The early success of wireless sensor networks has led to a new generation of increasingly sophisticated sensor network applications, such as HP's CeNSE. These applications demand high network throughput that easily exceeds the capability of low-power 802.15.4 radios that are most commonly used in today's sensor nodes. To address this issue, this paper investigates an energy-efficient approach to supplementing an 802.15.4 based sensor network with high bandwidth, high power, longer range radios such as 802.11. Exploiting a key observation that the high bandwidth radio achieves low energy consumption per transmitted bit of data due to its inherent transmission efficiency, we propose a hybrid network architecture that utilizes an optimal density of dual-radio (802.15.4 and 802.11) nodes to augment a sensor network having only 802.15.4 radios. We present a cross-layer mathematical model to calculate this optimal density, which strikes a balance between the low energy per bit of the high-bandwidth radio and the low sleep power of 802.15.4 radio. Experimental results obtained using a wireless testbed reveal that our architecture improves the average energy per bit, the time elapsed before half of the nodes drain their battery, and the end-to-end delay by 62%, 106%, and 73% respectively, compared to a network that uses only 802.15.4 radios.

It is important to get an idea of the events occurring in an embedded wireless node when it is deployed in the field, away from the convenience of an interactive debugger. Such visibility can be useful for post-deployment testing, replay-based debugging, and for performance and energy profiling of various software components. Prior software-based solutions to address this problem have incurred high execution overhead and intrusiveness. The intrusiveness changes the intrinsic timing behavior of the application, thereby reducing the fidelity of the collected profile. Prior hardware-based solutions have involved the use of dedicated ASICs or other tightly coupled changes to the embedded node's processor, which significantly limits their applicability.

Traffic gatekeeping, typically implemented using firewalls, is an essential functionality in today's networked computing systems such as desktop PCs. Traffic gatekeeping provides protection against a variety of over-the-network security attacks and can also be used to implement various communication resource management policies. With the development of technologies such as IPv6 and 6LoWPAN that pave the way for Internet-connected embedded systems and sensor networks, traffic gatekeeping will soon become a must-have for these systems as well. Towards this, we present Aegis, a lightweight, rule-based traffic gatekeeping framework for sensor networks. We present an overview of the Aegis architecture, its implementation, and two usage scenarios.

BACKGROUND: New short-read sequencing technologies produce enormous volumes of 25-30 base paired-end reads. The resulting reads have vastly different characteristics than produced by Sanger sequencing, and require different approaches than the previous generation of sequence assemblers. In this paper, we present a short-read de novo assembler particularly targeted at the new ABI SOLiD sequencing technology. RESULTS: This paper presents what we believe to be the first de novo sequence assembly results on real data from the emerging SOLiD platform, introduced by Applied Biosystems. Our assembler SHORTY augments short-paired reads using a trivially small number (5 - 10) of seeds of length 300 - 500 bp. These seeds enable us to produce significant assemblies using short-read coverage no more than 100x, which can be obtained in a single run of these high-capacity sequencers. SHORTY exploits two ideas which we believe to be of interest to the short-read assembly community: (1) using single seed reads to crystallize assemblies, and (2) estimating intercontig distances accurately from multiple spanning paired-end reads. CONCLUSION: We demonstrate effective assemblies (N50 contig sizes approximately 40 kb) of three different bacterial species using simulated SOLiD data. Sequencing artifacts limit our performance on real data, however our results on this data are substantially better than those achieved by competing assemblers.