ETSI TR 125 956 V16.0.0 (2020-08)

Universal Mobile Telecommunications System (UMTS); Universal Terrestrial Radio Access (UTRA) repeater planning guidelines and system analysis (3GPP TR 25.956 version 16.0.0 Release 16)

RTR/TSGR-0425956vg00

General Information

• Status: Not Published
• Technical Committee: 3GPP RAN 4 - Specification for radio performance
• Current Stage: 12 - Completion
• Completion Date: 19-Aug-2020

Standards Content (Sample)

ETSI TR 125 956 V16.0.0 (2020-08)






TECHNICAL REPORT
Universal Mobile Telecommunications System (UMTS);
Universal Terrestrial Radio Access (UTRA)
repeater planning guidelines and system analysis
(3GPP TR 25.956 version 16.0.0 Release 16)

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3GPP TR 25.956 version 16.0.0 Release 16 1 ETSI TR 125 956 V16.0.0 (2020-08)



Reference
RTR/TSGR-0425956vg00
Keywords
UMTS
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3GPP TR 25.956 version 16.0.0 Release 16 2 ETSI TR 125 956 V16.0.0 (2020-08)
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ETSI

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3GPP TR 25.956 version 16.0.0 Release 16 3 ETSI TR 125 956 V16.0.0 (2020-08)
Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 5
1 Scope . 6
2 References . 6
3 Definitions, symbols and abbreviations . 6
3.1 Definitions . 6
3.2 Symbols . 7
3.3 Abbreviations . 7
4 System Impacts of Repeaters . 7
4.1 Error Vector Magnitude (EVM) . 7
4.2 Peak Code Domain Error (PCDE) . 8
4.3 Frequency error . 8
4.4 Adjacent Channel Leakage Ratio (ACLR) . 8
4.5 Time Delay . 9
4.6 Location Services (LCS) . 10
4.6.1 OTDOA . 10
4.6.2 Cell coverage based positioning method . 11
4.6.3 Network assisted GPS methods . 11
4.7 Automatic Gain Control (AGC) . 11
4.8 Adjacent Channel Rejection Ratio (ACRR) . 12
5 Planning with Repeaters . 12
5.1 Sole System . 12
5.1.1 Antenna Isolation . 12
5.1.2 Coupling loss measurements. 13
5.1.3 Gain Settings . 13
5.1.4 Delay . 14
5.2 Co-existence with UTRA FDD . 14
5.2.1 Out of band gain . 14
5.2.2 Isolation . 14
5.2.2.1 Example on application of equations . 15
5.3 Co-existence with UTRA TDD . 16
5.3.1 Isolation . 16
5.4 Co-existence with GSM 900 and/or DCS 1800 . 16
5.4.1 Isolation . 16
5.5 Environments with low minimum coupling loss (MCL) . 16
5.5.1 Normal repeater parameters . 16
5.5.2 Repeater parameters adjusted to low MCL . 17
rd
5.6 Analysis of out of band gain in the 3 adjacent channel . 18
5.6.1 MCL=70 dB . 18
5.6.2 MCL=40 dB . 18
6 System Simulations and Analysis . 19
6.1 Down-link co-existence simulations . 19
6.2 Outdoor coverage (High CL ) . 21
Rep-UE
6.3 Indoor coverage (Low CL ) . 22
Rep-UE
6.4 Repeater up-link co-existence simulations . 23
6.4.1 General . 23
6.4.2 Simulation Assumptions . 25
6.4.3 Results . 25
6.4.4 Conclusion . 26
6.5 Repeater ACRR system impact simulations . 26
ETSI

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6.5.1 General . 26
6.5.2 Simulation Description . 27
6.5.2.1 Infrastructure . 27
6.5.2.2 Preparation . 27
6.5.2.3 Connection . 28
6.5.2.4 Iterations . 28
6.5.2.5 Parameters used through out the simulations . 29
6.5.3 Results . 31
6.5.3.1 288 m between repeater A and BSB . 31
6.5.3.2 164 m minimum distance between repeater A and BSB . 45
6.5.4 Conclusions. 58
6.5.5 Comments . 58
Annex A: Change History . 59
History . 60

