Repeatability, isolation and accuracy are the most desired factors while testing wireless devices. However, they cannot be guaranteed by traditional drive tests. Channel emulators play a major role in filling these gaps in testing. In this paper we present an efficient channel emulator which is better than existing commercial products in terms of cost, remote access, support for complex network topologies and scalability. We present the hardware and software architecture of our channel emulator and describe the experiments we conducted to evaluate its performance against a commercial channel emulator.

Deployment of Smart Grid networks throughout cities introduces a realistic scenario for a large scale sensor network. Smart Meters create a wireless mesh network for receiving commands and sending metering reports back to provider company. The challenges of reliable and timely communication call for a fresh review of the well studied topic of Wireless Sensor Networks (WSN). We provide a centralized MAC solution for data collection, ATR-MAC, that relaxes requirements in general purpose WSNs, but emphasizes on difficulties a Smart Metering deployment will face. ATR-MAC considers variable reuse distances for minimizing propagation delay. It also increases efficiency of collection deadline instead of energy efficiency, a common concern of general-purpose WSN MAC protocols. We provide time and buffer size analysis of our algorithm, prove its correctness and show experimental results using implementation on a testbed.

In several sensing applications the parameter being sensed exhibits a high spatial correlation. For example, if the temperature of a region is being monitored, there are distinct hot and cold spots. The area close to the hot spots is usually warmer than average, with a temperature gradient between the hot and cold spots. We exploit this correlation of sensor data to form a forest of logical trees, with the trees collectively spanning all the sensor nodes. The root of a tree corresponds to a sensor reporting the local peak value. The tree nodes represent the value gradient: each node's sensed value is smaller than that of its parent, and greater than that of its children. GrAFS provides a mechanism to maintain some information at the local peaks and the sink. Using this information the sink can answer several queries either directly, or by probing the region of the sensor field that holds the answer. Thus, queries can be answered in a time and/or bandwidth efficient manner. The GrAFS approach to data aggregation can easily adapt to changes in the spatial distribution of sensed values, and also cope with message losses and sensor node failures. Implementation on MICA2 motes and simulation experiments conducted using TinyOS quantify the performance of GrAFS.

Most researchers conduct wireless networking experiments in their laboratory or similar indoor environments. Such environments are veritable RF jungles, especially when we consider the ISM bands. In this paper we examine and test several common explicit and implicit assumptions that researchers tend to make about the wireless environment. Although these assumptions are acknowledged by most researchers, the extent of their impact is often underestimated. We find that because the environment is always in flux, it is almost impossible to reproduce the results of an experiment. Hence, there is a high risk of misinterpreting the data obtained from such experiments. Through this paper we try to caution experimenters against such risky assumptions when they venture into the RF jungle. After a successful proof-of-concept experiment, we advocate the use of wireless networking testbeds that provide experimenters better control over the RF environment by using coaxial cables, programmable attenuators and power dividers/combiners.

Software simulation has often been used to evaluate proposed protocols for wireless devices. Simulation allows for rapid development and testing, but does not provide a realistic RF environment. To compensate for this, field experiments are performed. However, problems encountered during field experiments can be difficult to locate and correcting problems on-site can be time-consuming. Emulations attempt to provide the advantages of simulation and field experiments without the suffering the disadvantages of both. This demo provides an overview of the hardware, software, and emulation capabilities of ASSERT, an emulation testbed.

Summary form only given. This work focuses on the problem of compressing the Web graph by means of eliminating some of the edges in its link structure. An algorithm is used to divide the task so that it can be executed on parallel processors. Ran on a test bed of generated Web graphs, the algorithm improved the compression ratio of both Huffman-coding schemes and Adler and Mitzenmacher's find reference algorithm tangibly. In the find reference case, improvement was up to 90%