Introduction to Microwave
Microwave is a line-of-sight radio communication engineering that uses high frequency beams of radio waves to provide high speed wireless connections that can send and receive voice, television, and data information .
Microwave links are are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna. This allows nearby microwave equipment to use the like frequencies without interfering with each other, as lower frequency radio waves do. Another advantage is that the high frequency of microwaves gives the microwave band a very large information-carrying capacity ; the microwave isthmus has a bandwidth 30 times that of all the rest of the radio spectrum below it .
Microwave radio transmission is normally used in point-to-point communication systems on the coat of the Earth, in satellite communications, and in trench space radio communications. other parts of the microwave radio band are used for radars, radio receiver navigation systems, detector systems, and radio astronomy .
The higher separate of the radio electromagnetic spectrum with frequencies are above 30 GHz and below 100 GHz, are called “ millimeter waves ” because their wavelengths are handily measured in millimeters, and their wavelengths range from 10 mm down to 3.0 millimeter. Radio waves in this band are normally strongly attenuated by the Earthly atmosphere and particles contained in it, particularly during moisture weather. besides, in wide band of frequencies around 60 GHz, the radio waves are strongly attenuated by molecular oxygen in the standard atmosphere. The electronic technologies needed in the millimeter wave band are besides much more complex and hard to manufacture than those of the microwave dance band, therefore price of Millimeter Wave Radios are by and large higher.
Reading: Microwave Technology – CableFree
History of Microwave Communication
James Clerk Maxwell, using his celebrated “ Maxwell ’ south equations, ” predicted the being of inconspicuous electromagnetic waves, of which microwaves are a part, in 1865. In 1888, Heinrich Hertz became the first gear to demonstrate the being of such waves by building an apparatus that produced and detected microwaves in the extremist high frequency region. Hertz recognized that the results of his experiment validated Maxwell ’ second prediction, but he did not see any virtual applications for these invisible waves. Later work by others led to the invention of wireless communications, based on microwaves. Contributors to this work included Nikola Tesla, Guglielmo Marconi, Samuel Morse, Sir William Thomson ( later Lord Kelvin ), Oliver Heaviside, Lord Rayleigh, and Oliver Lodge .
In 1931 a US-French consortium demonstrated an experimental microwave relay link across the English Channel using 10 foundation ( 3m ) dishes, one of the earliest microwave communication systems. Telephony, cable and fax data was transmitted over the 1.7 GHz beams 40 miles between Dover, UK and Calais, France. however it could not compete with cheap submarine cable rates, and a planned commercial organization was never built.
During the 1950s the AT & T Long Lines system of microwave relay links grew to carry the majority of US long outdistance telephone traffic, angstrom well as intercontinental television receiver net signals. The prototype was called TDX and was tested with a connection between New York City and Murray Hill, the localization of Bell Laboratories in 1946. The TDX system was set up between New York and Boston in 1947 .
Modern Commercial Microwave Links
A microwave connect is a communication system that uses a beam of radio waves in the microwave frequency range to transmit video, audio, or data between two locations, which can be from merely a few feet or meters to several miles or kilometers apart. Examples of Commercial Microwave links from CableFree may be see here. Modern Microwave Links can carry up to 400Mbps in a 56MHz channel using 256QAM intonation and IP header compaction techniques. operate Distances for microwave links are determined by antenna size ( reach ), frequency ring, and link capacity. The handiness of clear Line of Sight is crucial for Microwave links for which the Earth ’ randomness curvature has to be allowed
Microwave links are normally used by television broadcasters to transmit programmes across a country, for exemplify, or from an outside broadcast spinal column to a studio. mobile units can be camera mounted, allowing cameras the freedom to move about without trailing cables. These are often seen on the touchlines of sports fields on Steadicam systems .
CableFree Microwave links have to be planned considering the follow parameters :
- Required distance (km/miles) and capacity (Mbps)
- Desired Availability target (%) for the link
- Availability of Clear Line of Sight (LOS) between end nodes
- Towers or masts if required to achieve clear LOS
- Allowed frequency bands specific to region/country
- Environmental constraints, including rain fade
- Cost of licenses for required frequency bands
Microwave Frequency Bands
Microwave signals are much divided into three categories :
extremist eminent frequency ( UHF ) ( 0.3-3 GHz ) ;
ace high frequency ( SHF ) ( 3-30 GHz ) ; and
extremely high frequency ( EHF ) ( 30-300 GHz ).
