Hee-Sook Mo

Virtual Line-Based Data Dissemination for Mobile Sink Groups in Wireless Sensor Networks

Mobile sink groups such as rescue teams or platoons bring about a new challenging issue for handling mobility in wireless sensor networks. Recently, a flooding-based technique has been proposed to disseminate data to a mobile sinks group. However, since it simply use flooding of data within the sink group region, it leads to high energy consumption of sensor nodes and low data delivery ratio to sinks due to the broadcast storm problem. Thus, this letter proposes a protocol called Virtual Line-based Data Dissemination (VLDD) to achieve energy-efficient and reliable data dissemination. Instead of flooding, VLDD exploits a Virtual Line Structure (VLS) for data storage within the group region. While sources store their own data on the VLS, each sink retrieves data from the VLS at its location in a time of need. Analysis and simulation results show that VLDD achieves better performance than the existing protocol.

Adaptive Channel Hopping Algorithm for Reader Anti-collision in RFID systems

In RFID field, it is easy to interfere between adjacent channels as the frequency band and channel bandwidth are narrow. Especially, in case of the dense reader mode where the number of readers is more than the number of channels, the readers easily collide with each other. In this paper, we propose an algorithm to avoid reader collision in dense reader environment. First, we introduce the operation of our algorithm. And next, we show the simulation results of the proposed algorithm. Simulation results show performance improvement of our algorithm compared to existing LBT algorithm.

Energy efficient data dissemination protocol for a mobile sink group in WSNs

In wireless sensor networks, there have recently been studies on mobile sinks groups such as groups of soldiers on battlefields, which are characterized by geographically collective movement. Although the existing protocols for individual mobile sinks can support the mobile sinks groups, they suffer from high congestion and control overhead due to location updates by each sink in the groups. To solve the location update problem by individual sinks, a protocol, called M-Geocasting only updates the region information of the mobile sink groups to sources. However, since M-Geocasting uses the flooding within the group regions for data delivery to member sinks, it excessively consumes the energy of sensor nodes in the group region. Moreover, the flooding potentially causes broadcast storms within the group region when many events exist. Thus, in this paper, we propose an efficient data dissemination protocol which can avoid the flooding within the group region for supporting mobile sink group. The proposed protocol introduces a virtual pipe in the group region for data dissemination as data storage. In the proposed protocol, a source sends data to the pipe and member sinks retrieve data directly from the pipe. Simulation results show that the proposed protocol is superior to the existing protocols in terms of the energy consumption and the data delivery ratio.

Pipe-Based Energy Efficient Data Dissemination Scheme for Mobile Sink Groups on WSNs

For WSNs, many data dissemination protocols have been proposed for mobile sink groups, in which sinks are spatially apart each other in their close proximity and move together according to group mobility. Most previous works cannot be directly applied to mobile sink groups due to the control overhead caused by the individual mobility in the group. M-geocasting protocol considers both of data dissemination and group mobility, but regional flooding leads to energy inefficiency. Energy consumption is increased in proportion to the spatial size of the group. In addition, the more frequent events generated in a source have more potential of broadcast storms and failures in data reception in some sinks exist in the group. In the paper, we propose an energy efficient scheme for data dissemination called Pipe Based Data Dissemination (PBDD), in which flooding combines with a virtual pipe, preventing the problems in flooding and data loss in group mobility. The virtual pipe is a unit of data storage for stable data dissemination, while flooding is utilized only for location discovery. Simulation results show that the PBDD outperform the existing protocols in terms of energy consumption and successful delivery rate.

CCSDS packet data processing of KOMPSAT MCE system

The mission control element (MCE) is a control and monitoring system of Koreas Multi-purpose Satellite (KOMPSAT). The MCE receives telemetry from the satellite, and send telecommands via the S-band. This paper describes the Consultative Committee for Space Data Systems (CCSDS) standards for telecommand and telemetry, and the telecommand and telemetry format of the KOMPSAT based on the standard form of the CCSDS. This paper also explains how the satellite operations subsystem (SOS) can process the telecommand and telemetry of KOMPSAT and the fault tolerance mechanism for the high reliability of the SOS operations.

Blending of satellite SST products using ensemble Bayesian model averaging (EBMA)

ABSTRACT Sea surface temperature (SST) is an important parameter in understanding atmosphere–ocean circulation processes and monitoring global climate change. In addition to in situ observations of SST, a series of satellite-borne instruments provide global coverage of SST through infrared and microwave remote sensing. This study was the first application of the ensemble Bayesian model averaging (EBMA) method to the blending of satellite SST products to minimize inherent uncertainties and improve the validation statistics. Monthly SST products from moderate resolution imaging spectroadiometer, Advanced Very High Resolution Radiometer and Advanced Microwave Scanning Radiometer-EOS were used as ensemble members. The mean bias and root-mean-square error (RMSE) of the EBMA method were better than those of the individual members or generic methods such as ensemble mean and median. This is because the weighting scheme adjusted by the expectation–maximization algorithm was based on the suitability of each member derived from training procedures. The errors of EBMA in our experiment had almost no spatial and temporal autocorrelation with regard to the latitude and month, which implies that the EBMA method can serve as a viable option for blending of satellite SST, although more experiments are necessary to determine its feasibility in more detail.

Data-centric Dissemination to Mobile Sink Group in Wireless Sensor Networks

In WSNs, there have been studies on mobile sink group such as groups of soldiers on battlefields who move together as a single entity. The sinks in the group move randomly within a geographically-restricted region. Although the existing data dissemination protocols can support for mobile sink groups, these protocols suffer from high energy consumption since they only count on flooding scheme. Furthermore, the protocol cannot be scaled effectively because they do not consider multiple sources in which most sensors around the mobile sink group should be considered as sources. When data from multiple sources are sent to the mobile sink group, the sinks cannot differentiate received data according to the source. Thus, this paper proposes grid-based virtual pipes for efficient data dissemination that considers multiple sources. The pipe is localized in a grid within a group region as a rendezvous area for each source. Thus, a source sends data to the assigned virtual pipe, and member sinks retrieve data from the pipe while roaming in the group region. The simulation results demonstrate that the proposed protocol outperforms the existing protocols in terms of energy consumption and the data delivery ratio.