Orthogonal Frequency Division Multiplex (OFDM) Tutorial 1
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3 Characterization of Communication Signals and Systems
63 3 Characterization of Communication Signals and Systems 3.1 Representation of Bandpass Signals and Systems Narrowband communication signals are often transmitted using some type of carrier modulation. The resulting transmit signal s(t) has passband character, i.e., the bandwidth B of its spectrum S(f) = s(t) is much smaller F{ } than the carrier frequency fc. S(f) B f f f − c c We are interested in a representation for s(t) that is independent of the carrier frequency fc. This will lead us to the so–called equiv- alent (complex) baseband representation of signals and systems. Schober: Signal Detection and Estimation 64 3.1.1 Equivalent Complex Baseband Representation of Band- pass Signals Given: Real–valued bandpass signal s(t) with spectrum S(f) = s(t) F{ } Analytic Signal s+(t) In our quest to find the equivalent baseband representation of s(t), we first suppress all negative frequencies in S(f), since S(f) = S( f) is valid. − The spectrum S+(f) of the resulting so–called analytic signal s+(t) is defined as S (f) = s (t) =2 u(f)S(f), + F{ + } where u(f) is the unit step function 0, f < 0 u(f) = 1/2, f =0 . 1, f > 0 u(f) 1 1/2 f Schober: Signal Detection and Estimation 65 The analytic signal can be expressed as 1 s+(t) = − S+(f) F 1{ } = − 2 u(f)S(f) F 1{ } 1 = − 2 u(f) − S(f) F { } ∗ F { } 1 The inverse Fourier transform of − 2 u(f) is given by F { } 1 j − 2 u(f) = δ(t) + . -
Replacing Digital Terrestrial Television with Internet Protocol?
This is a repository copy of The short future of public broadcasting: Replacing digital terrestrial television with internet protocol?. White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/94851/ Version: Accepted Version Article: Ala-Fossi, M and Lax, S orcid.org/0000-0003-3469-1594 (2016) The short future of public broadcasting: Replacing digital terrestrial television with internet protocol? International Communication Gazette, 78 (4). pp. 365-382. ISSN 1748-0485 https://doi.org/10.1177/1748048516632171 Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version - refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher’s website. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ The Short Future of Public Broadcasting: Replacing DTT with IP? Marko Ala-Fossi & Stephen Lax School of Communication, School of Media and Communication Media and Theatre (CMT) University of Leeds 33014 University of Tampere Leeds LS2 9JT Finland UK [email protected] [email protected] Keywords: Public broadcasting, terrestrial television, switch-off, internet protocol, convergence, universal service, data traffic, spectrum scarcity, capacity crunch. -
Bit & Baud Rate
What’s The Difference Between Bit Rate And Baud Rate? Apr. 27, 2012 Lou Frenzel | Electronic Design Serial-data speed is usually stated in terms of bit rate. However, another oft- quoted measure of speed is baud rate. Though the two aren’t the same, similarities exist under some circumstances. This tutorial will make the difference clear. Table Of Contents Background Bit Rate Overhead Baud Rate Multilevel Modulation Why Multiple Bits Per Baud? Baud Rate Examples References Background Most data communications over networks occurs via serial-data transmission. Data bits transmit one at a time over some communications channel, such as a cable or a wireless path. Figure 1 typifies the digital-bit pattern from a computer or some other digital circuit. This data signal is often called the baseband signal. The data switches between two voltage levels, such as +3 V for a binary 1 and +0.2 V for a binary 0. Other binary levels are also used. In the non-return-to-zero (NRZ) format (Fig. 1, again), the signal never goes to zero as like that of return- to-zero (RZ) formatted signals. 1. Non-return to zero (NRZ) is the most common binary data format. Data rate is indicated in bits per second (bits/s). Bit Rate The speed of the data is expressed in bits per second (bits/s or bps). The data rate R is a function of the duration of the bit or bit time (TB) (Fig. 1, again): R = 1/TB Rate is also called channel capacity C. If the bit time is 10 ns, the data rate equals: R = 1/10 x 10–9 = 100 million bits/s This is usually expressed as 100 Mbits/s. -
AM / FM / DAB / XM Tuner
