• Journal of Space Technology and Applications
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• v.3 no.1
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• pp.72-85
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• 2023

Most Nanosatellites are launched in nanosatellite deployers. Nanosatellites in the deployer are turned off during launch, and they start boot sequence after deploying at their mission orbit. For this reason, nanosatellites must have deployment switch. Most of the nanosatellite deployment switch has two part, first is electric switch to boot the satellite system and second is mechanical assembly to push the switch. In most cases, electric switches are installed in the satellite main body, and the switch operations are translated via the mechanical assembly. These implementations are mechanically complicated and hard to guarantee the appropriate operation without the problems due to friction between pusher and satellite structure. This paper proposes the another implementation method of deployment switch for nanosatellites by installing the electric switch outside the main body without any kind of mechanical parts.

• International journal of advanced smart convergence
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• v.1 no.1
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• pp.19-26
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• 2012

The deployment of mobile femtocellular networks can enhance the service quality for the users inside the vehicles. The deployment of mobile femtocells generates a lot of handover calls. Also, numbers of group handover scenarios are found in mobile femtocellular network deployment. The ability to seamlessly switch between the femtocells and the macrocell networks is a key concern for femtocell network deployment. However, until now there is no effective and complete handover scheme for the mobile femtocell network deployment. Also handover between the backhaul networks is a major concern for the mobile femtocellular network deployment. In this paper, we propose handover control between the access networks for the individual handover cases. Call flows for the handover between the backhaul networks of the macrocell-to-macrocell case are proposed in this paper. We also propose the link switching for the FSO based backhaul networks. The proposed resource allocation scheme ensures the negligible handover call dropping probability as well as higher bandwidth utilization.

• International Journal of Computer Science & Network Security
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• v.23 no.3
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• pp.94-100
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• 2023

The primary goal of any communication spacecraft is to provide communication in variety of frequency bands based on mission requirements within the Indian mainland. Some of the spacecrafts operating in S-band utilizes a 6m or larger aperture Unfurlable Antenna (UFA for S-band links and provides coverage through five or more S-band spot beams over Indian mainland area. The Unfurlable antenna is larger than the satellite and so the antenna is stowed during launch. Upon reaching the orbit, the antenna is deployed using motors. The deployment status of any deployment mechanism will be monitored and verified by the telemetered values of micro-switch position before the start of deployment, during the deployment and after the completion of the total mechanism. In addition to these micro switches, a camera onboard will be used for capturing still images during primary and secondary deployments of UFA. The proposed checkout system is realized for validating the performance of the onboard camera as part of Integrated Spacecraft Testing (IST) conducted during payload checkout operations. It is designed for acquiring the payload data of onboard camera in real-time, followed by archiving, processing and generation of images in near real-time. This paper presents the architecture, design and implementation features of the acquisition, processing and Image generation system for Camera onboard spacecraft. Subsequently this system can be deployed in missions wherever similar requirement is envisaged.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.81-92
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• 2013

The satellite includes many release mechanisms such as solar array deployment, antenna deployment, cover to protect contamination in scientific equipment, pyro value of the propulsion subsytem, and bypass device in Li-Ion cell module. A drive the initiators is a critical to the successful mission because the initiators of release mechanism driving by the pyrotechnic circuit is operated in single short. The pyrotechnic circuit has to provide switching network for safety. A typical switching network has defect consisting of high current rating fire switch to handle switching transient current during fire the initiator. The pyrotechnic circuit is required some form of power conditioning to reduce the peak power demanded from the bus if the initiators are to be fired from the main bus. This paper design a pyrotechnic circuit synchronized to the fire-command to activate the fire switch to overcome use high current rating fire switch to handle switching transient current during fire the initiator. The pyrotechnic circuit provides a current limited widow pulse for fire current synchronized to the fire-command to insure that fire switch will only carry the current but never switch it. The current limited widow pulse for fire current can be possible to use low current rating and light mass switch in switching network. The current limit function in the pyrotechnic circuit reduces supply voltage to initiator and provides the effect of power conditioning function to reduce peak bus power. The pyrotechnic circuit to apply satellite development on geostationary orbit is verified the function by test in development model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5B
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• pp.741-752
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• 2010

