lzu1022056 r2a microwave transmission technology fundamentals - regulation

8/18/2019 LZU1022056 R2A Microwave Transmission Technology Fundamentals - Regulation

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Ericsson INTERNAL ONLY LZU 1022056 R2A

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This module was developed for E-Learning,

which may impact the graphics in the print copy.

Welcome to this Microwave Transmission Technology Fundamentals course

about frequency regulation and equipment standards.

After the course you will have a basic understanding of the following:

International Spectrum Recommendations and Equipment Standards

applicable to Microwave Systems

The role of National Regulation Authorities

Spectrum Licenses and the License Application Process

Radio Channels

To navigate in the course and jump between pages use the Menu button. The

Audio button allows switching the audio on or off and to read the subtitles. The

help button will give this navigation information in writing. The Notes button gives

access to a personal notes field. Click the replay button to view the animation

again and the play/pause button to start or stop the animation. And finally use the

Back or Next button to go to previous or next page.

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The agenda for the course:

Our first topic is to define why standardization is important in radio

communication.

Then we look at some relevant standardization bodies.

In the chapter Spectrum Standards we will look into how frequency bands are

defined and examples of how to subdivide into channels.

After this we will have a generic look at how to apply for a frequency license and

what is meant by “Light Licensing”.

The course is then ended by a summary.

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We start by having a look at why standardization is so important.

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The graph shows the electromagnetic spectrum from around 100 kilohertz and up to

approximately 100 gigahertz.

This frequency range is the natural resource available for radio communication.To make the most of this limited resource it is necessary to regulate and harmonize the use of it.

This regulation cannot be handled by each country alone. Radio signals don’t stop at national

borders. Also, agreements about international services are needed. Therefore the harmonization

work is shared between international regulators, or standardization bodies, and national

authorities.

Good examples of this are GSM and UMTS where standardization means that the same mobile

devices can be used in almost every country. Travelers carry and use their own mobile devices

when visiting other countries.

The GSM standardization also gives the user as well as the network operator the possibility to

choose equipment from different manufacturers. Thus, GSM standardization has helped create aglobal market for mobile phones and network equipment.

Other examples of where world-wide standardization is essential are air traffic control, ship to

shore and ship to ship communication, WiFi and satellite orbits.

Spectrum management aims to prevent interference between services and interference between

users within the same service.

Interference can occur when two transmitters use the same frequency. They can disturb each

other and both services can become unavailable. Spectrum management assigns frequencies so

that this will not happen, for example by making sure that stations that are close to each other

don’t use the same frequency.

Frequency assignments also have to ensure the efficient use of the spectrum.

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So, let us look at which the main standardization bodies are.

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The International Telecommunication Union in Geneva is the United Nations

specialized agency for information and communication technologies.

The subsidiary radio communication sector ITU-R is specialized in global

management of the radio-frequency spectrum and satellite orbits.

Every three to four years, ITU-R organizes the World Radio communication

Conference. At this conference directions for future use of the radio spectrum are

outlined and decided. Example of this is to assign an additional frequency band to

an existing service or a frequency band for a new service. Participants in the

conference are mainly national frequency authorities and network operators.

ITU-R also issues recommendations in various other Radiocommunication

matters.

The main outcome from the WRC is the Radio Regulations document collection

which is the international treaty that governs the use of the radio spectrum.

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The international Radio Regulations treaty specifies which part of the spectrum is

assigned to fixed services where the stations are not mobile.

The graph gives a summary of the frequency bands which are assigned for

microwave radio links. The ITU-R publishes a recommendation about frequency

range and alternatives for channel subdivision for each frequency band.

ITU-R also publishes other recommendations related to microwave radio links.

Examples are prediction methods for wave propagation and radio link

performance calculations. This is however out of the scope of this course.

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The Electronic Communications Committee, abbreviated ECC, is a European

organization for spectrum management.

It is a part of the European Conference of Postal and Telecommunications

Administrations, CEPT. As the name of the mother organization indicates ECC

mainly consists of national frequency authorities.

As within ITU-R the work within ECC is organized in work groups. Each work

group concentrates on a specific topic. Of most interest for microwave radio links

is the Spectrum Engineering work group 19, SE19. , This group deals with

spectrum management for fixed services, including microwave radio links. To put

it simply, ECC SE19 specifies how to apply the ITU-R spectrum

recommendations for fixed services in Europe. For example specification of

channel patterns for different channel bandwidths.

Members of the ECC with the right to vote are the European national frequency

regulation authorities and network operators. Equipment manufacturers, like

Ericsson, can participate as observers.

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The shown example is ECC recommendation 05 07.

