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无线网络中切换最小化算法

Algorithms for Handoff Minimization in Wireless Networks

  • 摘要: 本文着重研究无线网络中移动用户的切换最小化问题。该问题通过对在访问接入点容量限制下,用户移动的两种情况进行分析:1)所有的用户一起移动;2)在网内,每个用户可以拥有自己所选择的路径。在第一种情况中,我们为这个问题提出了一个最优竞争比算法。然而,在第二中情况中,基于连通性假设,也就是,"如果一个用户与一个访问接入点相连接,只要该点所收到的信号强度不小于某个特定的阈值,那么该用户应保持这个连接",我们证明了没有方法可以减少离线设置里非必要切换的数量。然而,没有连通性假设的情况下,我们针对在线设置的此类问题提出了一个竞争比为nΔ的最优确定算法,其中n为用户数,Δ表示环境里覆盖了任意单点的最大访问接入点数。同时,我们证明了算法的随机版本达到了预期竞争比O(logΔ).

     

    Abstract: This study focuses on the problem of handoff minimization for a set of users moving in a wireless network. This problem is analyzed by considering two cases for the user's movement under access point capacity constraints:1) all users move together, and 2) each user can have their chosen path within the network. In the first case, we propose an optimal competitive ratio algorithm for the problem. However, in the second case, having the connectivity assumption, that is, "if a user is connected to an access point so long that the received signal strength of the access point is not less than a specified threshold, the user should continue his/her connection", we prove that no approach can reduce the number of unnecessary handoffs in an offline setting. However, without connectivity assumption, we present an optimal deterministic algorithm with the competitive ratio of nΔ for this problem under online setting, where n is the number of users and Δ is the maximum number of access points which cover any single point in the environment. Also, we prove that the randomized version of the algorithm achieves an expected competitive ratio of O(log Δ).

     

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