Interference Analysis of TV-Band Whitespace

Cognitive radio (CR) has been suggested as a method for promoting more efficient spectrum usage through the principles of spectrum sensing and dynamic spectrum management. The IEEE 802.22 working group in particular is developing a wireless regional-area network (WRAN) standard that will employ unlicensed CR devices operating on a noninterfering basis in the commercial broadcast television (TV) bands. Before such TV-band CR networks can be deployed, the maximum levels of first adjacent and taboo channel interference that a digital television (DTV) receiver can tolerate must be determined. In this context, we will first provide an overview of the IEEE 802.22 WRAN system. Afterwards, we will report on an experimental study that was undertaken to characterize IEEE 802.22 WRAN interference limits into Advanced Television Systems Committee (ATSC) based DTV receivers. Lastly, we will discuss the implications of these WRAN interference limits in terms of the maximum allowable radiated power and out-of-band emission limits that are imposed on WRAN end-user devices.     

DTV repeater emission mask analysis

Terrestrial digital television (DTV) requires careful planning in the allocation of RF channels, especially during the transition period when intermixing both analog and digital signals in the same coverage area. One important issue to consider is adjacent channel interference, which limits the number of RF channels utilized in any given area. This issue is important in the deployment of not only full service stations, but also of secondary stations such as translators, on-channel repeaters, and low power television stations. Full service stations have FCC rules that limit the amount of adjacent channel splatter by requiring the splatter energy to remain below a rigid emission mask. Currently there are no FCC rules for translators and low power television stations. The paper discusses typical DTV transmitter splatter sidebands and their causes, as well as specific methods for interference analysis from adjacent channel DTV splatter into adjacent NTSC or DTV signals. Two rigid emission masks ("simple" and "stringent") are proposed and evaluated. Several filter designs are computer simulated and analyzed for minimizing adjacent channel splatter interference as well as in-band DTV signal degradation. Linear pre-correction techniques are analyzed for various length (15-tap and 31-tap) transversal filter equalizers. The simulation is verified by measuring and evaluating DTV system performance for two hardware band-pass filters individually placed at the output of a low power (30 W average) transmitter.     

Interference to UHF-DTTV Channels by Unlicensed Devices

With the transition to digital terrestrial television (DTV) in the U.S. scheduled to be complete by 2009, the Federal Communications Commission (FCC) has issued a notice of proposed rule making (NPRM) that, if adopted, would allow transmission by unlicensed devices on frequencies of vacated television channels. The FCC is required by statute to avoid harmful interference to licensed TV channels. This paper addresses two of the core questions related to the proposed introduction of unlicensed transmissions in the vacated TV channels: Do the proposed rules provide DTV stations adequate protection from interference from these devices? If not, what rules must be adopted to avoid harmful interference to terrestrial DTV service from these devices?     

Data Broadcasting and Interactive Television

This paper provides an overview of the digital television (DTV) data broadcast service and interactive service technologies that have been deployed over the last ten years. We show how these trials have led to the development of data protocol and software middleware specifications, worldwide. Particular attention is given to the series of standards established by the Advanced Television System Committee. Experimental deployments to both Personal Computer(PC) and Set-Top-Box (STB)/spl I.bar/receivers are considered, with an emphasis on the services that have introduced new business models for DTV operators.     

Adaptive Hybrid Beamformer for Mobile Reception of ATSC DTV

An adaptive hybrid beamformer is proposed to improve the reception performance of the advanced television system committee (ATSC) digital television (DTV) in a mobile environment. Dynamic multipaths and Doppler shifts severely degrade the reception performance of the ATSC DTV receiver. Accordingly, a hybrid beamformer, called a Capon and least mean square (CLMS) beamformer, is presented that uses direction of arrival (DOA) information and the least mean square (LMS) beamforming algorithm. The proposed CLMS algorithm efficiently removes dynamic multipaths and compensates for the phase distortion caused by Doppler shifts in mobile receivers. When the CLMS beamformer has an insufficient degree of freedom (DOF), the subsequent use of an equalizer removes any residual multipath effects, thereby significantly improving the performance of DTV receivers. The performances of the proposed CLMS, Capon, and LMS beamformers are compared based on computer simulations. In addition, the overall performance of the CLMS beamformer followed by an equalizer is also considered.     

浅析数字电视接收机电磁兼容标准

介绍了数字电视接收机电磁兼容标准,并针对数字电视接收机和模拟电视接收机的不同进行了对比说明,以使广大测试人员和生产企业更好地掌握新标准.     

