• Title/Summary/Keyword: 링크 에러율

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A Geographic Routing Algorithm to Prolong the Lifetime of MANET (MANET에서의 네트워크 수명을 연장시키는 위치기반 라우팅 기법)

  • Lee, Ju-Young
    • Journal of the Korea Society for Simulation
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    • v.19 no.2
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    • pp.119-125
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    • 2010
  • In ad-hoc networks, dynamically reconfigurable and temporary wireless networks, all mobile devices cooperatively maintain network connectivity with no assistance of base stations while they have limited amounts of energy that is used in different rates depending on the power level. Since every node has to perform the functions of a router, if some nodes die early due to lack of energy, it will not be possible for other nodes to communicate with each other and network lifetime will be shortened. Consequently, it is very important to develop a technique to efficiently consume the limited amounts of energy resources so that the network lifetime is maximized. In this paper, geographical localized routing is proposed to help making smarter routing decision using only local information and reduce the routing overhead. The proposed localized routing algorithm selects energy-aware neighbors considering the transmission energy and error rate over the wireless link, and the residual energy of the node, which enables nodes to achieve balanced energy-consumption and the network lifetime to prolong.

Improved ROHC Optimistic Mode for Efficient Utilization of the Resources in Mobile WiMAX (모바일 와이맥스 환경에서의 효율적인 무선링크 자원 활용을 위한 ROHC Optimistic 모드의 개선 방안)

  • Kim, Joo-Young;Woo, Hyun-Je;Lee, Mee-Jeong;Kwon, Jeong-Min
    • The KIPS Transactions:PartC
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    • v.16C no.1
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    • pp.57-64
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    • 2009
  • In order to efficiently provide IP based Wireless Broadband services in Mobile WiMAX, schemes for more efficiently utilizing a limited bandwidth in radio links are needed. Robust Header Compression (ROHC), a standard header compression scheme proposed by IETF, Bi-directional Optimistic (O) mode provides higher compression efficiency and robustness compared with Payload Header Suppression (PHS) which is an optional header compression scheme for mobile WiMAX [1, 2]. However, if consecutive packet losses occur because of a Shadow Region of Mobile WiMAX or bit errors, header decompression failure rate of the ROHC O mode increases due to inconsistency of the compression information between the Compressor and the Decompressor. Therefore, a complementary mechanism is needed. In this paper, we propose an approach for the dynamic adjustment of an optimistic parameter, which has an effect on both the compression efficiency and the robustness, for improving the performance of ROHC O mode. We also analyze the performance of the proposed approach using an OPNET simulator.

Compensation Characteristics of Distorted Channels in 200 Gbps WDM Systems using Mid-Span Spectral Inversion Method (200 Gbps WDM 시스템에서 Mid-Span Spectral Inversion 기법을 이용한 채널 왜곡의 보상 특성)

  • 이성렬
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.8
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    • pp.845-854
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    • 2003
  • In this paper, the characteristics of compensation for WDM channel signal distortion due to both chromatic dispersion and Ken effect in 1,000 km 200 Gbps(5${\times}$40 Gbps) WDM systems was investigated. The WDM system has a path-averaged intensity approximation(PAIA) mid-span spectral inversion(MSSI) as a compensation method. This system has a highly nonlinear dispersion shifted fiber(HNL-DSF) optical phase conjugator(OPC) in the mid-way of transmission line. In order to evaluate the degree of compensation, 1 dB eye opening penalty(EOP), bit error rate(BER) characteristics and power penalty of 10$\^$-9/ BER are used. It is confirmed that HNL-DSF is an useful nonlinear medium in OPC fur wideband WDM system with PAIA MSSI and that the optimal compensation for WDM channel distortion is achieved by the selection of pump light power of OPC, which equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length, dispersion coefficient of fiber, OPC pump light wavelength, conversion efficiency of WDM channel in OPC.

Distortion Minimization Resource Allocation Scheme for Multiuser Video Transmission Over OFDM Network with Proportional Rates (다수 사용자 OFDM 시스템에서의 비디오 전송을 위한 비례 율 적용 왜곡 최소화 자원 할당 방법)

  • Ha, Ho-Jin;Yim, Chang-Hoon;Kim, Young-Yong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.7B
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    • pp.583-591
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    • 2008
  • This paper proposes a resource allocation algorithm for minimizing the overall distortion of multiple users in orthogonal frequency division multiplex (OFDM). The proposed algorithm exploits the diversity of multiuser and the rate-distortion function using packet distortion model in a system with limited resources. We first induce a rate-distortion function considering error concealment and error propagation properties of H.264 video structures. Then we perform adaptive resource allocation utilizing multiuser diversity for minimizing the overall video quality degradation. We also consider the proportional rate which is pre-determined for each user. Simulation results show that compared to the previous time division multiple access method and the resource allocation method maximizing data rate, the proposed rate allocation algorithm substantially improves the received video quality.

Extended ROHC Compression Algorithm for The Efficient Data Traffic Transmission in the IPv6 (차세대 IP체계에서 효율적인 데이터 전송을 위한 확장된 ROHC 알고리즘)

  • Kim Kyung-shin;Kang Moon-sik
    • Journal of the Korea Society of Computer and Information
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    • v.10 no.5 s.37
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    • pp.187-198
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    • 2005
  • In this paper, we propose the enhanced header compression scheme for the efficient data traffic transmission in Ipv6 networks. The bandwidth of wireless links and IP networks will probably be limited due to properties of the physical medium and regulatory limits on the use of frequencies for radio communications. That is major cause of user throughput reduction. Therefore, We discuss the IPHC(RFC2507) and ROHC(RFC3095) scheme. IPHC is simple header compression scheme and ROHC is enhanced header compression that have fast optimal recovery scheme. We have studied the enhanced header compression scheme in ROHC. We will show that indication of compression context values preventing from packet losses can provide the fast recovery of compression state. Computer simulations show that the proposed scheme has better performance than the previous one.

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A Coding Packet Group-Based ARQ Scheme for File Delivery Services in a Multi-Hop Wireless Network (다중 홉 MANET에서의 파일 전송 응용을 위한 코딩 패킷 그룹 기반 ARQ 기법)

  • Kim, Youngsil;Kang, Kyungran;Cho, Young-Jong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.38A no.7
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    • pp.612-622
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    • 2013
  • In this paper, we propose a coding packet group-based ARQ scheme (rNC) for file delivery in wireless networks. rNC assumes multiple network coding points between the source and the destination. Each network coding point gathers and codes a group of packets according to the queue polling system. A queue polling system makes a few or several packets available for coding in a queue while polling the other queues in the system. Thus, we assuem a queue polling system at each network coding point. We call this group of packets as coded packet group. Each coding point acknowledges the reception of every code packet group to its previous coding point for reliable delivery. Thus, the intermediate coding points including the source can release its buffer before the packet is delivered to the destination. To guarantee the ultimate file delivery to the destination, the destination sends acknowledgement to the sender. We evaluate our proposed scheme using ns-2 and compare the performance with CodeCast. The results show that rNC works better than CodeCast in terms of packet delivery ratio and control overhead in unreliable wireless networks.