ENGLISH FRANÇAIS Owner’s Manual Owner’s ESPAÑOL ® ITALIANO AM / FM / DAB / XM Tuner /XM /DAB /FM AM M4 DEUTSCH NEDERLANDS SVENSKA РУССКИЙ IMPORTANT SAFETY INSTRUCTIONS ENGLISH 1. Read instructions - All the safety and operating instructions should be NOTE TO CATV SYSTEM INSTALLER read before the product is operated. This reminder is provided to call the CATV system installer’s attention to Section 820-40 of 2. Retain instructions - The safety and operating instructions should be the NEC which provides guidelines for proper grounding and, in particular, specifies that retained for future reference. the cable ground shall be connected to the grounding system of the building, as close 3. Heed Warnings - All warnings on the product and in the operating to the point of cable entry as practical. instructions should be adhered to. 4. Follow Instructions - All operating and use instructions should be FRANÇAIS followed. 5. Cleaning - Unplug this product from the wall outlet before cleaning. Do not use liquid cleaners or aerosol cleaners. Use a damp cloth for cleaning. 6. Attachments - Do not use attachments not recommended by the product manufacturer as they may cause hazards. 7. Water and Moisture - Do not use this product near water-for example, near a bath tub, wash bowl, kitchen sink, or laundry tub; in a wet basement; or near a swimming pool; and the like. ESPAÑOL 8. Accessories - Do not place this product on an unstable cart, stand, tripod, bracket, or table. The product may fall, causing serious injury to a child or adult and serious damage to the product. Use only with a cart, stand, tripod, bracket, or table recommended by the manufacturer, or sold with the product. -
Digital Audio Broadcasting : Principles and Applications of Digital Radio
Digital Audio Broadcasting Principles and Applications of Digital Radio Second Edition Edited by WOLFGANG HOEG Berlin, Germany and THOMAS LAUTERBACH University of Applied Sciences, Nuernberg, Germany Digital Audio Broadcasting Digital Audio Broadcasting Principles and Applications of Digital Radio Second Edition Edited by WOLFGANG HOEG Berlin, Germany and THOMAS LAUTERBACH University of Applied Sciences, Nuernberg, Germany Copyright ß 2003 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England Telephone (þ44) 1243 779777 Email (for orders and customer service enquiries): [email protected] Visit our Home Page on www.wileyeurope.com or www.wiley.com All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except under the terms of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission in writing of the Publisher. Requests to the Publisher should be addressed to the Permissions Department, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, or emailed to [email protected], or faxed to (þ44) 1243 770571. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. -
VHF and UHF Signal Characteristics Observed on a Long Knife-Edge Diffraction Path A
JOURNAL OF RESEARCH of the National Bureau of Standards- D. Radio Propagatior. Vol. 65D, No. 5, September- Odober 1961 VHF and UHF Signal Characteristics Observed on a Long Knife-Edge Diffraction Path A. P. Barsis and R. S. Kirby (R eceived April 6, 1961) Contribution from Central Radio Propagation Laboratory, National Bureau of Standards, Boulder, Colo. During 1959 and 1960 long-term transmission loss measurements were performed over a 223 kilom eter path in Eastern Colorado using frequencies of 100 and 751 megacycles per second. This path intersects P ikes P eak which forms a knife-edge type obstacle visible from both terminals. The transmission loss measurements have been analyzed in terms of diurnal a nd seaso nal variations in hourly medians and in instan taneous levels. As expected, results show t hat the long-term fading range is substantially less t han expected for t ropospheric seatter paths of comparable length. T ransmission loss levels were in general agreem ent wi t h predicted k ni fe-edge d iffraction propagation when a ll owance is made for rounding of t he knife edge. A technique for est imatin g long-term fading ra nges is presented a nd t he res ults are in good agreement with observations. Short-term variations in some case resemble t he space-wave fadeo uts commonly observed on within- the-horizon paths, a lthough other phe nomena may contribute to t he fadin g. Since t he foreground telTain was rough there was no evidence of direct a nd grou nd-refl ected lobe structure. -
Capacity of Flat and Freq.-Selective Fading Channels Linear Digital Modulation Review
Lecture 8 - EE 359: Wireless Communications - Winter 2020 Capacity of Flat and Freq.-Selective Fading Channels Linear Digital Modulation Review Lecture Outline • Channel Inversion with Fixed Rate Transmission • Comparison of Fading Channel Capacity under Different Schemes • Capacity of Frequency Selective Fading Channels • Review of Linear Digital Modulation • Performance of Linear Modulation in AWGN 1. Channel Inversion with Fixed Rate Transmission • Suboptimal transmission strategy where fading is inverted to maintain constant re- ceived SNR. • Simplifies system design and is used in CDMA systems for power control. • Capacity with channel inversion greatly reduced over that with optimal adaptation (capacity equals zero in Rayleigh fading). • Truncated inversion: performance greatly improved by inverting above a cutoff γ0. 