标题: | 在感知性网路中以部分探测马可夫决策过程为基础的频带换手机制 A POMDP-based Spectrum Handoff Protocol for Partially Observable Cognitive Radio Networks |
作者: | 马瑞廷 Ma, Rui-Ting 方凯田 Feng, Kai-Ten 电信工程研究所 |
关键字: | 频带换手;感知性网路;等待时间;部分马可夫决策;Cognitive Radio;Spectrum handoff;waiting time;POMDP |
公开日期: | 2008 |
摘要: | 近年的研究说明了静态的频带分配是造成频带使用缺少效率的主因,为了增进频带使用率,可动态侦测且使用认证频带的感知无线电(CR)因应而生。 如何提供有效率的频带换手在CR 中是个很重要的议题。现存的频带换手方法假定感知无线电的使用者(CR user)可以正确的侦测每一个频带以便找到适合的频带进行换手。然而,这个假设在实际的情况下是不实际的,因为CR 使用者侦测频带所花费的时间将会太高而影响主要使用者的品质。 在这篇论文中,藉由部分可知的环境下的Marcov 决策过程(POMDP)的帮助,可以透过探测部分的频带来估测整个网路环境 。此篇论文提出以POMDP 为基准的频带换手机制(POSH),其目的为藉由部分的通道状态来找出最适合进行 换手的频带。除此之外,为了适应多位使用者的环境,此篇论文本着将频宽资源充分分配给各使用者的概念提出了一个以POMDP 为基准的多使用者的换手机制(M-POSH)。 藉由POMDP 为基准的频带换手机制所选出的频带,可达到在每次换手时CR 使用者所需等待的时间最短,数据结果显示出此方法可有效率地让CR 使用者在每次频带换手时达到最少的等待时间。 Recent studies have been conducted to indicate the ineffective usage of licensed bands due to the static spectrum allocation. In order to improve the spectrum utilization, the cognitive radio (CR) is therefore suggested to dynamically exploit the opportunistic primary frequency spectrums. How to provide efficient spectrum handoff has been considered a crucial issue in the CR networks. Existing spectrum handoff algorithms assume that all the channels within the network can be correctly sensed by the CR users in order to perform appropriate spectrum handoff process. However, this assumption is considered impracticable in realistic circumstances primarily due to the excessive time required for the CR user to sense the entire spectrum space. In this paper, the partially observable Markov decision process (POMDP) is exploited to estimate the network information by partially sensing the frequency spectrums. A POMDP-based spectrum handoff (POSH) scheme is proposed to determine the optimal target channel for spectrum handoff according to the partially observable channel state information. Moreover, a POMDP-based multi-user spectrum handoff (M-POSH) protocol is proposed to adapt the POMDP policy into multi-user CR network by distributing CR users to opportunistic frequency spectrums. By adopting the policies resulted from the POSH and M-POSH algorithms for target channel selection, minimal waiting time at each occurrence of spectrum handoff can be achieved. Numerical results illustrate that the proposed spectrum handoff protocols can effectively minimize the required waiting time for spectrum handoff in the CR networks. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT079613549 http://hdl.handle.net/11536/41985 |
显示于类别: | Thesis |
文件中的档案:
If it is a zip file, please download the file and unzip it, then open index.html in a browser to view the full text content.