ETSI

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3GPP TR 25.956 version 16.0.0 Release 16 5 ETSI TR 125 956 V16.0.0 (2020-08)
Foreword
rd
This Technical Report has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
ETSI

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CL
RepA-UEA
CL
BSA-UEA
3GPP TR 25.956 version 16.0.0 Release 16 6 ETSI TR 125 956 V16.0.0 (2020-08)
1 Scope
The purpose of the following document is to describe planning guidelines and system scenarios for UTRA repeaters. In
addition it also contains simulations and analysis of the usage of repeaters in UMTS networks.
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
• References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 25.942
[2] R4-030365
3 Definitions, symbols and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply, unless otherwise stated:

EDoCL
BSA-RepA
BS Rep
A A
UE
A

Figure 3.1
ACRR Adjacent Channel Rejection Ratio for repeater A.
RepA
ACG Adjacent Channel Gain for repeater A.
RepA
CL Coupling Loss between Base Station A and the User Equipment A.
BSA-UEA
CL Coupling Loss between Repeater A and User Equipment A.
RepA-UEA
d Group delay of repeater A.
RepA
EDoCL Effective Donor Coupling Loss between the donor Base Station A and the Repeater A.
BSA-RepA
G Set gain of Repeater A.
RepA
ETSI

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CL

RepA-UEB
CL
-
BSB UEA
3GPP TR 25.956 version 16.0.0 Release 16 7 ETSI TR 125 956 V16.0.0 (2020-08)
Gmax The maximum Gain possible to set of Repeater A.
RepA
M Noise Margin for repeater A.
RepA
Noise Figure of repeater A.
NFRepA
P Output power of repeater A.
repA
PmaxRepA Maximum output power of repeater A.
Pmax Maximum output power of base station A
BSA

EDoCL
BSA-RepA
UE
BS Rep
B
A A
UE
BS
A
B

Figure 3.2
CL Coupling Loss between Base station B and the User equipment A.
BSB-UEA
CL Coupling Loss between Repeater A and User equipment B.
RepA-UEB
CL Coupling Loss between Bas station B and Repeater A.
BSB-RepA
CL Coupling Loss between base station B and User equipment B.
BSB-UEB
SsIR Signal to self Interference Ratio. (Described below)
3.2 Symbols
(void)
3.3 Abbreviations
(void)
4 System Impacts of Repeaters
4.1 Error Vector Magnitude (EVM)
The introduction of a repeater has an impact in the EVM of the system. The basic effect is reflected in a system noise
rise, which can be calculated from the EVM value the received signal exhibits. The formula is
Noise rise = 10 log(1 + EVM²)
In the scenario of a Repeater amplifying the signal the EVM of the signal is calculated according to the following
formula for uncorrelated processes:
(EVM_total)² = (EVM_NodeB)² + (EVM_Repeater)²
Taking the specified value of 17,5 % for both the Node B (as well as for the UE) and the Repeater result in a total EVM
of 24,7 %. Calculating the noise rise for the Repeater scenario gives a value of 0,26 dB in the area of the repeater's
coverage. This compares to a noise rise in a scenario without Repeater of 0,13 dB. The difference between the two
ETSI
CL
BSB-UEB

