DIFFS: A Low Power,Multi-Mode,Multi-Standard Flexible Digital Front-End for Sensing in Future Cognitive Radios

Cognitive Radios provide communication devices with the flexibility to adjust to varying network and channel conditions. For this to be fully realizable spectrum sensing and signal reception have to happen simultaneously and have to require as little power as necessary to function in handheld devices. This work argues for the need of flexible digital-front ends as indispensable building block, able to perform control operations over the analog front-end and to perform sensing and synchronization procedures without the need of power consuming baseband processors. A low power, reconfigurable digital front-end that supports concurrent synchronization and sensing of high-throughput wireless standards is presented. Multiple operating modes, useful for various communication standards, such as LTE, WLAN and DVB-T are introduced and analyzed. The digital front-end has been implemented in 65 nm CMOS technology resulting in a chip area of 6.4 mm2. Fine grain clock gating allows synchronization at 4 mW and sensing at 7 mW power consumption. Experiments in combination with a reconfigurable analog front-end show that a 1.7 GHz wide frequency band can be scanned based on energy detection in an exceptionally low time window of 10 ms while consuming 13 mW power and that coarse energy detection can speed-up the sensing process. Furthermore, advanced feature detection for DVB-T and LTE signals is implemented and measured. Low power sensing of DVB-T signals shows that a target false alarm rate of 10 % and a detection probability of 90 % at an input power level of?106 dBm while consuming 7 mW power are possible. Synchronization-aided FFT-based LTE sensing with leakage cancellation was experimentally validated for various bandwidths showing a power consumption of maximum 20 mW.     

Cochannel and adjacent channel interference in actual terrestrial TV scenarios - part II: MATV systems laboratory tests

For pt.I, see Sanchez, M.G. et al., ibid., p.111-15. The results of an extensive study on analog PAL signals interfered with by digital DVB-T signals are presented. The study covers a theoretical evaluation of the interference problems, field and laboratory measurements and a national survey among TV installation companies. Field measurements are reported in part I. These measurements explain the origin of cochannel and some of the adjacent channel interference problems. However, interference was reported in areas where the field measurements showed that the protection ratios for PAL signals interfered with by DVB-T adjacent channel signals were met. As these reports came from multistorey buildings with master antenna TV (MATV) installations, the study was extended to analyze the role of these installations in the interference problems. Part of the interference problems are due to the MATV system amplifiers which are unable to cope with adjacent channel DVB-T signals. The nonlinear amplifiers give rise to intermodulation problems. The ITU-R recommendations (see ITU-R BT.1368, 2000) recognize that such nonlinear amplifiers could be a source of problems and that higher protection ratios may be needed, but no value is given for the increase. Our laboratory tests of commercial amplifiers found that an increase in the protection ratios of between 12 to 16 dB is needed to avoid a significant degradation of the PAL TV signal in the amplifiers. It has also been found that most of the interference situations are not due to the interfering signal being a DVB-T format, but that any significant signal amplitude in the passband of the filter causes interference. Therefore, MATV system distribution needs planning factors associated with the distribution of any signals near the main signal. The results are presented of a survey conducted among companies who install communal telecommunication infrastructures in Spain.     

DVB-T中多速率DDC的设计与FPGA实现

针对DVB-T标准ETSI EN 300 744 V1.5.1,设计了可用于DVB-T接收整机的多速率DDC模块,并在FPGA中仿真实现.在复用数字振荡混频模块的基础上,根据输入信号的不同带宽(6M/8MHz)选择不同的抽取滤波器组完成抽取因子为3或4的多速率处理任务,利用两级半带滤波器(HBF)级联完成4倍抽取滤波,单级奈奎斯特滤波器完成3倍抽取滤波.     

Analysis of the DVB-T Signal Variation for Indoor Portable Reception

A study of DVB-T (Digital Video Broadcasting - Terrestrial) signal variability for indoor reception environments is stated in this paper. A commercial signal was measured and analyzed in order to obtain C/N threshold values that account time and space fluctuations. In this way, results increase the accuracy of the values provided by the ETSI (European Telecommunications Standards Institute) standard and other studies that assume static propagation channels. On the other hand, the fading influence due to people walking near the reception antenna has been proved as critical for correct reception. Characterization of this effect has been made in terms of its depth and duration. The results obtained results improve DVB-T network planning and could be also relevant for other technologies sharing similar frequencies and bandwidths.      

