On the SIR of a cellular infrared optical wireless system for an aircraft

In this paper, first, path loss models are developed for infrared optical wireless transmission inside an aircraft cabin. Second, a cellular network in the aircraft is considered and signal-to-interference ratio (SIR) maps are determined via simulation. For this purpose, a Monte Carlo ray-tracing (MCRT) simulation is performed in a geometric computer-aided design (CAD) cabin model with defined position, azimuth (AZ), elevation (EL) and field of view (FOV) properties of transmitters and receivers. Mathematical models are developed for line-of-sight (LOS) and non-line-of-sight (NLOS) path losses along particular paths, including estimation of the path loss exponent and the shadowing component. The shadowing is modeled according to a log-normal distribution with zero mean and standard deviation ?. The validity of this model is confirmed in the paper. It is shown that irradiance distribution under LOS conditions experiences an attenuation with a path loss exponent of 1.92 and a shadowing standard deviation of 0.81dB. In NLOS conditions, however, the path loss exponent varies, depending on the nature of the NLOS cases considered. The presented NLOS scenarios yield path loss exponent values of 2.26 and 1.28, and shadowing standard deviation values of 1.27dB and 0.7dB, respectively. Finally, the cabin is divided into cells and SIR maps are presented for different frequency reuse factors. It is shown that at the edges of the circular cells with diameter of 2.8m, a SIR of -5.5dB is achieved in a horizontal cross section of the cabin for frequency reuse of 1, and -2dB and 3dB for frequency reuse factors of 2 and 3, respectively. This means that in an aircraft cabin, for reuse factors less than three, viable communication at the cell edges is not feasible without additional interference avoidance or interference mitigation techniques.     

Numerical modeling for LEMP effect evaluation inside atelecommunication exchange

This paper presents a numerical modeling method developed for evaluating electromagnetic (EM) interference on the equipment inside a telecommunication exchange caused by a direct lightning stroke to a telecommunication tower close (i.e., a few meters) to the exchange building. Considering two different bonding configurations, EM interference is evaluated by calculating the electrical parameters: the EM fields, voltages, and currents. A special method of moment (MOM) wire-grid procedure using “dipole” and “loop” type basis and test functions was used as a numerical tool. A simple model was also developed for simulating the equipment mechanical structures which modify the field distribution inside the building. The voltages and currents induced on shielded cables were evaluated by means of a mixed technique, where the MOM procedure is combined with a SPICE analysis. Numerical modeling was used for two different situations: to simulate some experimental tests carried out in the field, where a 1.6 kA lightning current of a pulse generator was injected on the top of the 25 m high telecommunication tower close to a small exchange building; and to calculate the same parameters when a real lightning current strikes the telecommunication tower     

Co-Channel Interference in Body Area Networks with Indoor Measurements at 2.4 GHz: Distance-to-Interferer is a Poor Estimate of Received Interference Power

Inter-network interference is likely to be a significant source of difficulty for wireless body area networks. Movement, proximity of networks, the large number of nodes per network and the lack of central coordination make cellular approaches to interference modeling ineffective. We examine the interference power of multiple Body Area Networks (BANs) when people move randomly within an indoor office environment. The power-loss trend over 3 m is overwhelmed by random variations in the signal power. Distance-to-interferer is a poor estimate of instantaneous received interference power, and an even less reliable estimate of instantaneous signal-to-interference ratio (SIR). We develop a lognormal statistical model for the signal-to-interference which incorporates the distance effect.     

一种提高协作通信性能的新方法

传统的无线通信中,由于外部环境的干扰,信道的不稳定,网络的中断率比较高。在信道条件较差时,通信性能较差。本文利用无线通信节点间的合作,通过不同节点对信息的中继放大、解码（或者网络编码）,对直接传输的无线信道性能进行改进,大大提高了网络性能,降低网络的中断率;通过比较不同频谱效率下的不同转发方式的中断率性能,选择合适的传输方法。仿真实验得到：频谱效率小于一定值的情况下,利用放大和网络编码转发方式的性能大大高于直接传输方式。     

EM channel characteristics and their impact on MAC layer performance in underwater surveillance networks

Wireless communications and multihop networking based on electromagnetic (EM) radios have been considered as an alternative to acoustic communications in seawater because in typical applications for networked underwater sensing, EM waves are much less susceptible to multipath distortion and environmental noise. In this paper, we discuss the characteristics of EM channels in seawater and derive a novel EM signal propagation model. Based on the propagation model, we implement in the QualNet network simulator an EM underwater surveillance network for studying the impact of these unique characteristics of underwater EM channels on the media access control (MAC) layer performance. Both a single‐hop network model and a multihop network model are simulated. Simulation results show that the carrier sense multiple access without or with acknowledgement (CSMAWithoutACK or CSMAWithACK, respectively) has advantages over ALOHA and multiple access with collision avoidance in terms of packet average delay, packet delivery ratio, and MAC scheme overhead. In the multihop network model, the use of CSMAWithoutACK significantly reduces the packet average delay and the MAC scheme overhead, and both CSMAWithoutACK and CSMAWithACK achieve more than 90% packet delivery ratio. Therefore, CSMAWithoutACK (with no handshaking via request‐to‐send and clear‐to‐send control packets) is the most appropriate MAC protocol to be used in multihop EM‐based underwater surveillance networks. © Her Majesty the Queen in Right of Canada 2014. Reproduced with the permission of the Minister of Industry Canada     