In addition, microwave frequency bands are designated by specific letters. The designations by the Radio Society of Great Britain are given below.
Microwave frequency bands
Designation Frequency scope
L band 1 to 2 GHz
S band 2 to 4 GHz
C band 4 to 8 GHz
X band 8 to 12 GHz
Ku band 12 to 18 GHz
K band 18 to 26.5 GHz
Ka band 26.5 to 40 GHz
Q band 30 to 50 GHz
U band 40 to 60 GHz
V band 50 to 75 GHz
E band 60 to 90 GHz
W band 75 to 110 GHz
F band 90 to 140 GHz
D band 110 to 170 GHz
The terminus “ P band ” is sometimes used for extremist high frequencies below the L-band. For other definitions, see letter Designations of Microwave Bands
Lower Microwave frequencies are used for longer links, and regions with higher rain fade. conversely, Higher frequencies are used for shorter links and regions with lower rain evanesce .
Rain fade refers chiefly to the assimilation of a microwave radio frequency ( RF ) sign by atmospheric rain, snow or ice, and losses which are specially prevailing at frequencies above 11 GHz. It besides refers to the degradation of a signal caused by the electromagnetic interference of the leading edge of a storm front. Rain fade can be caused by precipitation at the uplink or downlink localization. however, it does not need to be raining at a placement for it to be affected by rain fade, as the sign may pass through precipitation many miles away, specially if the satellite dish has a broken look angle. From 5 to 20 percentage of rain languish or satellite signal attenuation may besides be caused by rain, snow or ice on the uplink or downlink antenna reflecting telescope, radome or prey horn. Rain fade is not limited to satellite uplinks or downlinks, it besides can affect tellurian point to point microwave links ( those on the earth ’ s surface ) .
possible ways to overcome the effects of rain fade are locate diversity, uplink power control, variable rate encode, receiving antennas larger ( i.e. higher acquire ) than the compulsory size for normal weather conditions, and hydrophobic coatings.
Read more: Baked Potato In The Microwave
Diversity in Microwave Links
In planetary microwave links, a diverseness scheme refers to a method for improving the dependability of a message signal by using two or more communication channels with different characteristics. Diversity plays an authoritative character in combatting evanesce and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of attenuation and intervention. multiple versions of the same signal may be transmitted and/or received and combined in the telephone receiver. alternatively, a excess forward mistake correction code may be added and different parts of the message transmitted over different channels. Diversity techniques may exploit the multipath propagation, resulting in a diversity profit, frequently measured in decibels .
The be classes of diversity schemes are distinctive in Terrestrial Microwave Links :
- Unprotected: Microwave links where there is no diversity or protection are classified as Unprotected and also as 1+0. There is one set of equipment installed, and no diversity or backup
- Hot Standby: Two sets of microwave equipment (ODUs, or active radios) are installed generally connected to the same antenna, tuned to the same frequency channel. One is “powered down” or in standby mode, generally with the receiver active but transmitter muted. If the active unit fails, it is powered down and the standby unit is activated. Hot Standby is abbreviated as HSB, and is often used in 1+1 configurations (one active, one standby).
- Frequency diversity: The signal is transmitted using several frequency channels or spread over a wide spectrum that is affected by frequency-selective fading. Microwave radio links often use several active radio channels plus one protection channel for automatic use by any faded channel. This is known as N+1 protection
- Space diversity: The signal is transmitted over several different propagation paths. In the case of wired transmission, this can be achieved by transmitting via multiple wires. In the case of wireless transmission, it can be achieved by antenna diversity using multiple transmitter antennas (transmit diversity) and/or multiple receiving antennas (reception diversity).
- Polarization diversity: Multiple versions of a signal are transmitted and received via antennas with different polarization. A diversity combining technique is applied on the receiver side.
