Understanding usage patterns in wireless local-area networks (WLANs) is critical for those who develop, deploy, and manage WLAN technology, as well as those who develop systems and application software for wireless networks. This paper presents results from the largest and most comprehensive trace of network activity in a large, production wireless LAN. For eleven weeks we traced the activity of nearly two thousand users drawn from a general campus population, using a campus-wide network of 476 access points spread over 161 buildings. Our study expands on those done by Tang and Baker, with a significantly larger and broader population. We found that residential traffic...

Most of the multicast routing protocols for ad-hoc networks today are based on shared or source-based trees; however, keeping a routing tree connected for the purpose of data forwarding may lead to a substantial network overhead. A different approach to multicast routing consists of building a shared mesh for each multicast group. In multicast meshes, data packets can be accepted from any router, as opposed to trees where data packets are only accepted from routers with whom a "tree branch" has been established. The difference among multicast routing protocols based on meshes is in the method used to build these structures. Some mesh-based protocols require the flooding of sender or receiver announcements over the whole network. This paper presents the Core-Assisted Mesh Protocol, which uses meshes for data forwarding, and avoids flooding by generalizing the notion of core-based trees introduced for internet multicasting. Group members form the mesh of a group by sending join...

common, but little is known about how they are used. A clear understanding of usage patterns in real WLANs is critical information to those who develop, deploy, and manage WLAN technology, as well as those who develop systems and application software for wireless networks. This paper presents results from the largest and most comprehensive trace of network activity in a large, production wireless LAN. For eleven weeks we traced the activity of nearly two thousand users drawn from a general campus population, using a campus-wide network of 476 access points spread over 161 buildings. Our study expands on those done by Tang and Baker, with a significantly larger and broader population.

this paper is to describe challenges of integrating mobility management, QoS management and charging issues in the emerging wireless Internet to enable the provision of real-time services. The organisation of the rest of the paper is as follows. We first give an overview of some techniques used in the Internet environments for managing mobility and QoS. In the next two sections, we provide details of various issues associated with integrating Internet QoS and IP mobility management techniques. We then describe the current development on resolving the charging and accounting on mobile multimedia services. Finally, we provide a conclusion in the last section

Contents 1 Introduction 1 1.1 Mobile Wireless Internet . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.2 Heterogeneous Mobile Wireless Networking Environment . . . . . . . . 3 1.2.1 Link Layer -- Heterogeneous Wireless Technologies . . . . . . . . 3 1.2.2 Network (IP) Layer -- Heterogeneous Mobility Mechanisms . . . 5 1.2.3 Application Layer -- Heterogeneous QoS Requirements of Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.3 Needs for Smart Mobility Control . . . . . . . . . . . . . . . . . . . . . 7 1.4 Research Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.5 Thesis Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2 The Mobile Internet Protocol 11 2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.2 Requirements of Mobile IP Protocol . . . . . . . . . . . . . . . . . . . . 11 2.3 Mobile IPv4 Entities and Mechanisms . . . . . . . . . . . . . . . . . . . 12

Abstract: Today Computer Supported Cooperative Work (CSCW) is used in broad areas of human cooperation. With the propagation of radio-based communication and ad hoc networking it may enter new areas of human cooperation. One important aspect is the new quality in CSCW of being independent from special network-enabled places. Another aspect is the more intuitive support of face-to-face cooperation utilizing personal mobile devices. To open this field of collaboration our approach featuring Distributed Cooperative Knowledge Spaces specifically addresses conceptual issues pertaining to the transition from classical, server-centered to mobile, distributed collaboration environments. With this concept we introduce persistent and personal knowledge spaces as well as so-called temporary knowledge areas and groups. Our prototypical application for spontaneous collaboration implements this approach. We are able to draw here on many years of experience in the development and testing of our concept of Cooperative Virtual Knowledge Spaces. 1

Ad hoc networks are gaining more and more acceptance due to the potential of applications, the facility to deploy them as well as the cost economy in term of infrastructure. However, they introduce a lot of challenges in term of routing algorithms, QoS assurance, security, management and so on. The aim of this paper is to present a state of art of these technologies as well as the various problems it introduces. One aspect, we are addressing is the quality assurance. In the proposed approach, we aims to introduce policies in order to control the behaviour of the virtual ad hoc network so that some priority groups get more QoS then others.

The problem of Code Division Multiple Access (CDMA) code assignment to eliminate primary and hidden collisions in multihop packet radio networks has been widely researched in the past. However, very little work has been done on the very realistic distributed, dynamic version of the CDMA transmitter-oriented code assignment (TOCA) problem in an ad-hoc network. None of the existing dynamic TOCA CDMA algorithms in literature are efficient, in terms of maximum code index assigned in the network, or number of times a mobile has to change its code. We present a set of local, distributed recoding strategies for the TOCA CDMA problem in an ad-hoc network where mobiles can arbitrarily 1) connect and disconnect, 2) move about, and 3) increase or decrease their transmission power- all these may need some mobiles to be recoded, to avoid new collisions. Our strategies, unlike those proposed earlier in literature, guarantee minimal recoding, that is, given a current network-wide code assignment and one of the above events, our strategies change the codes of the minimum number of mobiles needed to eliminate all collisions. Minimal recoding can be very important in reducing the effect of frequent code changes on the performance and criticality of distributed applications. Performance results that evaluate our dynamic minimal strategies are also presented. 1.

With the rapid progress in the development of wireless technology, the bandwidth of wireless local area network (WLAN) is getting higher and its outdoor transmission distance is also getting longer. It becomes feasible to build a regional communication infrastructure in local areas, e.g., in the campus of an institute or a university, using WLAN. Thus, the design of new generation on-board PCs aims not only to provide conventional navigation services in rural or urban areas, but also to deploy integrated multimedia services in regional areas such as campuses. In this paper we present our design of in-vehicle navigation and location-based multimedia applications in an 802.11b wireless environment. It supports mobile communication based on IETF mobile IP standards with route optimization, smooth handoff, and fast handoff. Furthermore, in order to encourage fast deployment and to reduce system costs, we utilized open technologies in designing our prototype system. The developed AutoPC is a real-time embedded system platform on a singleboard PC with GPS, featured by a downsized embedded Linux and a bilingual windows system. The platform supports applications such as in-vehicle navigation, real-time traffic information, MP3 player, and MPEG-4 streaming through mobile IPv4. This prototype is evaluated on a campus-wide 802.11b network, where two neighboring access points are placed about 150 meters apart from each other along the roadside such that a road in the campus is fully covered by 802.11b radio signals. Our preliminary experiments show that the low handoff overhead makes it possible for an invehicle AutoPC to run video streaming application seamlessly on the road even when the car speed is up to 50 km/hr. Besides, a 486level platform is powerful enough to support inv...

Networked Surfaces are surfaces such as desks which provide network connectivity to specially augmented devices, for example handheld computers. When the devices are physically placed on top of the surface, they can connect to different kinds of services – mainly, but not exclusively to send and receive data. This paper discusses challenges in implementing Networked Surfaces, paying particular attention to data flow issues, focusing on how the various software and hardware entities comprising the Surface interact to transport data to and from objects.