Cochannel and adjacent channel interference in actual terrestrial TV scenarios - part I: field measurements

The results of an extensive study on analog PAL signals interfered with by digital DVB-T signals are presented. The research work covers field measurements, laboratory measurements, a theoretical evaluation of the interference problems and a national survey among TV installation companies. The main objective is the identification and explanation of the interference problems reported since the start of DVB-T broadcasting. The report is organized in two parts. This paper, part I, describes the field measurements, whereas the laboratory measurements and the poll results are described in part II (see Acuna, M.A. et al., ibid., p.116-22). It has been found that the frequency plan is part of the source of the interference problems, particularly in the case of cochannel interference. Another source of problems is use of different radiation elements at the same site for broadcasting DVB-T and analog TV signals. As stated in ETSI documents (see ETSI TR-101-190, 1997), the use of a different antennas for DVB-T may require ERP restrictions to protect existing analog services. The power ratios between digital and analog TV signals at the broadcasting station should be adjusted to meet the protection ratios everywhere within the coverage area. The required power ratio depends on the specific shape of the radiation pattern of each antenna. Finally, it has been found that an important part of the interference problems is due to the amplifiers of the master antenna television (MATV) systems in buildings. The results of the laboratory tests and the theoretical analysis conducted to determine the increment of the protection ratio required by the presence of these amplifiers are presented in part II.     

L-band DAB Eureka 147 field trials and coverage measurements in urban areas

This paper presents the field trials and the coverage measurements carried out in urban areas in the first experimental terrestrial DAB (T-DAB) network at L-band in Spain. The trials focused on obtaining the parameters that characterize the propagation channel for different urban environments. The results are discussed taking into consideration recommended parameters and values given by international organizations (ITU-R, ETSI) as well as the ones obtained in former experimental networks worldwide.     

Rainfall Dynamics Over Two Indian Tropical Stations for Radio Communication

The influence of rainfall on radio wave propagation at frequencies above 10 GHz is crucial over ground to space radio links, especially in tropical regions because of the high intensity rainfall. This often makes direct-to-home; very small aperture terminal systems operating at these frequencies to be subjected to many fade occurrences due to heavy rain. In addition to annual and worst month’s cumulative statistics, dynamic characteristics of seasonal and diurnal variations, together with average event length and separation over the day are needed to give the detailed insights for system design. This paper presents the characteristics of rain distribution based on 5-year rainfall data over two locations in India. Rain intensities for the average year and the average worst months, and monthly and diurnal dynamic characteristics of rain events were obtained. The resulting rain intensities are also compared with the relevant ITU-R recommendations. These results are useful to estimate signal outages in a year over the region and for proper planning of radio-communication in the location.     

Terrestrial DVB (DVB-T): A Broadcast Technology for Stationary Portable and Mobile Use

Digital video broadcasting-terrestrial (DVB-T) is the name of the terrestrial transmission system which was developed by the DVB Project. DVB-T is in operation in many countries around the world. This paper analyzes the features of the system. It describes its capabilities with a special emphasis on mobile reception and looks at the introduction of DVB-T in Germany using the launch of DVB-T in this country as a case study. In order to analyze how an MPEG transport stream at the input of a DVB-T modulator is turned into a DVB-T signal, we consider the channel coding and modulation used. Then we look at various aspects of the system performance. The next section deals with mobile reception. Network planning issues, antenna diversity concepts for mobile receivers, and handover procedures will be considered. Finally, the introduction of DVB-T in Germany is presented as a case study. In contrast to various other countries Germany decided to offer DVB-T as a means of providing the "anywhere TV" experience. This implies that DVB-T signals can be received with mobile and portable receivers. In regions with DVB-T coverage analogue terrestrial TV services were discontinued just a few months after the launch of DVB-T.     

