Design and investigations on a compact,UWB, monopole antenna with reconfigurable band notches for 5.2/5.8 GHz WLAN and 5.5 GHz Wi‐MAX bands

This article represents a microstrip line–fed novel circular monopole antenna with ultra‐wideband (UWB) characteristics. The compact antenna provides reconfigurable notches at WLAN (5.2/5.8 GHz) and Wi‐MAX (5.5 GHz) frequency bands. The band rejection is achieved by etching an open‐ended L‐shaped slot in the ground plane, which effectively mitigates the interference between WLAN, Wi‐MAX, and UWB systems with an effective patch area of 36.26%. The proposed antenna operates from 3.05 to 12.11 GHz with VSWR 2 except at stopband (3.89‐5.93 GHz) to filter the WLAN and Wi‐MAX signals. The simulated return loss, gain, and radiation pattern of the proposed antenna has been experimentally verified with the fabricated one which holds a good agreement.     

Annular‐ring slot antenna designs with circular polarization radiation

The design of a microstrip‐fed annular‐ring slot antenna (ARSA) with circular polarization (CP) radiation is initially studied. To obtain CP radiation with broad 3‐dB axial ratio (AR) bandwidth that can cover the WiMAX 2.3 GHz (2305–2320 MHz, 2345–2360 MHz) and WLAN 2.4 GHz (2400–2480 MHz) bands, a novel technique of extending an inverted L‐shaped slot from the bottom section of the annular‐ring is proposed. To suppress the harmonic modes induced by the CP ARSA, the technique of integrating a defected ground structure into the annular‐ring slot is further introduced. From the measured results, 10‐dB impedance bandwidth and 3‐dB AR bandwidth of 44.86 and 9.68% were achieved by the proposed harmonic suppressed CP ARSA. Furthermore, average gain and radiation efficiency of ～4.7 dBic and 71%, respectively, were also exhibited across the bands of interest. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:337–345, 2015.     

A narrow-frame antenna for WWAN/LTE/WiMAX/WLAN mobile phones

In this paper, we present a novel narrow-frame antenna with a size of 75 × 8 × 5.8 mm³ for 5.7 in. mobile phones. The antenna mainly consists of a monopole with four branches that are coupled to a two-branch grounded strip. Our antenna is able to cover more bands than other narrow-frame antennas by excitation of several resonant modes. The improved range of the antenna covers the following eleven bands: LTE700, GSM850, GSM900, DCS, PCS, UMTS, LTE2300, LTE2500, LTE3400 (3400–3800 MHz)/WiMAX3.5 GHz (3400–3650 MHz), WLAN5.2 GHz (5150–5350 MHz) and WLAN5.8 GHz (5725–5875 MHz). Another advantage of the proposed antenna is that it does not need any lumped element to match the antenna. The working principles of the proposed antenna are thoroughly studied. A prototype of the proposed antenna is fabricated and measured, with the results in good agreement with the simulation results.     

A low-distortion multi-bit sigma–delta ADC with mismatch-shaping DACs for WLAN applications

A low-distortion feed-forward MASH2_4b-2_4b sigma–delta analog-to-digital converter (ADC) for wireless local area network (WLAN) applications was presented. The converter exhibits improved performances than the ADCs which have been presented to date by adding a feedback factor in the second stage and employing a 2nd-order noise-shaping dynamic element matching (DEM) scheme. The feedback factor induces a zero in the noise transfer function (NTF) and therefore improves the in-band signal to noise and distortion ratio (SNDR) of the modulator. The mismatch-shaping DEM was introduced and applied to the 4-bit DACs in this paper to improve the resolution and linearity of the ADC. Fabricated in a 0.18 μm CMOS process with single 1.8 V supply voltage, the converter achieves a peak SNDR of 85.4 dB over a 10 MHz bandwidth which implies an effective number of bits (ENOB) of 13.90-bit. The spurious free dynamic range (SFDR) is –94 dB for a 1.25 MHz@–6dBFS input signal at 160 MHz sampling frequency. The occupied area is 0.44 mm² and dissipation power 23.4 mW.     

农村无线宽带覆盖方式探讨

在国家“宽带中国”的战略要求下,针对有线宽带难以到达的分散农村区域,通过理论分析和试点验证论述了WLAN和GSM-Hi两种无线宽带模式的覆盖效果,并结合多地试点推行情况,对两种农村无线宽带模式从技术、业务和效益进行了评估和对比,最后给出了农村无线宽带建设建议。     

在WLAN网络下构建P2P僵尸网络处理机制的研究

僵尸网络日益猖獗。其危害从终端用户到国家,甚至军方与政府也不断遭受着僵尸网络的攻击。越来越多与僵尸网络密切相关的词汇进入人们的视线：恶意软件、身份财务信息盗取、恶意广告弹窗、垃圾邮件、网络钓鱼。WLAN作为公共使用的网络环境,能够从源头入手处理僵尸网络获得良好效果,因此本文从网络结构开始,对时下最难防护与处理的P2P网络进行分析,并提供在WLAN环境下实际可行的处理机制。     

Asymmetric CPW-fed SRR patch antenna for WLAN/WiMAX applications

In this paper, a compact asymmetric coplanar waveguide (CPW) feed with split-ring resonator (SRR) is proposed to resonate at dual-band operations for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The asymmetric CPW-fed SRR patch (ACSP) antenna consists of a meander line, square-shaped split ring, and CPW ground plane. The proposed ACSP antenna resonates at two operating frequencies, namely, 2.48 GHz (2.4–2.74 GHz) and 3.49 GHz (3.25–3.64 GHz) with reflection coefficients (S₁₁) of −16.65 dB and −32.67 dB, respectively. The measured results agree closely with the simulation results of the proposed antenna.     

Greening campus WLANs: Energy-relevant usage and mobility patterns

The past years have witnessed a significant increase in the number of WLANs deployed in most of the enterprises, campuses and public areas to provide high-speed Internet connectivity. These WLANs typically consist of APs densely installed to assure enough capacity to meet users demand during the peak period of activity. At the same time, it translates into a serious energy wastage during low-utilization periods, when capacity is not needed at the APs. To reduce this wastage, many proposed solutions consist of adapting the active capacity to the actual needs, introducing switching strategies able to turn on and off the APs. The effectiveness and potential benefit of these strategies strongly depend on the user behavior and traffic patterns.In this paper, we focus our analysis on the real usage characteristics of a dense WLAN (such as users’ behavior and users’ mobility patterns) in a university campus and evaluate potential energy savings and benefits achievable when introducing AP on/off switching strategies. We discuss different strategies, in which decisions are based either on: (1) historical behavior in the campus, or on (2) current AP utilization. In addition, considering the large overlapping coverage available in dense WLANs, we investigate users’ mobility patterns to derive further improvements to AP switching strategies. The results show that, due to the repetitiveness of users’ patterns and large differences in WLAN usage between days and nights, as well as between weekdays and weekends, large savings of up to 40% can be easily achieved. Moreover, by fine-tuning the strategies in different areas of the campus, additional savings are possible. The deployment of these strategies leads to energy saving and, as a practical consequence, to a remarkable reduction of electricity costs.     

银行系统WLAN部署方案

本文对银行系统WLAN部署方案进行了深入研究,根据银行系统营业网点场景和业务特点,结合业务模型和计算公式,分析了该场景下的无线覆盖、业务承载、业务安全、认证及运营等方案,旨在指导银行系统WLAN部署实际工程规划和建设.