CEPT
ECC PT1(17)096
ECC
Electronic Communications Committee
ECC PT1 # 55
Berlin, Germany, 24-28 April 2017
Date issued:
18/04/2017
Source:
France
Considerations on IMT2020 systems beam pointing for use in Sharing
studies under AI 1.13
Subject:
Group membership required to read? (Y/N)
N
Summary:
This contribution provides some elements related to the statistic of the IMT2020 Base Station
(BS) and User Equipment (UE) pointing antenna (electrical tilt, scanning azimuth) when forming the
beams.
It aims at providing a methodology for deriving statistical distribution of pointing antenna of
IMT2020 systems for different scenarios. The application of the methodology is provided for one
case (suburban hotspot at the edge of the building when it is not facing an open area).
Proposal:
It is proposed to ECC/PT1 to consider these elements for discussion when dealing with the
IMT2020 parameters for sharing and update, if appropriate, any section/document addressing this
issue accordingly with the material of this contribution.
Background:
During the last ECC/PT1 meeting held in Cascais, a Correspondence Group (CG) was established
in order to make progress in sharing studies for the 26GHz band. The CG has elaborated a draft
document gathering the IMT2020 parameters required to undertake the compatibility analysis
between IMT2020 systems and other incumbent services operating within the same band or
nearby. It was recognized during the physical meeting on the protection of the Inter-Satellite service
that some information related to the statistic of the IMT2020 Base Station (BS) and User Equipment
(UE) pointing antenna (electrical tilt, scanning azimuth) when forming the beams was missing when
performing the aggregated calculation of the interference coming from those systems.
Introduction
The purpose of this document is to describe an approach for deriving the statistic of the
IMT2020 BS & UE beam pointing of the antenna, i.e. electrical tilt and phi scan angles, for the
sake of undertaking sharing studies under AI 1.13 WRC(19) (in particular when deriving
IMT2020 antenna gains). This analysis is based on elements from
-
WP5D on IMT2020 Sharing parameters
Recommentation ITU-R M.2101
On-going discussions held in ECC/PT1 Correspondence Group.
I: Methodology to get the distribution of the angles of BS antenna beam forming
In order to derive these parameters, there is a need to clearly describe the way the
urban environment is modelled as well as the distribution of the UE locations with the serving
cell with capacity requirements. That’s why the following steps are presented in the following
sections:
Step 1: Setting the environment
Step 2: Calculate the required 5th percentile spectral efficiency SreqIMT-2020
For each Cell Range R
-
Step 3: Performing Link Budget calculation
Step 4: Deriving the experienced 5th percentile spectral efficiency SexpIMT-2020
Step 5: Compare SreqIMT-2020 with SexpIMT-2020 in order to increase/reduce R
End for
Output: optimal Cell Range R*.
Step 6: Compute the distribution of the BS electrical tilt, phi scan towards UEs that are
connected with the expected QoS for R=R*, where R* depicts the optimal cell range1.
II: Selection of the dense suburban/urban area (Step 1)
Within an urban/suburban environment, the hotspot BSs (at the open space, below the roof of
the building) may be deployed in a regular (see Rec ITU-R M.2101 section 3.1.2) or in an
irregular (similarly to heterogeneous network see Rec ITU-R M.2101 Section 3.1.4) way. When
considering a BS
1. Angular sector shaped is defined by the 120° coverage angle in the horizontal
plane of the BS hotspot antenna.
1
Optimal in the sense that any for any analysis radius R>R* over which UEs are located, the 5 th
percentile user spectral efficiency requirement is not ensured.
2
2. Uniform distribution of (sufficiently high e.g. 100000 samples) N UE locations
within T, but non-uniform resulting UE locations connected to the serving basestation because of
i. High building penetration loss issues above 24.25GHz
ii. A larger portion of the indoor component (compared to outdoor ones) in T
area although it is possible to have a few portion of outdoor users in
balcony building,
iii. Asymmetric apportionment of UE indoor/outdoor usage (5% for indoor
and 95% for outdoor)
III: Assessment of the required user throughput (Step 2)
In order to determine the cell range featuring the covered (angular sector) area, it is necessary
to set the Quality of Service that has to be met, which can be expressed in terms of throughput
(bits/s/Hz).