DVB-T BER measurements in the presence of adjacent channel andco-channel analogue television interference

This paper presents some laboratory tests carried out to measure the BER degradation caused by an analogue PAL-G television interference on a COFDM 8 K digital television signal. The tests made include co-channel and both upper and lower adjacent channel interference situations. Previously, the ITU-R has presented some protection ratios to be sought when planning DVB-T networks. The results of the work presented here include a wider range of power ratios and their effect on the BER rather than the limit protection values. The new digital services will share the same frequency bands as the conventional analogue television so the exact characterization of mutual interference is a major concern of broadcasters during the transition period when both systems have to co-exist     

基于抛物方程的3.6 GHz典型应用场景传播特性分析

文中利用抛物方程(parabolic equation, PE)方法,从纵向剖面和区域覆盖两个维度,对3.6 GHz频点在都市、郊区、乡村三种典型场景下的传播特性进行分析,并将仿真结果与ITU-R P.1546方法仿真结果进行对比分析. 分析结果表明:PE方法能够描述信号传输直射、绕射、反射波束,与各场景传播特点相匹配,具有较好的适用性;PE方法与ITU-R P.1546方法变化趋势有着较好的一致性;PE方法结合地形的不规则变化,覆盖仿真结果更为细致,体现出“确定性预测”的优势. 本文研究成果可为5G毫米波典型应用场景传播特性预测提供支撑,对5G通信系统设备部署及网络布局具有重要的工程意义.     

PAPR reduction in mobile WiMAX: a novel DST precoding based random interleaved OFDMA uplink system

Mobile WiMAX is a 3rd generation broadband wireless technology that enables the convergence of mobile and fixed broadband networks through a wide area radio-access. Since January 2007, the IEEE 802.16 working group has been developing a new amendment the IEEE 802.16 standard i.e. IEEE 802.16 m as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for 4G systems. The mobile WiMAX air interface adopts orthogonal frequency division multiple access (OFDMA) as multiple access technique for its uplink and downlink to improve signal performance affected by multipath distortion. All OFDMA based networks, including mobile WiMAX, experience the problem of high peak-to-average power ratio (PAPR). This paper presents a discrete-sine-transform precoding technique based random-interleaved OFDMA (RI-OFDMA) uplink system for PAPR reduction in mobile WiMAX. The PAPR of proposed system is analyzed with root-raised-cosine pulse shaping filter to keep out of band radiation low and to fulfill the spectrum mask requirements. Simulation results show that, the proposed system has low PAPR compared to the Hadamard transform precoded RI-OFDMA uplink systems and the conventional RI-OFDMA uplink systems.     

An Improved Wavelet Denoising Algorithm for Wideband Radar Targets Detection

A novel denoising technique based on wavelet transform modulus maxima (WTMM) is proposed for processing wideband radar spread targets detection signal in a clutter environment. Combined with the improved adaptive Bayes–Shrink threshold and Lipschitz exponents, we propose the path pruned approach at each scale terms as full-scale to split the signal. The estimation of WTMM over each scale has been optimized, thus, the signal and the noise can be split effectively. Additionally, to improve the computational efficiency, a fast method based on a piecewise polynomial interpolation algorithm is applied for the split signal reconstruction. Statistical results are quite promising and perform better than the conventional denoising algorithms: compared with the classical WTMM algorithm, the improved WTMM full-scale denoising algorithm not only increases the signal-to-noise (SNR) ratio by over 10 % but also reduces the processing time by 88 % and reduces the root-mean-square-error (RMSE) by over 35 %. More generally, the proposed algorithm has better performance than that of several typical algorithms in its denoising quality and singularity detection.     

Precision enhancement in ETSI‐Hata propagation model tuning using experimental data in a dense urban area

In this paper an enhanced ETSI‐Hata propagation model tuning is presented. The three‐dimensional (3D) digital terrain map (DTM) was included in the simulation process. For the enhancement of the model tuning process and precision verification of ETSI‐Hata model, the real 3D map of the buildings of the simulated area was incorporated over the DTM. Multiple knife edge diffraction method and the antenna effective height method were used to calculate the diffraction loss. This method was applied for a real urban scenario. For every sector in the coverage area, a tuned model was exploited. Using a genetic algorithm, frequency planning for the entire urban area was performed, which resulted in an improvement in the quality of service. Copyright © 2009 John Wiley & Sons, Ltd.     

