• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2018.10a
• /
• pp.490-492
• /
• 2018

This paper presents an analysis of the AMR speech data as a basic work to study the technique of inputting and transmitting AMR voice data which is widely used in the public cell phone. AMR consists of HEADER and Speech Data, and it is transmitted in bit format and has 8 bit-rate modes in total. HEADER contains mode information of Speech Data, and the length of Speech Data differs depending on the mode. We chose the best mode which is best to input into QR code and analyzed that mode. It is a goal to show a higher compression ratio for voice data by the analysis and experiments. This analysis shows improvement in that it can transmit voice data more effectively.

• ETRI Journal
• /
• v.30 no.5
• /
• pp.685-695
• /
• 2008

The Network Mobility (NEMO) and IPv6 over Low power WPAN (6LoWPAN) protocols are the two most important technologies in current networking research and are vital for the future ubiquitous environment. In this paper, we propose a compressed packet header format to support the mobility of 6LoWPAN. Also, a Lightweight NEMO protocol is proposed to minimize the signaling overhead between 6LoWPAN mobile routers and 6LoWPAN gateways by using a compressed mobility header. Performance results show that our Lightweight NEMO protocol can minimize total signaling costs and handoff signaling delay.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.10d
• /
• pp.619-624
• /
• 2007

향상된 성능의 3 세대 무선 인터넷 서비스를 제공하기 위해 등장한 IEEE 802.16 표준은 VoIP를 적용 할 수 있는 QoS 기능을 규정하고 있으며 WiMAX 포럼의 장비 제조사들은 저마다의 scheduling 기법 구현을 통해 WiMAX 네트워크에서 voice service가 가능하도록 장비를 설계하고 있다. 그럼에도 불구하고, WiMAX 무선 구간에서 사용되는 MAC header는 제한된 RF 자원의 사용에 부담을 주고 있으며, BS(base station)와 BSC(BS controller)간에 사용되는 tunneling protocol의 헤더 역시 VoIP packet에 붙게 되어 대역폭의 비효율화를 초래한다. 유선상에서의 overheader는 저렴한 Gigabit Ethernet 링크를 사용하면 대역폭이 충분히 커지므로 별 문제가 되지 않지만 무선 상의 overheader는 반드시 줄여져야만 효율적인 무선 자원 이용 및 voice quality의 향상을 가져올 수 있다. 따라서 본 연구에서는 지금까지 제안된 IP/UDP/RTP 헤더 압축 기법 및 WiMAX MAC header 압축 기법을 분석하여, 무선 구간 WiMAX 네트워크에서 VoIP 서비스를 효율적으로 제공할 수 있는 방안을 제시하고자 한다.

• KIPS Transactions on Software and Data Engineering
• /
• v.12 no.5
• /
• pp.207-216
• /
• 2023

For decoding-compatible parallel Deflate algorithm, this study proposed a new method of the control header being made in such a way that essential information for parallel compression and decompression are stored in the Disposed Bit Area (DBA) of the non-compression block and being inserted into the compressed blocks. Through this, parallel compression and decompression are possible while maintaining perfect compatibility with the existing decoder. After applying this method, the compression time was reduced by up to 71.2% compared to the sequential processing method, and the parallel decompression time was reduced by up to 65.7%. In particular, it is well known that parallel decompression is impossible due to the structural limitations of the Deflate algorithm. However, the decoder equipped with the proposed method enables high-speed parallel decompression at the algorithm level and maintains compatibility, so that parallelly compressed data can be decoded normally by existing decoder programs.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.5
• /
• pp.1019-1024
• /
• 2005

MPEG-2 achieves high compression radio, by exploiting the temporal and spatial correlations in real image sequence, using the motion compensated prediction and the transform coding, respectively. However, as the image sequence is more highly compressed, the encoded bitstream becomes more vulnerable to transmission error over the noisy channels. Furthermore, er개rs in the headers are fatal to decoding processes, because the header parameters in the video coding standard include a lot of important information connected to the syntax elements, fables, and decoding process. In this paper, we propose a new error resilience method using LSB coding for header parameters in MPEG-2 coded video transmissions. The experimental results for football and susie video sequence demonstrate that the proposed error resilience method for header parameters in MPEG-2 bitstream has good performance.

• Journal of information and communication convergence engineering
• /
• v.5 no.4
• /
• pp.305-310
• /
• 2007

In this paper, an analysis has been done on the performance of SCTP header compression by using Robust Reader Compression (ROHC)[1] method. And it is assumed that the operating mode for ROHC is unidirectional mode (U-Mode) and the possible states are IR and SO states. The throughput of SCTP packets in wireless link and the impact of size of W-LSB encoding window on throughput are discussed.

