybrid between the global (static) and the distance-based local (dynamic), location update strategies, and clearly improves the performance when compared with previous proposals. Selective paging with delay constraint has also been considered. It can be implemented in standard cellular systems     

Delay-tolerant networking: an approach to interplanetary Internet

Increasingly, network applications must communicate with counterparts across disparate networking environments characterized by significantly different sets of physical and operational constraints; wide variations in transmission latency are particularly troublesome. The proposed Interplanetary Internet, which must encompass both terrestrial and interplanetary links, is an extreme case. An architecture based on a "least common denominator" protocol that can operate successfully and (where required) reliably in multiple disparate environments would simplify the development and deployment of such applications. The Internet protocols are ill suited for this purpose. We identify three fundamental principles that would underlie a delay-tolerant networking (DTN) architecture and describe the main structural elements of that architecture, centered on a new end-to-end overlay network protocol called Bundling. We also examine Internet infrastructure adaptations that might yield comparable performance but conclude that the simplicity of the DTN architecture promises easier deployment and extension.     

Control-on-demand: an efficient approach to router programmability

Control-on-demand is a paradigm for network programmability at the network transport level. Prior work on active and programmable networking at this level either achieves flexibility by inserting significant software in the critical path of forwarding or achieves efficiency by sacrificing functionality and relegating programmability to connection management. In contrast, control-on-demand acts both in the control plane and in the data plane, still without adding software in the critical forwarding path. Rather than applying essential programs to every datagram, our approach is to apply the installed service logic asynchronously from data forwarding. This way we avoid essential processing in the critical forwarding path, applying the (user) installed service logic for service enhancement only. In this paper, we describe control-on-demand and how its service model provides sufficient richness to act in the data path. Set is restrictive enough to avoid the significant performance overhead of other in-data path approaches. The expressiveness of the programmable model is limited to observing and suggesting to the forwarding engine, but is never essential for correct processing, thus significantly reducing security and robustness concerns. Consequently, control-on-demand is efficient enough to make it viable for elementary services. Rather than replacing the interoperability layer, control-on-demand represents an evolution of router (switch) control functionality. As the required modification of router forwarding engines is insignificant, control-on-demand is viable in practice in the near future. These concepts have been prototyped as part of the Pronto Control Platform. In this paper, we describe our IPv6 router prototype implementation and discuss the application of control-on-demand on a number of interesting problems     

Control of an industrial robot subjected to base mobility

To remove the cell size limitation and to make cellular manufacturing systems more flexible, research has been conducted in which an industrial robot has been given base mobility via an air pallet base and use of existing joint actuators and strategically located, compliant posts. For investigating this new approach of robot mobility within a cell, an appropriate control system has been designed and implemented that interfaces with the standard industrial controller. This paper is a presentation of the resulting control system consisting of multiple-sensor integration into its hierarchical levels. Using the concept of logical sensors, experimental verification is presented for each of the logical sensor subsystems and its successful integration with the existing industrial controller. Experimental results obtained for the fully integrated robot controller illustrate the effectiveness of the multiple-sensor, hierarchical controller for self-propelled mobile robots operating within a manufacturing cell     

HAWAII: a domain-based approach for supporting mobility inwide-area wireless networks

Mobile IP is the current standard for supporting macromobility of mobile hosts. However, in the case of micromobility support, there are several competing proposals. We present the design, implementation and performance evaluation of HAWAII (handoff-aware wireless access Internet infrastructure), a domain-based approach for supporting mobility. HAWAII uses specialized path setup schemes which install host-based forwarding entries in specific routers to support intra-domain micromobility. These path setup schemes deliver excellent performance by reducing mobility related disruption to user applications. Also, mobile hosts retain their network address while moving within the domain, simplifying quality-of-service (QoS) support. Furthermore, reliability is achieved through maintaining soft-state forwarding entries for the mobile hosts and leveraging fault detection mechanisms built in existing intra-domain routing protocols. HAWAII defaults to using Mobile IP for macromobility, thus providing a comprehensive solution for mobility support in wide-area wireless networks     

Lightpath communications: an approach to high bandwidth opticalWAN's

An architectural approach that meets high bandwidth requirements by introducing a communication architecture based on lightpaths, optical transmission paths in the network, is introduced. Since lightpaths form the building block of the proposed architecture, its performance hinges on their efficient establishment and management. It is shown that although the problem of optimally establishing lightpaths is NP-complete, simple heuristics provide near optimal substitutes for several of the basic problems motivated by a lightpath-based architecture     

PSM: an object-oriented synthesis approach to multiprocessor systemdesign

Although multiprocessor systems are becoming a trend today, few synthesis tools currently available can actually automate the design of multiprocessor systems. Performance synthesis methodology (PSM) is an object-oriented system-level synthesis approach to multiprocessor system design. Since PSM was designed specifically for the synthesis of multiprocessor systems, it is not only much more efficient when synthesizing parallel systems, but also produces better parallel systems than currently available uniprocessor system-level synthesis tools. Colored Petri nets used in modeling system components and object modeling technique used in the design process have both contributed to the shortening of system development time and to the reduction of design cost. First, user specification consisting of functional models and performance constraints is translated into architecture models. Then, the system is configured by selecting the method of control, the memory organization, the type of processor, and the type of system interconnection. Finally, a heuristic design space exploration algorithm is used to generate several near-optimal design alternatives. The best architecture is chosen by evaluating the design alternatives using a flexible performance estimation formula that mainly considers system level design features, such as system throughput, utilization, reliability, scalability, fault-tolerance, and cost. Several systems were successfully synthesized using this top-down object-oriented PSM, thus showing its feasibility as a design automation tool for parallel systems     