Diverse Path Resilient Failover
In sublunar distributor point to point microwave systems ranging from 11 GHz to 80 GHz, a parallel backup connect can be installed aboard a rain fade prone higher bandwidth connection. In this agreement, a elementary liaison such as an 80GHz 1 Gbit/s fully duplex microwave bridge may be calculated to have a 99.9 % handiness rate over the period of one class. The calculate 99.9 % handiness pace means that the yoke may be down for a accumulative sum of ten or more hours per year as the peaks of rain storms pass over the area. A secondary lower bandwidth liaison such as a 5.8 GHz based 100 Mbit/s bridge may be installed parallel to the primary liaison, with routers on both ends controlling automatic pistol failover to the 100 Mbit/s bridge when the primary 1 Gbit/s connection is down due to rain slice. Using this arrangement, high frequency point to point links ( 23GHz+ ) may be installed to service locations many kilometers farther than could be served with a one link requiring 99.99 % uptime over the course of one class .
Automatic Coding and Modulation (ACM)
Link adaptation, or Adaptive Coding and Modulation ( ACM ), is a term used in wireless communications to denote the match of the modulation, code and other signal and protocol parameters to the conditions on the radio connect ( e.g. the pathloss, the interference due to signals coming from early transmitters, the sensitivity of the recipient, the available transmitter power allowance, and so forth ). For example, EDGE uses a rate adaptation algorithm that adapts the intonation and coding scheme ( MCS ) according to the quality of the radio groove, and therefore the bit rate and robustness of data transmission. The march of associate adaptation is a active one and the bespeak and protocol parameters change as the radio receiver link conditions change .
The goal of Adaptive Modulation is to improve the operational efficiency of Microwave links by increasing net capacitance over the existing infrastructure – while reducing sensitivity to environmental interferences.
adaptive Modulation means dynamically varying the modulation in an errorless manner in order to maximize the throughput under fleeting generation conditions. In early words, a system can operate at its maximum throughput under clear flip conditions, and decrease it
gradually under rain slice. For model a connection can change from 256QAM down to QPSK to keep “ link alive ” without losing connection. Prior to the exploitation of Automatic Coding and Modulation, microwave designers had to design for “ worst case ” conditions to avoid link outage The benefits of using ACM include :
- Longer link lengths (distance)
- Using smaller antennas (saves on mast space, also often required in residential areas)
- Higher Availability (link reliability)
Automatic Transmit Power Control (ATPC)
CableFree Microwave links feature ATPC which mechanically increases the convey office during “ Fade ” conditions such as big rain. ATPC can be used individually to ACM or together to maximise link uptime, stability and handiness. When the “ fade ” conditions ( rain ) are over, the ATPC system reduces the transmit ability again. This reduces the stress on the microwave world power amplifiers, which reduces world power pulmonary tuberculosis, hotness generation and increases expected life ( MTBF )
- Backbone links and “Last Mile” Communication for cellular network operators
- Backbone links for Internet Service Providers (ISPs) and Wireless ISPs (WISPs)
- Corporate Networks for Building to Building and campus sites
- Telecommunications, in linking remote and regional telephone exchanges to larger (main) exchanges without the need for copper/optical fibre lines.
- Broadcast Television with HD-SDI and SMPTE standards
Because of the scalability and flexibility of Microwave technology, Microwave products can be deployed in many enterprise applications including building-to-building connectivity, disaster convalescence, network redundancy and irregular connectivity for applications such as data, voice and data, video services, aesculapian imagination, CAD and technology services, and fixed-line carrier bypass .
Mobile Carrier Backhaul
Microwave Links are a valuable tool in Mobile Carrier Backhaul : Microwave technology can be deployed to provide traditional PDH 16xE1/T1, STM-1 and STM-4, and Modern IP Gigabit Ethernet backhaul connectivity and Greenfield mobile networks. Microwave is far quicker to install and lower Total Cost of Ownership for Cellular Network Operators compared to deploying or leasing fiber ocular networks
Read more: Microwave Baked Potato – Baking Mischief
Low Latency Networks
CableFree Low Latency versions of Microwave links uses low Latency Technology, with absolutely minimal stay between packets being transmitted and received at the early end, except the Line of Sight propagation delay. The speed of Microwave propagation through the air is approximately 40 % higher than through character optics, giving customers an immediate 40 % decrease in reaction time compared to fibre optics. In summation, fiber eye installations are about never in a heterosexual channel, with realities of build up layout, street ducts and requirement to use existing telecommunication infrastructure, the fiber run can be 100 % longer than the conduct Line of Sight way between two end points. Hence CableFree Low Latency Microwave products are democratic in Low Latency Applications such as high frequency Trading and other uses .
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