• The KIPS Transactions:PartC
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• v.15C no.5
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• pp.399-408
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• 2008

Mobile WiMAX provides wireless broadband services for data communication based on IP protocol. The limitation of physical bandwidth in the radio links may cause performance degradation in providing wireless broadband services in WIMAX. To enhance the efficiency of the radio link utilization, Payload Header Suppression (PHS) is defined as an optional header compression mechanism for mobile WiMAX. It has, however, a very limited compression capability since it has very restrictive compression fields. In this paper, hence, we assumed the application of Robust Header Compression (ROHC), a header compression scheme proposed for links characterized by high bit error ratios, long round-trip times (RTT), and scarce resource, to Mobile WiMAX, and studied its performance. Previous studies on ROHC performance merely focused on the impact of high bit error rate. However, bit error is virtually transparent to ROHC in the wireless systems like WiMAX, since the MAC provides the bit error checking function. In order to evaluate the performance of ROHC in the Mobile WiMAX environments, therefore, we evaluated the performance of ROHC with respect to the packet losses instead of bit error. We investigated the impact of the ROHC parameters that are recommended for the implementation in the ROHC and compared the performance of ROHC with PHS.

• Journal of IKEEE
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• v.5 no.1 s.8
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• pp.8-15
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• 2001

This paper remarks IETF based requirements for IP/UDP/RTP header compression issued in 3GPP2 All IP Ad Hoc Meeting and protocol stacks of the next generation mobile station. All IP Network, for real time application such as Voice over IP (VoIP) multimedia services based on 3GPP2 3G cdma2000. Frames for various protocols expected in the All IP network Mobile Station (MS) are explained with several figures including the bit-for-bit notation of header format based on IETF draft of Robust Header Compression Working Group (ROHC). Especially, this paper includes problems of IS-707 Radio Link Protocol (RLP) for header compression which will be expected to modify in All IP network MS's medium access layer to accommodate real time packet data service[1]. And also, since PPP has also many problems in header compression and mobility aspects in MS protocol stacks for 3G cdma2000 packet data network based on Mobile IP (PN-4286)[2], we introduce the problem of solution for header compression of PPP. Finally. we suggest the guidelines for All IP network MS header compression about expected protocol stacks, radio resource efficiency and performance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.8 s.101
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• pp.988-995
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• 2005

Vibration has been severly increased at the branch pipe of main steam header since the commercial operation of nuclear power plant. Intense broad band disturbance flow at the discontinuous region such as elbow, valve, and header generates the acoustical pulsation which is propagated through the piping system. The pulsation becomes the source of low frequency vibration at piping system. If it coincide with natural frequency of the pipe system, excessive vibration is made. High level vibration due to the pressure pulsation related to high dynamic stress, and ultimately, to failure probability affects fatally the reliability and confidence of plant piping system. This paper discusses vibration effect for the branch pipe system due to acoustical pulsations by broad band disturbance flow at the large main steam header in 700 MW nuclear power plant. The exciting sources and response of the piping system are investigated by using on-site measurements and analytical approaches. It is identified that excessive vibration is caused by acoustical pulsations of 1.3 Hz, 4.4 Hz and 6.6 Hz transmitted from main steam balance header, which are coincided with fundamental natural frequencies of the piping structure. The energy absorbing restraints with additional stiffness and damping factor were installed to reduce excessive vibration.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.435-440
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• 1996

Large Loss-of-Coolant Accidents analyzed in Final Safety Analysis Reports are usually covered by Reactor Inlet Header. Reactor Outlet Header and Primary Pump Suction breaks as representative cases. In this study we analyze the total (guillotine) break of an Emergency Core Cooling System (ECCS) pipe located at the ECCS injection point into the Primary Heat Transport System (PHTS). It was expected that thermal-hydraulic behaviors in the PHT and ECC systems are different from those of a Reactor Inlet Header break, having an equivalent break size. The main purpose of this study is to get insights on the differences occurred between the two cases and to assess these differences from the phenomenon behavior point of view. It was also investigated whether the ECCS line break analysis results could be covered by header break analysis results. The study reveals that as the intact loop has almost the same behavior in both analyzed cases. broken loop behavior is different mostly regarding sheath temperature in the critical core pass and pressure decrease in the broken Reactor Inlet Header. Differences are also met in the ECCS behavior and in event sequences timings.