A Coverage-Based Scheduling Algorithm for WSNs

Node scheduling in wireless sensor networks (WSNs) plays a vital role in conserving energy and lengthening the lifetime of networks, which are considered as prime design challenges. In large-scaled WSNs, especially where sensor nodes are deployed randomly, 100 % coverage is not possible all the times. Additionally, several types of applications of WSNs do not require 100 % coverage. Following these facts, in this paper, we propose a coverage based node scheduling algorithm. The algorithm shows that by sacrificing a little amount of coverage, a huge amount of energy can be saved. This, in turns, helps to increase the lifetime of the network. We provide mathematical analysis, which verifies the correctness of the proposed algorithm. The proposed algorithm ensures balanced energy consumption over the sensor networks. Moreover, simulation results demonstrate that the proposed algorithm almost doubles the lifetime of a wireless sensor network by sacrificing only 5–8 % of coverage.     

三种宽色域视频信号兼容传输处理方案

宽色域数字电视标准ITU-R BT.1361限定伽马校正前的基色信号幅度范围为-0.25-+1.33,笔者用遍历法计算了其相应的最宽可感知色域,导出了对应的新三基色,证明其色域覆盖率达60.65%.为使该色域信号能在现行ITU-R BT.709常规色域视频系统兼容传输,依据IEC61966-2-4许用量化级范围,提出了...     

HIPERACCESS: an access system for the information age

This paper introduces the ETSI Project on Broadband Radio Access Networks (EP-BRAN). BRAN systems will be used for local-area applications with limited mobility (HIPERLAN/2); fixed access with area coverage in urban and rural areas (HIPERACCESS); and short-range high-speed point-to-point links (HIPERLINK). They will support transport of either IP or ATM protocols, supporting managed quality of service. Such systems are needed to provide access to the future broadband core networks supporting multimedia applications. The paper focuses on HIPERACCESS. It addresses the motivation and market demand for broadband radio access networks; the objectives and scope of the Project; the operational and technical requirements; the types of networks to be standardised; the scope of the standards; and the issue of spectrum     

Mobile broadcasting of DVB-T signals

Utilising the DVB-T specification fully will allow broadcasters choose from different modulation formats including QPSK for transmission of MPEG-2 signals over difficult media. Very rugged signals with excellent power and echo performance can be selected with DVB-T modems for contribution circuits. This paper details preliminary results of the transmission of a 6 Mbit/sec MPEG-2 signal from a mobile vehicle to a main station on an upper adjacent channel to existing PAL I broadcasts. It shows that it is possible to use DVB-T signals for contributions from mobile transmitters without signal degradation     

Design of a 300 GHz Band TWT with a Folded Waveguide Fabricated by Microelectromechanical Systems

For future broadband wireless links, we have designed a 300 GHz band traveling wave tube (TWT) with a folded waveguide fabricated by microelectromechanical systems (MEMS). The TWT operates at a beam voltage of 12 kV and a beam current of 8.3 mA. The classical large signal simulation code predicts the output power greater than 1 W and gain larger than 20 dB over the bandwidth from 280 to 300 GHz.     

基于ITU-R P.1546模型的场强预测软件设计与实现

本文介绍了基于ITU-R P.1546传播模型、在GIS平台上实现本地化广播电视信号场强预测的软件设计与实现,重点介绍了软件设计思路和一些关键算法,并简要分析了预测误差。     

Microwave and Millimeter Wave Characteristics and Attenuation of Clouds over some Malaysian Equatorial Stations

Based on radar range height indicator (RHI) measurements, cloud characteristics in relation to radiowave propagation over three locations in different geographical region in western Malaysia have been presented. It is seen that low cloud occurrence over these locations are quite significant. Cloud attenuation and noise temperature can result in serious degradation of telecommunication link performances. This paper presents cloud coverage in different months, 0°C isotherm height and cloud attenuation results at 12 GHz, 20 GHz, 36 GHz, 50 GHz, 70 GHz and 100 GHz over measurement site. The low level cloud over the measurement sites has been found to occur for many days and nights and particularly in the months of April to May and October to December. Such results are useful for satellite communication and remote sensing application in Malaysia.