5.25 GHz CMOS cascode power amplifier for 802.11a wireless local area network

The authors investigate a 5.25 GHz highly integrated CMOS class-AB power amplifier for IEEE 802.11a wireless local area network. The proposed power amplifier is implemented with a two gain-stage structure which is followed by an off-chip output matching circuit. Moreover, transistor-level compensation techniques are employed to improve the linearity. The power amplifier is designed with an on-chip input matching circuit, whereas the output matching circuit translates the signal power from 50 to 20 V load resistance. The measured results indicate over 20% power-added efficiency, over 20 dBm output power and 28.6 dBm output IP3. All the specifications are based on 50 V input impedance at 2.4 V supply voltage.     

Triple-band wireless local area network monopole antenna

A triple-band Bluetooth (BT) and wireless local area network (WLAN) monopole antenna has been proposed based on concepts called capacitive loading/de-loading and inductive loading/de-loading. It has been demonstrated that BT and triple-band WLAN operations, including the BT 2.4 GHz (2.4-2.484 GHz), the WLAN IEEE 802.11 2.4 GHz (2.4-2.484 GHz), 5.2 GHz WLAN (5.15-5.35 GHz) and WLAN 5.8 GHz (5.725- 5.825 GHz) can be achieved by using the monopole antenna with an overall size 8.0 x 11.5 x 1.0 mm³, which is one of the most compact WLAN monopole antennas covering the three frequency bands.     

Body area network for wireless patient monitoring

Patient data monitoring is a key issue for health and disease management. The use of wireless sensors within a body area network (BAN) makes this task seamless and easy. A BAN system is presented, which allows the connectivity of a wide range of heterogeneous body sensors to a portable hub device that is connectable to external networks (IEEE 802.11, GPRS). This BAN is based on the use of Zigbee/IEEE 802.15.4 standard technology and off-the-shelf modules. It is currently being used at the European level for the detection and the prediction of the human physiological state in relation to wakefulness, fatigue, and stress applications in which users carrying out daily activities are monitored in an unobtrusive and comfortable way. Characterised by its low power consumption, low cost, and ability to connect a wide range of heterogeneous sensors, this system can substantially improve the performance of different services, especially those that are health related.     

Testbed for a scalable terabit optical local area network

The design of a fiber-optic local area network (LAN) demonstration system is described. A complete LAN system would consist of an array of 16 personal computers (PC's), where each PC has a network interface card (NIC) with a parallel fiber-optic datalink to a centralized optoelectronic switch core. The centralized core switches the data generated by 16 NIC's, up to 128 Gbit/s of bandwidth. The demonstrator is designed to scale to terabits of bandwidth by use of an emerging optoelectronic technology, i.e., integrated complementary metal-oxide semiconductor (CMOS) substrates with vertical-cavity surface-emitting laser (VCSEL) and photodetector optical input and output. A subset of the complete system was constructed and is operational. A prototype NIC card, with Motorola Optobus VCSEL transceivers for the optical datalinks, was constructed and is described. A prototype high-speed bipolar switch core, with statically configurable electrical positive-emitter coupled-logic 16 x 16 crossbar switches, CMOS field-programmable gate arrays, and Motorola Optobus transceivers, was constructed and is described. We successfully demonstrated the transmission of high-speed packetized data from one NIC card, through 10 m of parallel fiber ribbon and the centralized switch core, and back to the NIC. We summarize our experiences on the design and testing of our first demonstration system and our development toward a terabit switch core.     

