spectrum standards

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 microwave

transmission and how they are divided into channels.

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

Radio communication 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 Radio communication 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.

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.

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.