【作者】 赵静；

【导师】 陈向东；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2005， 硕士

【摘要】 无线传感器网络(WSN)是由大量低成本且具有传感、数据处理和无线通信能力的传感器结点自组织构成的多跳网络。可以在大范围内用于收集、处理和发布复杂的环境数据。无线传感器网络中的节点一般采用电池供电,可以使用的电量非常有限,而且对于有成千上万节点的无线传感器网络来说,对电池的更换是非常困难的甚至是不可能的。但是无线传感器网络的生存时间却要求长达数月甚至数年,因此,如何提高网络的有效性,增长网络的生存期是无线传感器网络研究中的重要问题。 无线传感器网络大多采用分层结构。由于同簇节点通信使用同一信道,簇的大小直接关系到每个节点究竟具有多少通信能力。当簇内节点个数处于一个合适的范围时,网络才能发挥最好的性能。通常,无线传感器网络的节点是通过撒播的,节点分布不均,分布密度无法预测。成簇后,簇内节点数疏密不一。而簇内节点数是由簇头的覆盖范围决定的,簇头的覆盖范围又是由簇头的发射功率决定的,因此,我们希望通过调节簇头的发射功率使簇内节点数控制在一个合理范围内。 CDMA的功率控制机制已比较成熟,无线传感器网络的“簇头—成员”结构与CDMA的“基站—移动台”结构相似,可以采用CDMA的功率控制机制对无线传感器网络的最小ID分簇算法进行优化。本文详细对改进算法进行了描述,并给出控制簇头发射功率的流程图。 另外,提出了一种采用模糊技术调整簇头功率以改变拓扑结构的方案。通过测量簇内节点数与理想节点数的差异,调整簇头发射功率。当簇内节点数离目标值较远时,通过比较大的步长使系统迅速逼近目标值。越趋近于目标值,步长每步调得越少,可以缩短系统的响应时间,减小系统的过调量,增加系统的稳定性。 最后进行了仿真,实验结果证明通过分簇大小控制以后,网络的生存时间和通信量都有增加。更多还原

【Abstract】 Wireless sensor networks(WSNs) are multiple-hop network self-organized with lots of low-cost sensors with ablities of sensing,data processing and wireless communication.Wireless sensor networks configured automatically are highly valuable in both civil aspect and military aspect. They can be used to collect, process and issue complicated environmental data within a large range.In wireless sensor networks ,The power of the nodes is usually supplied by batteries which energy is limited.It is very difficult, even impossible to replace all batteries used in the wireless sensor networks, which are composed of thousands of nodes.But wireless sensor networks are demanded to have their lifetime persist as long as several months, even several years. Consequently,the most important problem is how can improve validity of networks, increase life of networks.Hiberarchy is mostly used in WSNs,all nodes in same cluster use same channel.The traffic of such nodes is affected by cluster size. Great performance of networks will be represented,when the real number of cluster nodes is close to ideal numbers. The nodes in WSNs broadcasted randomly cause that the distribution density of nodes and the clusters can’t be forecasted.The number of cluster nodes is decided by the range of cluster head overlay which is decided by the transmit power of cluster head. Therefore,we expect that the number of cluster nodes is controlled in reasonable range by adjusting the transmit power of cluster heads.Power control mechanism in CDMA comes to maturity.They are similar between ’clusterhead-member’in wireless sensor networks and ’basestation-mobile’in CDMA.Therefore, power control mechanism in CDMA can be used in optimizing Lowest-ID Clustering of wireless sensor network . Improved algorithm is described in detail.Flow chart of controlling clusterhead transmit power is given.In addition ,a power control scheme in wireless sensor networks is proposed,using fuzzy technology to adjust power of the cluster heads for changing framework of topology. Adjust power of the cluster heads according as thedifference between the number of cluster nodes and ideal numbers.While the real number of cluster nodes is far away from ideal numbers,system approaches ideal numbers fastly using long step. While the number of cluster nodes is close to ideal numbers,the step is shorter and shorter.lt can decrease the response time and over adjustment,improve system stability.Finally,simulation and results are shown in the end of paper.The results prove that lifetime and capacity will be increased after controlling the distribution of cluster nodes.更多还原