基于路测数据的TD-SCDMA网络室外传播模型校正研究

无线传播模型是用来对无线电波的传播特性进行预测的一种模型。传播特性的预测是无线网络规划的基础,其准确性影响到网络规划的准确性和质量。本文针对连续波测试传播模型校正方法所存在的低效率和低准确性等问题,提出了一种利用现网路测数据进行传播模型校正的方法,从理论上证明了路测信号可以替代连续波测试信号用于传播模型校正。本文使用校正的传播模型是SPM模型。     

基于TD-SCDMA系统的传播模型校正的研究

为了提高路径损耗预测的准确性,提出一种快速且精确的传播模型校正方法.该方法基于最小二乘理论,在现有校正方法和本地连续波(CW)实测数据的基础上对本地标准宏蜂窝传播模型进行校正.仿真结果表明,该方法的计算复杂性明显减少,且校正后的模型最大预测错误率减少20.5%,与本地无线传播环境更加匹配.     

无线传播模型及其校正原理

在无线网络规划工作中,对信号传播损耗的预测是依据无线传播模型来进行的,因此确定准确的传播模型是无线网络规划的重要基础。本文首先对了无线传播模型的原理进行分析,并以此为基础对校正过程中需要关注的问题给出自己的建议。     

无线传播模型研究

分析了电波传播模型校正原理,探讨了无线传播模型的校正方法,并根据上述原理和方法对武汉密集市区的无线传播模型进行了校正.     

TD-LTE系统在城市中的覆盖模型研究与校正

无线传播模型是移动无线网络规划的基础,传播模型的准确性关系到网络规划的合理性,大多数传播模型是对无线电波传播路径损耗的预测,然而在利用计算机的模拟软件进行仿真分析时,仿真结果的准确性很大程度上依赖于模拟中所使用的无线传播模型是否能有效的匹配当地的无线传播环境,所以在进行系统级仿真前,必须要进行传播模型的校正,从而得到一个与当地无线传播环境相匹配的传播模型.     

如何用Eagle进行TD—SCDMA传播模型测试

由于TD—SCDMA网络在覆盖、容量和QoS之间存在相互影响，因此在网络建设之前，需要对网络进行合理规划。其中，传播模型校正是整个过程的关键之一，其准确度将直接影响无线网络规划的规模、覆盖预测的准确度以及基站的布局情况。为了获得符合本地区实际环境的无线传播模型，提高覆盖预测的准确性，需要对各种地形地貌的传播模型进行校正。     

第三代移动通信无线传播模型校正

本文分析了移动通信系统无线传播模型校正的必要性以及应用于实际网络工程的校正和评估方法,并采用CW即连续波测试方法对第三代移动通信的无线传播模型进行了校正。     

如何用Eagle进行TD-SCDMA传播模型测试

1 仪表的选择 由于TD-SCDMA网络在覆盖、容量和QoS之间存在相互影响,因此在网络建设之前,需要对网络进行合理规划.其中,传播模型校正是整个过程的关键之一,其准确度将直接影响无线网络规划的规模、覆盖预测的准确度以及基站的布局情况.为了获得符合本地区实际环境的无线传播模型,提高覆盖预测的准确性,需要对各种地形地貌的传播模型进行校正.     

基于改进粒子群算法的无线传播模型校正

为提高无线网络规划中路损预测精度,本文在分析无线传播模型校正理论及基本粒子群算法的基础上,提出了合理的适应度函数和粒子编码形式设计,研究了改进的粒子群算法在无线传播模型校正领域的应用.仿真结果表明,该算法正确有效,且校正结果精度优于传统算法.     

GSM无线网的传播模型校正案例

结合GSM全向基站的传播模型校正实例,简要介绍了无线传播模型的种类和校正原理,以及无线传播模型校正的基本流程。     

Algorithms for supporting disconnected write operations for wireless Web access in mobile client-server environments

In a wireless mobile client-server environment, a mobile user may voluntarily disconnect itself from the Web server to save its battery life and avoid high communication prices. To allow Web pages to be updated while the mobile user is disconnected from the Web server, updates can be staged in the mobile host and propagated back to the Web server upon reconnection. In this paper, we analyze algorithms for supporting disconnected write operations for wireless Web access and develop a performance model to identify the optimal length of the disconnection period under which the cost of update propagation is minimized. The analysis result is particularly applicable to Web applications which allow wireless mobile users to modify Web contents while on the move. We show how the result can be applied to real-time Web applications such that the mobile user can determine the longest disconnection period such that it can still propagate updates to the server before the deadline so that a minimum communication cost is incurred.     

DRM传输系统服务质量的研究

数字调幅广播（DRM）是先进的数字广播系统,30MHz以下中短波信号通过地波或天波传播,无线环境变化大,文章提出一种实用的DRM服务质量监控系统来保证在服务区内良好的信号覆盖质量。     

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.     

Intelligent actor mobility in wireless sensor and actor networks

In wireless sensor and actor network research, the commonly used mobility models for a mobile actor are random walk model, random waypoint mobility model, or variants thereof. For a fully connected network, the choice of mobility model for the actor is not critical because, there is at least one assured path from the sensor nodes to the actor node. But, for a sparsely connected network where information cannot propagate beyond a cluster, random movement of the actor may not be the best choice to maximize event detection and subsequent action. This paper presents static and dynamic intelligent mobility models that are based on the inherent clusters’ information of a sparsely connected network. Simulation results validate the idea behind the intelligent mobility models and provide insights into the applicability of these mobility models in different application scenarios.     

