Showing papers by "Shahram Latifi published in 2005"

A survey on data compression in wireless sensor networks

Abstract: Wireless sensor networks (WSNs) are resource constraint: limited power supply, bandwidth for communication, processing speed, and memory space. One possible way of achieve maximum utilization of those resource is applying data compression on sensor data. Usually, processing data consumes much less power than transmitting data in wireless medium, so it is effective to apply data compression before transmitting data for reducing total power consumption by a sensor node. However, existing compression algorithms are not applicable for sensor nodes because of their limited resource. Therefore, some of compression algorithms, which have been specifically designed for WSNs, are presented in this paper: coding by ordering, pipelined in-network compression, low-complexity video compression, and distributed compression.

Document analysis by processing JBIG-encoded images

Abstract: Techniques are presented to directly process JBIG-encoded document images. Two experimental processing pipelines are designed to evaluate the performance of the methods from the application perspective. They are document segmentation for obtaining the global layout and the form processing system for form type identification and the form dropout. The JBIG coding context is employed to perform horizontal smearing and connected-component detection concurrently in the course of decoding the base layer of the JBIG images. It is shown that, using a simple segmentation algorithm, the global layout is identified 50 times faster compared to the case of processing the full resolution images. In addition, an original solution is presented for form type identification by use of the Hough transform of the JBIG base layer images, thus expediting it by a factor of 16 in the designed form dropout system. Advantages of the compressed domain processing include fast procedures, reduced memory requirements, and the possibility of hardware implementation.

A reliable and resource aware framework for data dissemination in wireless sensor networks

Abstract: Distinctive from traditional wireless ad hoc networks, wireless sensor networks (WSN) comprise a large number of low-cost miniaturized nodes each acting autonomously and equipped with short-range wireless communication mechanism, limited memory, processing power, and a physical sensing capability. Since sensor networks are resource constrained in terms of power, bandwidth and computational capability, an optimal system design radically changes the performance of the sensor network. Here, a comprehensive information dissemination scheme for wireless sensor networks is performed. Two main research issues are considered: (1) a collaborative flow of information packet/s from the source to sink and (2) energy efficiency of the sensor nodes and the entire system. For the first issue, we designed and evaluated a reactive and on-demand routing paradigm for distributed sensing applications. We name this scheme as IDLF-Information Dissemination via Label Forwarding. IDLF incorporates point to point data transmission where the source initiates the routing scheme and disseminates the information toward the sink (destination) node. Prior to transmission of actual data packet/s, a data tunnel is formed followed by the source node issuing small label information to its neighbors locally. These labels are in turn disseminated in the network. By using small size labels, IDLF avoids generation of unnecessary network traffic and transmission of duplicate packets to nodes. To study the impact of node failures and to improve the reliability of the network, we developed another scheme which is an extension to IDLF. This new scheme, RM-IDLF - Reliable Multipath Information dissemination by Label Forwarding, employ an alternate disjoint path. This alternate path scheme (RM-IDLF) may have a higher path cost in terms of energy consumption, but is more reliable in terms of data packet delivery to sink than the single path scheme (IDLF). In the latter scheme, the protocol establishes multiple (alternate) disjoint path/s from source to destination with negligible control overhead to balance load due to heavy data traffic among intermediate nodes from source to the destination. Another point of interest in this framework is the study of trade-offs between the achieved routing reliability using multiple disjoint path routing and extra energy consumption due to the use of additional path/s. Also, the effect of the failed nodes on the network performance is evaluated within the sensor system. Performance of the label dissemination scheme is evaluated and compared with the classic flooding and SPIN. (Abstract shortened by UMI.)