2. Comparison of Fading Channel Capacity under Different Schemes: • Fading generally decreases channel capacity. • Rate/power adaptation have similar capacity as rate adaptation alone. • Rate adaptation alone has same capacity as no adaptation (RX CSI only) but rate adaptation is more practical due to complexity of ML decoding over long blocklengths that experience all fading values. This ML decoding is necesssary to achieve capacity in the RX CSI only case. • Truncated channel inversion is more practical than rate adaptation, with significant capacity gain over full channel inversion, which has zero capacity in Rayleigh fading. 3. Capacity of Frequency Selective Fading Channels • Capacity for time-invariant frequency-selective fading channels is a \water-filling” of power over frequency. • For time-varying ISI channels, capacity is unknown in general. Approximate by di- viding up the bandwidth subbands of width equal to the coherence bandwidth (same premise as multicarrier modulation) with independent fading in each subband. -
2 the Wireless Channel
CHAPTER 2 The wireless channel A good understanding of the wireless channel, its key physical parameters and the modeling issues, lays the foundation for the rest of the book. This is the goal of this chapter. A defining characteristic of the mobile wireless channel is the variations of the channel strength over time and over frequency. The variations can be roughly divided into two types (Figure 2.1): • Large-scale fading, due to path loss of signal as a function of distance and shadowing by large objects such as buildings and hills. This occurs as the mobile moves through a distance of the order of the cell size, and is typically frequency independent. • Small-scale fading, due to the constructive and destructive interference of the multiple signal paths between the transmitter and receiver. This occurs at the spatialscaleoftheorderofthecarrierwavelength,andisfrequencydependent. We will talk about both types of fading in this chapter, but with more emphasis on the latter. Large-scale fading is more relevant to issues such as cell-site planning. Small-scale multipath fading is more relevant to the design of reliable and efficient communication systems – the focus of this book. We start with the physical modeling of the wireless channel in terms of elec- tromagnetic waves. We then derive an input/output linear time-varying model for the channel, and define some important physical parameters. Finally, we introduce a few statistical models of the channel variation over time and over frequency. 2.1 Physical modeling for wireless channels Wireless channels operate through electromagnetic radiation from the trans- mitter to the receiver. -
The Trade-Off Between Transceiver Capacity and Symbol Rate
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by UCL Discovery The Trade-off Between Transceiver Capacity and Symbol Rate L. Galdino, D. Lavery, Z. Liu, K. Balakier, E. Sillekens, D. Elson, G. Saavedra, R. I. Killey and P. Bayvel Optical Networks Group, Dept. of Electronic & Electrical Engineering, University College London, UK [email protected] Abstract: The achievable throughput using high symbol rate, high order QAM is investigated for the current generation of CMOS-based DAC/ADC. The optimum symbol rate and modula- tion format is found to be 80GBd DP-256QAM, with an 800Gb/s net data rate. OCIS codes: (060.0060) Fiber optics and optical communications; (060.2360) Fiber optics links and subsystems 1. Introduction A key goal when designing a new optical transmission system is to increase the amount of data sent for a given cost. One way to reduce the cost-per-bit is to increase the channel symbol rate, which will maximise the amount of information sent over one channel and reduce the number of transceivers for a given transmission bandwidth. Currently, the upper limit on the available signal-to-noise ratio (SNR), and therefore channel highest achievable information rate (AIR) in a coherent optical transmission system, in the absence of fiber nonlinearity, is bounded by the transceiver subsystems, such as digital-to-analog converter (DAC) and analog to digital converter (ADC). The SNR of an ideal DAC / ADC is defined by the number of bits (N) which sets the quantization noise floor of the device [1]. -
Distortion Exponent of Parallel Fading Channels
