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arXiv 0912.4115cs.NI
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无线网络中的不连续约束路由研究

On Channel-Discontinuity-Constraint Routing in Wireless Networks

Swaminathan Sankararaman, Alon Efrat, Srinivasan Ramasubramanian, Pankaj K. Agarwal

摘要:

多信道无线网络越来越多地被用作基础设施网络,例如在大都市区域中。这些网络中的节点经常采用定向天线来提高空间吞吐量。在这样的网络中,给定源和目的地,感兴趣的是计算路径中的每个链路上的最优路径和信道分配,使得路径带宽与链路带宽相同,并且这样的路径满足路径上没有两个连续链路被分配相同信道的约束,称为“信道不连续性约束”(CDC)。CDC路径对于TDMA系统也是非常有用的,其中优选地沿着路径的每个连续链路被分配不同的时隙。本文件载有若干贡献。首先,我们提出了一个$O(N^{2})$分布式算法发现给定的源和目的地之间的最短CDC路径。这提高了Ahuja等人的$O(N^{3})$集中式算法的运行时间。我们的第二个结果是CDC-路径的广义$t$ -算法;对于任何$θ>0$,我们展示了如何构造一个只包含$O(\frac{N}θ)$边的子网络,使得任意源和目的地之间的最短CDC-路径的长度最多只增加$(1-2\sin{\tfracθ{2}})^{-2}$。我们提出了一种新的算法来计算在一个分布式的方式,只使用$O(n\log{n})$消息的最小值。该方案的一个重要结论是在使用定向天线的情况下。在这种情况下,只考虑每个圆锥中两个最近的节点就足够了。

英文摘要:

Multi-channel wireless networks are increasingly being employed as infrastructure networks, e.g. in metro areas. Nodes in these networks frequently employ directional antennas to improve spatial throughput. In such networks, given a source and destination, it is of interest to compute an optimal path and channel assignment on every link in the path such that the path bandwidth is the same as that of the link bandwidth and such a path satisfies the constraint that no two consecutive links on the path are assigned the same channel, referred to as "Channel Discontinuity Constraint" (CDC). CDC-paths are also quite useful for TDMA system, where preferably every consecutive links along a path are assigned different time slots. This paper contains several contributions. We first present an $O(N^{2})$ distributed algorithm for discovering the shortest CDC-path between given source and destination. This improves the running time of the $O(N^{3})$ centralized algorithm of Ahuja et al. for finding the minimum-weight CDC-path. Our second result is a generalized $t$-spanner for CDC-path; For any $θ>0$ we show how to construct a sub-network containing only $O(\frac{N}θ)$ edges, such that that length of shortest CDC-paths between arbitrary sources and destinations increases by only a factor of at most $(1-2\sin{\tfracθ{2}})^{-2}$. We propose a novel algorithm to compute the spanner in a distributed manner using only $O(n\log{n})$ messages. An important conclusion of this scheme is in the case of directional antennas are used. In this case, it is enough to consider only the two closest nodes in each cone.

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