microwave planning and design pdf

Microwave Planning And Design Pdf

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Jetzt bewerten Jetzt bewerten. A comprehensive guide to the design, implementation, and operation of line of sight microwave link systems The microwave Line of Sight LOS transport network of any cellular operator requires at least as much planning effort as the cellular infrastructure itself. The knowledge behind this design has been kept private by most companies and has not been easy to find. Microwave Line of Sight Link Engineering solves this dilemma. It provides the latest revisions to ITU reports and recommendations, which are not only key to successful design but have changed dramatically in recent years.

Microwave Transmission Networks: Planning, Design, and Deployment Second Edition

Library of Congress. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized.

Artech House cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. Over the years these digital radio systems have evolved in terms of capacity and functionality to such an extent that they can now support all fixed and mobile data and voice applications along with associated transport protocols.

Within the mobile backhaul arena, the majority of cell sites around the globe are connected within the access domain by point-to-point digital microwave radio systems. As advanced mobile broadband and VoIP technologies are deployed, there is no reason why microwave radio systems cannot continue to provide this vital connectivity into the operators transport backbone.

This second edition of Trevor s Microwave Radio Transmission Design Guide provides all the theoretical and practical advice required for students or practicing engineers to gain the necessary knowledge to start planning and deploying modern digital microwave radio systems.

Ten years later, the challenge in the industry is now how to upgrade radio networks to incorporate packet-based traffic, and the majority of the new material addresses this aspect. In this second edition, I have also updated the various reference standards and added further real-world examples and formulas so that this book can still be used as a handy reference guide for people designing and maintaining microwave radio systems from UHF up to the millimeter bands. It is my view that the problems in the industry result from a paradoxical mix of attitudes, in which one group feels microwave radio design is so well established as to be trivial, yet often is using outdated analog-based design methods, and another group believes that digital microwave systems are binary in nature and forgets that the RF carrier is still analog and therefore subject to all the adverse affects of a complex analog radio signal traveling in a constantly varying atmosphere and thus having to overcome all the adverse weather effects.

A key purpose of this book is to provide a thorough and accurate treatment of the fundamental principles of microwave transmission, which have been forgotten over the years, together with a fully updated approach to what happens in the real world in modern digital radio systems using the latest radio equipment.

I am grateful to the various microwave manufacturers who have provided white papers that have technically supported the new material that I have written. Included in this list are Harris Stratex Inc. I would also like to thank Eskom, Andrew Antennas, Alcatel, and Microflect for the material that is still relevant from the first edition.

I thank Andy Sutton from France Telecom, Orange group, for various useful discussions and for writing the foreword of the book. Lastly, I thank my son Sean for the excellent new diagrams he has produced for this new edition of the book. The requirement to backhaul mobile radio traffic quickly and reliably led to exponential growth of this industry before the turn of the twenty-first century.

It is often predicted that fiber optic transmission will stunt this growth. As these access networks grow, fiber is also being pushed deeper into the network requiring last-mile connections that will further fuel growth of microwave technology. This phenomenal growth is set with the backdrop of an industry that still uses outdated design rules that are adapted from the old analog systems without understanding the impact on deployment costs or performance degradation.

There is also growing public resistance to more radio sites being established, together with additional physical structures, such as wind farms that can potentially interfere with the microwave line-of-sight conditions, and these factors will force a more pragmatic approach to be adopted in order to get links to work reliably in nonideal conditions. A challenge for transmission engineers is that they need to provide capacity for an exponential bandwidth explosion from new data services, without equivalent additional subscriber revenue.

Both the RF and baseband channels thus have to be optimized to carry traffic more efficiently than in the past and it is inevitable that Ethernet will be a key technology to transport data efficiently over these networks. The transition from TDM to packet-based transport systems is a key challenge for microwave system designers. Lastly, there is often an unfounded resistance to using radio, as it is perceived as being unreliable, usually due to a bad previous experience of radio due to poor system design.

In digital radio systems the 1. However, when any interference or adverse weather conditions occur, the radio system s performance is impaired. With good system design these conditions can be overcome and a very reliable network built with radio that even exceeds the reliability of fiber networks.

This book is an attempt to combine a solid theoretical treatise of radio theory and standards with pragmatic and real-world recommendations based on field experience.

