• Title/Summary/Keyword: handoff algorithm

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An Adaptive Hard Handoff Algorithm for Mobile Cellular Communication Systems

  • Zhu, Huamin;Kwak, Kyung-Sup
    • ETRI Journal
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    • v.28 no.5
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    • pp.676-679
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    • 2006
  • In this letter, we propose an adaptive hard handoff algorithm with a dynamic hysteresis value based on the received signal strength from the serving base station, for mobile cellular communication systems. A discrete-time method is presented to evaluate handoff algorithms analytically. Performance is evaluated in terms of the average number of handoffs, the probability of link degradation, and the average handoff delay. Numerical results and simulations demonstrate that the proposed algorithm outperforms the handoff algorithm with fixed hysteresis values and the handoff algorithm using both threshold and hysteresis.

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Analysis of Velocity Adaptive Handoff Algorithm (속도적응 핸드오프 알고리즘 분석)

  • 김영일;진용옥
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.4
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    • pp.748-760
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    • 1997
  • The handoff failure probability has to be enhanced efficiently to enhance the performance of PCS system. In this paper a new scheme called velocity adaptive handoff algorithm for reducing handoff failure probability and maintaining the carried traffic constantly in PCS systems, by assigning low handoff threshold value for high mobility calls, and assigning high handoff threshold value for low mobility calls, is presented. The performance of evaluation of this new scheme is carried out in terms of tranffic characteristics. Also velocity estimation algorithm for this new scheme is presented. According to the result, the handoff failure probability of velocity adaptive handoff algorithm is enhanced about 60%.

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Handoff Algorithm based on One-way Trip Time for Wireless Mesh Network (Wireless Mesh Network을 위한 OTT 기반 핸드오프 알고리즘)

  • Park, Cha-Hee;Yoo, Myung-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.5
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    • pp.16-24
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    • 2007
  • Wireless mesh network extends the limited coverage of conventional wireless service from one-hop access point to wider area. It is recognized as an important issue to provide seamless handoff in the wide coverage of wireless mesh network. A long handoff delay may cause high packet loss and disconnection of service, degrading the network performance. The handoff delay is mainly introduced from the channel scanning process obtaining information to make handoff decision and the unnecessary handoffs due to inaccurate handoff decision. In this paper, we propose the handoff algorithm based on one-way trip time (OTT) to expedite the handoff procedure. As compared to the handoff algorithm based on the receiving signal power, the proposed algorithm takes advantage of OTT to obtain the necessary handoff information in a relatively shorter time and reduce the unnecessary handoffs. The performance of proposed algorithm is evaluated through the simulations. It is verified that the proposed handoff algorithm can effectively enhance the handoff accuracy, and therefore reduce the handoff delay and unnecessary handoffs.

A New Frame Offset Assignment Algorithm For Reducing the Soft Handoff Blocking Probability Due to Lack of Frame Offset Capacity (Frame Offset의 불일치로 인하여 발생하는 Soft Handoff Blockig Probability를 줄이기 위한 새로운 Frame Offset Assignment Algorithm)

    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.9B
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    • pp.1624-1630
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    • 1999
  • Code division multiple access (CDMA) is a promising air interface technique for cellular systems. When an MS (Mobile Station) moves to an adjacent cell, the handoff between the serving cell and the target cell is needed. Compared with the hard handoffs, the soft handoffs between two CDMA channels with the identical frequency assignments and frame offsets can provide a better quality of service by minimizing the undesirable ping pong phenomenon of back-and forth handoffs between two adjacent cells in conventional hard handoffs. For the soft handoff of a call to an adjacent cell to be successful, the adjacent cell should assign to the call the same frame offset as that being used in the original cell by the call. In this paper, considering the assignment states of the frame offsets of the adjacent cells, a frame offset assignment algorithm for the originated call is proposed. And analytic method for the handoff blocking probability due to the lack of the frame offset capacity is also presented to show the advantage of the proposed algorithm with respect to the soft handoff blocking probability.

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Performance Analysis of a Novel CDMA Soft Handoff Algorithm Using Mobile Terminal Profiles (단말의 프로필을 이용한 새로운 CDMA 소프트 핸드오프 알고리즘의 성능 분석)

  • 정다위
    • Journal of the Korea Society for Simulation
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    • v.7 no.2
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    • pp.153-165
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    • 1998
  • In the Is-95 soft handoff scheme of CDMA, there occurs a tradeoff between improving quality due to the space diversity and additional resource management like updates of the active set during soft handoffs. In addition, if a mobile terminal is alternating two adjacent cells, a well-known phenomenon called ping-ping causes the resource management to be seriously degraded. By noting that in general the probability that a user initiates additional handoffs is exponentially decreased as the user has already handed over one or more times, we present a soft handoff algorithm making use of handoff profiles of mobile terminals to improve resource utilization. In the proposed algorithm the number of handoffs made so far during the call is recorded in the mobile profile and the profile data is used for adjusting handoff parameters such as the value of add or drop threshold (T_ADD or T_DROP). Through simulations, the result of the proposed algorithm is shown to improve the handoff performance by lowering the number of handoffs while simultaneously reducing resource waste.

