Accurate CAD model of stopping distance to compute conductor loss of CPW

The theoretical and experimentally extracted closed-form models of stopping distance are presented that provides the CAD oriented simple model to compute conductor loss of CPW with average deviation within 5.4% against the experimental results from three independent sources. Whereas the models of Holloway and Kuester has 14.6% error and model of Ponchak et al. has 17.1% error, against same sets of experimental results. The accuarcy of the models is examined in frequency range 1–120 GHz.     

Subcarrier assignment considering path loss for multiuser OFDM systems with proportional fairness

This article studies downlink subcarrier assignment problem to maximize rate-sum capacity subject to total power and proportional rate constraints in orthogonal frequency division multiplexing （OFDM） systems. Previous algorithms assume that the initial power is equally distributed over all subcarriers. The presence of path loss makes the assumption not correct any more. This article proposes a novel subcarrier assignment algorithm which makes full use of path loss and rate proportionality information to improve rate-sum capacity. The proposed algorithm determines optimal initial power allocation according to path losses and rate proportionalities of different users, assigns subcarriers to users in a greedy fashion, and then exchanges subcarfiers between users to obtain fairer rate distribution. Simulation results show that the proposed algorithm approximately achieves double the capacity of static assignment schemes, such as fixed frequency band approach, and obtains better performance than previous subcarrier assignment algorithms in the presence of different path losses and proportional rate requirements..     

New upper and lower bounds line of sight path loss model for mobile propagation in buildings

This paper proposes a method to predict line-of-sight (LOS) path loss in buildings. We performed measurements in two different types of buildings at a frequency of 1.8 GHz and propose a new path loss model with its upper and lower bounds. The upper and lower bounds depend on max and min values of sampled path loss data. This makes our model limit path loss within the boundary lines. The model includes time-variant effects from the object movement from people in the building and cars in parking areas. These influence reasonably on wave propagation. The results have shown that the proposed model will be useful for the design of the indoor wireless communication systems.     

树冠中电波传播路径损耗的研究及模型的建立

运用随机介质中波的传播和散射理论,解出了电波经过树叶和树枝时散射场的表达式,然后利用平均场的近似方法,计算出电波经过树冠时传播常数的表达式,建立了树冠中电波传播路径损耗的数学模型.通过实验测量了常见树种的相关参数,并代入该模型进行了计算,计算结果与文献提供的测量值吻合较好.     

蒸发波导高度水平非均匀性对路径损耗的影响

探讨了对流层波导模型参数的水平非均匀性.利用抛物方程法,通过仿真分析了蒸发波导高度和逆变层基底高度的水平非均匀性对对流层波导条件下电波路径损耗分布的影响.仿真结果表明：某些条件下蒸发波导高度的水平非均匀性不能忽略,并由此提出新的对流层波导模型.此外,还应用新的模型对路径损耗进行了反演.仿真结果显示,新反演模型可以有效改善反演计算的效果.     

变电站内2.4 GHz无线信道路径损耗建模

为了评估变电站内电磁干扰对电力通信系统的干扰,采用频域测量方法对某市110 kV变电站、220 kV变电站的2.4 GHz电磁波路径损耗进行了测量和分析.针对测量数据,分别利用最小均方差和累积法对路径损耗模型中路径损耗指数和标准差相关参数进行估计,并建立了路径损耗模型,仿真结果表明,模型估计结果与测量值相差不大.另外,搭建了ZigBee仿真系统,在信噪比为5 dB和10 dB的情况下,仿真出误码率随距离的变化关系,为通信设备布置在变电站环境中提供了研究依据.     

Environmental-adaptive indoor radio path loss model for wireless sensor networks localization

In the received signal strength indicator (RSSI) based indoor wireless sensor networks localization system, RSSI measurements are very susceptible to multipath fading, anisotropy of antenna, low supply voltage of node and so on, which will cause the system failure to achieve a high location accuracy. This paper presents an environmental-adaptive path loss model. In the process of localization, the calibrated coefficient LSV of low supply voltage, which can be determined by monitoring the supply voltage of the sender, is used to calibrate ranging errors caused by its low supply voltage. The blind node utilizes the absolute value of RSSI to generate the phase of the corresponding receiver's location so as to determine the correction coefficient of indoor multipath fading R_i. Furthermore, in order to improve the accuracy of RSSI measurements, we also take full consideration of the effect of antenna to accurately determine the corresponding path loss model of the two communication nodes. The proposed path loss model is suitable for the majority of wireless location systems that are on the basis of RSSI-based ranging techniques. Experiment results show that the estimation accuracy and adaptability of the proposed path loss model are significantly higher than that of the traditional one.     