This is the European specification of how to deploy the frequency band 71 to 76

and 81 to 86 Gigahertz for fixed services. Like all ECC spectrumrecommendations, the document can be downloaded from the ECC web site.

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The European Telecommunications Standards Institute, ETSI, is an European

independent, non-profit organization with the task to produce technical standards

for telecommunication equipment.

ETSI produces European standards and is recognized by the European Union

and national regulatory authorities within the EU. The standards are however

produced to be globally applicable and are recognized also by regulatory

authorities in many non-European countries.

Equipment standards issued by ETSI describe technical characteristics for many

parts of microwave systems, for example for transmitters, receivers and

antennas.

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The ETSI standardization work is organized in technical committees subdivided

into work groups.

Standards for microwave transmission equipment are produced mainly within the

ETSI workgroup Transmission and Multiplexing 4, TM4, which is a part of the

Access, Terminals, Transmission and Multiplexing Committee, ATTM.

Members with voting rights are equipment manufacturers, like Ericsson, and

network operators.

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To allow the usage of microwave transmission equipment, all European and many

non-European national authorities require that the equipment must meet the ETSI

standards.

ETSI standards are published in different series. Here are two examples; EN

302 217 and EN 300 019.

Series EN 302 217 is the main standard for point to point microwave transmission

equipment. It consists currently of six different publications and states technical

specifications for radio equipment and antennas.

Series EN 300 019 is a more generic standard for electronic equipment which

specifies under what environmental conditions the equipment shall be

operational. This is specified for equipment intended for indoor and outdoor useand in operation, storage and transportation.

ETSI standards are available for download from the ETSI web site, etsi.org.

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There are several additional standardization institutes which are relevant to telecommunications

equipment.

ITU-T, the Telecommunication sector of the ITU, issues recommendations for nearly everyaspect of telecommunication. The given example, ITU-T recommendation G 703, is the

electrical specification for PDH, SDH and Sonet interfaces which are very common in

Microwave equipment.

However, most new microwave deployments are now for Ethernet traffic. Ethernet interfaces

and traffic handling is specified by the Institute of Electrical and Electronics Engineers IEEE (“I

triple E”). I triple E recommendations 802.3 are examples of standards which are fundamental

for Ethernet technology

Internet Protocols are widely used for management of microwave networks. Protocols and

standards for Internet traffic are specified in so called Request for Comments, RFC, from theInternet Engineering Task Force, IETF. An example of an IETF standard is the RFC 791 which

is basic for data communication over the Internet.

A perhaps somewhat simplified way to summarize is that ITU-T specifies TDM traffic and

interfaces, IEEE Ethernet Layer 2 interfaces and traffic and the IETF IP Layer 3 Internet

Protocol.

The International Electrotechnical Commission IEC is a standardization body which specifies

equipment building practice and electrical safety requirements.

Requirements for equipment enclosures are for example standardized in recommendation EN

60 950-1.

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Spectrum usage and radio equipment specification requirements are handled by the national

regulatory authority in each country. It has the final decision over the national spectrum usage. The

task is to ensure most efficient use of available spectrum.Each national regulatory authority can chose to strictly follow the ITU-R or for example ECC

recommendations or to deviate from them. Since national authorities are members of the ITU-R

and ECC such national variations are often included in the recommendations.

On request, the national authorities will give the right to use a specific channel or part of the

spectrum to a network operator or other user. This process is called “frequency licensing”. To keep

track of the licenses awarded each authority is maintaining a database over the national spectrum

usage. Before a new license is given, the authority will verify that already licensed spectrum users

will not be affected.

Equipment properties are essential for good spectrum economy. For this reason radio equipmenttypically has to be technically certified before it is allowed to be put into service. This certification is

referred to as Homologation and is carried out in lab tests by the national authority itself or by an

appointed test institute. The baseline for the Homologation can be national technical specifications

or for example the ETSI equipment standards.

The national authority can also make technical requirements as a condition for granting a

frequency license in order to ensure efficient use of spectrum.

For Microwave transmission, this could mean mandatory use of Automatic Transmitter Power

Control or dual polarization with Cross Polar Interference Canceller.

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In order to separate different transmitters, frequency bands are subdivided into

sections called channels.

In this chapter we will see which main frequency bands there are for microwavetransmission and how they are divided into channels.

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Here we see which frequency bands are currently assigned to fixed microwave.

Remember, this assignment is done by ITU-R and the World

Radiocommunication Conference.

The bands which are indicated by blue color are the traditional bands which have

been in use for long time. They are quite heavily used today. In some countries it

can be hard to find free spectrum for new deployments in these bands.

Because of this, new bands have been assigned. Quite recently the bands 42, 60

and 80 gigahertz were opened by the World Radiocommunication Conference.

