• Journal of Advanced Navigation Technology
• /
• v.17 no.3
• /
• pp.285-291
• /
• 2013

This paper proposed a new STM-based media streaming scheme to assure the wireless ad hoc link quality. The proposed scheme can assure the link quality by the stream monitoring, assurance, and update procedure, and it can be monitored the media frame by streaming time $t_{new}$. This paper minimizes the link error rate and re-transmission rate using the media streaming update based on the frame size. The simulation results show thst the proposed scheme outperforms STCP and RMST.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2012.11a
• /
• pp.741-742
• /
• 2012

This paper gives an asynchronously adaptive message passing scheme for selective retransmission of dropped packets based on a different fragment in size according to both the type of cause that makes packet loss and variation of traffic load in vehicle wireless communication networks. With the proposed scheme, it is possible to enhance the correctness for under-standing awareness of current network situation and to reduce the number of control packets by increasing or decreasing the size of a fragment along with the changes in network traffic load.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2004.05a
• /
• pp.1417-1420
• /
• 2004

The combination of Fast-Handoff and Hierarchical Mobile IPv6 (F-HMIPv6) allows the anticipation of the layer3 handoff such that data traffic can be efficiently redirected to the mobile node's new location before it moves there. However, after moving to the new Access Router (NAR), if the mobile node (MN) sends the Local Binding Update (LBU) to the Mobility Anchor Point (MAP) before receiving all of the buffered packet from the NAR, the MN may receive the general packet from the MAP. That is, the MN may simultaneously receive two types of packet which has different sequence number. These cause the confusion in packet order, and the MN sends the dup ack for the packet retransmission to the CN. It results in the degradation of the TCP performance. Therefore, we propose the scheme for minimizing the out-of-sequence packet in F-HMIPv6.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2011.04a
• /
• pp.597-600
• /
• 2011

멀티패스 전송은 단대 노드간 다중 경로를 동시에 사용함으로써 효과적인 대용량 전송을 실현하는 미래 인터넷 설계의 한 부분이다. 이에 따라 draft-‘TCP Extensions for Multipath Operation with Multiple Addresses'에서 MPTCP 가 언급되었으며 기존 TCP 를 활용한 다중 전송에서 발생할 수 있는 다양한 오픈 이슈가 나오게 되었다. 본 논문에서는 위 논의로부터 나온 다양한 오픈 이슈 중 수신측에서 발생 할 수 있는 패킷의 재조합(packet reordering)을 줄이는데 초점을 둔다. 패킷의 재조합은 불필요한 에너지 소비와 빈번한 패킷 재전송(packet retransmission) 문제를 초래하며, 특히 에너지 효율이 중요한 모바일기기에 있어 반드시 해결되어야 문제라 할 수 있다. 이를 해결하기 위해 본 논문에서는 전송 경로들의 RTT 값을 비교하여 패킷의 스케줄링 하는 기법을 제안하였으며 시뮬레이션을 통해 성능을 검증하였다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2011.11a
• /
• pp.97-100
• /
• 2011

Underwater Wireless Acoustic Sensor Networks have become an important area of research over the recent decades. Designing an underwater network, especially a media access control (MAC) protocol, faces many challenges due to the peculiarities of underwater environment. One of the most important problems is resulted from long and variable propagation delay of the acoustic wave. In this paper, we propose a new method, namely Dynamic Timeout over Multiple Access with Collision Avoidance (DT/MACA), which is designed to handle long and high variable propagation delay in underwater acoustic sensor networks. In this proposed method, the difference timeout intervals are evaluated and applied to each network transmission. Simulation results show that our work not only improves the network throughput, but also decreases the unnecessary retransmission and end-to-end delay.

• Journal of Electrical Engineering and information Science
• /
• v.1 no.1
• /
• pp.17-22
• /
• 1996

Adaptive code rate change schemes in DS-SSMA systems are proposed. In the proposed schemes, the error correcting code rate is changed according to the channel states. Two channel states having significant effects on the bit error probability are considered: one is the effective number of users, and the other is the fading environment. These channel states are estimated based on retransmission requests. The criterion for the change of the code rate is to maximize the throughput under given error bound.

• Journal of Electrical Engineering and information Science
• /
• v.1 no.1
• /
• pp.23-28
• /
• 1996

In this series of two papers, adaptive code rate change schemes in DS-SSMA systems are proposed. In the proposed schemes the error correcting code rate is changed according to the channel states. Two channel states having significant effects on the bit error probability are considered: one is the effective number of users considered in Part 1, and the other is the fading environment considered in Part 2. These channel states are estimated based on retransmission requests. The criterion for the change of the code rate is to maximize the throughput under given error bound. Simulation results show that we can transmit maximum amount of information if we change the code rate based on the channel states.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.46 no.1
• /
• pp.48-59
• /
• 2009

Next generation mobile communication system will have various access networks and provide seamless multimedia data service to mobile nodes. The WiNGS system, one of these access network, has superior RAT(Radio Access Technology) and network connectivity other than previous ones. In this paper, we propose link-layer SR-ARQ between mobile node and WAGW to solve packet re-ordering problem during handover. In the proposed scheme, we apply the adaptive timer at the SR-ARQ sender to reduce unnecessary packet retransmission during handoff and delayed NAK algorithm at the SR-ARQ receiver for delaying NAK response due to temporary out-of-sequenced frames. We evaluate the performance of the proposed scheme by implementing the new SR-ARQ protocol at the link-layer using ns-2 simulator, and show the handover performance is improved greatly by preventing unnecessary retransmission.

• Journal of Korea Society of Industrial Information Systems
• /
• v.19 no.1
• /
• pp.13-18
• /
• 2014

Sensor nodes are used for monitoring and collecting the environmental data via wireless sensor network. The wireless sensor network with various sensor nodes draws attention as a key technology in ubiquitous computing. Sensor nodes has very small memory capacity and limited power resource. Thus, it is essential to have energy efficient strategy for the sensor nodes. Since the sensor nodes are operating on the same frequency bands with ISM frequency bands, the interference by the devices operating on the ISM band degrades the quality of communication integrity. In this paper, the convolutional code is proposed instead of ARQ for the error control for the sensor network. The proposed convolutional code was implemented and the BER performance is measured. For the fixed transmitting powers of -19.2 dBm and -25dBm, the BER with various communication distances are measured. The packet loss rate and the retransmission rate are calculated from the measured BER. It is shown that the porposed method obtained about 9~12% and 12-19% reduction in retransmission rate for -19.2 dBm and -25 dBm respectively.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.12
• /
• pp.2249-2260
• /
• 2017

IMO (International Maritime Organization) has been providing GMDSS (Global Maritime Distress and Safety System) and mandating to install distress and safety systems according to SOLAS. Digital-HF(High-Frequency) coast station communication system maintains interoperability between ship and coast station and digital data exchange in maritime mobile service by digitizing existing analog base voice communication. In this paper, we analyze ITU-R M. 1798-1 established by ITU for digital HF communications and propose Advanced annex2 and new Annex 5 to improve the problems of the existing Annex 2 and Annex 4. The proposed OFDM protocol basically adopts ARQ (Automatic Retransmission Request) which retransmits when an error occurs in a half-duplex manner between an information transmitting side (ISS) and an information receiving side (IRS) and we propose a digital HF communication system and its operational concept which is more reliable and superior than the existing ITU-R M. 1798 by implementing technical development on implementation and performance improvement.