CL
BSB-RepA

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numbers is the worst-case closed loop power rise in an otherwise perfect system that would occur with a Repeater being
used.
4.2 Peak Code Domain Error (PCDE)
In the specification of the Peak Code Domain Error value of the Repeater -35 dB is used. The number for the Node B is
-33dB. If we assume the processes in the Repeater that lead to the PCDE being independent of the equivalent process in
the Node B we can assume that they can be treated as noise. In this case the resulting value for PCDE is calculated from
the linear addition of the two signals that will lead to -31 dB. This is a 2 dB degradation to the value of the Node B. For
the repeated cell the degradation might be negligible. In case of a neighbour cell the might be affected to some extend.
Presumably the soft handover gain will be reduced by the tenth of a dB.
4.3 Frequency error
The effect of the additional frequency error will be a reduction of the maximum speed. In the repeater core specification
the minimum requirement on frequency stability is 0,01 ppm. Hence, with the 0,05 ppm minimum requirement for the
base station frequency stability the resulting "worst case" for a signal that have been amplified by the repeater is 0,06
ppm.
4.4 Adjacent Channel Leakage Ratio (ACLR)
With regard to the mentioned ACLR we have to investigate the behaviour of the Repeater. For this reason we use the
model shown in the following Figure 4.1:

Figure 4.1: Simplified Repeater model.
The Repeater in its basic function is bi-directional amplifier of RF signals from Base Stations in the downlink path and
from Universal Equipments (UE) as mobile stations in the uplink path. The operating bands in which the Repeater
amplifies is determined by the IF filter in its bandwidth and by the duplexer filter in its frequency range for operational
configuration. In our discussion we will use the parameters defined in Table 4.1.
Table 4.1: Parameters of the Repeater model.
Parameter Description Unit Assumed Comment
value
G Repeater gain dB 90 dB UL and Dl gain should be the
same for a balanced link.
Pout_DL_max maximum Repeater average output dBm 30 dBm DL value
power measured with WCDMA
signal according to model 1 of
TS25.141.
Pout_UL_max maximum Repeater average output dBm 12 dBm UL value
power measured with WCDMA
signal according to model 1 of
TS25.141.
NF Repeater Noise Figure dB 5 dB valid for UL and DL
N_therm Thermal Noise Power density in a dBm / -129 dBm / -174 dBm/Hz (at 25 °C) +
(30 kHz) Bandwidth of 30 kHz 30 kHz 30kHz 45 dB
S (30 kHz) WCDMA Signal Power Density dBm / Pout - 21 dB the factor of 21 dB is the
30 kHz relation of channel
bandwidth to 30 kHz

ETSI

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The Repeater output noise density can be calculated according to the formula:
N_Rep (30kHz) = N_therm (30kHz) +NF + G = -34 dBm/30 kHz .
Considering the output of the Repeater in the Downlink path we will find an average power 30 dBm in the WCDMA
channel. This is resulting in a signal density of
S_Downlink = +9 dBm/30 kHz.
This leads to a signal-to-noise ratio of the Downlink of:
S / N_Downlink = 43 dB.
The Adjacent Channel Leakage Ratio (ACLR) as defined for BS is stating -45 dB for the first adjacent channel and -
50 dB for the second adjacent channel. This situation is illustrated in Figure 4.2.
In the Repeater case the resulting output frequency spectrum is shown below.
WCDMA Signal with ACLR
according BS Spec.
S/N
thermal Output Noise
Frequency in MHz

Fig. 4.2: Repeater output frequency spectrum.
It is obvious that the ACLR cannot be measured in the Repeater case due to the fact that the this signal is below the
amplifier thermal noise of the Repeater amplifier chain.
This even get worse when the Uplink is considered. As in this path the maximum average value of the output power is
reduced to 12 dBm resulting in a signal power density of S = -9dBm / 30 kHz, the signal-to-noise ratio will be even
smaller:
S / N_Uplink = -9 dBm / 30 kHz - (-43 dBm / 30 kHz) = 34 dB.
This collision is the reason why the ACLR requirement as it is written for the BS equipment cannot be met with a
Repeater. The ACLR measurement will be limited by the thermal noise of the Repeater amplifier chain.
Spectral components (noise, ACP, intermodulation products, spurious signals, .) falling outside the operating band are
fully addressed in the TS 25.106 subclause 9.
4.5 Time Delay
Using common narrow band filter technologies (SAW) the IF-filtering process introduces a time delay of about 5-6 μs
to the signal. This puts a requirement on the length of the receiver’s search window. It is, however, believed that the
channel models now specified in TS 25.104 are sufficient for guaranteeing the receiver’s performance in an area
covered by both a repeater and a base station.
ETSI
Power Density in dBm/Hz