The 50, 52 and 55 gigahertz bands are assigned for future microwave

deployments…

…and the 95 gigahertz band is currently under study by the standardization

bodies for future deployment as well.

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The ITU-R publishes one recommendation document per frequency band.

These recommendations specify high and low band ends as well as channel

arrangement. Alternative channel arrangements, or band limits, which are applied

by other standardization bodies, like ECC, are often referred to in annexes to the

main recommendation.

ITU documents are numbered. The document numbers for the ITU-R channel

arrangement recommendations start with the letter F. The examples shown are

recommendation F 385 for the 7 gigahertz band, F 637 for the 23 gigahertz band

and F 2006 for the 80 gigahertz band.

ITU-R recommendations can be downloaded from the ITU-R website.

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The ITU-R recommends Frequency Division Duplex for most fixed services.

Frequency Division Duplex means that one channel is assigned for

communication in each direction. In this way the system can transmit

simultaneously in both directions. Together these two channels form one channel

pair.

A channel pattern is created by equally dividing the frequency band into a lower

and an upper half band. Each channel pair will consist of one channel in each half

band.

The difference between lower and upper channel center frequency is the same

for all channel pairs within a certain channel pattern. It is called duplex frequency

or duplex distance.

The diagram shows a pattern with five channel pairs.

Channels in the lower half band are labeled f 1 to f 5. Channels in the upper half

band are labeled f prime 1 to f prime 5.

Each channel pattern specifies channel spacing between the center frequencies

of adjacent channels. Channel spacing is always the same in upper and lower

half band.

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This is an example of a channel pattern for the 7 gigahertz band which is taken

from ECC recommendation 02 06. This pattern has five channel pairs.

Lower band end for this pattern is specified to 7425 megahertz, upper band end

to 7725 megahertz and band center to 7575 megahertz.

The channel spacing is 28 megahertz, meaning the centre frequencies of

adjacent channels are 28 megahertz apart.

The duplex frequency in this pattern is 154 megahertz.

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The available bandwidth for each channel is the same as the channel spacing.

This is 28 megahertz in this case. There are no gaps between the channels.

For example channel 2 in lower half band, f 2, occupies the frequency range

between 7456 and 7484 megahertz and in the upper band, f prime 2, between

7614 and 7642 megahertz.

The channel spacings and bandwidths are the same in the lower and upper half

bands of each channel pattern. This way the same amount of bandwidth is

available for the two directions of a radio hop.

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ITU-R, ECC and commonly also national channel patterns specify alternatives for

different channel spacing and thereby different channel bandwidth.

This channel pattern example is from ECC recommendation T R 13 02 for the 23

gigahertz band. It shows how the frequency band can be subdivided into many

channels with narrow bandwidth or just a few wide channels.

So the same band can be used for 168 channels with 3.5 megahertz each or 5

channels of 112 megahertz.

If the band is divided into many narrow channels, many radio link hops can

coexist in the same geographical area without interfering with each other.

If wide channels are used, each hop can transport a higher traffic capacity but atthe same time the number of hops that can coexist without interfering with each

other will be reduced.

It is the task of microwave radio planners at the regulatory authority, or in some

cases at an operator, to find the optimum use of the spectrum while considering

needed traffic capacities and interference.

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Technical evolution has over the years made it possible to make better use of the available spectrum. We will here see

some examples of how this has been achieved.

The first example shows a typical channel usage in an older technology multicarrier system. Such systems could

commonly not isolate adjacent channels well enough from each other. Applying adjacent channels would result in

unacceptably high interference and consequently poor hop performance. The solution to this was to only use every second

channel and to leave the channels in between unused as so called guard channels. From a spectrum efficiency point of

view this was of course not a perfect solution.

Better spectrum efficiency was achieved by the introduction of the configuration Adjacent Channel Alternating Polarization,

ACAP. In this adjacent channels are using different antenna polarization. The extra isolation this gives helped to eliminate

destructive interference between adjacent channels. By this there was no longer need for unused guard channels. ACAP

used to be an attractive solution because it offered double data rate in the same spectrum. At the time this was well worth

the additional costs for a more complex system with two polarizations

ACAP has today lost its spectrum advantage and it is now rarely used in new deployments. The only very rare situation

where it still may have relevance is to avoid channel overlap in systems where for some reason the channel bandwidth is

allowed to be larger than the channel spacing.

When the technical evolution had made it possible to introduce radio equipment with good enough isolation between

adjacent channels the configuration Adjacent Channel – Co Polarization, ACCP, was introduced.

Compared to ACAP the spectrum efficiency is still the same. The benefit is that it can now be achieved with a less complex

and less expensive antenna system.

