The MM200 is anideal solution for both new and retrofit microwave link installations.Maximum flexibility is achieved by an internal data multiplexer thatcombines up to four user selectable data paths into a single datastream. Interface choices for each include OC3 Optical, DS3, E3,STS-1, STM-1, SMPTE, DVB, ASI, Parallel, Overhead andT1/E1(Wayside). The IF can be field-configured with 1 to 4 chan-nels providing total flexibility. Each channel can operate up to 7Mbaud. The 2U chassis can be configured for simplex, duplex orspace diversity
Nucomm, Inc, is proud to introduce the MM200 SeriesMicrowave Modem. This innovative and highly flexible platform isconfigurable for data rates between 1 and 200 Mbps. The unitallows complete control over modulation density and channel band-width for efficiencies up to 6 Bps/Hz. The unique architecture of theMM200’s IF allows large improvements to fading and multi-pathvia multiple digital equalizers when used with the NucommFT6/FR6 microwave Transmitter and Receiver.
FEATURES
• Up to four user-selectable data/overhead interfaces
• 4, 16, 32, 64, 128 and 256 QAM operation
• Space diversity option
• Seamless hot-standby switching (optional)
• Ideal for new microwave links, upgrades or retrofits
• Wayside and/or overhead options• Reed-solomon forward error correction
• Adaptive equalization• Remote control from network or serial interface
• Companion to the Nucomm’s FT6/FR6 microwave system
High Speed 200 Mbps Microwave Modem Ebook download
Ericsson’s medium capacity point-to-point microwavesolution, MINI-LINK E, is designed for operation inany type of network. The compact microwave radiocontains cutting edge technology and provides maximumreliability. With a Mean Time Between Failure (MTBF)exceeding 30 years MINI-LINK E offers continuoushigh performance. Standardized interfaces ensure opera-tion in all types of networks.MINI-LINK E can be configured to meet any networkrequirement for capacity and range. It provides radiotransmission links from 2 up to 17x2 Mbit/s, operatingwithin the 7 to 38 GHz frequency bands.
Download Free Ebook Ericsson Mini Link Microwave Radio Link PDF file
Before getting to the nuts and bolts of designing a link, some fundamental terms and concepts need to be reviewed
Free Space Loss.
Fresnel Zone.
Receive signal level.
Receiver sensitivity
Antenna gain
Transmit Power.
Effective Isotropic Radiated Power
System Operating Margin.
Multipath Interference.
Signal-to-Noise Ratio.
Why Perform an SOM Calculation?
What Is the Minimum SOM Needed?
But even if your Fresnel zone is partially blocked, it is still possible to get a link, provided that your system was designed to have a strong signal at the other end of the link. In planning long-range microwave links where you are not sure that you have unobstructed line-of-site and clear Fresnel zone, an RF path analysis should be done. There are many software packages available that have terrain data and can create a path profile from a set of latitude/longitude coordinates. But these programs can only indicate for certain if a link will not work due to terrain obstruction. A clear path on paper is not a guarantee that your link will work, since it does not show trees or buildings. So even a “clear” link might have 80-foot trees in the way that could block the signal
Question 1: Define RF Signals?
Answer : Radio Frequency Signals are high frequency AC Signals Composed of EM Energy.
Question 2: When we get the higher signal strength in RF?
Answer: If Amplitude of the RF signal is higher then Signal Strength will be higher so as vice versa.
Question3 : why we Prefer Transmission through RF and Microwave ?
Answer : Broadband Information Signals required High Frequency Signals.
Question4: what is the speed of prorogation of RF Signals.
Answers : Speed of Propagation of RF Signals is equal to that of speed of light.
Question5 : what happens when multi path reflection occurs in RF Signal.
Answer : Signal Degradation and Holes in Coverage area of Microwave Network.
Question6: How the Antenna Gain is Calculated?
Answer : First of all direction is determined and then we calculate what would be power level at the same distance from the isotropic radiator.
Question7: when VSWR(Voltage standing Waves Ratio? occurs.
Answer7 : when their is mismatch in impedance and signal is reflected at point of impedance , which will result in decreased amplitude.
Question8: which is the commonly used transmission line RF and Microwave.
Answer: Coaxial Line.
Loss , Reflection , Refraction , Diffraction , Polaraziation , Scattering , Absorption , Fading , Intereference , Attenuation are the parameters of microwave radio communication system which will be discussed here by.
Loss : loss means decrease in siganl amplitude , which can caused because of many reasons like : resistance of cable , connectors , loss because of heat impedance mismatch.
WPC and SACFA has declared the microwave frequency range as.
6 and 7 GHz frequency range for Distance 5-50 Kms also called as Long Haul.
15,18 and 23 GHz Frequency Band are used for Access Networks distance 1-15 Km also called as Short Haul.
WPC : Wireless Planning committee , it is a government wing which take charges from operator for use of microwave frequency pair.charges they take are based on bandwidth used and annual gross revenue of the company.
SACFA : Standard Advisory Committee for frequency Allocation , it is government wing which allocates frequency and also gives tower height clearance to the telecom operators.
SACFA,ensures this thing that their is no inter fence between existing users before allocations of frequency.
SACFA, Checks before giving tower height clearance that , it should not cause obstruction to existing microwave links of other operators and should not be in a funnel zone of aircraft.
