ETSI TR 103 230 V1.1.1 (2018-01)

ETSI TR 103 230 V1.1.1 (2018-01)






TECHNICAL REPORT
Fixed Radio Systems;
Small cells microwave backhauling

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2 ETSI TR 103 230 V1.1.1 (2018-01)



Reference
DTR/ATTM-04027
Keywords
BWA, radio, transmission

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3 ETSI TR 103 230 V1.1.1 (2018-01)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Abbreviations . 8
4 Small Cell Application Scenario . 8
4.1 Small Cell Definition. 8
4.2 Small Cell Use Cases Choice . 10
4.3 Small Cell Backhauling Requirements . 11
4.3.0 General . 11
4.3.1 Capacity . 11
4.3.2 Latency and delay . 13
4.3.3 Security . 13
4.3.4 Frequency and Time Synchronization . 13
4.3.5 Availability/Objectives . 13
4.3.6 Ethernet Features . 14
5 Radio Specific Aspects Overview . 14
5.1 Channel transport capacity . 14
5.2 Link Planning . 15
5.2.0 General . 15
5.2.1 Propagation Model Suitable for Application Scenario . 15
5.2.2 FDD & TDD . 17
5.3 Frequency Bands . 17
5.4 Line-Of-Sight (LOS) . 20
5.5 Non-Line-Of-Sight (NLOS)/Mixed LOS and NLOS Solutions Coexistence . 20
5.6 Antennas . 20
Annex A: Depolarization field test in NLoS scenarios . 22
A.1 Introduction . 22
A.1.0 General . 22
A.1.1 Diffraction test . 22
A.1.2 Reflection test . 23
A.1.3 Tree leaf penetration scenario . 24
A.2 Impact of depolarization effect in NLoS . 24
A.3 Insight in Physical Phenomena on Depolarization . 25
A.3.1 Overview . 25
A.3.1.0 General . 25
A.3.1.1 Reflection scenario . 25
A.3.1.2 Diffraction scenario . 26
A.3.1.3 Further analysis . 27
A.4 Conclusion . 27
Annex B: Bibliography . 28
History . 29