ACCP is today used in cases where spectrum availability is not a limiting factor or where dual polarization is not advisable

because of propagation conditions

With modern equipment the best spectrum economy is achieved by the configuration Co Channel Dual Polarization, CCDP.

Adjacent channels are used and each channel is used in both antenna polarizations. Compared to ACCP and ACAP the

data rate is doubled without using more bandwidth.

The introduction of the signal processing technique Cross Polar Interference Canceller, XPIC, opened for today’s wide use

of CCDP. By this technique a CCDP system will have the same hop performance as an ACCP system. And twice the

capacity.

Technical achievements have in these and other ways over the years made it possible to use the spectrum in more efficient

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ways. The evolution will not stop here; it is likely that the future will see new technical

achievements that will further increase the efficient use of the limited natural resource frequency

spectrum.

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Assignment of spectrum is handled by national authorities.

In this chapter we will discuss how to apply for a frequency license.

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The absolute majority of the radio spectrum is regulated. To be allowed to

transmit requires a frequency license from the national frequency regulation

authority. The purpose of regulation is to avoid interference between neighboringservices and users and to ensure best possible use of available spectrum.

Some frequency ranges, typically used for consumer applications, are however

unregulated. Examples are microwave ovens, Wireless LAN, Bluetooth and baby

alarms which all can be operated without applying for a frequency license.

However, this can cause issues when many users access the same spectrum –

an effect that is well known to many of us who live in apartment buildings where

every neighbor has his own wireless LAN.

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Frequency bands assigned for microwave radio are with a few exemptions all

regulated and so frequency licenses are required.

Examples of unregulated microwave bands are parts of the 5 gigahertz band and

the lower part of the 60 gigahertz band. Due to the physical propagation

properties the lower part of the 60 gigahertz band can only be used for very short

ranges, typically between close by buildings. Because of the short range it is not

considered necessary to regulate this part of the band.

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So how does the licensing procedure work? Naturally the details are different

between countries – but the essentials are these:

An operator who wants to install and use a microwave radio link hands in a

license application to the national frequency authority. The application shall at

least state the location of the two end stations, the intended type of equipment,

and the type of traffic. In some cases the operator can also suggest a frequency

channel.

The frequency authority checks its database for already used channels in the

area and assigns a channel pair that will not harmfully interfere with existing

users. The database is updated with frequency channel, coordinates, and

required equipment properties for the new hop.

The license given to the operator might read like this:

“You may use channel pair number 2 according to ITU-R F.637 with vertical

polarization between coordinates x and y for the next 5 years. You have to use

antennas of ETSI Class 3 or higher. You have to use ATPC and may not exceed a

transmit power of 30dBm. You have to pay an annual license fee.”

After paying the fee, the Operator can install the radio hop and put it into

operation.

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Frequency licenses can be given on a hop by hop basis, which is the most

common, or as a frequency block allocation to a network operator.

In the hop by hop case the frequency authority specifies which channel shall be

used for each individual hop. The authority analyses the interference between

hops and assigns channels so that all hops work properly. This often requires

taking into account interference between equipment deployed or planned by

competing operator companies. These companies will normally not be prepared

to share information about their networks with each other. So only the authority

has the required information about all hops in an area to say what frequencies

are still free.

In the block allocation case the operator is given a certain spectrum range that it

can freely use within a defined geographical area, for example a city.

The operator is responsible for subdividing the spectrum into channels and to use

it in the optimum way within its network. Separate spectrum licenses for each hop

are not required. The operator can do its own interference analysis because no

other operators are allowed to use the assigned spectrum in the same area.

Authorities tend to prefer hop-by-hop allocation over block allocation since it is

considered to give more efficient spectrum usage.

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Authorities in some countries use a simplified licensing process for some frequency

bands. Propagation conditions in the 80 gigahertz band, for example, allow only limited

ranges, so some authorities have chosen to apply so-called “Light Licensing”.

Light Licensing is done on a hop by hop basis according to the first come first served

principle..

Here is an overview of the process:

The national regulation authority keeps a publically accessible database of already

installed radio links in Light Licensing bands. The database contains operator name,

used channel pair, location, and equipment properties.

The operator starts by checking the database and hopefully finds a channel pair whichcan be used. In the selection process a predefined value for maximum allowed

interference to already installed links is used.

The operator records the data for the new hop into the database and can now install the

new hop and take it into operation. There is no need to wait for an approval from the

authority.

The process has gained large interest among authorities and operators because of its

simplicity. However it is not quite clear yet if this simplified licensing process can

adequately handle spectrum conflicts between users.

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By this we have covered the topics in the course and it is time to summarize.

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By this the course is ended.

I thank you for your interest and hope you have found it to be useful.

lzu1022056 r2a microwave transmission technology fundamentals - regulation

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