基于单片机STC89C52的无线可见光发射机

白光LED在提供室内照明的同时可被用作通信光源进而有望实现室内无线高速数据接入,并有望成为下一代高速无线通信的模式。利用KEIL软件实现了基于单片机STC89C52的无线可见光发射机的设计,采用脉冲位置调制(PPM)编码方式对数据进行了调制编码,并通过电路搭建和实验测试验证了该系统的可行性。     

基于DMT/QAM和STBC的室内MIMO光无线通信

针对室内漫射光无线通信问题,提出一种采用离散多音/正交幅度调制和空时块编码的多输入多输出(MIMO)光无线通信技术.基于离散多音/正交幅度调制技术,并通过考虑室内全光无线信道的脉冲响应和其噪声特性,建立起室内红外光无线链路的信道模型;再采用空时块编码技术,提出一种实现室内漫射光无线通信的MIMO无线通信系统,并通过分析...     

扩频技术在室内无线通信网中的应用

本文主要介绍了扩频技术在室内无线通信网中应用的一些特点,并简介了国外采用DPSK调制的室内扩频终端的设计与实验结果。最后,建议研究小型室内扩频无线通信网。     

基于微波光子六倍频的光载无线通信系统

构建了基于微波光子倍频的光载无线传输系统。基于偏振调制器实现了六倍频光毫米波产生,利用马赫增德尔调制器实现了QAM信号调制并进行光载无线传输,测试了41.5GHz QAM信号调制和10km光载无线传输光纤传输之后的QAM信号星座图。该系统实现了远距离音视频或高清数字信号传输。     

智能型自适应电源电压匹配减小能量消耗

无线传输网络以一种惊人的速度把世界互联并伸展到每个角落。在新型的调制机制下，使用较少的带宽就可以完成大量的数据传输。下一代的无线传输网络有望在世界的每个角落都实现高速的数据传输。伴随着高速基础网络的建成，人们势必将大量的使用无线通讯设备，这对便携式设备的性能就会有     

LMDS中QPSK调制技术的DSPs实现

对宽带无线接入方式LMDS中采用的调制方式进行了讨论,并对其中的QPSK调制解调提出了DSP实现的思路,给出了具体的实现方案。     

无线激光DH-PIM室内通信系统性能分析

研究了加性高斯白噪声和多径码间串扰下采用双头脉冲间隔调制(DH-PIM)的无线激光室内通信系统的性能,对DH-PIM系统的符号结构、带宽、差错率特性等方面进行了分析,并与OOK,PPM和DPIM调制方式做了比较。     

基于AT89S52型单片机的红外无线PPM发射机设计

脉冲位置调制(PPM)具有功率利用率高的优点,在室内红外无线局域网中得到广泛的应用。利用AT89S52型单片机和编程软件Visual C++设计了一种基于计算机串口的红外无线PPM发射机,介绍其硬件电路原理及计算机和单片机的软件设计方法。实现了PPM光脉冲的发送。     

红外无线传输在以太网(Ethernet)中的应用

在本文中设计了一种应用于以太网的点对点红外无线传输方案,将室内以太网的传输媒质从有线的铜缆双绞线转换为红外光线,来实现有效的无线数据传输.通过编解码芯片,将以太网的曼彻斯特编码转换成适于红外传输的脉冲位置调制(4PPM)编码,同时将以太网帧格式在物理层上进行处理,能够实现计算机间的兼容于以太网的红外无线(Ethernet-over-IrDA)空间数据传输.     

高码率无线红外室内传输系统的通信性能

讨论仿真室内的红外漫射通信系统,并观测在提高系统传输码率情况下无线红外室内通信系统的性能。系统使用NRZ的OOK调制,在室内环境下,采用漫反射传输会导致多径效应,而多径传输又必然会带来码间干扰,因此采用均衡器来减弱码间干扰对系统性能的影响。仿真结果显示高码率无线红外室内通信的可行性。     

Line of sight model for visible light communication using Lambertian radiation pattern of LED

This paper illustrates line of sight model for visible light source and a photodiode in wireless communication. Light‐emitting diodes (LEDs) are predominantly used everywhere like in houses and factories as light source due to development in technology of light sources. Haitz's law predicts an exponential rise in light output and efficiency of LEDs over a period of time. Light‐emitting diodes are having an average life of 50 000 hours with efficiency of 140 lm/W. Light‐emitting diode light sources are used for an eco‐friendly world due to its advantages over conventional wireless communication systems. For communication purpose in the visible light range, the LED and photodiode are used. A visible light communication system with LED as the transmitter and photodiode as the receiver is simulated in MATLAB for line of sight and analyzed using a Lambertian radiation pattern with a different mode number, field of view, and half power angle.     

A real-time VLC to UART protocol conversion system

A real-time visible light communication(VLC) to universal asynchronous receiver/transmitter(UART) conversion system is made up of a transmitter with a light emitting diode(LED) and a receiver with a photodiode(PD), by which a VLC system is connected to traditional communication modes, and the data are transferred by wireless visible light. UART packets are converted to light packets by the modulation of a 10 k Hz on-off-keying(OOK) light signal, and the data losses in the transportation are avoided by the protection of a data buffer mechanism. The experimental results reveal that the real-time VLC to UART conversion system can provide a real-time VLC transmission way for two UART devices in not less than 10 m at a baud rate not less than 19 200 Bd with stable ambient lighting at the same time.     

