This paper reports on measurement results for the use of IEEE 802.11 networks in drive-thru scenarios:wehave measured transmission characteristics for sending and receiving high data volumes using UDP and TCP in vehicles moving at different speeds that pass one or more IEEE 802.11 access points at the roadside. We discuss possibilities and limitations for the use of scattered WLAN cells by devices in fast moving vehicles and provide an analysis of the performance that can be expected for the communication in such scenarios. Based on these observations, we discuss implications for higher-layer protocols and applications.

Abstract—Wireless LAN administrators often have to deal with the problem of sporadic client congestion in popular locations within the network. Existing approaches that relieve congestion by balancing the traffic load are encumbered by the modifications that are required to both access points and clients. We propose Cell Breathing, a well-known concept in cellular telephony, as a load balancing mechanism to handle client congestion in a wireless LAN. We develop power management algorithms for controlling the coverage of access points to handle dynamic changes in client workloads. We further incorporate hand-off costs and manufacturer specified power level constraints into our algorithms. Our approach does not require modification to clients or to the standard. It only changes the transmission power of beacon packets and does not change the transmission power of data packets to avoid the interactions with autorating. We analyze the worst-case bounds of the algorithms and show that they are either optimal or close to optimal. In addition, we evaluate our algorithms empirically using synthetic and real wireless LAN traces. Our results show that cell breathing significantly outperforms the commonly used fixed power scheme and performs at par with sophisticated load balancing schemes that require changes to both the client and access points. Index Terms—Wireless LAN, power control, cell breathing, algorithms. 1

Abstract — In this paper, we combine inertial sensing and sensor network technology to create a pedestrian dead reckoning system. The core of the system is a lightweight sensor-andwireless-embedded device called NavMote that is carried by a pedestrian. The NavMote gathers information about pedestrian motion from an integrated magnetic compass and accelerometers. When the NavMote comes within range of a sensor network (composed of NetMotes), it downloads the compressed data to the network. The network relays the data via a RelayMote to an information center where the data are processed into an estimate of the pedestrian trajectory based on a dead reckoning algorithm. System details including the NavMote hardware/software, sensor network middleware services, and the dead reckoning algorithm are provided. In particular, simple but effective step detection and step length estimation methods are implemented in order to reduce computation, memory, and communication requirements on the Motes. Static and dynamic calibrations of the compass data are crucial to compensate the heading errors. The dead reckoning performance is further enhanced by wireless telemetry and map matching. Extensive testing results show that satisfactory tracking performance with relatively long operational time is achieved. The paper also serves as a brief survey on pedestrian navigation systems, sensors, and techniques. Index Terms — Pedestrian navigation system, dead reckoning, wireless sensor network. I.

Wireless LANs (WLANs) have been deployed at a remarkable rate at university campuses, office buildings, airports, hotels, and malls. Providing efficient and reliable wireless communications is challenging due to inherent lossy wireless medium and imperfect packet scheduling that results in packet collisions. In this paper, we develop an efficient retransmission scheme (ER) for wireless LANs. Instead of retransmitting the lost packets in their original forms, ER codes packets lost at different destinations and uses a single retransmission to potentially recover multiple packet losses. We develop a simple and practical protocol to realize the idea and implement it in both simulation and testbed, and our results demonstrate the effectiveness of this approach.

Telematics is arguably the next-wave in mobile computing: with most cars of the future likely to be equipped with multiple embedded computing platforms, we shall witness the development of a variety of mobile services and applications with significant commercial potential. Telematics will only become a commercial reality when the underlying architecture is able to address significant concerns related to the security and privacy of telematics data, and is able to provide context information from and to a large number of mobile data sources in a scalable and device-independent manner. A telematics platform should utilize existing Internet components and technologies but cannot rely exclusively on these, especially since mobile commerce applications in the telematics environment impose specific requirements on the relationships between various services and data providers. In this paper we describe how we are developing an open standards telematics platform based on the ts-PWLAN wireless service environment and the Telematics Resource Manager middleware. Our design employs existing web service interfaces coupled with novel technology for connecting to these through a wireless gateway. Our middleware acts as a common substrate for building and deploying a wide range of telematics applications. We describe how several of these applications are currently being built on our infrastructure.

As result of combining heterogeneous network technologies, network architectures become increasingly complex. Administrative domains, representing functional or nonfunctional responsibilities and obligations, and their relationships in terms of reference points are used to find appropriate abstractions and thus managing the complexity. In this paper domain models, as organization of environments of autonomous administrative control and reference points, are suggested and applied as a method to develop a threat analysis and find suitable security mechanisms.

The Internet architecture was developed to support a number of key goals. Security was not among them. Indeed, in David Clark’s classic paper, “The Design Philosophy of the DARPA Internet Protocols, ” the word security is not used once. By any accounting, security mechanisms have been added to the Internet in a fashion both post hoc and ad hoc, with minimal accommodations from the surrounding communications framework. Inevitably, these mechanisms have provided only an approximation to the security properties motivating their creation and have frequently conflicted with the existing network architecture in which they operate. The network firewall represents a classic example of this tension. A firewall is expected to help enforce an access control policy on traffic traversing its links and yet is unable to make any strong statements about the sender of a piece of traffic or the import of the content it contains. Moreover, in enforcing crude controls, firewalls routinely violate the end-to-end properties of protocols that traverse them. We contend that many of these problems result from a mismatch between the level of abstraction provided by today’s network architecture and the level necessary to describe real security properties. Real-world security policies are invariably about “who ” and “what, ” while the Internet’s architecture answers “where” and “how. ” For example, Internet addresses describe topological endpoints that are inherently virtual. Due to hot spots, spoofing, route hijacking, etc., an IP address in a packet may have only a transient relationship