• Journal of the Korean Society of Safety
• /
• v.24 no.2
• /
• pp.17-22
• /
• 2009

Thermal stress and elastic creeping stress analysis was conducted by finite element method to simulate start-up process of a boiler header of 500MW standard fossil power plant. Start-up temperature and operating pressure history were simplified from the real field data and they were used for the thermal stress analysis. Two kinds of thermal stress analysis were considered. In the first case only temperature increase was considered and in the second case both of temperature and operating pressure histories were considered. In the first analysis peak stress was occurred during the temperature increase from the room temperature. Hence cracking or fracture may occur at the temperature far below the operating maximum temperature. In the results of the second analysis von Mises stress appeared to be higher after the second temperature increase. This is due to internal pressure increase not due to the thermal stress. When the stress components of radial(r), hoop($\theta$) and longitudinal(z) stress were investigated, compression hoop stress was occurred at inner surface of the stub tube when the temperature increased from room temperature to elevated temperature. Then it was changed to tension hoop stress and increased because of the operating pressure. It was expected that frequent start-up and shut-down operations could cause thermal fatigue damage and cracking at the stub tube hole in the header. Elastic-creeping analysis was also carried out to investigate the stress relaxation due to creep and stabilized stress after considerable elapsed time. The results could be used for assessing the creep damage and the residual life of the boiler header during the long-tenn service.

• Journal of Korea Multimedia Society
• /
• v.11 no.10
• /
• pp.1359-1365
• /
• 2008

The portion of header in H.264 gets higher than those of previous standards instead of its better compression efficiency. Therefore, this paper proposes a new technique to compress the header of H.264. Unifying a sentence elementary in H.264, H.264 does not consider the distribution of element which be encoded and uses existing Exp-Golomb method, but it is uneffective for variable length coding. Most of the header are block type(s) and motion vector difference(s), and there are redundancies in the header of H.264. The redundancies in the header of H.264 which are analyzed in this paper are three. There are frequently appearing symbols and non-frequently appearing symbols in block types. And when mode 8 is selected in macroblock, all of four sub-macroblock types are transferred. At last, same values come in motion vector difference, especially '0.' This paper proposes the algorithm using type code and quadtree, and with them presents the redundant information of header in H.264. The type code indicates shape of the macroblock and the quadtree does the tree structured motion compensation. Experimental results show that proposed algorithm achieves lower total number of encoded bits over JM12.4 up to 32.51% bit reduction.

• Journal of the Korea Society of Computer and Information
• /
• v.14 no.10
• /
• pp.101-110
• /
• 2009

The 6LoWPAN(IPv6 Low-power Wireless Personal Area Network) performs IPv6 header compression, TCP/UDP/IGMP header compression, packet fragmentation and re-assemble to transmit IPv6 packet over IEEE 802,15.4 MAC/PHY. However, from the point of view of security. It has the existing security threats issued by IP packet fragmenting and reassembling, and new security threats issued by 6LoWPAN packet fragmenting and reassembling would be introduced additionally. If fragmented packets are retransmitted by replay attacks frequently, sensor nodes will be confronted with the communication disruption. This paper analysis security threats introduced by 6LoWPAN fragmenting and reassembling, and proposes a re-transmission mechanism that could minimize re-transmission to be issued by replay attacks. Re-transmission procedure and fragmented packet structure based on the 6LoWPAN standard(RFC4944) are designed. We estimate also re-transmission delay of the proposed mechanism. The mechanism utilizes timestamp, nonce, and checksum to protect replay attacks. It could minimize reassemble buffer overflow, waste of computing resource, node rebooting etc., by removing packet fragmentation and reassemble unnecessary.

• Proceedings of the Korean Information Science Society Conference
• /
• 2006.10d
• /
• pp.324-329
• /
• 2006

PTT(Push-To-Talk)란 모든 IP기반의 유, 무선 통합 인터넷 환경으로 진화하고 있는 이동통신망을 통하여 음성 및 텍스트 기반의 일대일 및 그룹 즉시 통신을 제공하기 위한 서비스이다. 스위치를 누르고 말하면서 즉시 의사소통을 할 수 있으므로 일반적인 통화 유형의 대기 시간에 비해 매우 빠른 통화 서비스를 제공함에 따라 각 업체 및 사무실에서 사용하고 있으며 카메라폰에 이은 새로운 어플리케이션으로 부상하고 있다. 현재 이동통신망은 기본의 TDM 방식의 코어 망에서 IP방식의 코어 망으로 천이하고 있으며, 인터넷의 보급과 확산에 따른 인터넷 기술의 발전과 IMT-2000, WIBRO 등의 시스템 도입에 의해 점차 이동통신망 내의 모든 NE를 권고하고 있다. 그러나 무선망에서의 음성 통신은 기존의 통신망에서 보다는 대역폭을 많이 차지하는 단점이 있다. 또한 통화 연결에서 1:1이 아닌 1:N의 관계에 의해 통화 연결이 폭발적으로 일어나기 때문에 대역폭의 확보가 필요하며 안정적인 주파수 사용률 확보가 필요하다. 따라서 본 논문에서는 VoIP망에서의 SIP를 이용한 PTT를 서비스를 설계하고 위와 같은 문제점을 해결하기 위하여 ROHC 알고리즘을 적용하여 PTT 서비스를 설계한다.