Microwave Archives - Page 6 of 9

Class 4 Microwave Antennas

What is a Class 4 Microwave Antenna?

Class 4 Antennas explained:

Class 4 antennas provide the current best RF performance allowing mobile operators and Wireless Internet Service Providers (WISP) to increase the link capacity of a network by deploying new microwave links where high levels of interference are present. Class 4 antennas will allow customers to offer the highest performance in even the most congested environments. The higher side lobe suppression supports networks in ultra-dense areas and enables earlier reuse of frequencies. The lower interference increases the carrier-to-interference-ratio and allows smaller antennas with better link throughput, reducing tower leasing fees. The lower interference also enables higher modulation schemes, increasing the data capacity per antenna.

Benefits of a Class 4 Antenna

Increase the link capacity of the network
– Improved radiation patterns for ETSI Class 4 providing better performance
– Less interference and higher carrier-to-interference ratio
– Allows radios to operate at higher modulation levels
• Minimize the total cost of ownership
– Improved network efficiency
– Facilitates better re-use of a frequency channel
– Small antennas with better link throughput reduces tower leasing fees

Intended Use for Class 4 Antennas

Class 4 antennas are intended for “extremely high interference potential” situations, according to ETSI. For a more detailed treatment of antenna classifications and radiation patterns, see the ETSI document “Fixed Radio Systems; Point to Point Antennas.”

Wider channels, larger capacity

For situations where the operator needs to increase capacity from a wireless backhaul site, the easiest way remains widening the channel size. But at sites that experience extremely high interference, the operator may not be able to coordinate radio frequency pairs in wide channels with Class 3 antennas. However, moving up to Class 4 antennas would allow the operator to optimize the signal-to-noise ratio and let higher modulations come into play, so wide channels could be coordinated with correspondingly higher data rates

Smaller is Better

In cases of high interference, larger antennas can be used to reduce it. For a subset, smaller Class 4 antennas can be used instead of their oversize Class 3 counterparts. Thus, operators who deploy Class 4 antennas gain the added benefit of dropping down a parabolic dish antenna size as compared to a Class 3 antenna in the same application. In general, smaller dishes advantage the operator due to their lighter weight and lower opex tower charges, albeit with an initially bigger upfront capex. Because Class 4 antennas represent an elevated level of precision tooling and more detailed manufacturing versus lower class antennas, capex of these passive, higher-performance infrastructure pieces always weighs in the balance.

According to Andy Sutton, Principal Network Architect at EE:

Using Comsearch’s iQ.linkXG microwave planning software, CommScope analyzed the technical and commercial benefits of using Class 4 Sentinel antennas in the network. The results were most impressive. For the two frequency bands of the microwave backhaul network studied, which is comprised of over 6,200 links in total, the core findings were:

Potential savings of $5 million in total cost of ownership (TCO) over five years by enabling a greater link density and therefore reducing the need for third party Ethernet Leased Lines

Greater utilization of owned block allocated spectrum reduced the need for link by link licensing (from the national regulator) and therefore could save $44,000 in license fees over five years

$4.5 million could be saved per year based on optimizing capacity by freeing congested channels while still ensuring new links met the strict quality of service criteria

96 percent and 31 percent of links which couldn’t be planned due to frequency congestion in 40 and 10 GHz could be assigned a channel, respectively

A strong opportunity to trade some of the above by reducing antenna size and thus reducing TCO on tower lease costs

(content from EE above reproduced with acknowledgement from Commscope. Other content including photos from RFS).

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Mean Square Error (MSE) for Microwave Links

What is Mean Square Error ?

Mean Square Error (MSE) is similar to Signal-to-Noise Ratio (SNR) except that it accounts for distortion and interference in addition to noise power.

Mean Square Error MSE Microwave Link — CableFree Microwave ODU

Distortion may come from several sources such as bad Ethernet cables (poor shield, damaged, or low quality), path degradations such as multipath, or Fresnel zone encroachment.