An efficient local improvement operator for the multi-objective wireless sensor network deployment problem

Wireless sensor network layout, also known as sensor node deployment, is a complex NP-complete optimization task that determines most of the functioning features of a wireless sensor network. Coverage, connectivity and lifetime (handled through its opposing parameter, power consumption), are three of the most important characteristics of the service, and are taken into consideration in this article within a multi-objective approach of the problem. Leveraging on the specific properties of the wireless sensor nodes and networks, the Proximity Avoidance Coverage-preserving Operator (PACO) for local improvement is presented, described and tested. The testbed consists of a set of state-of-the-art multi-objective optimization algorithms with different configurations, and problem instances of varying size. In all the scenarios, and more specially in the algorithmic settings that already produce high performance solutions, PACO has proven to be a robust enhancement to the raw optimization technique, without requiring additional computation, that easily scales through problem complexity.     

Direct conversion RF front-end with a low-power consumption technique for 2.4 GHz ISM band

The implementation and performance measurements of RF front-end are presented. The low-power RF front-end designed in TSMC 0.18 mm process for 2.4 GHz ISM band direct conversion is presented. The proposed RF front-end is comprised of the folded mixer, fully differential low-noise amplifier (LNA) and interstage matching network. Gilbert-cell mixers using the folded technique and current reused LNA are designed for low power consumption. The folded mixers are implemented by using PMOS devices in the switching stage of mixers with a resonating inductor for low flicker noise. The proposed RF front-end consumes 7.2 mW from the 1.2 V supply and a conversion gain of 23 dB is achieved. The third-order intercept point (IIP3) is 210.5 dBm, and the proposed RF front-end has good linearity. By using PMOS devices and the folded technique, low flicker noise of 10 dB at 10 kHz is achieved, and thus the proposed RF front-end can be used in the direct conversion receiver for narrow bandwidth.     

Achieving higher throughput in ieee 802.11 wireless local area networks with burst transmission methods

As extensions in the emerging 802.11e for quality-of-service provisioning, burst transmission and the acknowledgment aggregation are the two important operations to improve the channel efficiency of IEEE 802.11-based wireless local area networks (WLANs). However, only a few works have been done on these operations, and usually assumed the networks to be operated under saturated traffic conditions and error-free channels. In practice, the assumptions may not be valid because real-time traffic with proper rate control will not saturate the networks and the channel is generally error-prone. Thus, the authors consider two new methods resulted from these operations and analyse their performance under unsaturated and error-prone WLANs, with a Markov chain model. The results show that the new methods generally have better throughput than the conventional IEEE 802.11 medium access control (MAC) in the WLANs.     

无线网络节点的均匀性度量

考虑到无线传感器网络定位精度除受节点密度和覆盖程度影响外,锚节点分布的不均匀性是一个重要影响因素,对基于近似偏差的网络节点分布均匀性度量方法进行了改进,提出了定量描述锚节点均匀程度的Gabriel图和Voronoi图相结合的均匀性测度(GVGUM)方法,GVGUM方法使用Gabriel边表征节点的疏密,使用Voronoi单元的面积表征节点控制区域的大小,比基于近似偏差的方法能更好地表征节点的均匀程度。     

基于局部网络拓扑特征的鲁棒节点定位算法

针对无线传感器网络的较大测距误差严重影响定位算法精度和鲁棒性的问题,利用节点均匀部署网络的拓扑特征,提出了一种基于局部网络拓扑特征的鲁棒节点定位算法(LFLS算法).该算法通过构建节点测距高估粗差阈值参数和测距低估粗差阈值参数,在对未知节点1跳测距数据集进行粗差识别及剔除等预处理滤波的基础上,使用高斯加权最小二乘定位算法实现节点定位.仿真结果表明,基于局部网络拓扑特征的鲁棒节点定位算法的定位精度明显优于未采用局部网络拓扑特征进行粗差预处理的加权最小二乘定位算法,其中粗差测距直接相关节点的定位精度改进尤为明显.     

