• Title/Summary/Keyword: 불공평성

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A Scheduling Algorithm of AP for Alleviating Unfairness Property of Upstream-Downstream TCP Flows in Wireless LAN (무선 랜에서의 상.하향 TCP 플로우 공평성 제고를 위한 AP의 스케쥴링 알고리즘 연구)

  • Lim, Do-Hyun;Seok, Seung-Joon
    • Journal of Korea Multimedia Society
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    • v.12 no.11
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    • pp.1521-1529
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    • 2009
  • There is a serious unfairness problem between upstream and downstream flows of AP in IEEE 802.11 Wireless LAN. This problem is because Wireless LAN's DCF MAC protocol provides AP with equal channel access priority to mobile noded. Also, it makes this problem worse that the TCP's Data segment loss is more effective on throughput than the TCP's ACK segment. In this paper, we first make several simulations to analysis the unfairness in the various point of view and to find reasons of the unfairness. Also, this paper presents AP's scheduling scheme to alleviate the unfairness problem and evaluate the scheme through ns2 simulator.

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Study on The Throughput Unfairness of High-power transmission in The Transmission Power Controlled Wireless Networks Considering Green Computing (그린 컴퓨팅을 위한 무선 네트워크 전송 파워 조절에서 고출력 전송의 성능 불공평성에 대한 연구)

  • Lee, Hee-Jin;Kim, Jong-Kwon
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.10
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    • pp.27-35
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    • 2010
  • In wireless packet networks, energy and wireless resource efficiency is critical issue to addressed for wide deployment. To achieve the both goals of saving the mobile station's energy and increasing the wireless capacity, transmission power control is introduced to wireless packet networks. In the transmission power controled networks, it is not deeply studied on unfairness among transmissions with different power levels that reaches starvation. Through the performance analysis, this paper explains the throughput unfairness of high power transmission with the unfair media access probability owing to the contending node number difference and proposes a simple PHY-MAC cross layer approach.

Task Synchronization Mechanism for Round Robin based Proportional Share Scheduling (라운드 로빈 기반 비례지분 스케줄링을 위한 동기화 기법)

  • Park, Hyeon-Hui;Yang, Seung-Min
    • Journal of KIISE:Computer Systems and Theory
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    • v.36 no.4
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    • pp.291-303
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    • 2009
  • Round robin based proportional share scheduling(RRPS) defines weight which determines share for each task and allocates CPU resource to each task in proportional to its respective weight. RRPS uses fairness as the measure of performance and aims at high fairness of scheduling. However, researches for scheduling fairness problem due to synchronization among tasks have been rarely investigated. In this paper, we discuss that scheduling delay due to synchronization may result high unfairness in RRPS. We explain such a situation as weight inversion. We then propose weight inheritance protocol(WIP), a synchronization mechanism, that prevents weight inversion. We also show that WIP can reduce unfairness using fairness analysis and simulation.

History-Aware RED for Relieving the Bandwidth Monopoly of a Station Employing Multiple Parallel TCP flows (다수의 병렬 TCP Flow를 가진 스테이션에 의한 대역폭 독점을 감소시키는 History-Aware RED)

  • Jun, Kyung-Koo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.11B
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    • pp.1254-1260
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    • 2009
  • This paper proposes history-aware random early detection (HRED), a modified version of RED, to lessen bandwidth monopoly by a few of stations employing multiple parallel TCP flows. Stations running peer-to-peer file sharing applications such as BitTorrent use multiple TCP flows. If those stations share a link with other stations with only a small number of TCP flows, the stations occupy most of link bandwidth leading to undesirable bandwidth monopoly. HRED like RED determines whether to drop incoming packets according to probability which changes based on queue length. However it adjusts the drop probability based on bandwidth occupying ratio of stations, thus able to impose harder drop penalty on monopoly stations. The results of simulations assuming various scenarios show that HRED is at least 60% more effective than RED in supporting the bandwidth fairness among stations and at least 4% in utilization.

Performance Analysis of Mesh WLANs based on IEEE 802.11 protocols (IEEE 802.11 프로토콜 기반 메쉬 무선랜의 성능분석)

  • Lee, Kye-Sang
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.2
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    • pp.254-259
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    • 2008
  • Mesh WLANs, which consist of wireless mesh routers connecting each other in a mesh topology and self-operate after their autoconfiguration, have several advantages in convenience, swiftness and flexibility of deployment and operation over existing WLANs the expansions of which are done by connecting the APs with wires. However, many technical issues still remain to be solved. Among them, network performance degradations due to the interference between the adjacent hops in multi-hop mesh WLANs, and the reusability of the existing wireless network protocols are critical problems to be answered. This work evaluates the VoIP support performance of IEEE 802.11a/g-based mesh WLANs with multiple wireless interfaces with simulations. The results show that there exit an unfairness in VoIP packet delay performances among mobile routers located at different hops, and that although the capacity of the admitted calls can be increased by increasing the size of voice packet payload it is far less than the expected one. This suggests that the existing 802.11 MAC protocols have their limitation when applied in mesh networks and their enhancement or even a newer one nay be required.