• Journal of the Korea Society of Computer and Information
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• v.18 no.10
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• pp.55-61
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• 2013

The important issue in header compression would be how to compress the dynamic field increasing constantly between consecutive packets in the head of IP wireless networks. Existent header compression scheme that can eliminated repeated field in header are RFC2507, RFC3095 and E-ROHC scheme. In this paper, I propose a new method of compressing TS fields, which are the Dynamic fields of the RTP packet, into BCB (Basic Compression Bits) basic bits or NCB (Negotiation Compression Bits, BCB + additional bits) bits. In order to verify the proposed header compression method, I have simulation about proposed video packets of IP wireless networks. using Visual SLAM.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1696-1702
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• 2005

Real Time Transport Protocol (RTP) is the Internet standard protocol for transport of real time data audio/video IP Telephony, Multimedia Seivece. In case of 8kbps voice codec, the size of packet per data is 20bytes and become more large to minimal 40bytes with adding each layer's header in RTP/UDP/IP. To solve this problem, various header compression skill were suggested on point-to-point networks. But it compress even IP header and cannot be suitable to apply to end-to-end network Thus, We will renew header compression protocol to apply wired router-based network.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.346-350
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• 2010

Since sensor nodes have restriction of using resources in Zigbee network, number of study on improving efficiency is currently ongoing[1]. Clustering mechanism based on hierarchy structure provides a prevention of duplicated information and a facility of a network expansion[2]. however overheads can occurs when the cluster header is elected and the election of a incorrect cluster header causes to use resources inefficiently. In this paper, we propose that the cluster header election mechanism using distances between nodes and density of nodes in accordance with the operation of the central processing system in which the sync nodes are having information of location and energy with respect to general nodes based on hierachy clustering mechanism.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.197-200
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• 2006

A scene changing detection using histogram and header information of H.264 video stream is presented in this paper. The method using histogram is normal to be detect the changing scene. But this technique results in a lot of processing time because video data is compressed and decompressed to video stream and calculated the difference of histogram between scenes on the each frame. The method using H.264 header information is available to detect the scene change at real time without the process of calculation. Histogram and header information is more rapid for scene change detection with being the same performance in precision and recall.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.3
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• pp.7-13
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• 2019

To improve the flow distribution at channel locations in the welded plate heat exchanger with "L"-type inflow, the flow visualization of Model 1 was carried out. Besides, the characteristics of flow distribution was investigated experimentally according to the header shape. The inlet flow rate for each channel location was increased at the side channels but decreased at the central channels. In the case of Model 2, which has a slant structure added to the basic header of Model 1, the unevenness of inlet flow increased by 23% from 0.019 to 0.023 as compared to Model 1. On the other hand, Model 3, which has a baffle structure added to Model 2, showed 0.064 unevenness in inlet flow, which was a 36% reduction one compared to Model 1. To improve the distribution at each channel in the welded plate heat exchanger with "L"-type flow, it is necessary to improve the header external shape for the guide of flow as well as the baffle structure for reduction of vortex flow.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.4
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• pp.1819-1831
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• 2018

This paper focuses on a header compression method for the Authentication Header (AH) and Encapsulation Security Payload (ESP) for application to 6LoWPAN. Based on the context, an extendible compression method is developed by analysing each field of the AH and ESP. The method is carried out by resetting the AH and ESP header compression formats, adding a MOD field, and setting different working modes. Authentication, encryption, and a mixture of certification and encryption are provided as flexible options. In addition, the value of the original IPv6 extensible header ID (EID) field can be retained, while the number of occupied NHC_ID values can be decreased for future extendibility. The experimental results show the feasibility and validity of the current compression method. By comparison with other solutions, the new mechanism is demonstrated to be advantageous in terms of compression ratio, flexibility and extendibility.