机舱环境路径损耗和功率覆盖特征分析

针对典型机舱内无线信道的实际测量数据,分析了中心频率3.52 GHz的无线信号在机舱环境下的路径损耗特征,统计了机舱中不同位置的路径损耗因子、截距和最小均方误差,为建立机舱内无线信道模型提供了参考。比较了分布式系统和集中式系统在机舱内的功率覆盖情况,分析结果表明:在机舱环境中,当发射功率相同时,分布式系统比集中式系统有着更均匀的功率覆盖效果,且能够更充分地利用发射功率。     

利用匹配追踪算法提取变电站内路径损耗参数

为了衡量变电站内电磁环境对无线通信设备的干扰,尤其是对无线信道的干扰,采用频域测量方法在110 kV和220 kV变电站内分别对430 MHz和470 MHz通信频段电磁波路径损耗进行了测量。针对变电站内电磁环境相对复杂的情况,提出了一种利用匹配追踪算法滤除噪声,提取路径损耗参数的方法。根据测量信号的特征,构建了与测量信号匹配而对噪声不敏感的高斯脉冲原子库。与常规的Gabor原子库相比,基于构建的高斯脉冲原子库的匹配追踪算法比传统的基于Gabor原子库的匹配追踪算法运算速度要快3~4倍,提高了匹配追踪算法的运算速度,减少了计算时间,获得了较好的降噪和信息提取的效果,为变电站内布置无线通信设备提供了理论依据和指导意义。     

A rain attenuation model for satellite link attenuation predictions incorporating the spatial inhomogeneity of rainrate

A model describing the spatial inhomogeneity of rainrate within a rain cell is derived and incorporated into a specific attenuation model to yield a more exact relationship than has been used heretofore relating rainrate and the attendant attenuation at frequencies above 10 GHz. The resulting unified attenuation model relates terrestrial and slant path attenuation, effective propagation distance and path diversity gain to parameters characterizing the earth-station or stations (e.g. location, height, latitude, elevation angle and baseline distance from another station), the frequency of operation, and the two possible raintypes admitted into the model (i.e. convective rain and residual or debris rain). The model is particularly suited for the theoretical investigation of path diversity gain since this concept owes its existence to spatial inhomogeneity of rainrate. This inhomogeneous rain attenuation model can be interfaced with an appropriate statistical rainrate prediction model, such as the Crane two-component model, to yield more precise attenuation predictions.     

基于PCNN的迷宫最短路径求解算法

本文根据脉冲耦合神经网络(PCNN)并行运行的特点,提出了基于PCNN模型的迷宫最短路径搜索算法。从理论上对该算法进行了分析和讨论,并给出了具体的算法和实验结果,验证了该方法的有效性。与其他算法相比,该方法可以在最短的时间内完成最短路径的搜索。     

Millimeter‐wave directional‐antenna beamwidth effects on the ITU‐R building entry loss (BEL) propagation model

Assuming omnidirectional antenna reception, the ITU‐R recently developed a new propagation model on building entry loss (BEL) for 5G millimeter‐wave frequency sharing and compatibility studies, which is a simplified outdoor‐to‐indoor path loss model. Considering the utilization of high‐gain narrow‐beamwidth beamforming, the omnidirectional‐based ITU‐R BEL model may not be appropriate to predict propagation characteristics for directional beamforming scenarios. This paper studies the effects of beamwidth on the ITU‐R BEL model. This study is based on field measurements collected with four different beamwidth antennas: omnidirectional, 10° horn, 30° horn, and 60° horn. The measurement campaigns were conducted at two types of building sites: traditional and thermally efficient buildings. These sites, as well as the measurement scenarios, were carefully chosen to comply with the ITU‐R BEL measurement guidelines and the ITU‐R building types. We observed the importance of accurate beam alignment from the BEL variation range. We were able to quantify the beamwidth dependency by fitting to a model that is inversely proportional to the beamwidth.     