The performance and efficiency of envelope elimination and restoration transmitters for future multiple-input multiple-output wireless local area networks

The inefficiency of contemporary power amplifiers (PAs), when operating in their linear region, is a major obstacle to mobile operation of wireless local area networks (WLANs) based on IEEE 802.11n. Therefore the use of more efficient envelope elimination and restoration (EER) transmitter architectures is considered. In addition to high efficiency it is also necessary to satisfy the spectral mask and achieve satisfactory link-level performance. Link-level simulations of a contemporary WLAN PA show that, at the power back-offs necessary to achieve sufficient linearity, the power added efficiency (PAE) is only ~1% for a system with four transmit antennas. In contrast, simulations of a phase feedback EER PA architecture show that it is possible to achieve an average PAE of 70%, while satisfying the spectral mask, with only a small degradation in link-level performance.     

Operating systems and network protocols for wireless sensor networks

Sensor network protocols exist to satisfy the communication needs of diverse applications, including data collection, event detection, target tracking and control. Network protocols to enable these services are constrained by the extreme resource scarcity of sensor nodes-including energy, computing, communications and storage-which must be carefully managed and multiplexed by the operating system. These challenges have led to new protocols and operating systems that are efficient in their energy consumption, careful in their computational needs and miserly in their memory footprints, all while discovering neighbours, forming networks, delivering data and correcting failures.     

用于无线传感器网络的光伏微能源系统设计

微型传感器节点通常采用能量有限的电池供电,电池的使用寿命限制了传感器节点的寿命.针对传感器网络的特征和需求,设计了光伏微能源系统,并与微型传感器节点集成,形成自供电的微系统.光伏微能源系统主要包括光伏电池、聚合物锂电池和能源管理子系统.本文阐述了光伏微能源系统的设计,并对微系统的实验测试结果进行了分析.实验结果证明,光伏微能源系统能够自行补充能量,延长传感器网络的使用寿命.     

Terabit optical local area networks for multiprocessing systems

The design of a scalable optical local area network formultiprocessing systems is described. Each workstation has aparallel-fiber-ribbon optical link to a centralized complementarymetal-oxide silicon (CMOS) switch core, implemented on a singlecompact printed circuit board (PCB). When the Motorola Optobusfiber technology is used, each workstation has a data bandwidth of 6.4Gbits/s to the core. A centralized switch core interconnecting 32workstations supports a 204-Gbit/s aggregate data bandwidth. Theswitch core is based on a conventional broadcast-and-selectarchitecture, implemented with parallel CMOS integrated circuits(IC's). The switch core scales well; by incorporation of theCMOS optoelectronic IC's with optical input-output, the electricalcore can be reduced to a single-chip optoelectronic IC with terabitcapacities. A prototype of an optoelectronic switch core has been fabricated and is described. The appeal of the architectureincludes its reliance on commercially available parallel-fibertechnology, its reliance on the well-developed markets of local areanetworks and networks of workstations, and its smooth scalability from the electrical to optical domains as technology matures.     

面向机械振动监测的无线传感器网络节点的设计

针对机械振动信号监测的特点和现有无线传感器网络节点的不足,提出了一种基于MEMS加速度传感器的无线传感器网络大容量测振节点的设计.节点采用了模块化的设计思想,主要包括AVR微控制器、可编程逻辑器件CPLD、多通道16位A/D转换器、SD卡存储器和MEMS传感器,初步解决机械振动信号采集和大容量存储的难题.通过实验验证了该设计方案的可行性.     

Two-terminal reliability analyses for a mobile ad hoc wireless network

Reliability is one of the most important performance measures for emerging technologies. For these systems, shortcomings are often overlooked in early releases as the cutting edge technology overshadows a fragile design. Currently, the proliferation of the mobile ad hoc wireless networks (MAWN) is moving from cutting edge to commodity and thus, reliable performance will be expected. Generally, ad hoc networking is applied for the flexibility and mobility it provides. As a result, military and first responders employ this network scheme and the reliability of the network becomes paramount. To ensure reliability is achieved, one must first be able to analyze and calculate the reliability of the MAWN. This work describes the unique attributes of the MAWN and how the classical analysis of network reliability, where the network configuration is known a priori, can be adjusted to model and analyze this type of network. The methods developed acknowledge the dynamic and scalable nature of the MAWN along with its absence of infrastructure. Thus, the methods rely on a modeling approach that considers the probabilistic formation of different network configurations in a MAWN. Hence, this paper proposes reliability analysis methods that consider the effect of node mobility and the continuous changes in the network's connectivity.     