The ability to seamlessly switch between the macro networks and femtocell networks is a key driver for femtocell network deployment. The handover procedures for the integrated femtocell/macrocell networks differ from the existing handovers. Some modifications of existing network and protocol architecture for the integration of femtocell networks with the existing macrocell networks are also essential. These modifications change the signal flow for handover procedures due to different 2-tier cell (macrocell and femtocell) environment. The handover between two networks should be performed with minimum signaling. A frequent and unnecessary handover is another problem for hierarchical femtocell/macrocell network environment that must be minimized. This work studies the details mobility management schemes for small and medium scale femtocell network deployment. To do that, firstly we present two different network architectures for small scale and medium scale WCDMA femtocell deployment. The details handover call flow for these two network architectures and CAC scheme to minimize the unnecessary handovers are proposed for the integrated femtocell/macrocell networks. The numerical analysis for the proposed M/M/N/N queuing scheme and the simulation results of the proposed CAC scheme demonstrate the handover call control performances for femtocell environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.11
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• pp.2215-2227
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• 1994

A multicast switch, which can provide a single uniform switching function for vastly different classes of traffic, is crucial for the successful deployment of intergrated broadband networks. In this paper, we study the call blocking probability of heterogeneous circuit emulated traffic in a multicast switch. A previous work on the analysis of homogeneous traffic, where all calls have the same fan-out, show the performance showed that the call blocking probability increases rapidly as fan out increases. We study the performance of heterogeneous traffic, which consists of calls of different fan out, and show the performance gaps between larger fan-out traffic and smaller fan-out traffic are larger than those of homogeneous traffic these results indicate the necessity of efficient resource allocation policies to improve the performance of multicast calls. We conclude the paper introducing several methods to improve the performance of multicast traffic.

• Journal of Communications and Networks
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• v.9 no.3
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• pp.330-341
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• 2007

This work analyzes the performance of the parallel packet switch (PPS) with a sliding window (SW) method. The PPS involves numerous packet switches that operate independently and in parallel. The conventional PPS dispatch algorithm adopts a round robin (RR) method. The class of PPS is characterized by deployment of parallel low-speed switches whose all memory buffers run more slowly than the external line rate. In this work, a novel SW packet switching method for PPS, called SW-PPS, is proposed. The SW-PPS employs memory space more effectively than the existing PPS using RR algorithm. Under identical Bernoulli and bursty data traffic, the SW-PPS provided significantly improved performance when compared to PPS with RR method. Moreover, this investigation presents a novel mathematical analytical model to evaluate the performance of the PPS using RR and SW method. Under various operating conditions, our proposed model and analysis successfully exhibit these performance characteristics including throughput, cell delay, and cell drop rate.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5223-5242
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• 2017

In the last decade, the 2.4 GHz band of IEEE 802.11 WLANs has become heavily congested due to the explosive increase in demand of Wi-Fi connectivity. With the current deployment of enterprise WLANs, channel switching mechanism continues to exhibit inefficiencies because it cannot adapt to real-time channel condition and the inability to support seamless channel switching. Software Defined Networking (SDN) as an emerging architecture is promising to introduce flexibility and programmability for wireless network management. Leveraging SDN to existing enterprise WLANs, channel switching method can be improved significantly. This paper presents a software-defined enterprise WLAN framework with a load aware automatic channel switching solution, which utilizes AP load and channel interference factor (CIF) to provide seamless channel switching. Two automatic channel switching algorithms named Single Switch (SS) and Double Switch (DS) are proposed to improve the overall user experience and the experience of users with highest traffic load respectively. Experiment results demonstrate that our solution can efficiently improve user experience in terms of jitter, transmission delay and network throughout when compared to the conventional channel switching mechanism.

• KNOM Review
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• v.21 no.2
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• pp.26-34
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• 2018

With the proliferation of cloud computing and services, the internet traffic and the demand for better quality of service are increasing. For this reason, server virtualization and network virtualization technology, which uses the resources of internal servers in the data center more efficiently, is receiving increased attention. However, the existing hardware Test Access Port (TAP) equipment is unfit for deployment in the virtual datapaths configured for server virtualization. Virtual TAP (vTAP), which is a software version of the hardware TAP, overcomes this problem by duplicating packets in a virtual switch. However, implementation of vTAP in a virtual switch has a performance problem because it shares the computing resources of the host machines with virtual switch and other VMs. We propose a vTAP implementation technique based on the extended Berkeley Packet Filter (eBPF), which is a high-speed packet processing technology, and compare its performance with that of the existing vTAP.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.4
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• pp.491-497
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• 2018

Most of the applications for distribution system operation highly rely on the voltage and current managements from the field devices. Voltage from the remote controlled switch contains unacceptably large measurement error due to the nonlinear characteristics of the bushing potential transformer. This paper proposes a new voltage magnitude estimation method by calculating voltage drop using current measurement, line impedance and loads deployment data. Contract demand power and pole transformer capacity managed by NDIS are used as a key element to improve accuracy of the proposed method. Various case studies using Matlab simulation have been performed to verify feasibility of the propose voltage estimation method.