Progressive refinement approach to MLE: an application to carrierfrequency recovery

Carrier frequency estimation plays an important role in digital communication receivers. A progressive refinement approach to maximum-likelihood estimation is proposed as a means to improve the performance of a suboptimal estimation algorithm and achieve different tradeoffs among complexity, accuracy and dynamic range. As an example, an application is described for carrier frequency recovery in burst-mode digital transmissions. The Luise and Reggiannini (1995) synchronization algorithm is employed as the master frequency estimator. The performance of the algorithm is demonstrated by means of a simulation study, assuming quadrature phase-shift keying modulation; the results show that the progressive refinement approach can be usefully exploited, for example to improve the estimation range of the LR algorithm, without losing the accuracy and the computational complexity     

Putting reader roles to the test: an ethnomethodological approach

That readers read within roles has long been argued by literary theorists and more recently by technical communication theorists. Yet few scholars have attempted to put their theories to a test. The study reported in this paper attempts to do by using a conversation analysis tool called ethnomethodology. In an experimental setting, subjects were videotaped reading and responding to a set of instructions. Their responses indicate that: readers will often choose to play a role different from the one embedded in a text, especially if the text role offends them in some way; readers with similar education and interest may display different reader roles, making these roles difficult to predict; and within a single reading, a reader may change roles frequently. The paper concludes by discussing the implications of the findings and the appropriateness of ethnomethodology for reader-role research     

Computing the unmeasured: an algebraic approach to Internet mapping

Distance estimation is important to many Internet applications. It can aid a World Wide Web client when selecting among several potential candidate servers or among candidate peer-to-peer servers. It can also aid in building efficient overlay or peer-to-peer networks that react dynamically to changes in the underlying Internet. One of the approaches to distance (i.e., time delay) estimation in the Internet is based on placing tracer stations in key locations and conducting measurements between them. The tracers construct an approximated map of the Internet after processing the information obtained from these measurements. This work presents a novel algorithm, based on algebraic tools, that computes additional distances, which are not explicitly measured. As such, the algorithm extracts more information from the same amount of measurement data. Our algorithm has several practical impacts. First, it can reduce the number of tracers and measurements without sacrificing information. Second, our algorithm is able to compute distance estimates between locations where tracers cannot be placed. To evaluate the algorithm's performance, we tested it both on randomly generated topologies and on real Internet measurements. Our results show that the algorithm computes up to 50%-200% additional distances beyond the basic tracer-to-tracer measurements.     

Protected core networking: an architectural approach to secure and flexible communications

Protected core networking (PCN) is a concept intended to be used to implement a flexible transport infrastructure that supports future military operations based on network enabled capability (NEC). PCN is based on creating a loose coupling between information domains and the transport infrastructure, and focusing on the provision of high service availability, also in high-threat environments. This architectural approach highlights a number of emerging and novel concepts where research and development is needed to properly support NEC.     

Side-tunnel fibre: an approach to polarisation-maintaining optical waveguiding scheme

A new type of polarisation-maintaining fibre is proposed, analysed, and preliminary fabrication and measurement are described. The new fibre features two `side tunnels? bored on both sides of the core, and exhibits an absolutely single-polarisation characteristic or a relatively strong modal birefringence. The normalised birefringence obtained so far is 0.73×10?4. This value is appreciably lower than expected. Two possible reasons are discussed.     

Spontaneous networking: an application oriented approach to ad hocnetworking

An ad hoc network must operate independent of a preestablished or centralized network management infrastructure, while still providing administrative services needed to support applications. Address allocation, name resolution, service location, authentication, and access control policies represent just some of the functionality that must be supported-without preconfiguration or centralized services. In order to solve these problems, it is necessary to leverage some aspect of the environment in which the network operates. We introduce the notion of a spontaneous network, created when a group of people come together for some collaborative activity. In this case, we can use the human interactions associated with the activity in order to establish a basic service and security infrastructure. We structure our discussion around a practical real-world scenario illustrating the use of such a network, identifying the key challenges involved and some of the techniques that can be used to address them     

Virtual engineering: an integrated approach to agile manufacturing machinery design and control

A virtual manufacturing approach for designing, programming, testing, verifying and deploying control systems for agile modular manufacturing machinery are proposed in this paper. It introduces the concepts, operations, mechanisms and implementation techniques for integrating simulation environments and distributed control system environments so that the control logic programs that have been programmed and verified in the virtual environment can be seamlessly transferred to the distributed control system environment for controlling the real devices. The approach looks to exploit simulation in a much wider range of applications with great advantages in the design and development of manufacturing machine systems. In particular, it facilitates the verification of the runtime support applications using the simulation model before they are applied to the real system. Mechanisms that allow runtime data to be collected during operation of the real machinery to calibrate the simulation models are also proposed. The system implemented delivers a powerful set of software tools for realising agile modular manufacturing systems.     

An approach based on particle swarm computation to study the electron mobility in wurtzite GaN

The properties of gallium nitride (GaN) make it a promising material for a variety of different electronic and optoelectronic devices. GaN has a wide direct bandgap and a resulting high breakdown field. Further progress in the development, design and optimization of GaN-based devices necessarily requires new theory and modeling techniques that capture the physics of electron transport accurately and efficiently. So, the objective of this work is to provide an optimized analytical model for low- and high-field electron mobility in wurtzite (hexagonal) GaN in wide temperature and concentration ranges basing on the particle swarm optimization (PSO) algorithm. A Monte Carlo transport simulations developed in this work has been evaluated and serve as the basis for the model development. The proposed model describes the dependence of the mobility on carrier concentration, temperature, and electric field. Good agreement between our results and measured data has been obtained. Thus, the presented mobility models can be used in device simulations to design and optimize different GaN device structures.