Xem 1-20 trên 82 kết quả Radio channel
  • The cognitive radio paradigm is based on the ability of sensing the radio environment in order to make informed decisions. This paper describes the effects of sensing on the cognitive radio channels capacity region. Sensing is modeled as a compression channel, which results in partial knowledge of the primary messages at the cognitive transmitter. This model enables to impose constraints on the sensing strategy. First, the dirty paper channel capacity is derived when the channel encoder knows partially the side information.

    pdf52p huemanvdoc 23-11-2009 103 22   Download

  • Parametrization – a Technique for SDR Implementation Friedrich Jondral University of Karlsruhe Mobile communications is mainly a service driven business. But there are important marginal conditions from physics and technology that may not be ignored when developing a mobile communications system; the frequency spectrum is a scarce resource. Therefore terminals, mobile as well as base station transceivers, have to work efficiently with respect to spectrum. Mobile radio channels are complicated due to multipath propagation, reflections, scattering, time, or frequency dispersion, etc. ...

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  • Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Achievable Rates and Scaling Laws for Cognitive Radio Channels

    pdf12p sting10 24-02-2012 12 5   Download

  • Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Identification of LOS in Time-Varying, Frequency Selective Radio Channels

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  • Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Article Employing Coordinated Transmit and Receive Beamforming in Clustering Double-Directional Radio Channel

    pdf10p sting10 07-03-2012 16 2   Download

  • In the nineteenth century, scientists, mathematician, engineers and innovators started investigating electromagnetism. The theory that underpins wireless communications was formed by Maxwell. Early demonstrations took place by Hertz, Tesla and others. Marconi demonstrated the first wireless transmission. Since then, the range of applications has expanded at an immense rate, together with the underpinning technology. The rate of development has been incredible and today the level of technical and commercial maturity is very high.

    pdf546p namde01 10-04-2013 37 17   Download

  • Digital Processing Tradeoffs This chapter addresses digital hardware architectures for SDRs. A digital hardware design is a configuration of digital building blocks. These include ASICs, FPGAs, ADCs, DACs, digital interconnect, digital filters, DSPs, memory, bulk storage, I/O channels, and/or general-purpose processors. A digital hardware architecture may be characterized via a reference platform, the minimum set of characteristics necessary to define a consistent family of designs of SDR hardware....

    pdf35p tienvovan 11-09-2010 53 11   Download

  • This book explains the basic components, technologies used, and operation of IS-95 CDMA systems. You will discover why mobile telephone service providers have upgraded from 1st generation analog systems to more efficient and feature rich 2nd generation system. You will also discover how 2nd generation systems are gradually evolving into 3rd generation broadband multimedia systems. This book starts with the system components and basic services that the IS-95 CDMA system can provide.

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  • In the latest years much research effort was devoted to envision a new paradigm for wireless transmission. Results from recent works (Wireless Word Research Forum, 2005) indicate that a possible solution would lie in utilizing in a more efficient manner the diverse Radio Access Technologies1 (RATs) that are available nowadays, with the purpose of enabling interoperability among them and convergence into one global telecom infrastructure (beyond 3G).

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  • Segment Design Tradeoffs I. OVERVIEW The six steps in the systems-level design process associated with the software radio are illustrated in Figure 6-1. The tradeoffs proceed from front end to back end. The choice of antennas (step 1 in the figure) determines the number and bandwidth of RF channels (step 2). This, in turn, constrains the numbers and bandwidths of ADCs (step 3). Some waveforms may require dedicated ASICs (e.g., W-CDMA despreaders) in front of the ADCs. Additional parallel IF processing and ADC paths may be necessary to support multiple-service bands simultaneously....