基于博弈论功率控制的串行干扰消除算法

无线网络实现串行干扰消除算法可以提高网络吞吐量,在采用串行干扰消除算法的无线网络系统中,如何控制节点间传输功率使系统效用最大化是一个NP-Hard难题。针对此问题提出非合作博弈算法来解决节点间的传输功率控制,提出了串行干扰消除算法功率控制的非合作博弈,证明了纳什均衡,所提算法可以获得较高的无线网络吞吐量,仿真实验证实了分析结果并展示了算法的优越性。     

Characterizing 802.11 wireless link behavior

Since wireless signals propagate through the ether, they are significantly affected by attenuation, fading, multipath, and interference. As a result, it is difficult to measure and understand fundamental wireless network behavior. This creates a challenge for both network researchers, who often rely on simulators to evaluate their work, and network managers, who need to deploy and optimize operational networks. Given the complexity of wireless networks, both communities often rely on simplifying rules, which frequently have not been validated using today’s wireless radios. In this paper, we undertake a detailed characterization of 802.11 link-level behavior using commercial 802.11 cards. Our study uses a wireless testbed that provides signal propagation emulation, giving us complete control over the signal environment. In addition, we use our measurements to analyze the performance of an operational wireless network. Our work contributes to a more accurate understanding of link-level behavior and enables the development of more accurate wireless network simulators.     

Saturation throughput analysis of a carrier sensing based MU-MIMO MAC protocol in a WLAN under fading and shadowing

In wireless local area networks (WLANs), the traditional carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol cannot use the full benefits from multiuser multiple-input multiple-output (MU-MIMO) technique due to random medium access of the users. In this paper, we propose a carrier sensing based MAC protocol for a MU-MIMO based WLAN with full utilization of MU-MIMO technique. By modeling the WLAN system under the proposed MAC protocol as a discrete time Markov chain, we develop an analytical model for computing the saturation throughput in presence of path loss, Rayleigh fading and log-normal shadowing. The analytical model is then validated via simulation. By means of numerical and simulation results, we demonstrate that the proposed MAC protocol significantly improves throughput performance than the traditional CSMA/CA MAC protocol. Further, we compare the performance of the proposed MAC protocol with a MU-MIMO MAC protocol called Uni-MUMAC protocol and find that the proposed MAC protocol performs better than the Uni-MUMAC protocol. We also explore the effect of some of the network and wireless channel parameters on the performance of the proposed MAC protocol.

     

无线信道干扰概率对网络性能影响分析

通过对无线网络中信道受干扰程度的研究,提出无线信道干扰概率思想,依据干扰概率得到无线信道的通断特性及干扰等级,进而分析无线信道干扰概率与系统可靠度和业务传输成功率等性能指标的关系。利用OPNET工具构建无线网络和算法模型,仿真分析干扰概率对网络性能的影响,为设计无线网络抗干扰路由协议、提高无线网络抗干扰性能提供理论基础。     

A市WCDMA无线传播模型校正技术研究

在3G无线网络规划时,为了尽可能减少误差,提高无线覆盖预测和干扰预测的精度,需要对采用的传播模型进行参数校正。本文从传播模型校正原理和方法入手,结合测试环境,对A市市区WCDMA无线传播模型进行校正,并对校正结果进行验证。     

2.4GHz频段家庭电磁环境下蓝牙性能分析与实验

对工科医(ISM)频段的家庭电磁环境进行了分析与测量,给出了测试波型与数据.应用一个通用的同频段干扰模型,对蓝牙无线网络在此电磁环境下的性能进行了仿真.测试了蓝牙无线网络在无线局域网(WLAN)和微波炉干扰下的性能影响.实验结果表明:蓝牙无线网络在家庭电磁环境干扰下性能最高下降了42%,工作受到了严重影响.说明如今的家庭电磁环境十分恶劣,应给予足够的重视.     

Susceptibility analysis of wiring in a complex system combining a3-D solver and a transmission-line network simulation

This paper deals with the application of electromagnetic field-to-transmission-line coupling models for large cable systems analysis. It emphasizes the use of Agrawal's (1980) model applied here in a numerical simulation of an electromagnetic susceptibility problem up to 500 MHz. Based on the concepts of EM topology, the proposed methodology consists in calculating the incident fields with a three-dimensional (3-D) computer code and the coupling on cables with a multiconductor transmission-line network computer code. In order to validate the efficiency of this methodology in an industrial context, an experiment has been performed on a prototype wiring installed in a Renault Laguna car, stressed by an EM plane wave. Numerous validation configurations have been carried out. First, the prototype cable network under study has been tested on a ground plane to validate the coupling model but also, to validate the cable-network topology itself. Second, EM fields have been measured onto the structure and inside the structure. Then, they have been compared to 3-D calculations, performed with an FDTD code. Third, comparisons between measurements and calculations of bulk currents and voltages on 50 Ω loads on the wiring have been achieved     