ETSI

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4 ETSI TR 103 230 V1.1.1 (2018-01)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Access, Terminals, Transmission and
Multiplexing (ATTM).
Modal verbs terminology
In the present document "should", "should not", "may", "need not", "will", "will not", "can" and "cannot" are to be
interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The present document studies the main characteristics of the Small Cell Backhauling.
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5 ETSI TR 103 230 V1.1.1 (2018-01)
1 Scope
The present document investigates the possible impacts to standard documentations in charge to ETSI TM4 working
group.
The starting point is represented by the definition of Small Cell coming from Standards, Mobile Operators and
Technical Literature and the characterization of one or more (maximum three) deployment scenario(s).
Preliminary studies, based on recognized Small Cell backhauling requirements, would be carried on within TM4 and,
whenever encouraging results happen, other SDO's, e.g. ECC SE19, will be involved for possible review of the issues
from regulatory point of view.
Frequency bandwidths from sub 6 GHz, trough traditionally coordinated MW bands (6 GHz to 56 GHz) and up to
mmWV (above 57 GHz) are inside the scope of the present document.
Satellite, White Space, WiFi applications and frequency bands together with Wired solutions are considered out of the
scope of the present document.
Backhaul carried on by Point to Multipoint systems, and backhaul realized by means of complex system mechanisms
(e.g. multiple distributed MIMO) are outside the scope of the present document.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] NGMN White Paper: "Small Cell Backhaul Requirements", June 2012.
[i.2] NGMN White Paper: "Guidelines for LTE Backhaul Traffic Estimation", July 2010.
[i.3] Report ITU-R M.2290-0: "Future spectrum requirements estimate for terrestrial IMT".
[i.4] ETSI EN 302 217-4-2 (V1.5.1): "Fixed Radio Systems; Characteristics and requirements for point-
to-point equipment and antennas; Part 4-2: Antennas; Harmonized EN covering the essential
requirements of article 3.2 of the R&TTE Directive".
[i.5] ETSI EN 302 217-4-1: "Fixed Radio Systems; Characteristics and requirements for point-to-point
equipment and antennas; Part 4-1: System-dependent requirements for antennas".
[i.6] Recommendation ITU-R P.530: "Propagation data and prediction methods required for the design
of terrestrial line-of-sight systems".
[i.7] Recommendation ITU-R P.526: "Propagation by diffraction".
[i.8] Recommendation ITU-R P.1410: "Propagation data and prediction methods required for the design
of terrestrial broadband radio access systems operating in a frequency range from 3 to 60 GHz".
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6 ETSI TR 103 230 V1.1.1 (2018-01)
[i.9] Recommendation ITU-R P.1411: "Propagation data and prediction methods for the planning of
short-range outdoor radiocommunication systems and radio local area networks in the frequency
range 300 MHz to 100 GHz".
[i.10] ETSI TS 133 401: "3GPP System Architecture Evolution (SAE); Security architecture". Digital
cellular telecommunications system (Phase 2+); Universal Mobile Telecommunications System
(UMTS); LTE; 3GPP System Architecture Evolution (SAE); Security architecture
(3GPP TS 33.401).
[i.11] Recommendation ITU-R M.1768-1: "Methodology for calculation of IMT spectrum".
[i.12] ECC/REC/14-03: "Harmonised radio frequency channel arrangements and block allocations for
low and medium capacity systems in the band 3400 MHz to 3600 MHz".
[i.13] CEPT/ERC/REC 12-08: "Harmonised radio frequency channel arrangements and block allocations
for low, medium and high capacity systems in the band 3600 MHz TO 4200 MHz".
[i.14] ECC/REC/(14)01: "Radio frequency channel arrangements for FS systems operating in the band
92-95 GHz".
[i.15] ECC/REC 14-02: "Radio frequency channel arrangements for high, medium and low capacity
digital fixed service systems operating in the band 6425 to 7125 MHz".
[i.16] ECC/REC/(02)06: "Channel arrangements for digital fixed service systems operating in the
frequency range 7125 -8500 MHz".
[i.17] CEPT/ERC/REC 12-05: "Harmonised radio frequency channel arrangements for digital terrestrial
fixed systems operating in the band 10.0 - 10.68 GHz".
[i.18] ERC/REC 12-06: "Preferred channel arrangements for fixed service systems operating in the
frequency band 10.7-11.7 GHz".
[i.19] ERC/REC 12-02: "Harmonised radio frequency channel arrangements for analogue and ditigal
terrestrial fixed systems operating in the band 12.75-13.25 GHz".
[i.20] ERC/REC 12-07: "Harmonised radio frequency channel arrangements for digital terrestrial fixed
systems operating in the bands 14.5 - 14.62 GHz paired with 15.23 - 15.35 GHz".
[i.21] CEPT/ERC/REC 12-03: "Harmonised radio frequency channel arrangements for digital terrestrial
fixed systems operating in the band 17.7 GHz to 19.7 GHz".
[i.22] Recommendation T/R 13-02: "Preferred channel arrangements for fixed service systems in the
frequency rang 22.0 - 29.5 GHz".
[i.23] ECC/REC/(11)01: "Guidelines to FWS in 24.5-26.5/ 27.5-29.5/ 31.8-33.4 GHz".
[i.24] ERC/REC(01)02: "Preferred channel arrangements for fixed service systems operating in the
frequency band 31.8 - 33.4 GHz".
[i.25] Recommendation T/R 12-01: "Preferred channel arrangements for fixed service systems operating
in the frequency band 37.0 - 39.5 GHz".
[i.26] ECC Recommendation (01)04: "Recommended guidelines for the accommodation and assignment
of multimedia wireless systems (MWS) and point-to-point (P-P) fixed wireless systems in the
frequency band 40.5 - 43.5 GHz".
[i.27] ERC Recommendation 12-11: "Radio frequency channel arrangements for fixed service systems
operating in the bands 48.5 to 50.2 GHz / 50.9 to 52.6 GHz".
[i.28] ERC Recommendation 12-12: "Radio frequency channel, arrangement for Fixed Service Systems
operating in the band 55.78 to 57.0 GHz".
[i.29] ECC/REC/(09)01: "Use of the 57 - 64 GHz frequency band for point-to-to point fixed wireless
systems".
[i.30] ECC/REC/(05)02: "Use of the 64-66 GHz frequency band for fixed service".
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7 ETSI TR 103 230 V1.1.1 (2018-01)
[i.31] ECC/REC/(05)07: "Radio frequency channel arrangements for fixed service systems operating in
the bands 71-76 GHz and 81-86 GHz".
[i.32] Recommendation ITU-R F.635-6: "Radio-frequency channel arrangements based on a
homogeneous pattern for fixed wireless systems operating in the 4 GHz (3 400-4 200 MHz) band".
[i.33] Recommendation ITU-R F.382-8: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 2 and 4 GHz bands".
[i.34] Recommendation ITU-R F.1099-4: "Radio-frequency channel arrangements for high- and
medium-capacity digital fixed wireless systems in the upper 4 GHz (4 400-5 000 MHz) band".
[i.35] Recommendation ITU-R F.383-8: "Radio-frequency channel arrangements for high-capacity fixed
wireless systems operating in the lower 6 GHz (5 925 to 6 425 MHz) band".
[i.36] Recommendation ITU-R F.384-11: "Radio-frequency channel arrangements for medium- and
high- capacity digital fixed wireless systems operating in the the 6 425-7 125 MHz band".