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  • Mobile Satellite Communication∗ In principle communications satellites provide the same connectivity as terrestrial (wireless and wireline) networks. The advantages of satellites, such as fast wide-area coverage, flexible transmission parameters and cost independence due to distance, are compared with the disadvantages, such as restricted channel capacity because of the frequencies available, orbital positions, need for line-of-sight connectivity and high initial investment besides relatively long signal propagation times.

    pdf57p huggoo 20-08-2010 37 7   Download

  • Software Component Characteristics This chapter addresses the structure and function of low-level software components. These include algorithms, modules (e.g., Ada packages, C++ objects), and APIs. The perspective is bottom-up, with the emphasis on computational complexity. Low-level algorithms may be simple at first, but complexity can increase over time. The increases in complexity can occur with research advances. Measures taken to compensate for a performance problem in one area (e.g., noisy voice channel) can increase complexity of an algorithm (e.g.

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  • Fundamentals of VHF and UHF Propagation Having established the suitability of the VHF and UHF bands for mobile communications and the need to characterise the radio channel, we can now develop some fundamental relationships between the transmitted and received power, distance (range) and carrier frequency. We begin with a few relevant de®nitions. At frequencies below 1 GHz, antennas normally consist of a wire or wires of a suitable length coupled to the transmitter via a transmission line.

    pdf17p tienvovan 16-09-2010 52 5   Download

  • Sounding, Sampling and Simulation In the earlier chapters we discussed the characteristics of mobile radio channels in some detail. It emerged that there are certain parameters which provide an adequate description of the channel and it remains now to describe measuring equipment (channel sounders) that can be used to obtain experimental data from which these parameters can be derived.

    pdf42p tienvovan 16-09-2010 36 5   Download

  • Other Mobile Radio Channels A great deal of attention has been given to propagation in built-up areas, in particular to the situation where the mobile is located in the streets, i.e. when it is outside the buildings. It is apparent, however, that other important scenarios exist. For example, hand-portable equipment can be taken inside buildings, and in recent years there has been a substantial increase in the use of this type of equipment.

    pdf31p tienvovan 16-09-2010 32 4   Download

  • In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world....

    pdf0p kimngan_1 05-11-2012 25 2   Download

  • GSM (Global System for Mobile Communications, originally Groupe Spécial Mobile), is a standard set developed by the European Telecommunications Standards Institute (ETSI) to describe technologies for second generation (2G) digital cellular networks. Developed as a replacement for first generation (1G) analog cellular networks, the GSM standard originally described a digital, circuit switched network optimized for full duplex voice telephony.

    pdf178p zicokim 19-03-2010 286 202   Download

  • Our first chapter puts LTE into its historical context, and lays out its requirements and key technical features. We begin by reviewing the architectures of UMTS and GSM, and by introducing some of the terminology that the two systems use. We then summarize the history of mobile telecommunication systems, discuss the issues that have driven the development of LTE, and show how UMTS has evolved first into LTE and then into an enhanced version known as LTE-Advanced. The chapter closes by reviewing the standardization process for LTE....

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  • The third generation (3G) mobile communication system is the next big thing in the world of mobile telecommunications. The first generation included analog mobile phones [e.g., Total Access Communications Systems (TACS), Nordic Mobile Telephone (NMT), and Advanced Mobile Phone Service (AMPS)], and the second generation (2G) included digital mobile phones [e.g., global system for mobile communications (GSM), personal digital cellular (PDC), and digital AMPS (D-AMPS)].

    pdf568p nhq_khtn 12-03-2011 92 38   Download

  • Hard to fathom, but it really wasn't all that long ago that even a plain old telephone was a luxury item. But, as we all know, technology's only constant is change. In this day and age, many folks need to be accessible everywhere, whether they're at work or play, in the office or at home. To meet this demand, the GSM standard (Global System for Mobile Communications) for mobile telephony was introduced in the mid- 1980s. Today, GSM is the most popular mobile radio standard in the world. A boom is underway, such that many GSM users find life without their phone practically inconceivable....

    pdf54p ruavanguom 22-10-2012 53 20   Download

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