Influence of Node Dynamics on Cluster Global Time Continuity

The cluster global time can change in wireless sensor networks due to leader re-elections and node disabilities between two successive synchronizations,which will affect temporal relationships.This paper analyzes cluster global time continuity,using global time change models for the node dynamics.The results prove that defining the global time using the cluster average time(AGT) is more stable than defining it using a single node’s local time(SGT).With normally distributed clock-parameter assumptions,the AGT change bounds are at most 70.7% of those for the SGT’s.The impacts of the initial phase and frequency skew distributions on the global time continuity are also investigated to show that the initial phase variations may strongly influence the continuity.Simulations show that the AGT is more stable with less disabled nodes or larger clusters.The appropriate cluster size is 20-40 when there are less than 15 disabled nodes.     

Improved Adaptive Compression Arbitration System for Wireless Sensor Networks

Previous studies have indicated that data compression in wireless sensor networks is not always beneficial to energy conservation due to the additional computational energy costs. This work gives an energy-efficient arbitration mechanism that enhances the performance of compression algorithms by avoiding unnecessary energy losses. The adaptive compression arbitration system uses a new prediction modeling and adaptation. Tests show that the modeling method gives better predictions with the adaptive mechanism...     

使用背靠背MOS变容管的低噪声全数控LC振荡器

为了解决全数控电感电容振荡器(fully digitally controlled inductor-capacitor oscillator, DCO)大信号工作时所引起的数控变容管的非线性问题,在对该种非线性进行分析的基础上,提出一种背靠背串联数控金属氧化物半导体(metal oxide semiconductor, MOS)变容管.该结构通过将两支MOS变容管反方向串联,有效改善了非线性,从而降低了DCO的相位噪声.在中芯国际0.18 μm 互补MOS工艺下设计了采用背靠背串联数控MOS变容管的DCO.仿真结果表明: 当该DCO振荡在3.4 GHz的中心频率时,在1.2 MHz频偏处的相位噪声为-129.4 dBc/Hz, 与使用普通数控MOS变容管的DCO相比,其相位噪声最多可改善8.1 dB.