Approach 1: (using user experienced data rate metric) we assume that R=100Mb/s is shared
(as user experienced data rate for UMi dense) among all users served by the same BS,
corresponding to 100Mb/s/3 users is equivalent to Ruser=33.3Mb/s per user
If the channel bandwidth W=200MHz is shared between 3 users, this leads to Wuser=66.6MHz
per user,
Leading to spectrum efficiency SEuser = Ruser /Wuser (based on equation 3 from DNR
IMT2020Min Tech Perf Req)
= 33.3/66.6=0.5 b/s/Hz,
Approach 2: (using given 5th percentile user spectral efficiency metric) Based on the 5th
percentile user spectral efficiency provided in DNR [IMT2020 Min Tech Perf Req] for the
Dense Urban DL eMBB
-
2
Macro BS: 0.225 bits/s/Hz2
micro BS: Report ITU-R M.2134 Table 2 indicates 5th 0.075 bits/s/Hz value for DL IMTAdvanced.Rec. According to the ITU-R Rec M.2083, spectral efficiency for IMT2020 is
DNR [IMT-2020.TECH PERF REQ], Table 1 (Note 1)
3
expected to be three times higher compared to IMT-Advanced value. As there is no
certainty
that this objective will be met for frequencies above 24.25GHz3, values that are
assumed is expected to be (1-3) times higher for frequency bands above 24.25GHz, i.e.
0.075..0.225 bits/s/Hz. It should be noted that the 5th percentile user spectral efficiency
depends on the number of active users sharing the channel. The values from IMTAdvanced case are obtained under the assumption which the active user number is
NIMT-Adv=10 in the ITU evaluations (See Report ITU-R M.2135 Table 8-5). In our case
(NIMT-2020=3 users/BS), the equivalent 5th percentile user spectral efficiency S needs
to be adjusted leading to: SIMT-2020=(1..3)*SIMT-Adv*( NIMT-Adv/ NIMT-2020 )
=0.075..0.225*10/3
=0.25..0.75 bits/s/Hz
IV: Calculation of the BS/UE antenna gains towards the UE/BS (Step 3.1)
Accounting the positioning of the BS antenna (e.g. 10° mechanical downtilt for hotspot
below the roof, 15° mechanical downtilt for hotspot in open area) and the location of UE, it is
possible to derive the electrical tilt used from the BS antenna to form the beam toward the UE
through distance(UE,BS) as well as difference in antenna height between UE and BS. The BS
antenna gain GBS(ϕscan,e-tilt, ϕ,θ) can then be derived.
The UE antenna gain calculation requires the knowledge of the UE antenna panel
positioning (with respect of the BS panel). For sake of simplification, all UEs have the same
panel positioning as being the reverse one of the BS, i.e. with BS ϕ axis (i.e. x’ and y’ compared
to x and y) in the reverse direction (see Figure below).
z’
X
’
y’
Figure 1: References for BS (left side) and UE (right side) antenna panel
V: Calculation of the PathLoss(BS, UE) value (Step 3.2)
3
Because IMT2020 systems are expected to be also deployed in several bands below 6GHz, e.g. 34003800MHz in CEPT where it may be possible and easier to meet the x3 spectrum efficiency improvement
requirements because of a lower building penetration loss issues.
4
PathLoss between BS and UE in urban/suburban environment is calculated by considering
either deterministic locations (e.g. buildings) or stochastic positions:
-
-
Based on deterministic topology: the generation of a grid of buildings (e.g. Manhattan
grid)
o LOS/NLOS: the knowledge of UE, BS locations as well as building positioning
enables to (roughly4) assess whether LOS/NLOS has to be applied.
o UE location: based on indoor/outdoor apportionment, there is UE dropping
process consisting in not accounting (randomly) several generated UE locations
if the required amount of indoor or outdoor UE locations is reached.
Based on stochastic topology: hotspot BS could be located in a non-uniform way
o LOS/NLOS: Using LOS probability in order to estimate whether LOS/NLOS
conditions have to be applied to the PathLoss calculation
o UE location: based on indoor/outdoor apportionment
The following analysis assumes a deterministic topology with buildings displayed in a Manhattan
grid way assuming that building size is 75m5, street width=15m1 as depicted below
75m
m
15m
m
Based on IMT2020 Sharing parameters document, the building height is set to a constant value
equal to 15m.
-
-
Comparison of LOS probability for UMi (from DNR IMT2020 Evaluation) and derived
LOS probability for UMi from deterministic topology (extract distance_2D_(BS,UE) for all
UE locations, compute LOS_or_NLOS status for all UE locations
Based on DNR IMT2020.Evaluation, selecting the Urban Micro (Umi) scenario. It is
possible to perform the pathloss calculation considering this parameter as a gaussian
4
It is recognized that (slow and fast) fadings (e.g. passing vehicles) which could cause obstruction
(resulting in NLOS propagation) are not considered.