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CandidateCasting Fast HANDOFF Algorithm for MIP using MAC Layer Information at Wireless LAN (무선 랜에서 MAC계층의 정보를 이용한 고속 L3 핸드오프 알고리듬 - CandidateCasting Fast Handoff)

  • 신일희;이채우
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.12A
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    • pp.991-1001
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    • 2003
  • CCFH(Candidatecasting Fast Handoff) algorithm excels the performance of existing fast handoff schemes using multicasting in terms of handoff latency and B/W efficiency. The scheme uses L2 information(BSSID) at Wireless LAN and starts multicasting before L2 handoff. So it can reduce L3 handoff latency. At this article, we would show that Candidatecasting Fast Handoff Scheme is clearly new scheme using L2 information and has the good performance.

Relay Station based Optimal Handoff Prioritization Control Algorithm (Relay Station 기반 최적 핸드오프 우선화 제어 알고리즘)

  • Yu, Hye-In;Kang, Hae-Lynn;Kim, Nak-Myeong
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.7
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    • pp.24-31
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    • 2009
  • Resource reservation scheme is an effective method to guarantee QoS for handoff calls in the next generation multimedia mobile communication systems, but it causes negative impacts on blocking probability of new calls. In this paper, to optimize the tradeoff between dropping probability of handoff calls and blocking probability of new calls, relay station based handoff prioritization control algorithm is proposed. In this algorithm, the relay station participates in handoff procedure and enables mobile stations to have guaranteed prompt service after handoff by providing highly efficient data transmission. In this paper, Markov chain models of the proposed handoff prioritization schemes are developed, and dropping probability of handoff packets and blocking probability of new packets are derived. By numerical analysis, the proposed algorithm has been proved to outperform conventional handoff prioritization schemes in terms of dropping probability of handoff packets and blocking Probability of new packets.

QoS Guaranteed Fast Handoff Algorithm for Wireless LAN (무선 랜 환경에서의 QoS 보장형 고속 핸드오프 알고리듬)

  • 신일희;이채우
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.40 no.12
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    • pp.59-70
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    • 2003
  • Proposed CCRSVP (Candidate Casting RSVP) algorithm is a new fast handoff method which uses advanced multicasting method and RSVP for IEEE 802.11 Wireless LAN (WLAN) environments. The proposed algorithm shows good performance in the handoff latency and the B/W efficiency aspect and guarantees QoS because it uses L2 information (BSSID) of WLAN and starts to reserve resources and multicast packets before L2 handoff completes. We also propose a Markov chain performance analysis model in which we can analyze the handoff performance of various handoff algorithms. Using the model, we compare bandwidth efficiency of the proposed algorithm with existing handoff algorithms which use RSVP by analyzing blocking probability of session, resource usage, and the average number of ongoing session in a cell. The results show that the proposed algorithm shows better performance than the existing algorithms in the above three performance aspects.

Design and Implementation of a Novel Fast Handoff Algorithm for Streaming Service in Wireless LANs (무선랜에서 스트리밍 서비스를 위한 새로운 고속 핸드오프 알고리즘의 설계 및 구현)

  • Choi, Jung-Hee;Min, Sang-Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.1B
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    • pp.1-6
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    • 2011
  • We have considered fast handoff algorithms to support seamless streaming in wireless LANs. It is impossible to provide seamless streaming service while moving within wireless LANs, In this paper, we proposed a new handoff algorithm where the critical value for handoff can be adjusted according to peripheral wireless circumstances. This algorithm can prevent an unnecessary scanning job and save handoff delay time through the active scanning procedure to the specific channel groups. Also, we evaluated the handoff performance of our proposed algorithm, and compared it with the performance of the existing wireless LAN. We can see that the performance with our proposal is better than that of the general wireless LAN.

A Fast Handoff Algorithm for IEEE 802.11 WLANs using Dynamic Scanning Time (가변적인 탐색시간을 이용한 IEEE 802.11 무선랜의 고속 핸드오프 알고리듬)

  • 권경남;이채우
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.2A
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    • pp.128-139
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    • 2004
  • As the Internet usage grows, people want to access the Internet while they are moving. To satisfy this requirement economically, IEEE 802.11 Wireless LANs(WLANs) are rapidly deployed. In order to support mobility, WLANs must provide smooth handoff mechanism. Recent studies show, however, handoff delay of WLANs exceeds 300ms, most of which is due to slow scanning mechanism finding a new AP. With this handoff delay, current WLANs is not suitable to provide seamless realtime interactive services such as VoIP sevice. In this paper, we analyze the current handoff method of IEEE 802.11 and we propose a new handoff algorithm which can decrease time needed for searching a new AP and thus reduce overall handoff time. We show by simulation that the proposed algorithm has shorter handoff delay than current handoff method.