FWACC (00)02
SE PT19(2000)….
DRAFT
Source:
Date:
Subject:
RA
January 2000
Nominated Bandwidth Concept
Introduction
The concept of Nominated Bandwidth was introduced by ETSI TC SES (Satellite
Earth Stations) to deal with unwanted emissions from competing radio systems using
different technolgies in the same frequency band. The concept, subsequently adopted
and approved by ITU-R1, may be applicable to other radio services and systems, for
example Fixed Wireless Access (FWA), where the existing ITU-R definitions for
necessary bandwidth2 and occupied bandwidth3 may not provide sufficient flexibility
or efficiency of spectrum use. This paper proposes that the concept of nominated
bandwidth be taken into account when developing standards and guidelines for FWA.
Nominated bandwidth
There are several parts to the definition currently used for nominated bandwidth.
These are explained below. The definition of nominated bandwidth adopted and
approved by ITU-R is also provided, since the ITU-R definition is explained in
mathmatical terms. However, the ITU-R definition was constructed for a particular
case (mobile satellite earth stations terminals sharing the 1610 – 1626.5 MHz band).
Specific parts of the definition may therefore not be applicable to other applications.
i.
Nominated bandwidth of the [stations] frequency transmission is nominated
the the manufacturer. This provides manufacturers with a degree of flexibility
when deciding on the necessary bandwidth of the equipment. It allows for
mixed technology solutions (e.g. TDD/TDMA and DS/CDMA) to be
implemented in one product standard or specification. It makes no
assumptions regarding channel or block arrangements based on the technical
requirements of equipments, e.g. bit rate, voice/data, spectrum mask.
ii.
The nominated bandwidth shall encompass all close-in spectral elements of
the transmission which have a level greater than the specfied spurious levels.
This deals with single line spectra arising from the modulation scheme (access
code) used. It was recognised at an early stage that spectrum mask definitions
could work to the disbenefit of certain modulation schemes where descrete
line spectra are produced as a function of the scheme. It still provides inter-
1
ITU-R M 1343.
Necessary bandwidth: For a given class of emission, the width of the frequency band which is just
sufficient to ensure the transmission of information at the rate and with the quality required under
specified conditions.
3
Occupied bandwidth: The width of a frequency band such that, below the lower and above the upper
frequency limits, the mean powers emitted are each equal to a specified percentage /2 of the total
mean power of a given emission.
2
service and intra-service, inter-system protection outside the nominated
bandwidth.
iii.
The nominated bandwidth shall be wide enough to take account of the transmit
carrier frequency stability. This is used to address the overall frequency
stability of the equipment. Where competing systems occupy adjacent
frequency bands, and use different modulation/coding schemes (e.g. CDMA
and FDMA/TDMA), the guardband for each is different. Frequency drift can
increase frequency overlap between the systems, increasing system noise
levels. An increase in system noise usually results in a decrease in traffic
capacity. This decrease in capacity will vary according to the
modulation/code scheme used. When considering the flexible use of a
frequency band it is important that the operators can take this into account
through the technical definitions used to specify their requirements.
iv.
The nominated bandwidth shall be within the [stations] transmit frequency
band within which the [station] operates. On the assumption that a station
would be licensed to operate in accordance with the Table of Allocations of
the Radio Regulations, this part of the definition limits the nominated
bandwidth to the allocated band. It affords protection to other radio services.
ITU-R definition
ITU-R Recommendation M.1343 defines nominated bandwidth (Bn) in the following
manner.
The Bn of the [stations] radio-frequency transmission is wide enough to encompass all
spectral elements of the transmission which have a level greater than the specified
levels of unwanted emissions. The Bn is defined relative to the [stations] actual carrier
frequency fc.
Bn is the width of the frequency interval (fc-a, fc+ b), where a and b, which is specified
by the terminal manufacturer, may vary with fc.
The frequency interval (fc-a, fc+ b) does not encompass more than either:
i)
ii)
iii)
when a = b, 4 nominal carrier frequencies for narow-band systems;
when a  b, 1 nominal carrier frequency for narrow-band systems; or
1 nominal carrier frequency for wide-band systems.
The frequency interval (fc-a, fc+ b) is within the assigned band of the [stations]
terminals.
It is interesting to note that no definitions for narrow-band or wide-band systems are
given by the Recommendation.
Unwanted emissions
To clarify where out-of-band4 and unwanted emissions5 apply, current ETSI standards
specify that unwanted emissions are those falling outside the nominated bandwidth.
Proposal
Operators wishing to roll out FWA systems are searching for flexible band plans that
facilitate technical and business development. They are keen to achieve economies of
scale based on harmonised spectrum plans and a favourable regulatory framework.
Administrations are keen to assist operators and to ensure, as far as possible, that
spectrum is efficiently used.
It is propsed that SE PT19 consider the nominated bandwidth concept as a tool for
frequency engineering and management of FWA spectrum.
_______________________
4
Out-of-band: Emission on a frequency or frequencies which are outside the necessary bandwidth
which results from the modulation process, but excluding spurious emissions.
5
Unwanted emission: Consist of spurious emissions and out-of-band emissions.