Development of Fair Scheduler for Quality Improvement in Wireless Differentiated Service (차등화 서비스의 성능 개선을 위한 보상 기법)

  • Jung, Jong-Hwa;Ha, Ran
    • Proceedings of the Korean Information Science Society Conference
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    • 2002.10e
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    • pp.136-138
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    • 2002
  • 지연 차등화 모델은 각 클래스의 지연 차별 변수에 따라 차등화된 서비스를 제공한다. 따라서 각 클래스의 패킷별 평균 대기시간이 지연 차별 변수에 비례한다. 유선 환경의 지연 차등화 모델인 WTP를 무선 환경에 적용시킨 WWTP는 큐의 처음 패킷의 블록으로 인한 큐의 전송 중단 현상을 개선하였다. 이로 인해 클래스별 서비스 불공평성이 줄어든다. 그러나 여전히 채널 오류기간에 비례하여 전송의 편중과 중단현상이 발생하는 단점이 있다.본 논문은 WWTP에서 발생하는 서비스 편중과 중단 현상을 개선하기 위한 보상 정책을 제안하는 스케쥴러를 제안한다. 제안된 모델은 에러 기간동안 에러 프리 서비스를 가상적으로시뮬레이션하여 정상 서비스와의 차이를 알아내고 이를 바탕으로 보상 정책을 수행한다. 결과적으로 지연 차등화 모델인 WWTP에서 발생하는 서비스 중단을 개선하면서 정상적인 채널상태와 유사한 서비스를 제공한다.

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Rate Adaptation Scheme for Layered Multicast using MSS in Mobile Network (무선 환경에서 이동 지원국을 이용한 계층형 멀티캐스트 전송률 조절 기법)

  • 이승익;윤원용;이동만
    • Proceedings of the Korean Information Science Society Conference
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    • 2001.10c
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    • pp.130-132
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    • 2001
  • 멀티미디어 통신을 위한 계층형 멀티캐스트를 무선 환경으로 화장할 때에는 무선 네트워크의 낮은 대역폭에 의한 네트워크 혼잡 및 핸드오프에 의한 전송률 불안정 현상이 나타나게 된다. 이러한 문제를 효과적이고 능동적으로 해결하기 위해 본 논문에서는이동 지원국 (MSS) 을 이용한 능동적인 전송률 조절 기법과 우선 순위에 따른 패킷 누락 기법을 제안한다. MSS는 네트워크 계층의 전송 큐 사용량을 통해 현재의 네트워크 상태를 파악해, 네트워크 혼잡 시 이동 호스트(MH)의 가입 실험 (Join-experiment) 을 막거나 수신 계층의 제거를 종용할 수 있다. 그리고 MSS에서 직접 계층별 우선 순위를 부여함으로써 핸드오프에 의한 전송량 불안정성 및 대역폭 분배 불공평성을 해결하고자 한다.

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Delayed CTS Transmission Scheme for Fairness Enhancement in UWASNs (수중 센서네트워크에서 공평성을 위한 CTS 전송 지연 기법)

  • Lee, Dong-Won;Kim, Sun-Myeng;Yang, Yeon-Mo
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.49 no.3
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    • pp.19-25
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    • 2012
  • Underwater sensor networks (UWSNs) employ acoustic channels for communications. One of the main characteristics of the underwater acoustic channel is long propagation delay. Previously proposed MAC (medium access control) protocols for wireless sensor networks cannot be directly used in UWSNs due to the long propagation delay. The long propagation delay and uneven nodes deployments cause spatial fairness in UWSNs. Therefore, a new MAC protocol for UWSNs needs to be developed to provide efficient communications. In this paper, we propose an efficient MAC protocol in order to alleviate the fairness problem. In the proposed scheme, when a node receives a RTS packet, it does not immediately send back but delays a CTS packet. The node collects several RTS packets from source nodes during the delay time. It chooses one of the RTS packets based on the queue status information. And then, it sends a CTS packet to the source node which sent the chosen RTS packet. The performance of the proposed scheme is investigated via simulation. Simulation results show that our scheme is effective and alleviates the fairness problem.

Distributed Cognitive Radio MAC Protocol Considering User Fairness and Channel Quality (사용자의 공평성과 채널품질을 고려한 분산형 무선인지MAC 프로토콜)

  • Kwon, Young-Min;Park, Hyung-Kun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.20 no.1
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    • pp.37-44
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    • 2016
  • It is important that using of efficient radio resource because of deficiency spectrum problem, so that related to this problem many researches are have proceeded. To solve this problem, Cognitive Radio(CR) was suggested. The channels are allocated to the secondary users when the primary users don't use the channels, and unfairness of secondary users can be serious problem and channel quality of multichannel can be different due to the different traffic pattern of primary users. In this paper, we propose MAC prtocol both of the user's fairness and channel quality in CR networks. Simulation results show the comparison with CR MAC protocols.

TCP Uplink Station-Level Fairness Support in IEEE 802.11 Networks (IEEE 802.11 네트워크에서 TCP 업링크 스테이션 간 공평성 지원)

  • Jun, Kyoog-Koo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.6B
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    • pp.553-558
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    • 2009
  • There have been various research efforts to support the fairness between uplink and downlink of TCP streams in IEEE 802.11 networks. Existing methods, which have been effective for the fairness, however could not provide the solution for the unfairness caused by the situation in which a station which is having multiple TCP uplink streams monopolizes the uplink bandwidth. This paper proposes a method that AP allocates token buckets for each uplink TCP station. The proposed method is also able to support the fairness between the uplink and downlink. To remedy the underutilization which may happen under token bucket-based schemes, it allows the movement of redundant tokens among the token buckets. By controlling the token movements, it can balance the fairness and the utilization. Simulation results show that the proposed method is able to support the fairness of the TCP uplink stations, as well as the fairness between the uplink and downlink.