Martin Kappes

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— In this paper, we study the inherent limitations of the 802.11 (a/b) distributed coordination function (DCF) in supporting VoIP calls over a wireless LAN. Specifically, we evaluate the upper bound on the number of simultaneous VoIP calls that can be placed in a single cell of an 802.11(a/b) network. Making one additional VoIP call in that cell would(More)
—In this paper, we present experimental studies on the throughput of IEEE 802.11b wireless networks for UDP and VoIP traffic. Our experiments show that the maximum data throughput of a single station sending out UDP traffic is 6.1 Mbps. The maximum number of VoIP calls in a single cell of an IEEE 802.11b network is six if the ITU G711a-Law codec is used(More)
— In this paper, we propose a metric for measuring the utilization of an IEEE 802.11b wireless network and outline how this metric can be accurately estimated using data that is readily available in most Access Points. We furthermore describe how this metric can be used to perform admission control for VoIP traffic and describe experiences with a prototype(More)
Over the last 30 years or so many results have appeared on the descriptional complexity of machines with limited resources. Since these results have appeared in a variety of different contexts, our goal here is to provide a survey of these results. Particular emphasis is put on limiting resources (e.g., nondeterminism, ambiguity, lookahead, etc.) for(More)
In this paper, we propose a new metric for admission control of VoIP traffic for IEEE 802.11b networks. Due to the large fixed overhead in IEEE 802.11b, the bandwidth available at the payload sizes typical for VoIP traffic is far less than the bandwidth available when using the network for data traffic. Hence, bandwidth is inappropriate as criterion whether(More)
— Current " best practice " recommendations for enterprise wireless deployments suggest the use of VPNs from a wireless client for both authentication and privacy. In this paper, we demonstrate a security issue with such deployments, which we refer to as the hidden wireless router vulnerability. This vulnerability is inherent in the VPN-based wireless LAN(More)
With fast deployment of wireless local area networks (WLANs), the ability of WLAN to support real time services with stringent quality of service (QoS) requirements is attracting ever-increasing research interest. In this paper, we evaluate the capability of the point coordination function (PCF), which is part of the medium access control (MAC) mechanisms(More)