5G共存分析中地物附加损耗模型研究

第五代（the 5th Generation,5G）移动通信共存分析需要传播模型的支撑,地物附加损耗模型是其中非常重要的一个模型.首先介绍了国际电信联盟（International Telecommunications Union,ITU）提供的统计地物附加损耗模型,并指出该模型的一些问题;然后,提出了一种确定性地物附加损耗预测模型,该模型主要考虑建筑物对传播的影响,通过预测过建筑物顶部的绕射、建筑物两侧的侧向绕射,并进行综合得到确定性地物附加损耗预测模型.本文提出的地物附加损耗预测模型可为5G系统的共存与兼容研究提供传播模型支撑.

     

盲区条件下一种基于记忆机制的移动机器人快速路径规划方法

如何在存在盲区的条件下实现机器人路径规划,是现实中的一大难点问题。本文利用路口点表征自由路径,通过估算盲区内路口点位置及其存在的概率,实现对历史感知数据的记忆与利用。建立评价函数对盲区内路口点及感知范围内的路口点进行评价,同时利用了历史感知信息与当前感知信息。与传统局部路径规划方法相比,该方法避免了盲区带来的徘徊、规划失败等问题。仿真表明了该方法的有效性。     

运动红外单站跟踪空中目标的方向估计方法

红外探测器只能测量运动目标的方位角和俯仰角,难以获取目标的距离信息.运动红外探测器所测量的运动目标不完全信息,无法在直角坐标系下有效对三维运动目标进行滤波与跟踪.针对这一问题,提出了运动红外单站跟踪运动目标的参数航迹滤波方法:该方法利用传感器测量到的目标方位角和俯仰角信患,根据假设的目标运动模型,直接对目标航迹方向进行...     

基于BP神经网络对汽油辛烷值损失预测模型的构建

汽油燃烧尾气中含有的硫、烯烃等混合物对环境造成了极大的污染,但企业脱硫降烯的过程也会降低代表企业利润的辛烷值含量.通过数据关联或机理建模,可以刻画化工过程与辛烷值含量的关系,为解决传统的数据关联模型中变量相对较少、机理建模对原料的分析要求高、对过程优化的响应不及时等问题,本文利用Matlab软件,基于粒子群优化算法,通...     

LTE传播模型浅析

针对特定的无线环境和采用的频率,选择良好的传播模型是准确进行网络规划和优化的基础.在评述目前国内外基于LTE所采用的经验传播模型、半经验模型及确定性模型的基础上,对各类传播模型进行了分析与比较,并给出了相同条件下不同传播模型的衰减损耗对比.在此基础上,给出了LTE在密集市区场景下的传播模型选择建议.     

山地场景下SPM传播模型的应用可行性分析

山地场景地势起伏,海拔高度落差大,会从几十米到上千米。山地场景的无线网络规划是否可以使用传统经验模型,还缺少相关验证。本文主要通过在云南临沧山区进行CW测试,并分析传播模型和模型校正的结果。可以看出传统SPM模型并不适用于山区场景。     

Power supply noise in accurate delay model for the sub-threshold domain

Ultra-Low-Power circuits demand has dramatically increased in the last few years. One of the main challenges in designing these circuits is that transistors often run in the sub-threshold regime and their on current is exponentially dependent on the gate-to-source voltage, thus making sub-threshold gates extremely susceptible to power and ground noise phenomena. This paper provides a complete mathematical model in closed form for the delay of sub-threshold CMOS inverters. The novel model can predict the behavior of inverters output signal and therefore it can be extremely useful in the design phase to analyze the variations caused by noise on the output over/undershoot and the gate delay. The proposed model has a general validity since it considers the ground and supply noises completely uncorrelated both in frequency and in amplitude. When a commercial CMOS 45 nm process technology is referenced, the proposed model exhibits a maximum error of only ~16% under different conditions in terms of output load capacitance, input signal rising/falling time, noise phase and frequency.