5
Based on 3GPP TR.942
5
variable with a mean (corresponding to the PathLoss formula provided in DNR
IMT2020.Evaluation) and a standard deviation (provided in addition to the previous
formula) components.
VI : Calculation of the SNIR C/(N+I) (Step 4.1)
-
Calculation of the Noise Power N
Calculation of received power at the UE C
Since cells are more coverage limited than interference limited (because of the directivity
of the millimeter waves), interference I can be neglected (i.e. disregarded) resulting as
not considering the interference impact from adjacent cells (to the serving one).
VII: Analysis of the experienced spectrum efficiency for all UE locations (Step 4.2)
-
Using the formula from WP5D IMT2020 Sharing parameters: αlog2(1+SINR) with α=0.6
for DL (and bounded with SINRmin and SINRmax values),
For all kept UE locations, extract the 5% percentile of the distribution of the received
throughput.
VIII: Compare 5% percentile of the experienced spectrum efficiency Sexp user with the 5th
percentile user spectral efficiency Suser (Step 5)
if Sexp user > Suser then the requirement is met and the considered cell range R could be
increased while ensuring the 5th percentile user spectral efficiency,
if Sexp user < Suser then the requirement is not met and cell range R should be reduced so that the
QoS requirement is achieved.
Let’s denote R* as the cell range.
IX: Distribution of the electrical tilt and phi scan when forming beaming from the BS for
R* cell range (Step 6)
1. Cell Range estimation
As depicted by DNR IMT2020 Evaluation, the pathloss through indoor may involve low and
high loss components with significant gap (e.g. 37.6dB for high, 17.6dB for low resulting in 20dB
for 27 GHz). Moreover, the same document has not yet solved the formula for this parameter
when considering the open issue by apportioning Low and High loss components. That’s why
the following analysis performs a sensitivity study by assuming 3 categories of building
penetration loss values: Low loss, High loss and a combination of both. The experienced 5th
percentile user spectral efficiency (bits/s/Hz) is computed for each cell range R.
Outdoor users are assumed to be located in the streets, meaning that the case of outdoor
users on the terrace/balcony of a building is not addressed in this analysis.
The antenna of the hotspot is considered to be located at edge of roof and no open area is
facing the building.
3 cases are addressed in this section:
Case 1: At the middle of the building (without any open area)
When the hotspot is located at the middle of the building, the BS antenna is front of another
building:
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Cell Range R (m)
140
136
135
134
133
132
130
125
124
123
120
Pathloss HighLoss for 0->I
0,22
0,27
0,27
0,29
0,30
0,34
0,35
0,48 0,50
0,51
0,61
Pathloss
1/2HighLoss+1/2LowLoss
for 0->I
0,40
0,46
0,48
0,49
0,50
0,53
0,56
0,68 0,71
0,73
0,82
Pathloss LowLoss for 0->I
0,45
0,51
0,52
0,54
0,56
0,57
0,63
0,74 0,76
0,78
0,85
Table 1: 5th percentile user spectral efficiency for hotspot open area in the middle of the building
Based on the required 5th percentile user spectral efficiency (0.5 bit/s/Hz), the cell range
varies along the building penetration loss value enabling for the low loss case to meet the
requirement (0.5bit/s/Hz)at some cell ranges e.g. for cell range=136m (0.51 bit/s/Hz) while in
the high loss situation, a lower spectral efficiency will be achieved (0.27 bit/s/Hz). The cell range
would be located within the 123m..136m interval.
Figure 2: Impact of penetration loss on the indoor coverage (high loss: left side, low loss: right side)
-
Case 2: At the middle of the building (with open area)
7
Cell Range R (m)
136
135
134
133
125
124
123
Pathloss HighLoss for 0->I
0.27
0.28
0.29
0.32
0.48
0.49
0.53
Pathloss
1/2HighLoss+1/2LowLoss
for 0->I
0.44
0.46
0.49
0.52
0.68
0.71
0.71
Pathloss LowLoss for 0->I
0.49
0.5
0.53
0.55
0.72
0.75
0.78
-
Case 3: At the corner of the building
When a hotspot antenna is located at the corner of the building, (as depicted in the figure
below)
there are 2 different ways to position the 120° angular sector antenna panel. As the
buildings are squared, the ratio of indoor/outdoor component of the area of study remains
constant if the antenna panel points to the left/right side or to the north/south, leading to
conclude that similar results would have been obtained with another angular positioning of the
BS antenna panel with a BS fixed location.
