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D. Schwab

Bio: D. Schwab is an academic researcher from University of Saskatchewan. The author has contributed to research in topics: Wireless network & Base transceiver station. The author has an hindex of 1, co-authored 1 publications receiving 137 citations.

Papers
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Proceedings ArticleDOI
07 Mar 2004
TL;DR: A week-long traffic trace was collected in January 2003, recording address and protocol information for every packet sent and received on the wireless network to answer questions about where, when, how much, and for what the network is being used.
Abstract: We present the results of an analysis of the usage of our new campus-wide wireless network. A week-long traffic trace was collected in January 2003, recording address and protocol information for every packet sent and received on the wireless network. A centralised authentication log was used to match packets with wireless access points. The trace was analysed to answer questions about where, when, how much, and for what our wireless network is being used. Such information is important in evaluating design principles and planning for future network expansion.

137 citations


Cited by
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Proceedings ArticleDOI
26 Sep 2004
TL;DR: This paper analyzes an extensive network trace from a mature 802.11 WLAN, including more than 550 access points and 7000 users over seventeen weeks, and defines a new metric for mobility, the "session diameter," to show that embedded devices have different mobility characteristics than laptops, and travel further and roam to more access points.
Abstract: Wireless Local Area Networks (WLANs) are now commonplace on many academic and corporate campuses. As "Wi-Fi" technology becomes ubiquitous, it is increasingly important to understand trends in the usage of these networks.This paper analyzes an extensive network trace from a mature 802.11 WLAN, including more than 550 access points and 7000 users over seventeen weeks. We employ several measurement techniques, including syslogs, telephone records, SNMP polling and tcpdump packet sniffing. This is the largest WLAN study to date, and the first to look at a large, mature WLAN and consider geographic mobility. We compare this trace to a trace taken after the network's initial deployment two years ago.We found that the applications used on the WLAN changed dramatically. Initial WLAN usage was dominated by Web traffic; our new trace shows significant increases in peer-to-peer, streaming multimedia, and voice over IP (VoIP) traffic. On-campus traffic now exceeds off-campus traffic, a reversal of the situation at the WLAN's initial deployment. Our study indicates that VoIP has been used little on the wireless network thus far, and most VoIP calls are made on the wired network. Most calls last less than a minute.We saw greater heterogeneity in the types of clients used, with more embedded wireless devices such as PDAs and mobile VoIP clients. We define a new metric for mobility, the "session diameter." We use this metric to show that embedded devices have different mobility characteristics than laptops, and travel further and roam to more access points. Overall, users were surprisingly non-mobile, with half remaining close to home about 98% of the time.

566 citations

Journal ArticleDOI
TL;DR: This paper analyzes the mobility patterns of users of wireless hand-held PDAs in a campus wireless network using an eleven week trace of wireless network activity and develops two wireless network topology models for use in wireless mobility studies.
Abstract: In this paper, we analyze the mobility patterns of users of wireless hand-held PDAs in a campus wireless network using an eleven week trace of wireless network activity. Our study has two goals. First, we characterize the high-level mobility and access patterns of hand-held PDA users and compare these characteristics to previous workload mobility studies focused on laptop users. Second, we develop two wireless network topology models for use in wireless mobility studies: an evolutionary topology model based on user proximity and a campus waypoint model that serves as a trace-based complement to the random waypoint model. We use our evolutionary topology model as a case study for preliminary evaluation of three ad hoc routing algorithms on the network topologies created by the access and mobility patterns of users of modern wireless PDAs. Based upon the mobility characteristics of our trace-based campus waypoint model, we find that commonly parameterized synthetic mobility models have overly aggressive mobility characteristics for scenarios where user movement is limited to walking. Mobility characteristics based on realistic models can have significant implications for evaluating systems designed for mobility. When evaluated using our evolutionary topology model, for example, popular ad hoc routing protocols were very successful at adapting to user mobility, and user mobility was not a key factor in their performance.

392 citations

Journal ArticleDOI
TL;DR: This paper analyzes an extensive network trace from a mature 802.11 WLAN, including more than 550 access points and 7000 users over seventeen weeks, and defines a new metric for mobility, the ''session diameter,'' to show that embedded devices have different mobility characteristics than laptops, and travel further and roam to more access points.

373 citations

Journal ArticleDOI
11 Aug 2006
TL;DR: This paper presents a system called Jigsaw, a system that uses multiple monitors to provide a single unified view of all physical, link, network and transport-layer activity on an 802.11 network, and believes this is the first analysis combining this scale and level of detail for a production 802.
Abstract: The combination of unlicensed spectrum, cheap wireless interfaces and the inherent convenience of untethered computing have made 802.11 based networks ubiquitous in the enterprise. Modern universities, corporate campuses and government offices routinely de-ploy scores of access points to blanket their sites with wireless Internet access. However, while the fine-grained behavior of the 802.11 protocol itself has been well studied, our understanding of how large 802.11 networks behave in their full empirical complex-ity is surprisingly limited. In this paper, we present a system called Jigsaw that uses multiple monitors to provide a single unified view of all physical, link, network and transport-layer activity on an 802.11 network. To drive this analysis, we have deployed an infrastructure of over 150 radio monitors that simultaneously capture all 802.11b and 802.11g activity in a large university building (1M+ cubic feet). We describe the challenges posed by both the scale and ambiguity inherent in such an architecture, and explain the algorithms and inference techniques we developed to address them. Finally, using a 24-hour distributed trace containing more than 1.5 billion events, we use Jigsaw's global cross-layer viewpoint to isolate performance artifacts, both explicit, such as management inefficiencies, and implicit, such as co-channel interference. We believe this is the first analysis combining this scale and level of detail for a production 802.11 network.

334 citations