Search

High-rate low-density parity-check (LDPC) codes are the focus of intense research in magnetic recording because, when decoded by the iterative sum-product algorithm, they show decoding performance close to the Shannon capacity. However, cycles, especially short cycles, are harmful to LDPC codes. The paper describes the partition-and-shift LDPC (PS-LDPC) codes, a new class of regular, structured LDPC codes that can be designed with large girth and arbitrary large minimum distance. Large girth leads to more efficient iterative decoding and codes with better error-floor properties than random LDPC codes. PS-LDPC codes can be designed for any desired column weight and with flexible code rates. The paper details the girth and distance properties of the codes and their systematic construction and presents analytical and simulation performance results that show that, in the high signal-to-noise ratio region, PS-LDPC codes out- perform random codes, alleviating the error floor phenomenon. [ABSTRACT FROM AUTHOR]

In this paper, we present Sensor Andrew, an infrastructure for Internet-scale sensing and actuation across a wide range of heterogeneous devices designed to facilitate application development. The goal of Sensor Andrew is to enable a variety of ubiquitous large-scale monitoring and control applications in a way that is extensible, easy to use, and secure while maintaining privacy. To illustrate the requirements of Sensor Andrew, as well as the capabilities and limitations of the system, we outline one such application in which multiple classes of energy sensors are combined with environmental sensors to not only monitor energy usage but also identify energy waste within buildings. [ABSTRACT FROM AUTHOR]