As a back haul radio For Mobile Coverage.
Long Haul for STM1 connectivity.
Point of interconnect Connectivity.
Microwave Equipment for Customer Connectivity.
Basically microwaves are electromagnetic waves with wavelength shorter then one meter and longer then one millimeter or can say frequency ranging betweeen 300mhz to 300ghz combining UHF,SHF,EHF.
Whether your link is point-to-point or point-to-multipoint, the first thing to do is to verify that it will have not only clear line of sight, but at least 60 percent of the first Fresnel zone clear of obstructions as well.
The longer thedistance, the more important this is. If the Fresnel zone is blocked, then you will get a lower signal level on the distant end than expected — even if you can literally “see” the other antenna in the distance.But even if your Fresnel zone is partially blocked, it is still possible to get a link, provided that your system was designed to have a strong signal at the other end of the link.
In planning long-range microwave links where you are not sure that you have unobstructed line-of-site and clear Fresnel zone, an RF path analysis should be done. There are many software packages available that have terrain data and can create a path profile from a set of latitude/longitude coordinates. But these programs can only indicate for certain if a link will not work due to terrain obstruction.
A clear path on paper is not a guarantee that your link will work, since it does not show trees or buildings. So even a “clear” link might have 80-foot trees in the way that could block the signal.You could be wasting your time and money if you ignore Fresnel zone issues — or worse yet, no line-of-site and attempt to set up a link anyway. You will likely not have a reliable link, if one at all.
But assuming that you do have clear line-of-site and 60 percent of the first Fresnel zone clear (or nearly clear),how can you know if you will have a good link or not? How much gain do your antennas need to have? How much coax cable loss is too much? If your link is at 2.4 GHz, should external amplifiers be used? Or given your fixed base station antenna with a pre-set gain, how far can you reach with the different types of client antennas? And which clients will need amplification?
Radio waves travel in a straight line, unless something refracts or reflects them. But the energy of radio waves is not “pencil thin.” They spread out the farther they get from the radiating source — like ripples from a rock thrown into a pond.
The area that the signal spreads out into is called the Fresnel zone (pronounced fra-nell). If there is an obstacle in the Fresnel zone, part of the radio signal will be diffracted or bent away from the straight-line path. The practical effect is that on a point-to-point radio link, this refraction will reduce the amount of RF energy reaching the receive antenna.
The thickness or radius of the Fresnel zone depends on the frequency of the signal — the higher the frequency,the smaller the Fresnel zone.
Line of sight between transmitter and receiver is a straight line and ray bending due to K-value variation is added to the terrain heights.
The modification of terrain heights is given by
(d1 x d2) / (12.74 x k)
K=1.33 for path lengths between 5 to 15 Kms
K=0.66 for longer path lengths of 15 to 30 Kms
There must be a clearance for the first Fresnel zone to avoid diffraction loss in addition to free space loss.
Clearance of 100% or greater at k=4/3
Clearance of 60% or greater at lower k values
In case of space diversity, the antenna can have a 60% clearance at k=4/3 plus allowance for tree growth, buildings (usually 3 meter)
In free space, radio signals propagate like light ie. they follow a straight line. Such a line between the transmitter and receiver, is referred to as Line-of-Sight.Microwave radio communication requires a clear line-of-sight (LOS) condition.Under normal atmospheric conditions, the radio horizon is around 30 percent beyond the optical horizon.Radio LOS takes into account the concept of Fresnel ellipsoids and their clearance criteria.
Free Space Loss
As signals spread out from a radiating source, the energy is spread out over a larger surface area. As this
occurs, the strength of that signal gets weaker. Free space loss (FSL), measured in dB, specifies how much the signal has weakened over a given distance. Figure 1 shows the formula to calculate FSL and what the theoretical loss would be at sample distances. The type of antenna used has no effect on FSL, since at any appreciable distance all antennas look like a pointsource radiator. Note that the difference in FSL between a 2.4 GHz link and a 5.8 GHz link is always about 8 dB,regardless of the distance. This is one of the reasons why 802.11a wireless local area network (WLAN) devices will have less than half the range of a 2.4 GHz WLAN device (e.g., 802.11b).
- Microwave Radio Links Requires Recurring Licence Cost.
- Bandwidth is Limited to STM1(155Mb/s).
- Medium is Exposed to Many Atomspheric uncertainites.
Advantages of Microwave Radio Link Communication.
- Less prone to accidental damage.
- Increased Bandwidth Availability
- Very Much Reliable and Less fade due to LOS
- Power Requirement are pretty low .
- Links across mountains and rivers are more economically feasible.
- They are easy to deploy and maintain.
- The medium is free.
Microwave Networks communicaion can be deifned as several Digital Microwave links Connected in a tandem providing end to end connectivity between two points.
Fast Facts on Microwave Network Communications:
- Microwave frequencies range from 2 to 60 GHz.
- Frequencies between 30 GHz and 300 GHz are referred to by IEEE as Millimeter waves (MMW) instead of Microwaves as their wavelengths are between 1 and 10mm.
- Frequencies < 3 GHz are normally used by Low capacity systems.
- Frequencies between 3 and 15 GHz are used by Medium and Large capacity systems.
- Frequencies > 15 GHz are normally used Large capacity systems for short haul links.