A 60 GHz retrodirective array system with efficient power management for wireless multimedia sensor server applications

A 60 GHz retrodirective array system with efficient power management for wireless multimedia sensor server applications is proposed. The system consists of three sections: a retrodirective array, a local oscillator (LO) and a power management system. The proposed system is able to efficiently control battery power by turning off when it is not in use. In particular, the power management circuit controls the power of the LO by a rectenna for efficient battery operation. Although there is no interrogating signal, the system is in a sleeping mode where extremely low power consumption occurs. When the system is interrogated by an RF signal, the system is awaken and starts consuming full power. When the received power density is larger than 0.013 mW/cm ^{, the system turns on and starts working as a retrodirective array. Furthermore, the proposed system can avoid the use of an expensive LO by employing a fourth subharmonic mixer. Experimental data are used to verify the proposed idea.}     

面向机械振动信号采集的无线传感器网络节点设计

针对现有无线传感器网络节点的不足和机械振动信号采集的需求,设计了一种可实现机械振动信号采集和片上处理的无线传感器网络节点。该节点采用MEMS加速度传感器拾取振动信号,以低功耗FPGA芯片为控制核心,采用了可编程片上系统技术,将数据采集、存储、处理和传输等控制功能模块集成到单个FPGA芯片中。本文着重介绍了节点数据采集、存储和传输部分的硬件电路和控制逻辑设计,对比实验表明该节点能有效采集和监测机械振动信号。     

一种支持多跳无线网QoS业务的MAC层接入协议

提供一定的服务质量保证(QoS)是多跳无线网络研究中的热点和难点,本文基于TDMA/FDMA机制提出了一种支持多信道多跳无线网络话音级QoS业务的MAC层接入协议RA/SRN。该协议以RBRP协议思想为基础,针对无线信道中隐藏、暴露终端造成的信道利用率降低和分组冲突问题进行改进设计,减小了信道冲突概率,提高了信道利用率,降低了信道接入时延,为网络层QoS路由协议提供了良好的支持。     

Bridge Sampling Methods for Admittance Measurements from 500 kHz to 5 GHz

A two-channel time-domain sampler with common time base is used to compare voltages in coaxial lines driven by matched ratio arms from a pulse or sine-wave generator and terminated by unknown and reference admittances. Linear circuit analysis shows that the unknown can be determined from the bridge unbalance sampler outputs by simple calibrations of three frequency-dependent parameters. Design and uses of cells for dielectric measurements and reference terminations are described. Procedures for and results of test measurements are presented for time-domain measurements using a symmetrical power divider as ratio arms and for frequency-domain measurements using a 5O-? power splitter and 5-pF capacitative ratio arms.     

无线芯片域网络自适应多址调制方案的研究

为了解决多芯片构成的无线芯片域网络（WCAN）中的多用户网络通信问题,进行了WCAN自适应多址调制方案研究。结合WCAN的具体应用场景,首先研究了芯片内/间的无线信道特性,分析了多址跳时脉冲位置调制（TH PPM）技术的干扰噪声源及BER性能;然后在此基础上提出了自适应多址TH PPM方案,设计了智能化的传输机制,以对WCAN中芯片内/间的功率、误码率、传输速率进行权衡;最后通过仿真给出了其性能分析。研究结果显示,该方案在确保芯片内/间无线互连QoS可靠的同时,能够合理地分配系统资源,显著提高系统的传输性能,有效解决固定多址调制技术存在资源分配不均,系统性能不稳定的缺陷。