The birth of telecommunications was in when Alexander Graham Bell made the world s first telephone call with his famous words to his assistant, saying Come here, Mr Watson, I want you, somewhat demonstrating how devoid of any practical significance he felt his invention was. Today it almost seems inconceivable that we could function without telephones, with many of us owning three or four telephones, both fixed and mobile, usually with sophisticated additions such as high-resolution cameras, satellite tracking, and powerful personal computing capability.

The history of wireless transmission is often attributed to the brilliant Scottish professor, James Maxwell, who in published his famous paper A Treatise on Electricity and Magnetism, in which he mathematically predicted the existence of electromagnetic waves, and, more startlingly at the time, deduced the speed of light through his assumption that light traveled as an electromagnetic wave.

Prior to that, it had seemed an odd coincidence that the equations for electrostatic theory and magnetism were linked by a constant factor which was very close to the speed of light. However, as brilliant as these set of equations are, it was the difficulty in applying these equations with their mathematical concepts of divergence, curl, and partial differentiation to the challenge of designing real radio links that sparked the author to write this book, so no further mention will be made of them.

It should also be pointed out that Maxwell drew heavily on previous work by physicists such as Oersted, Coulomb, Faraday, and Ampere to formulate his equations. In Heinrich Hertz practically proved Maxwell s equations in his laboratory when he generated an electromagnetic oscillation using a metal loop with a spark gap at its midpoint, and then detected a similar spark some distance away with a circuit tuned to that frequency. Hertz had effectively invented the first dipole antenna that created radio waves.

For that reason, radio waves were originally called Hertzian waves and the frequency,. He, too, had no idea that his experiment had any practical significance and thought he was merely verifying the theoretical conclusions of Maxwell.

Guglielmo Marconi did see the commercial benefits of radio transmission and in founded the Wireless Telegraph and Signal Company. He applied for various patents to commercially exploit his inventions.

The first practical application was in transatlantic telegraphy. Despite these practical radio transmissions in the early twentieth century, it was only in the s that the first commercial terrestrial radio point-to-point systems were installed. It was during the study of the propagation effects of these analog radio systems that many design parameters such as k-factor, diffraction loss, and Fresnel zone clearances were defined, and in many ways it is the loss of this early expertise and understanding of radio in the industry that needs to be rediscovered, if radio systems are to be used as a reliable transmission medium.

In order to design and maintain reliable next generation radio networks, we should learn the lessons from history and build on the valuable knowledge base established, but we equally need to adapt the design rules to apply that knowledge to modern networks where data applications are becoming as important as voice and where voice itself is data, such as voice over IP VoIP. New thinking needs to be applied to old concepts to revolutionize the way we plan and operate microwave radio networks.

Microwave Fundamentals Microwave radio, in the context of this book, refers to point-to-point fixed digital links that operate in duplex mode. Duplex operation means that each radio frequency RF channel consists of a pair of frequencies for the transmit and receive directions, respectively. These are sometimes referred to as Go and Return channels or low-band and high-band channels. This is illustrated in Figure 1.

The difference between these two carriers is called the T to R spacing. The RF bandwidth is completely symmetrical, irrespective of the symmetry of the baseband traffic and always occupies the full bandwidth, unlike analog radios, because the modulator cannot discriminate between real or dummy zeros and ones.

The actual RF bandwidth is determined by the capacity of the link and the modulation scheme used. The digital baseband signal is modulated onto an analog RF carrier and is transmitted over the air as an electromagnetic wavefront. Both the transmit and receive frequencies are combined onto one antenna using frequency division duplexing FDD , as shown in Figure 1. Figure 1. The T-R spacing is set by the practical filtering requirements to achieve adequate isolation.

The new band nomenclature from A to M is shown in Table 1. In practice, commercial radio links cover the frequency spectrum from MHz to approximately 90 GHz. Table 1. Microwave energy thus has insufficient energy to ionize atoms and so. However, the debate about safety of microwave links is whether the heating effect of microwaves has an adverse effect on humans or could accelerate the growth of cancerous cells. The eyes and the testes are particularly vulnerable because they have a low blood flow and therefore do not efficiently dissipate the additional heat.

Once one is a few meters away from a microwave antenna, the signal strength is very low and thus is considered to be no risk to the general population. For maintenance personnel, especially those who may climb the towers that the antennas are mounted on, the risks are considered higher and the limits set are more stringent. Some telecoms equipment transmits kilowatts of power, and therefore it is often recommended that maintenance personnel wear a beeper to warn them of excessive power density levels and if necessary get the transmit power of some equipment turned down at a site during maintenance work.

