基于单片机的无线双向外语教学机的设计

针对目前语音实验室存在的种种不适应外语教学现状的不足之处,开发了基于单片机控制系统的无线双向外语教学机,该系统结合有线和无线语音室的优点,实现了外语听,说教学中基本的双向交流。

ABB无线技术及产品概述

概述ABB的无线技术和产品以及应用。陈述ABB在无线技术的开发及应用方面采取的一个实用的多样化的模式,以满足服务于其核心的电力及自动化业务领域。例举了一系列用于不同工业应用领域的ABB无线产品和解决方案。选择并特别强调富于创新性和独具特点的ABB无线产品,如用于工厂自动化实时通讯和无线供电的WISA,用于中压开关柜的无线波导通讯等。

A novel algorithm of channel resource allocation in wide-band WLAN

With the development of Wide-band wireless communications,MAC protocol in IEEE 802.11 can't satisfy user-individual quality of service(QoS) guarantees effectively and can't support high-speed mobility.A novel algorithm for channel allocation in Wide-band WLAN and an improved resource reservation mechanism applied into IEEE 802.11 MAC protocol are proposed in this article.The simulated results indicate that the advanced protocol makes the system throughput improved and delay decrease.Moreover,the improved system shows an excellent performance in the environment with high-speed mobility.

A time domain multiple-CFOs and CIRs estimation algorithm over wireless multimedia sensor networks

Channel parameters estimation in an orthogonal for the receiver station is a multi-dimensional （MD） frequency division multiple access （OFDMA） system optimization problem, because every user node has a separate local oscillator and every transmitter to receiver link has individual carrier frequency offset （CFO） and channel impulse response （CIR） parameters. In order to reduce the computational complexity for MD optimization, a time domain CFOs and CIRs estimation algorithm over the OFDMA based wireless multimedia sensor networks （WMSN） is proposed in this paper. In this algorithm, the receiver station can decouple the signal from every node by correlation based on specially designed training sequences, so that the MD optimization problem is simplified to an 1-D optimal problem. It is proved that the multiple CFOs can be identified from the correlation result using the phase shift of the consecutive training se- quences. Based on the CFOs estimation result, the CIRs can then he estimated according to the minimum mean square error （MMSE） criterion. The theoretic analysis and simulation results show that the proposed algorithm can effectively decouple the signal from different user nodes and the bit error rate （BER） per- formance curves are close to the ideal estimation when the user number is not large.

THE NOVEL COMMUNICATION ALGORITHM AND THE THROUGHPUT ANALYSIS FOR WIRELESS SENSOR NETWORKS

Aiming at the significance of the energy controls of wireless sensor networks, an economical energy consumption algorithm for wireless communicating in Wireless Sensor Networks (WSN) is presented. Based on the algorithm, the maximal system throughput of WSN is analyzed, and the upper bound of throughput of WSN is proposed and proved. Some numerical simulations are conducted and analyzed. The conclusions include that the transmitting radius of sensor node and the parameters of the energy cost function have significant influence upon the throughput, but the monitoring region radius has little influence. For the same transmitting distance, the more the hopping of information trans- mitting, the better the throughput of WSN. On the other hand, for the energy optimization of the whole WSN, the trade-off problem between the throughput capacity and the relay nodes is proposed, and the specific expression of relay hops that minimized the energy consumptions and the maximal throughput of WSN under the specific situation is derived.

On Minimizing Delay with Probabilistic Splitting of Traffic Flow in Heterogeneous Wireless Networks

In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.

马可尼:用无线电打开即时交流的大门

同学们在人教版九年级《物理》课本第二十章学习了《电与磁》,那你知道电磁波是怎么被发现的吗？无线电又是怎样被发明的呢？一起来看看吧!