Delay-aware reliable broadcast scheme based on power control for VANETs简

In vehicular Ad-hoc network（VANET）, many multi-hop broadcast schemes are employed to widely propagate the warning messages among vehicles and the key is to dynamically determine the optimal relay vehicle for retransmission. In order to achieve reliable and fast delivery of warning messages, this paper proposes a delay-aware and reliable broadcast protocol（DR-BP） based on transmit power control technique. First, a comprehensive model is derived to evaluate the transmission in vehicle-to-vehicle communications. This model considers the wireless channel fading, transmission delay and retransmissions characters occurring in the physical layer/medium access control（PHY/MAC） layer. Then, a local optimal relay selection mechanism based on the above model is designed. In DR-BP scheme, only the vehicle selected as the optimal relays can forward warning messages and the transmit power is time-varying. Finally, extensive simulations verify the performance of DR-BP under different traffic scenarios. Simulation results show that DR-BP outperforms the traditional slotted 1-persistence（S1P） and flooding scheme in terms of packets delivery ratio and transmission delay.     

Propagation of ultrawideband chaotic radio pulses through the slits of metal surfaces

The leakage of ultrawideband (UWB) chaotic radio pulses through the defects (holes, slits, cracks, etc.) of metal surfaces-an urgent problem arising from their application as information carriers in wireless sensor networks-is investigated. Experiments with UWB chaotic radio pulses leaking from the slits of metal surfaces are described, and the experimental results are analyzed. The signal attenuation has been estimated when chaotic radio signals propagate through slits of different size.     

Authentic delay bounded event detection in heterogeneous wireless sensor networks

When using wireless sensor networks for real-time event alarming, it is critical to ensure event notification in a timely manner. Additionally, it is extremely important to ensure the alarms generated by the sensors propagate securely through the network to the sink. Another important factor to consider is energy, as it is a limited resource in wireless sensor networks. Accordingly, maximizing network lifetime is always an optimization goal. To address the aforementioned concerns, in this paper we present the Authentic Delay Bounded Event Detection System (ADBEDS). ADBEDS works in rounds, and in each round an event detection tree is responsible for simultaneously detecting events, routing packets to a gateway node, and detecting injection of false packets. The ADBEDS can support k-watching composite events to allow event detection in a redundant manner. Additionally, the corresponding event alarm can be delivered within a user-specified bounded delay. The use of energy-based keying allows smaller, more efficient keys as input to security mechanisms, allowing further reduction in energy consumption of the ADBEDS. We evaluate the energy efficiency and reliability of ADBEDS using theoretical analysis and simulation.     

Geographic Data Propagation in Location-Unaware Wireless Sensor Networks: A Two-Dimensional Random Walk Analysis

For wireless sensor networks with many locationunaware nodes, which can be modeled as a planar Poisson point process, we investigate a protocol, dubbed BeSpoken, which steers data transmissions along a straight path called a spoke. BeSpoken implements a simple, spatially recursive process, where a basic set of control packets and a data packet are exchanged repeatedly among daisy-chained relays that constitute the spoke. Hence, a data packet originated by the first relay makes a forward progress in the direction of the spoke. Despite the simplicity of the protocol engine, modeling the spoke process is a significant challenge. Bespoken directs data transmissions by randomly selecting relays to retransmit data packets from crescent-shaped areas along the spoke axis. The resulting random walk of the spoke hop sequence may be modeled as a two dimensional Markov process. Based on this model, we propose design rules for protocol parameters that minimize energy consumption while ensuring that spokes propagate far enough and have a limited wobble with respect to the spoke axis. The energy efficiency is demonstrated through simulations of the BeSpoken-based data search, and a comparison with the energy consumption of a search based on directed diffusion.     

An Iterative Receiver for Uplink of Coded MIMO DS-CDMA System Employing Layered Space-Time Transmission

We consider a coded multiple-input multiple-output (MIMO) DS-CDMA system using layered space-time transmission in multipath wireless channels, where space-time signals from multiple antennas of multiple users propagate through rich scattering multipath fading. We propose a receiver employing iterative joint detection and decoding with a reduced-complexity detector using linear minimum mean squared error filtering with a priori information and parallel soft-input soft-output (SISO) decoders. Computer simulation results show that the proposed receiver for multi-user MIMO transmission provides high-spectral efficiency and performance approaching to single-user bound. Furthermore, the reduced-complexity receiver outperforms an iterative soft decision-directed maximal ratio combining (DD-MRC) receiver, RAKE receiver as well as a conventional non-iterative receiver.     

一种基站可移动传感器网络再编程协议

 本文针对基站可移动传感器网络实现了一再编程协议MovPro.该协议可以将新的二进制程序通过多跳的形式下发到网络内的节点上并使之运行.该协议的大致过程描述为,当基站在网络内移动时,基站将数据发送给它移动轨迹上的节点.节点收到部分二进制代码后通过窗口交换的形式将二进制代码传播到整个网络.MovPro是第一个在基站可移动传感器网络的真实系统.本文通过多种方式减少通信开销,并通过二级存储的方式减少外部flash的写次数.实验表明MovPro适用于基站可移动传感器网络.