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Figure 4.3 illustrates a case where the UE receives multipath signals, both from the repeater and from the BS. Here, the
repeater will introduce artificial multipaths. This could possibly reduce the effects from fading, but also increase the
number of paths that are needed to capture a certain percentage of the energy is increased and it is therefore important to
have a sufficient amount of RAKE fingers in the receiver.
However, traditionally the repeater is deployed to cover a smaller area compared to the BS and the number of
resolvable multipaths could therefore be believed to lower compare to that of macrocellular deployment.
BS
UE
Repeater

Fig. 4.3: Illustration of the excess multipaths that are introduced by the repeater in a scenario where
the UE is receiving the signal, from both the BS and the repeater.
4.6 Location Services (LCS)
The co-existence between repeaters and location services (LCS) is studied in this clause. Three methods for location
services are currently specified in TS 25.305: OTDOA, Cell coverage based positioning and Network assisted GPS.
4.6.1 OTDOA
The OTDOA method is based on measurements of the UTRA pilot signal (CPICH) made by the UE and the Location
Measurement Unit (LMU). The position of the UE is estimated by using the observed time difference of arrival
(OTDOA) from three, or more, base stations.
Figure 4.4 is an illustration of a network using repeaters. In this case the signal path from BS4 to the UE can be either
the direct path, with a time delay of τ4, or the path through the repeater, with a time delay of τRB+τd+τR, where τd is
introduced by the repeater. This extra time delay introduces an ambiguity when performing the location estimation.
ETSI

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τ
4
τ BS 4
1
UE
τ
BS 1
RB
τ
R
τ
2
τ
3
τ
d
BS 2
Repeater for BS 4
BS 3

Fig. 4.4: Illustration of the effect of a repeater installation in a network using OTDOA based LCS.
To avoid this ambiguity different mechanisms can be implemented:
1. For small cells one can exclude one of the signals if it has to long path delay (i.e. passed through a repeater).
Hence, for cells smaller than 1500 m (corresponding to 5 μs) it is detectable, whether or not, a repeater has
transmitted the signal.
2. If the UE detects more than three sites, as the case is in Figure 4.4, the measurement of the time delay from BS 3
can be excluded, based on a too large relative difference to the time delays from BS 1-3. The probability of
detecting three sites is much lower compared to that of detecting four or five sites. This result holds true for both
the urban and the suburban environment, when the UE uses 16 ideal periods.
4.6.2 Cell coverage based positioning method
The only impact is that the cells become larger using repeaters and that this method thereby has less accuracy compared
to a smaller cell. Other than that the repeater does not affect this LCS method.
4.6.3 Network assisted GPS methods
The UTRA network can assist the UE GPS receiver in several ways. E.g. by providing a frequency reference, since
UTRAN has a better frequency stability compared to GPS (0,05 ppm frequency error compared to 20 ppm). UTRAN
can also provide the UE with a timing reference to reduce the UE GPS search time and improve the accuracy.
If a repeater is deployed in the network this will lead to about 5 μs extra delay. This extra delay is not of the extent that
it will affect the performance of GPS assisted method. It is however important that the frequency stability of UTRAN is
maintained in the repeater.
4.7 Automatic Gain Control (AGC)
Repeaters use a function called Automatic Gain Control (AGC) to adjust the gain so that self-oscillation is avoided. The
gain of the repeater shall be adjusted so that there is a margin to the port isolation between the up- and down-link
directions as described in the sub-clause Gain Settings.
As a consequence the AGC is not intended to the constantly adjust the gain during the normal mode of operation. It
shall be seen as a fall back to prevent self-oscillation if, for some reason, the isolation between the ports is reduced
ETSI

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compared to the isolation measured during the deployment or an increase in input power to a level larger than the input
level creating the maximum output power.
The AGC is also slow in comparison to the fast power control (the range of several micros
...