Distortion Exponent of Parallel Fading Channels Deniz Gunduz, Elza Erkip Department of Electrical and Computer Engineering, Polytechnic University, Brooklyn, NY 11201, USA [email protected], [email protected] Abstract— We consider the end-to-end distortion achieved by the fading process. Lack of channel state information at the transmitting a continuous amplitude source over M parallel, transmitter prevents the design of a channel code that achieves independent quasi-static fading channels. We analyze the high the instantaneous channel capacity and requires a code that SNR expected distortion behavior characterized by the distortion exponent. We first give an upper bound for the distortion performs well on the average. We aim to design a joint source- exponent in terms of the bandwidth ratio between the channel channel code that achieves the minimum expected end-to-end and the source assuming the availability of the channel state distortion. Our main focus is the high SNR behavior of this information at the transmitter. Then we propose joint source- expected distortion (ED). This behavior is characterized by the channel coding schemes based on layered source coding and distortion exponent denoted by ¢ and defined as multiple rate channel coding. We show that the upper bound is tight for large and small bandwidth ratios. For the rest, we log ED provide the best known distortion exponents in the literature. ¢ = ¡ lim : (1) SNR!1 log SNR By suitably scaling the bandwidth ratio, our results would also apply to block fading channels. When we consider digital transmission strategies that first compress the source and then transmit over the channel at I. -
On Routing in Random Rayleigh Fading Networks Martin Haenggi, Senior Member, IEEE
IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 4, NO. 4, JULY 2005 1553 On Routing in Random Rayleigh Fading Networks Martin Haenggi, Senior Member, IEEE Abstract—This paper addresses the routing problem for large loss probabilities increase with the number of hops (unless the wireless networks of randomly distributed nodes with Rayleigh transmit power is adapted). fading channels. First, we establish that the distances between To overcome some of these limitations of the “disk model,” neighboring nodes in a Poisson point process follow a generalized Rayleigh distribution. Based on this result, it is then shown that, we employ a simple Rayleigh fading link model that relates given an end-to-end packet delivery probability (as a quality of transmit power, large-scale path loss, and the success of a service requirement), the energy benefits of routing over many transmission. The end-to-end packet delivery probability over short hops are significantly smaller than for deterministic network a multihop route is the product of the link-level reception models that are based on the geometric disk abstraction. If the probabilities. permissible delay for short-hop routing and long-hop routing is the same, it turns out that routing over fewer but longer hops may While fading has been considered in the context of packet even outperform nearest-neighbor routing, in particular for high networks [16], [17], its impact on the network (and higher) end-to-end delivery probabilities. layers is largely an open problem. This paper attempts to shed Index Terms—Ad hoc networks, communication systems, fading some light on this cross-layer issue by analyzing the perfor- channels, Poisson processes, probability, routing. -
Digital Baseband Modulation Outline • Later Baseband & Bandpass Waveforms Baseband & Bandpass Waveforms, Modulation
Digital Baseband Modulation Outline • Later Baseband & Bandpass Waveforms Baseband & Bandpass Waveforms, Modulation A Communication System Dig. Baseband Modulators (Line Coders) • Sequence of bits are modulated into waveforms before transmission • à Digital transmission system consists of: • The modulator is based on: • The symbol mapper takes bits and converts them into symbols an) – this is done based on a given table • Pulse Shaping Filter generates the Gaussian pulse or waveform ready to be transmitted (Baseband signal) Waveform; Sampled at T Pulse Amplitude Modulation (PAM) Example: Binary PAM Example: Quaternary PAN PAM Randomness • Since the amplitude level is uniquely determined by k bits of random data it represents, the pulse amplitude during the nth symbol interval (an) is a discrete random variable • s(t) is a random process because pulse amplitudes {an} are discrete random variables assuming values from the set AM • The bit period Tb is the time required to send a single data bit • Rb = 1/ Tb is the equivalent bit rate of the system PAM T= Symbol period D= Symbol or pulse rate Example • Amplitude pulse modulation • If binary signaling & pulse rate is 9600 find bit rate • If quaternary signaling & pulse rate is 9600 find bit rate Example • Amplitude pulse modulation • If binary signaling & pulse rate is 9600 find bit rate M=2à k=1à bite rate Rb=1/Tb=k.D = 9600 • If quaternary signaling & pulse rate is 9600 find bit rate M=2à k=1à bite rate Rb=1/Tb=k.D = 9600 Binary Line Coding Techniques • Line coding - Mapping of binary information sequence into the digital signal that enters the baseband channel • Symbol mapping – Unipolar - Binary 1 is represented by +A volts pulse and binary 0 by no pulse during a bit period – Polar - Binary 1 is represented by +A volts pulse and binary 0 by –A volts pulse.