认知无线网络中基于频谱态势的频谱接入方法研究

发布时间：2018-01-10 22:29

本文关键词：认知无线网络中基于频谱态势的频谱接入方法研究　出处：《重庆邮电大学》2016年硕士论文　论文类型：学位论文

【摘要】：在认知无线网络中,频谱态势是无线频谱资源在时-频-空域的当前状态和未来趋势,反映当前频谱特征,是动态频谱接入的重要依据。本文通过分析时-频-空域上的频谱态势,研究小尺度认知无线网络和大尺度认知无线网络下的频谱接入问题。主要研究内容有:在小尺度认知无线网络中,次用户(SU)间的距离比较近,网络半径较小,不同SU感知到的频谱态势相似,SU主要通过时间和频率上的频谱空洞进行频谱接入。本文提出基于信道时-频态势的混合频谱接入方法,通过两状态马尔科夫过程对信道状态进行建模,估计信道在时间和频率维度的状态,SU根据信道状态选择Overlay或者Underlay接入方式,然后以最大化系统容量为准则求解SU最优发射功率,并通过修正信道转移概率来降低频谱感知误差的影响。理论分析和仿真实验表明,本文方法下的认知系统容量优于单一的Overlay或Underlay系统。频谱态势图可以有效地估计不同地点的干扰和空白频带,指导不同位置的SU进行频谱接入和功率控制。针对传统插值法构建频谱态势图精度较低而且所需测量节点较多的问题,本文提出基于主用户(PU)信息构建频谱态势图的方法,针对PU发射功率未知的情况,首先基于接收信号强度利用最小二乘法建立定位模型,然后利用拉格朗日乘数法求解PU的位置和发射功率,最后根据PU空间信息和传播模型直接构建频谱态势图。实验表明本文方法比传统的空间插值法构建频谱态势图精度高而且所需测量节点数少。在大尺度认知无线网络下,SU网络半径较大并且分布较广,离PU较远的区域可能不存在PU的影响,空间频谱空洞由此产生。本文提出基于位置信息的空间频谱接入方法,首先分析主网络覆盖范围、主次用户之间距离以及认知网络容量之间的关系,然后根据主次用户的三种位置关系进行功率控制,解决主次用户在空间上并发通信的干扰问题,指导不同位置的SU进行频谱接入。在保证PU正常通信的情况下,为SU提供更多的空间频谱接入机会,提升认知系统的容量。
[Abstract]:In cognitive wireless networks, spectrum situation is the current state and future trend of wireless spectrum resources in time-frequency-spatial domain, reflecting the current spectrum characteristics. It is an important basis for dynamic spectrum access. This paper analyzes the spectrum situation in time-frequency-spatial domain. In this paper, the spectrum access problem in small scale cognitive wireless networks and large scale cognitive wireless networks is studied. The main research contents are as follows: in small scale cognitive wireless networks, the distance between secondary users is close. Because the radius of the network is small and the spectrum situation of different Su is similar, the spectrum access is mainly carried out through spectrum holes in time and frequency. A hybrid spectrum access method based on channel time-frequency situation is proposed in this paper. The channel state is modeled by two-state Markov process, and the channel state in time and frequency dimension is estimated. According to the channel state, the Overlay or Underlay access mode is selected. Then, the optimal transmit power of Su is solved by maximizing the system capacity, and the influence of spectrum sensing error is reduced by modifying the channel transfer probability. The theoretical analysis and simulation results show that. The capacity of cognitive system under this method is better than that of single Overlay or Underlay system. The spectrum situation map can effectively estimate the interference and blank frequency band of different locations. To guide the Su in different positions to access spectrum and control power. Aiming at the problems of low precision and more measurement nodes needed to construct spectrum situation map by traditional interpolation method. In this paper, a method of constructing spectrum situation map based on primary user information is proposed. In view of the unknown transmission power of pu, the location model is established based on the received signal strength using the least square method. Then the Lagrange multiplier method is used to calculate the position and power of pu. Finally, the spectral situation map is constructed directly according to pu spatial information and propagation model. The experimental results show that the proposed method is more accurate than the traditional spatial interpolation method and requires less points of measurement nodes. Under the network. Due to the larger radius and wider distribution of Su network, there may be no pu effect in the region far away from pu, and the spatial spectrum cavity may be generated. In this paper, a spatial spectrum access method based on location information is proposed. Firstly, the relationship among the main network coverage, the distance between the primary and secondary users and the cognitive network capacity is analyzed, and then the power control is carried out according to the three position relationships of the primary and secondary users. In order to solve the interference problem of concurrent communication between primary and secondary users in space, and guide the Su in different locations to access the spectrum, we can provide more access opportunities for Su in the case of normal communication of pu. Increase the capacity of the cognitive system.
【学位授予单位】：重庆邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN925

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