[i.37] Recommendation ITU-R F.385-10: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 7 110-7 900 MHz band".
[i.38] Recommendation ITU-R F.386-8: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 8 GHz (7 725 to 8 500 MHz) band".
[i.39] Recommendation ITU-R F.747-1: "Radio-frequency channel arrangements for fixed wireless
system operating in the 10.0-10.68 GHz band".
[i.40] Recommendation ITU-R F.387-12: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 10.7-11.7 GHz band".
[i.41] Recommendation ITU-R F.497-7: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 13 GHz (12.75-13.25 GHz) frequency band".
[i.42] Recommendation ITU-R F.636-4: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 14.4-15.35 GHz band".
[i.43] Recommendation ITU-R F.595-10: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 17.7-19.7 GHz frequency band".
[i.44] Recommendation ITU-R F.637-4: "Radio-frequency channel arrangements for fixed wireless
systems operating in the 21.2-23.6 GHz band".
[i.45] Recommendation ITU-R F.748-4: "Radio-frequency arrangements for systems of the fixed service
operating in the 25, 26 and 28 GHz bands".
[i.46] Recommendation ITU-R F.746-10: "Radio-frequency arrangements for fixed service systems".
[i.47] Recommendation ITU-R F.1520-3: "Radio-frequency arrangements for systems in the fixed
service operating in the band 31.8-33.4 GHz".
[i.48] Recommendation ITU-R F.749-3: "Radio-frequency arrangements for systems of the fixed service
operating in sub-bands in the 36-40.5 GHz band".
[i.49] Recommendation ITU-R F.2005: "Radio-frequency channel and block arrangements for fixed
wireless systems operating in the 42 GHz (40.5 to 43.5 GHz) band".
[i.50] Recommendation ITU-R F.1496-1: "Radio-frequency channel arrangements for fixed wireless
systems operating in the band 51.4-52.6 GHz".
[i.51] Recommendation ITU-R F.1497-1: "Radio-frequency channel arrangements for fixed wireless
systems operating in the band 55.78-66 GHz".
[i.52] Recommendation ITU-R F.2006: "Radio-frequency channel and block arrangements for fixed
wireless systems operating in the 71-76 and 81-86 GHz bands".
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8 ETSI TR 103 230 V1.1.1 (2018-01)
[i.53] Recommendation ITU-R F.2004: "Radio-frequency channel arrangements for fixed service
systems operating in the 92-95 GHz range".
3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
BS Base Station
BW BandWidth
ECC Electronic Communications Committee
EM Electro Magnetic (Field)
FDD Frequency Division Duplex
FS Fixed Service
FSL Free Space Loss
HH Horizontal Horizontal (Polarization)
HSPA High Speed Packet Access
IMT International Mobile Technology
ITS Intelligent Transportation System
LOS Line Of Sight
MIMO Multiple Input Multiple Output
mmWV millimetre WaVe
MW MicroWave
NGMN New Generation Mobile Networks
NLOS Non Line Of Sight
QAM Quadrature Amplitude Modulation
QoE Quality of Experience
RF Radio Frequency
SDO Standard Developing Organization
TDD Time Division Duplex
TR Technical Report
TS Technical Standard
UTD Uniform Theory of Diffraction
VV Vertical Vertical (Polarization)
XPIC Cross-Polar Interference Cancellor
4 Small Cell Application Scenario
4.1 Small Cell Definition
Small Cell definition is an input definition from SDO's, Mobile Operators and Technical Literature: "Small cells" is an
umbrella term for operator-controlled, low-powered radio access nodes, including those that operate in licensed
spectrum and unlicensed carrier-grade Wi-Fi.
Small cells are felt as a solution to cope with expected evolution of mobile networks, which will need higher traffic
densities than today.
Such traffic management could greatly benefit from provision of cells much smaller than actual macrocells, avoiding
the necessity of increasingly complex equipment to control a very high number of access devices in a big cell.
Small cells are generally understood as low-powered radio access nodes operating in licensed and unlicensed spectrum,
with a range of 10 to several hundred meters in urban applications, up to few kms outside, while actual mobile macro
cell might have a range of a few tens of kilometres.
NOTE: The range should be met the coverage requirement stated later.
To support the growth in mobile data traffic, mobile operators are using data off-load techniques as more efficient way
to use spectrum resources.
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9 ETSI TR 103 230 V1.1.1 (2018-01)
Data off-loading will be predominant in very dense urban areas but small cell may have also a role in coverage lacks in
rural areas.
In literature it is possible to find some different types of small cell:
• femtocells;
picocells;
microcells.
In the present document the interest is focused on hot spot (under macro Base station coverage) and not spot (without
macro Base station coverage) and not on residential/enterprise or distributed-antenna systems (DAS)/fronthaul
scenarios.
Such small cells can be controlled by small size devices, capable of allowing easy installations in urban contexts, such
as area coverage can be increased and higher capacity can be made available, provided that backhaul network has
sufficient traffic transport capability.
Backhaul is needed to connect the small cells to the macro base station or to other network nodes /points of presence
(e.g. other small cell acting as hub or other equipment).
Mobile operators, network planners and vendors often consider backhaul provision for small cells more challenging
than usual macrocell backhaul, due to the expected high number of installations, because:
• There could be a need for many small cells to be installed in hard-to-reach and less protected positions, near
street level, rather than in the clear and isolated locations above rooftops (NLOS situation may happen
frequently, pointing stability is not guaranteed…).
• Carrier grade connectivity, comparable to macro base station targets, needs to be provided at much lower cost
per bit.
An example of network including small cells is shown in figure 1.
Together with a traditional macro cell and network point of presence (PoP), some small cells are included, connected to
realize different topologies: star, linear, redundant linear and mesh.
Concerning connection links, four kinds are shown: type A connections require backhaul for a single small cell, type B
require backhaul for more than one small cell, type C and D represent traffic aggregation with higher capacity.
In this example, only type A and B are provided by radio, although in principle, there is no preclusion for implementing
also C and D type of connection by radio, provided that sufficient capacity and performance level can be guaranteed.
Conversely, also connection types A and B can be realized by cables/fibres, depending on specific installation /location
constrains.
Many different wireless and wired technologies have been proposed as solutions for future networks, and it is common
understanding that a "toolbox" of all possible available technologies will be needed to cover efficiently the overall range
of deployment scenarios.
Hereafter only wireless backhaul solution issues will be investigated.
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10 ETSI TR 103 230 V1.1.1 (2018-01)
B
B
CORE
B
B
B
Small-cells
A
A
D
Small-cells
A
A
C
C
C
B
C
Small-cells
B
B
A
PoP
Macro-cell

