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This paper analyzes the causes of packet loss in a 38-node urban multi-hop 802.11b network. The patterns and causes of loss are important in the design of routing and error-correction protocols, as well as in network planning.The paper makes the following observations. The distribution of inter-node loss rates is relatively uniform over the whole range of(More)
Over the past few years, wireless networking technologies have made vast forays into our daily lives. Today, one can find 802.11 hardware and other personal wireless technology employed at homes, shopping malls, coffee shops and airports. Present-day wireless network deployments bear two important properties: they are <i>unplanned</i>, with most access(More)
Increasingly, 802.11 devices are being used by mobile users. This results in very dynamic wireless channels that are difficult to use efficiently. Current rate selection algorithms are dominated by probe-based approaches that search for the best transmission rate using trial-and-error. In mobile environments, probe-based techniques often perform poorly(More)
Researchers have long faced a fundamental tension between the experimental realism of wireless testbeds on one hand, and the control and repeatability of simulation on the other hand. To overcome the stark tradeoff of these traditional alternatives, we are developing a wireless emulator that enables both realistic and repeatable experimentation by(More)
In wireless networking research, there has long existed a fundamental tension between experimental realism on one hand, and control and repeatability on the other hand. Hardware-based experimentation provides realism, but is tightly coupled to the physical environment and circumstances under which experiments are carried out. To overcome this, researchers(More)
As 802.11 deployment and use become ubiquitous, it becomes increasingly important to make efficient use of the bandwidth provided. Unfortunately, 802.11’s current access point selection model fails to enable efficient use of access point bandwidth. We discuss why the current 802.11 access point selection model fails, and evaluate alternative models via(More)
Pervasive computing applications are increasingly leveraging contextual information from several sources to provide users with behavior appropriate to the environment in which they reside. If these sources of contextual information are used and deployed in an ad hoc manner however they may provide overlapping functionality, fail to provide needed(More)
While there is growing interest in using Java for high-performance applications, many in the highperformance computing community do not believe that Java can match the performance of traditional native message passing environments. This paper discusses critical issues that must be addressed in the design of Java based message passing systems. Efficient(More)
Researchers and developers have long faced a fundamental tension between the experimental realism of wireless testbeds on one hand, and the control and repeatability of simulation on the other hand. This thesis introduces physical layer wireless network emulation – a new approach to wireless network experimentation that balances the stark tradeoff of(More)