干扰消除对无线Ad Hoc网络传输容量的影响

无线Ad Hoc网络是一个干扰受限系统,网络的容量取决于网络中的干扰信号功率的大小。在目前针对无线Ad Hoc网络容量进行研究的文献中没有使用有效的抑制干扰信号功率的方法,使得网络容量受到很大限制。提出通过设置保护区域的方法来降低干扰信号强度,重新对无线Ad Hoc网络进行建模,并推导了传输容量的上下界。通过仿真结果可以知道,设置保护区域能够极大程度降低网络中的干扰信号强度,合理地设置保护区域大小能有效提高传输容量。     

Design and Implementation of a Network‐Adaptive Mechanism for HTTP Video Streaming

This paper proposes a network‐adaptive mechanism for HTTP‐based video streaming over wireless/mobile networks. To provide adaptive video streaming over wireless/mobile networks, the proposed mechanism consists of a throughput estimation scheme in the time‐variant wireless network environment and a video rate selection algorithm used to increase the streaming quality. The adaptive video streaming system with proposed modules is implemented using an open source multimedia framework and is validated over emulated wireless/mobile networks. The emulator helps to model and emulate network conditions based on data collected from actual experiments. The experiment results show that the proposed mechanism provides higher video quality than the existing system provides and a rate of video streaming almost void of freezing.     

基于同道干扰统计模型的无线自组织网络性能分析

基于无线自组织网络中节点的分布特征,结合对同道干扰的定量分析结果,给出了 一种适用于无线自组织网络的同道干扰统计模型。分析了无线自组织网络中同道干扰的统计 特性,并基于建立的同道干扰模型研究了无线自组织网络的系统性能。结果表明,同道干扰 对无线自组织网络的系统性能有严重影响,需建立合理的干扰模型才能更准确地评估自组织 网络的系统性能。     

TD-SCDMA网络干扰浅析

时分同步码分多址系统（TD-SCDMA）采用了多项核心技术来解决网络中的干扰问题,但出于网络系统和无线环境的复杂性,干扰的出现很难避免。TD-SCDMA系统与全球移动通信系统（GSM）和码分多址系统（CDMA）的干扰模型有所差异,有着时分双工（TDD）系统特有的干扰存在方式,分析TD-SCDMA无线网络的干扰因素,需要在了解该网络特点的基础上,根据不同的干扰特征考虑不同的干扰存在方式,依据由内到外、频率相近的原则进行,从硬件故障到网络设计的不同角度进行干扰的定位和解决。     

基于完美信息博弈的多无线电信道分配算法

无线网络的信道分配博弈分析,可分为单冲突域和多冲突域建模。在ad hoc网络中,采用多冲突域建模更符合实际。将ad hoc网络建模为多冲突域模型,提出一种基于完美信息的非合作信道分配算法,验证了算法的收敛性,仿真结果表明该算法相比其他算法在多冲突域中更能最大化信道使用率。     

Partially overlapping channel assignment for WLANs using SINR interference model

The use of multiple channels in 802.11 wireless local area networks can improve network performance. Many efforts have been done to better exploit multiple non‐overlapped channels. However, the number of orthogonal channels in the Institute of Electrical and Electronics Engineers 802.11 standards is very much limited. Recent studies indicate that we can improve the full‐range channel utilization and the network throughput by properly utilizing the partially overlapping channels. However, little work was focused on channel assignment for partially overlapping channels. In this paper, we investigate the problem of partially overlapping channel assignment to improve the performance of 802.11 wireless networks based on the Signal to Interference–Noise Ratio interference model. Using the Signal to Interference–Noise Ratio model, we deduce a direct relationship between maximizing system throughput and minimizing total interference when partially overlapping channels are employed. After that, we propose a greedy method to minimize the total interference for throughput maximization. We evaluate our algorithm through extensive simulations and compare its performances with those of the state‐of‐the‐art. Copyright © 2013 John Wiley & Sons, Ltd.     

High-Dimensional Neural-Network Technique and Applications to Microwave Filter Modeling

Neural networks are useful for developing fast and accurate parametric model of electromagnetic (EM) structures. However, existing neural-network techniques are not suitable for developing models that have many input variables because data generation and model training become too expensive. In this paper, we propose an efficient neural-network method for EM behavior modeling of microwave filters that have many input variables. The decomposition approach is used to simplify the overall high-dimensional neural-network modeling problem into a set of low-dimensional sub-neural-network problems. By incorporating the knowledge of filter decomposition with neural-network decomposition, we formulate a set of neural-network submodels to learn filter subproblems. A new method to combine the submodels with a filter empirical/equivalent model is developed. An additional neural-network mapping model is formulated with the neural-network submodels and empirical/equivalent model to produce the final overall filter model. An $H$ -plane waveguide filter model and a side-coupled circular waveguide dual-mode filter model are developed using the proposed method. The result shows that with a limited amount of data, the proposed method can produce a much more accurate high-dimensional model compared to the conventional neural-network method and the resulting model is much faster than an EM model.