Limits on Fixed Broadband Devices for Interference-Free Operation in the DTV Spectrum

This paper examines the limits that must be imposed on single and multiple fixed cognitive broadband devices (BDs) transmitting simultaneously on multiple unused TV channels in order to avoid interference with the reception of licensed TV channels. Single and multiple fixed BDs are assumed to radiate 4W peak power relative to an isotropic source and transmit within 10 meters of the nearest digital television (DTV) set antenna. The power and separation limits are shown to depend on whether BDs are licensed, on whether mandated minimum front-end performance specifications for DTV sets are in place, and on the definition of an ldquounused channel.rdquo Short and long-term general conclusions are drawn regarding the maximum allowable directional power and regarding taboo channels for interference-free coexistence with DTV sets. It is shown that unlicensed BDs would result in the least efficient use of the available DTV spectrum because the ldquoworst caserdquo interference limits must be imposed in an unlicensed environment. The most efficient utilization of the DTV spectrum would be achieved if BDs were licensed and then allowed to migrate, together with DTV channels, into two blocks of contiguous channels, one for DTV and one for BDs.     

数字电视机顶盒的组成原理及设计方案研究

数字电视机顶盒是传统模拟电视时代向数字电视时代过度的必然选择,它由硬件平台、软件平台和智能卡三部分组成,主要完成数字电视信号的解调、解码和表现等功能.分析其组成原理的基础上,提出了数字电视机顶盒的一种优化设计方案.     

Joint VSB terrestrial digital TV indoor reception project

The reliability and efficacy of indoor reception of 8VSB digital terrestrial television (DTV) in four major U.S. cities was studied in an initial field measurement survey program and a subsequent data capture and processing program. Measurements from the initial survey identified problem sites for reliable DTV reception using currently available 2nd generation DTV receivers. Subsequent field dual channel data captures made at the identified problem sites provided data for testing and verification of new antenna diversity receiver algorithms destined for future generation DTV receivers. From data captures at selected problem sites of sufficient signal strength, but where currently available 2nd generation DTV receivers failed, it was found that in 70% of the cases DTV reception performance was satisfactory when using new antenna diversity receiver algorithms. These measurements and data captures corroborate the claim that the VSB DTV indoor reception problem may be less severe than implied from surveys using less advanced current 2nd generation receivers with a single antenna. For sites with severe multipath, 8VSB DTV reception could be potentially superior to NTSC, which would experience an unwatchable picture.     

超宽带信号与常规通信信号的共存性研究

文章简要介绍了脉冲式超宽带信号对GPS系统的影响,以及脉冲式超宽带信号、直接序列超宽带信号、MB-OFDM信号对卫星数字接收机性能的影响,特别分析了不同的信号特征对这些系统干扰的相关性,为了提高系统频率的利用效率,并保证潜在的其他通信系统的性能,超宽带设备需要具有干扰的检测和避让的技术能力。     

Filtered decision feedback channel estimation for OFDM-based DTVterrestrial broadcasting system

Orthogonal frequency division multiplexing (OFDM) is one of the transmission techniques used for digital television (DTV) terrestrial broadcasting. A high quality channel estimator with a low training overhead is the key to the successful delivery of DTV services which require high spectrum efficiency and robustness to strong and dynamic ghosts. Robustness to multipath distortion is especially important in a single frequency emission environment. This paper presents an application of a filtered decision feedback channel estimator for OFDM-based DTV systems using high order QAM modulations. The implementation and the performance of the channel estimator are discussed. Computer simulations were conducted to evaluate the performance of the channel estimator. The channel estimation loss is about 1.2 dB from the ideal case where the channel is assumed to be known by the receiver. For a given multipath spread, the loss can be further reduced by increasing the FFT size. The FFT size is however subject to an upper limit imposed by the Doppler spread     

Reception Power Estimation Using Transmitter Identification Signal for Single Frequency Network

In a single frequency network (SFN) based on the Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) system, receivers inevitably suffer from the interference generated by using the same frequency among multiple transmitters or repeaters. The amount of the interference can be handled by adjusting transmit power and time of each transmitter and repeater. Hence, it is crucial to estimate the individual reception power from each transmitter or repeater at the given point of interest. This paper presents an efficient method to estimate the individual reception power from each transmitter or repeater. The field test results are provided to evaluate the proposed method. The proposed method exploits the transmitter identification (TxID) signals which are embedded in existing 8-VSB signals.      