Technical staff should also ensure in a laboratory environment that they never look directly into a transmitting horn feed or antenna and do not walk across the beam of an operating microwave link for excessive periods Allocation of Spectrum The RF spectrum is part of the shared electromagnetic spectrum.

It can be regarding as a scarce resource such as coal or petroleum, as once is it used, it cannot be re-created and therefore requires sensible allocation and coordination.

Various services such as mobile radio, satellites, broadcasting, military, medical, and domestic must all share this common spectrum. Each service must be allowed to expand and grow without causing interference to any other service. The task of allocating and controlling the individual parts of this spectrum is the responsibility of the International Telecommunication Union ITU. The ITU-T handles standards for end-to-end circuits covering all mediums cable, satellite, radio , whereas the ITU-R specifically deals with radio links.

The ITU has divided the world into three regions, as shown in Figure 1. The electromagnetic wave has a sinusoidally varying electric field that is orthogonal to an in-phase, sinusoidally varying magnetic field and both are orthogonal to the direction of propagation. This is thus known as a transverse wave, as opposed to longitudinal waves e. The two fields interact with one another. A changing magnetic field induces an electric field, and a changing electric field induces a magnetic field.

The transverse electromagnetic TEM propagation is shown in Figure 1. In order to simplify this representation, we can regard the wavefront as an imaginary line that is drawn through the plane of constant phase and a ray as an imaginary line that is drawn in the direction of travel. This is shown in Figure 1. A plane wave is one that has a plane wavefront.

A uniform wavefront is one that has constant magnitude and phase. In a microwave signal, transmitted with parabolic antennas, the magnitudes of the electric and magnetic field vectors are equal and occur in phase, with the peaks and troughs occurring at the same time; thus, it is called a uniform plane wave Period The period of the wave is the length of time before the wave repeats itself and can be expressed as.

In air, the permittivity and permeability are approximately the same as in a vacuum, so the microwave beam travels at the speed of light, irrespective of frequency. In order to determine the velocity of propagation through a foam-filled cable, it would be necessary to look up the dielectric constant of foam Polarization The polarization of the signal corresponds to the plane of the electric field vector. If one imagines a sinusoidal wave traveling perpendicularly out of the page, the amplitude vector would swing from a positive maximum through zero to a negative maximum.

Apoint source of radiation that transmits energy uniformly in all. The demand for cost-effective, high-quality transmission systems is growing, to meet the demands of bandwidth hungry multimedia services in both fixed and mobile applications. Particularly in the mobile networks, third generation and fourth generation technology is allowing unprecedented user bandwidth in support of applications such as video downloads.

Technologies such as HSPA, LTE, and WiMAX provide high bandwidth capability to the user, but it has just pushed the bottleneck to the transmission network, which has to backhaul this traffic Benefits and Disadvantages of Microwave In an ideal world fiber optic transmission would be a perfect medium for this backhaul due to its virtually unlimited bandwidth, but the reality is that it is not widely available in the access part of the network.

This is despite the ongoing growth of fiber through initiatives such as next generation access NGA projects. The exorbitant cost, together with the inconvenience of digging up roads to provide more cables, means that it is unlikely to be available to deploy the next generation transmission access networks.

At one point property developers were providing fiber at the time of construction of new buildings and office complexes.

However, the business case for this was not justified and this is no longer the trend. The cost of right-of-way servitudes, the inconvenience of digging up roads, and the disturbances to existing infrastructure, together with the delays in obtaining them, are major disadvantages for new fiber routes.

Microwave radio has lower fixed costs associated with it, allowing the costs to be spread more evenly over the systems lifetime, thus matching the costs with revenue and reducing the investment risk.

Microwave Transmission Networks: Planning, Design, and Deployment Second Edition

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Microwave Transmission Networks ABOUT THE AUTHOR HARVEY LEHPAMER has 30 years of experience in the planning, design, and deployment of.

Microwave Transmission Networks: Planning, Design, and Deployment Second Edition

Library of Congress. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Artech House cannot attest to the accuracy of this information.

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At the end of this course the student will understand the essentials of Transmission engineering and will be able to design and manage microwave networks. This course is designed to teach students the essence of microwave path planning. Once completed they will be able to design and maintain cost effective solutions. The students will also be learn how to design paths that will not suffer from interference, or disturb other radio systems in the vicinity.

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