Figure 1: Example of network including small cells
4.2 Small Cell Use Cases Choice
Few small cell use cases are proposed in figure 2 and the connection types are described in the following table 1.
Both LOS and NLOS conditions are considered and in NLOS case use cases also diffraction, penetration and reflection
propagation models are included (figure 3).

Figure 2: Examples of Small cells use cases
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11 ETSI TR 103 230 V1.1.1 (2018-01)
Table 1: Macro Base station and Small Cells connection types
Small Cell Number Macro Base station Other Small Cell Visibility Note
Visibility
1 LOS None Roof to roof
2 NLOS LOS to 4 Reflection
3 NLOS NLOS to 4 Diffraction
4 NLOS LOS to 2, 5 & 6 / NLOS to 3 Diffraction
5 NLOS LOS to 4 & 6
6 NLOS LOS to 4 &5
7 NLOS None Penetration

Dfifracted/re fel cted
h
inter ferer
Dir ect ray is often
totally shadowed
(non-LoS
h1 propagation)
h2
D1
Se ve ral-time reflectedw avr One-timere fel cted wavr
D
Refl ected Wave Direct Wave
Diffracted Wave
Dominant Region Dominant Region
Dominant Region
Figure 3: Typical Propagation Situation
4.3 Small Cell Backhauling Requirements
4.3.0 General
Characteristics of traffic to be transported are essential to fix requirements.
If a single small cell is considered, the traffic behaviour is variable, depending on density and use of access customers.
In particular, measurements have shown that meaningful variations in user plane traffic exists between a 'busy time
loaded' state (high density of people accessing the cell working hours, Sundays) and a 'quiet time' (few subscribers
active, e.g. late evening, night) state.
The highest backhaul throughputs are generated during the quiet time, when the cell is serving a single user in good
signal conditions and there is low interference from other cells. In these conditions, cells can use most efficient
transmission condition (like higher spectral density) for very few users, generating peak rates in order of hundreds of
Mbps for some configurations.
During busy times, some users experience poor signal conditions and the cell's average spectral efficiency decreases.
Measurements have confirmed this expectation from theory.
In addition, busy time traffic is concentrated in same time for all cells in a macrocell, while quiet time peaks tend to be
uncorrelated.
Measured backhaul traffic generated during busy time from a single small cell (HSPA and LTE) is about 34 Mbit/s,
while during peak quiet time is in the order of 190 Mbit/s. In general, it is assumed that the "small cell" (named
eNodeB) is composed by 3 single cells covering 120 degrees, generating a 360 degrees coverage.
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