Preventing Interference to DTV Broadcasting in Every Market From Unlicensed or Uncontrolled Clusters of Broadband Devices on Unoccupied DTV Channels

The threat of interference to licensed DTV by clusters of unlicensed and uncontrolled broadband devices (BDs) transmitting simultaneously on unoccupied DTV channels remains. DTV channels in major U.S. cities could be victimized by interference from unlicensed or uncontrollable clusters. This paper shows how and why interference by clusters of broadband devices would be significantly higher than interference by individual broadband devices or by interference from clusters of single-tone devices. This paper also provides a real-world assessment of the maximum interference that consumer-grade receivers can accept from clusters of broadband devices operating on unoccupied DTV channels. To prevent interference to DTV and to maximize spectral efficiency individual base stations would have to be licensed as part of a network, and portable unlicensed devices would have to be equipped with dual DTV tuners with GPS chips.     

Performance analysis of error propagation effects in the DFE for ATSC DTV receivers

The paper analyzes the error propagation phenomenon in the decision feedback equalizer (DFE) for the receivers of Advanced Television Systems Committee (ATSC) digital television (DTV) and presents the performance upper-limits of the DFE by comparing various error propagation cases and the no-error propagation case. As one approach to the performance limit, we consider a blind DFE, adopting a trellis decoder with a trace-back depth of 1 as a decision device. Through simulation, we show how much the DFE performance in ATSC DTV receivers is affected by error propagation. We found that while blind equalization is preferable to decision-directed (DD) equalization at signal-to-noise ratio (SNR) values less than 18 dB, DD equalization is superior to blind equalization at SNR values greater than 18 dB. In addition, symbol error rate curves quantitatively show that the performance difference in the DFE caused by error propagation becomes clearer at the trellis decoder following the DFE. The analysis results presented are very informative for developing equalization algorithms for ATSC DTV receivers.     

数字电视测量实验的探索与设计

数字电视近年来得到了广泛的发展,各高校也对应的开设数字电视原理等理论课程,但其实验教学方法还处于发展初期.根据数字电视实验系统的组成结构,主要探讨了数字电视测量部分的实验,并设计出既有教学意义又有实用价值的实验.     

Performance degradation of analog FM system due to spread spectrum overlay

The investigation of spectrum overlay of a spread spectrum system on the existing narrowband FM broadcasting system is presented. The overlaid spread spectrum (SS) system is assumed to utilize direct sequence (DS) spreading, using maximal length pseudorandom sequences. We studied the performance degradation of the analog FM system due to the interference produced by the SS signal, through laboratory subjective and objective measurements, for various types of spreading scenarios and for different carrier frequency differences (/spl Delta/f). The RF protection ratios for the FM receivers are derived, along with SINAD measurements. Finally, these experimental results have been compared with the theoretical study of the FM receiver's audio frequency SNR output due to SS interference.     

广播电视技术发展地面数字电视传输技术分析

对地面数字电视传输技术的基本背景进行了阐述,结合显著提高音画质量、大幅扩充通信量级、兼容更多终端设备以及保有更广发展前景四个部分,分析了地面数字电视传输技术的优越效益;最后,从做好传输系统架设工作、实现传输质量持续提升以及注重技术策略优化创新三个角度入手,研究了地面数字电视技术的实践要点。     

立体电视技术综述

随着数字电视技术和平板显示技术的发展,立体电视技术逐渐成为当前电视技术发展的新热点。本文主要从获取、压缩和显示三方面入手,结合三维领域多年来的技术进展,对立体电视技术进行了全面的描述,对近期在三维领域出现的新技术、新方法进行了扼要的介绍,探讨了其在立体电视技术中应用的可能性和可行性,并对未来立体电视技术的发展作出展望。     

Personal Mobile DTV Cellular Phone Terminal Developed for Digital Terrestrial Broadcasting With Internet Services

Digital terrestrial broadcasting in Japan specifies a service profile not only for fixed receivers in the home, but also for personal mobile terminals such as acellular phones and PDAs. Services for personal mobile terminals are expected to become more attractive with sufficient functionality and flexibility by utilizing the network connectivity of mobile terminals. In order to verify the possibilities of digital television broadcasting (DTV) services for personal mobile terminals and clarify technical problems at the commercial level, we developed a prototype mobile terminal capable of receiving digital terrestrial broadcasting in addition to the Internet. This paper describes the assumed DTV service for personal mobile terminals and the technical architecture of the developed mobile terminal with regard to the hardware and the software. Several experiments using the developed mobile terminal were conducted and the performance was evaluated.     

Analog PAL-G signal degradation due to spread spectrum overlay

Performance degradation of an analog PAL-G signal due to direct sequence spread spectrum overlay is examined. An analytical expression between RF TV protection ratio (CIR) and baseband unweighted signal-to-noise ratio (SNRv), for co-channel spread spectrum and noise interference, is derived. Computer analysis results are presented and compared to experimental measurements for different spread spectrum RF bandwidths and carrier frequency offsets between the analog and digital signal. Image quality degradation is also presented and associated to different level of spread spectrum interference.