基于VLC的无线导览系统的设计和实现

提出了一种基于可见光通信技术的新型无线导览系统。在需要安装导览系统的地方对LED照明系统进行合适的改造,使LED发射带有识别码的可见光。当带有光电二极管的终端进入光照范围时,直接接受识别码,并经过跨阻放大器、滤波电路、电平判决器等电路处理后生成数字信号发送给后级微处理器,再通过解码、识别码比对等处理实现目标定位和无线导览的功能。利用FPGA开发套件及可见光发射机、接收机搭建了一个采用Manchester编解码和OOK调制方式的最简无线导览系统,并通过测试验证了系统的可行性。     

LED可见光模拟通信实验系统的设计

基于可见光通信原理设计了LED可见光模拟通信实验系统,该系统实现了短距离无线传输模拟信号。系统包括三个主要模块,分别为电源、发射端、接收端。实验系统的发射端采用大功率10W LED灯作为信号源,接收端采用高精度TDA2030音频专用功率放大器和20000HZ低通滤波器,用以提升该实验系统的传输距离和效果,经测试该系统可传输300—15000HZ的模拟信号,传输距离可达5m以上,接收到的信号强度大且无明显失真。     

A low power consumption CMOS differential-ring VCO for a wireless sensor

This paper describes a new three-stage voltage controlled ring oscillator (VCO) based on 0.35???m standard CMOS technology. The VCO was designed for a transmitter operating in the 863?C870?MHz European band for wireless sensor applications. The transmitter is designed for binary frequency-shift keying (BFSK) modulation, communicating a maximum data rate of 20?kb/s. In addition to the VCO, the transmitter combines a BFSK modulator, an up conversion mixer, a power amplifier and an 863?C870?MHz band pass filter. The modulator uses the frequency hopping spread spectrum and it is intended for short range wireless applications, such as wireless sensor networks. The oscillation frequency of the VCO is controlled by a voltage V_CTRL. Simulation results of the fully differential VCO with positive feedback show that the estimated power consumption, at desired oscillation frequency and under a supply voltage of 3.3?V, is only 7.48?mW. The proposed VCO exhibits a phase noise lower than ?126?dBc/Hz at 10?MHz offset frequency.     

Closed-loop architecture and protocols for rapid dynamic spreading gain adaptation in CDMA networks

We present a closed-loop architecture and protocols for rapid dynamic spreading gain adaptation and fast feedback between a transmitter and a receiver communicating with each other in CDMA networks. These protocols and architecture do not require the transfer of an explicit control message indicating the change of CDMA spreading gain from transmitter to receiver. Also, with these protocols, the transmitter can change the spreading gain symbol-by-symbol as opposed to frame-by-frame, and feedback information (e.g., the fast-varying channel condition) can be exchanged almost as frequently as the symbol rate. Thus, adaptation to the time-varying channel conditions of wireless networks and/or to the rate variation of traffic can be much faster than is possible with the existing frame-by-frame approach.     

Transmitter diversity for OFDM systems and its impact on high-ratedata wireless networks

Transmitter diversity and down-link beamforming can be used in high-rate data wireless networks with orthogonal frequency division multiplexing (OFDM) for capacity improvement. We compare the performance of delay, permutation and space-time coding transmitter diversity for high-rate packet data wireless networks using OFDM modulation. For these systems, relatively high block error rates, such as 10%, are acceptable assuming the use of effective automatic retransmission request (ARQ). As an alternative, we also consider using the same number of transmitter antennas for down-link beamforming as we consider for transmitter diversity. The investigation indicates that delay transmitter diversity with quaternary phase-shift keying (QPSK) modulation and adaptive antenna arrays provides a good quality of service (QoS) with low retransmission probability, while space-time coding transmitter diversity provides high peak data rates. Down-link beamforming together with adaptive antenna arrays, however, provides a higher capacity than transmitter diversity for typical mobile environments     

Wireless smart sensor with small spiral antenna on Si-substrate

This paper presents a wireless smart sensor (WSS) with a thermoelectric sensor, a wireless transmitter and a small spiral antenna on a single package. To transmit a sensor signal, the wireless transmitter was designed to consist of an amplifier, a modulator, an oscillator, a buffer stage and an antenna. The wireless transmitter used dual pulse position modulation for low-power transmission. The fabricated transmitter has a sampling frequency of 2.6 kHz and an output carrier wave frequency of 300 MHz band due to the higher far field radiation of the transmitted signals from inside the body. The small size spiral antenna on the chip was fabricated for the transmission of carrier waves. The antenna has a bandwidth of 270-360 MHz for VSWR<2 and a gain of −40 dBi. The fabricated sensor, transmitter and spiral antenna were packaged with bond-wire on a single package. The WSS consumed a power of about 16.9 mW at the supply power of 5 V. The electric field strength of the WSS was measured to be 64.6 dB μV/m at a distance of 3 m. The wireless operation of the fabricated WSS was confirmed by demonstrating that the sensor signal was modulated by the transmitter and that the modulated sensor data was transmitted through the small size spiral antenna.     

基于无线可见光通信的双向语音对讲系统

设计并实现了基于无线可见光通信(VLC)的双向语 音对讲系统。上下行链路均使用普通的1W发光二极管(LED)手电筒作为发射端光源, 同时实现语音传输和照明功能。系统采用开关键控-非归零码(OOK-NRZ)调制方式,在测 试LED的光电特性后,设计了LED 驱动电路和接收电路;使用单片机控制音频编解码芯片实现语音信号的采集、处理和传输, 通过异步收发传输接口(UART) 进行数据传输,实现了最远通信距离为40m、最高传输速率为2.5Mbit/s的全双工实时语音 对讲。本文系统实现复杂度低、成 本低和功耗小,并可应用于其他数据传输场合,具有良好的实用性和广泛的适用性。