Cell Range R (m)
143
142
140
139
136
132
128
126
124
123
122
Pathloss HighLoss for 0->I
0,31
0,32
0,33
0,34
0,36
0,42
0,46
0,47
0,48
0,48
0,50
Pathloss
for 0->I
0,45
0,46
0,49
0,51
0,54
0,60
0,66
0,69
0,74
0,76
0,75
0,50
0,51
0,53
0,54
0,59
0,66
0,73
0,77
0,82
0,85
0,86
1/2HighLoss+1/2LowLoss
Pathloss LowLoss for 0->I
Table 2: 5th percentile user spectral efficiency for hotspot open area at the corner of the building
One could notice that the achieved cell range is higher when the antenna of the suburban
(open area) BS is located at the corner of the building compared to when it is positioned in the
middle of the top of the building due to a higher portion of outdoor area within the celI, favoring
higher throughput. Thus, based on the values from these tables, it can be concluded that the
cell range for suburban hotspot open area should be in [122..142m].
2. Distribution of the electrical tilt
Cumulative density function of the BS antenna is also provided in the following graphic for 9
different configurations associated with R* cell range (R* being different for each scenario):
Scenarios 1.1,,1.2, 1.3: at the middle of the building (without open area) with high, medium, low
building penetration loss
Scenarios 2.1, 2.2, 2.3: at the middle of the building (with open area) with high, medium, low
building penetration loss
8
Scenarios 3.1, 3.2, 3.3: at the corner of the building (with open area) with high, medium, low
building penetration loss.
It has to be noted that electrical tilt is:
-
positive when the beam is located below the reference direction, corresponding to
the mechanical tilt
negative when the beam is located above the reference direction, corresponding to
the mechanical tilt.
The graphic above outputs the results for the 3 first and the 3 last scenarios6 and highlights
two things:
-
6
that the electrical tilt is generally distributed in a similar way for all considered
scenarios although the bounding curves (purple for the lower bound, orange for the
upper bound) correspond to scenarios related to different BS antenna positioning
over the façade of the building (middle and at the corner) and two extreme building
entry loss figures (high and low). A model could then be extracted e.g. by
interpolation within the envelope region delimited by the two bounding curves or by
taking the upper bound7 , noting that electrical tilt does not follow any of the uniform
or Gaussian law.
i.e. excluding the case of BS antenna located at the middle of the building and without an open area.
7
As a conservative approach (from the sharing studies perspective) to favor electrical tilt leading to beam
pointing close to the horizon.
9
-
a difference for the lower tilt values (corresponding to the pointing above the
mechanical tilt but still below the horizon) dependent of the building entry loss: for
the highest loss, the electrical tilt starts no lower than -8.7° while lower value than 12° may be achieved for lower losses (the lowest and mix loss). This may be
interpreted in the following way: for indoor users that are connected to the serving
BS, some of them may be located in high floors which leads to conclude that the
beam points below but closer to the horizon than it is for outdoor users. Note than
this phenomenon occurs for very small probability (<1%).
The following graphic compares the results for the 6 last Scenarios and it can be “seen” that 4
curves overlap each other: the curves related to the 3 Scenarios of BS hotspot at the roof
covering an open area (for low, medium and high loss penetration) are identical to the one for
the BS hostpot at the corner of the roof for low penetration loss.
3. Distribution of phi (azimuth) scan
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Based on the figure below, the (almost) same observation can be made in comparison to
the distribution of the electrical tilt which leads us to conclude that the difference in loss for the
building entry loss, the difference in location of the antenna hotspot (in the middle of the
building, at the corner of the building) won’t affect the statistics on the phi-scan of the BS to form
the beams.
The following graphic compares the results for the 6 last Scenarios and similarly to what was
obtained for the electrical tilt, it can be “seen” that 4 curves overlap each other: the curves
related to the 3 Scenarios of BS hotspot at the roof covering an open area (for low, medium and
high loss penetration) are identical to the one for the BS hostpot at the corner of the roof for low
penetration loss.
X: Conclusion
The document aims at providing a methodology for deriving statistical distribution of pointing
antenna of IMT2020 systems for different scenarios. The application of the methodology was
provided for the outdoor suburban open space hotspot (at the corner, at the middle of the
building when it is facing/it is not facing an open area) scenario.
Other scenarios should be addressed in order to undertake the sharing analysis between
IMT2020 systems and other services.
11