Abstract — Simulation has been the dominant research methodology in wireless and sensor networking. When mobility is added, real-world experimentation is especially rare. However, it is becoming clear that simulation models do not sufficiently capture radio and sensor irregularity in a complex, real-world environment, especially indoors. Unfortunately, the high labor and equipment costs of truly mobile experimental infrastructure present high barriers to such experimentation. We describe our experience in creating a testbed to lower those barriers. We have extended the Emulab network testbed software to provide the first remotely-accessible mobile wireless and sensor testbed. Robots carry motes and single board computers through a fixed indoor field of sensor-equipped motes, all running the user’s selected software. In real-time, interactively or driven by a script, remote users can position the robots, control all the computers and network interfaces, run arbitrary programs, and log data. Our mobile testbed provides simple path planning, a vision-based tracking system accurate to 1 cm, live maps, and webcams. Precise positioning and automation allow quick and painless evaluation of location and mobility effects on wireless protocols, location algorithms, and sensor-driven applications. The system is robust enough that it is deployed for public use. We present the design and implementation of our mobile testbed, evaluate key aspects of its performance, and describe a few experiments demonstrating its generality and power. I.

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Many real-world distributed, real-time, embedded (ORE) systems, such as multiagent military applications, are built using commercially available operating systems, middleware, and collections of pre-existing software. The complexity of these systems makes it difficult to ensure that they maintain high quality of service (QOS). At design time, the challenge is to introduce coordinated QOS controls into multiple software elements in a non-invasive manner. At run time, the system must adapt dynamically to maintain high QOS in the face of both expected events, such as application mode changes, and unexpected events, such as resource demands from other applications. We describe the design and implementation of a CPU broker for these types of ORE systems. The CPU broker mediates between multiple real-time tasks and the facilities of a real-time operating system: using feedback and other inputs, it adjusts allocations over tune to ensure that high application-level QOS is maintained. The broker connects to its monitored tasks in a non-invasive manner, is based on and integrated with industry-standard middleware, and implements an open architecture for new CPU management policies. Moreover, these features allow the broker to be easily combined with other QOS mechanisms and policies, as part of an overall end-to-end QOS management system. We describe our experience in applying the CPU Broker to a simulated DUE military system. Our results show that the broker connects to the system transparently and allows it to function in the face of run-time CPU resource contention.

In this paper, we present STP, a system in which communicating end hosts use untrusted mobile code to remotely upgrade each other with the transport protocols that they use to communicate. New transport protocols are written in a type-safe version of C, distributed out-of-band, and run in-kernel. Communicating peers select a transport protocol to use as part of a TCP-like connection setup handshake that is backwards-compatible with TCP and incurs minimum connection setup latency. New transports can be invoked by unmodified applications. By providing a late binding of protocols to hosts, STP removes many of the delays and constraints that are otherwise commonplace when upgrading the transport protocols deployed on the Internet. STP is simultaneously able to provide a high level of security and performance. It allows each host to protect itself from untrusted transport code and to ensure that this code does not harm other network users by sending significantly faster than a compliant TCP. It runs untrusted code with low enough overhead that new transport protocols can sustain near gigabit rates on commodity hardware. We believe that these properties, plus compatibility with existing applications and transports, complete the features that are needed to make STP useful in practice.