Interference can come from other transmitters on the tower, as well as from sources inside an indoor shelter. High power transmitters inside a shelter can cause interference when near the PoE device or when located very close to the cabling.

There are maximum acceptable MSE values for each modulation which are useful in determining the quality of the link. The MSE value reported is only relevant to one tx-rx path, so the MSE of each tx-rx path must be evaluated to verify the link is operating as expected. The lower the number the better, so a -35dB is better than a -30dB.

Other possible causes for unacceptable MSE

These include

XPIC parameters are incorrect
Insufficient isolation between polarisations on an XPIC link
Insufficient performance to support high QAM modulation
Inbalance between paths on an XPIC dual polarity link

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Microwave Rain Fade Planning ITU-R P.837-6

RECOMMENDATION ITU-R P.837-6

ITU-R P.837-6 P.0837-01 – Characteristics of precipitation for propagation modelling Radiowave propagation for Terrestrial Microwave Links and Radio Links for Point to Point (P2P, PTP) and Point to Multipoint (P2MP, PTMP) deployments.

Calculations can be made for Link Availability (%) for all frequency bands, to take into account link budgets, transmit power, receive sensitivity, antenna gain, target availability and other factors. Typical Link Availability Targets are 99.99%, 99.999% and higher.

ITU-R P.837-6 P.0837-01

Recommendation ITU-R P.837 contains maps of meteorological parameters that have been obtained using the European Centre for Medium-Range Weather Forecast (ECMWF) ERA-40 re-analysis database, which are recommended for the prediction of rainfall rate statistics with a 1-min integration time, when local measurements are missing.
Rainfall rate statistics with a 1-min integration time are required for the prediction of rain attenuation in terrestrial and satellite links. Data of long-term measurements of rainfall rate may be available from local sources, but only with higher integration times. This Recommendation provides a method for the conversion of rainfall rate statistics with a higher integration time to rainfall rate statistics with a 1-min integration time.

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OFCOM Channel Plans for E-band 70GHz-80GHz

Here is a chart showing channel plans for the UK

Uses & Applications

70GHz to 80GHz bands (E-band) are used for Point to Point (P2P) Microwave (Millimeter Wave, MMW) Radio Links

Sources of Data and Graphics

All contents (C) OFCOM and taken from:

OfW48 UK Frequency Allocations for Fixed (Point-to-Point) Wireless Services and Scanning Telemetry This document shows the current bands managed by Ofcom that are available for fixed terrestrial (point to point) links and scanning telemetry in the UK.

Technical regulations

The Radio Equipment and Telecommunications Terminal Equipment Directive
99/5/EC (R&TTED) has been implemented in ‘The Radio Equipment and Telecommunications Terminal Equipment Regulations 2000, Statutory
Instrument (SI) 730. In accordance with Articles 4.1 and 7.2 of the R&TTED
the:
• IR2000: The UK Interface Requirement 2000 contains the requirements for the licensing and use of fixed (point-to-point) wireless services in the UK.
• IR2037: The UK Interface Requirement 2037 applies for scanning telemetry services.
• IR2078: The UK Interface Requirement 2078 applies for the 60 GHz band

Notes specific to the frequency charts

The first column describes each available frequency band, represented by a diagram (not to scale). The frequency band limits are listed below the diagram; frequencies below 10 GHz are represented in MHz, while those above 10 GHz are in GHz. The width of each guard band is shown above the diagram, and is always specified in MHz.
The channel arrangements in some bands are staggered, so that the width and position of the guard band vary for different channel spacings. In these cases, a table underneath gives details of the guard bands for different spacings (with all frequencies in MHz).
The first column also includes the title of the relevant international recommendations for each band, produced by the European Conference of Postal and Telecommunications (CEPT) or the International Telecommunication Union (ITU). CEPT recommendations are available at https://www.cept.org/ecc/ and ITU Recommendations at https://www.itu.int.
The final column contains the channel spacing for duplex operation in each frequency band except for bands above 60 GHz. Details of standard systems assigned in the UK are shown in the relevant technical frequency assignment criteria.