CEPT
ECC
Electronic Communications Committee
CPG-15 PTD
CPG-15 PTD CG Mobile-DTT
Paris, 19 March 2014
Date issued:
XX March 2014
Source:
Broadcast Networks Europe
Subject:
INDCLUDING CORRELATION IN THE POSITION OF DTT RECIVERS AND LTE UE
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Summary:
Monte Carlo simulations used to assess interference from LTE UE to Digital Terrestrial
Television (DTT) reception assume no correlation between the position of the DTT receivers
and the UE. Whilst such an assumption helps to simplify the Monte Carlo simulations, it
doesn’t correctly represent the ‘real world’ and can lead to a significant underestimation of
the interference probability (IP).
To demonstrate this point, a ‘standard’ Monte Carlo simulation has been carried out for a
rural area and the results have been compared with a rural simulation that constrained the
position of UE with respect to DTT receivers. For this rural example, it has been shown that
the ‘standard’ Monte Carlo simulation can underestimate the interference by a factor of 6.
Proposal:
When considering the 700 MHz LTE UE out of band emission limits needed to protect DTT
reception account must be taken of the limitations of ‘standard’ Monte Carlo simulations and
that they do not take account of the likely location of the UE relative to the DTT receiver and
hence can significantly underestimate the interference probability.
Introduction
The Monte Carlo simulations being used to assess interference from LTE UE to DTT
reception assume that the UE and DTT receivers are randomly distributed across a LTE
sector. The results of these ‘standard’ Monte Carlo simulations show that interference
reduces as the LTE sector area increases, so the interference probability (IP) in a
suburban sector is lower than in an urban sector and in a rural sector the IP is lower
than in a suburban sector. Whilst this is convenient, from the point of view of
calculations, it ignores the tendency for people to use mobile phones in close proximity
to an active television. The risk of such an approach to simulating interference is best
demonstrated for a rural environment.
Whilst the area of a rural sector may be significantly greater than that of urban or
suburban sectors, much of the sector consists of areas where there are no DTT receivers
and UE are not used, e.g. fields. Consequently the area that UE typically operate in is a
small proportion of the total sector area. Also the areas UE are used in will be close to
locations in which DTT receivers are located. As such it would be reasonable to assume
that ‘standard’ Monte Carlo simulations underestimate the interference probability.
To test this, the results of ‘standard’ Monte Carlo simulations for a rural environment
have been compared with Monte Carlo simulations that constrain the position of UE
relative to DTT receivers.
Methodology
To model the effect of constraining the location of DTT receivers and LTE UE, a sample
10 km x 10 km rural area in Warwickshire (UK) has been used. Within this area an 8km
rural sector has been located. In this example area (10km2) there are 6,723 individual
postal addresses; these have been taken as the location of DTT receivers. These DTT
receiver locations are all located on buildings. As the position of buildings is known all
UE that operate indoor (50%) are assumed to be located within a building. As UE that
operate outdoor are concentrated in areas where people transit, i.e. not in fields, a
boundary of 50m has been put around all buildings. For the purpose of this study, of the
50% of UE that operate outdoor, the majority are assumed to be located within 50m of
buildings and only 1% of all UE operate in more remote locations, Table 1.
Indoor
Proportion of UE
Outdoor near
buildings
50%
49%
Table 1: UE proportion by location
Outdoor away from
buildings
1%
Figure 1 shows the lower left 5km x 5km of the 10km x 10 km sample area. In Figure 2
the full 10km x 10km area is shown with black areas being buildings, the red areas are
within 50m of buildings and yellow areas are open areas away from buildings –
predominately fields. The blue dot in Figure 2 represents the position of the cell site.
This is the position of an actual cell site that serves the sample area, Figure 3.
Monte Carlo simulations have been carried out that randomly select the DTT receiver
and randomly locate the UE in the correct environment, i.e. indoors (50%), outdoors
close to buildings (49%) or further from buildings (1%). The results of these
simulations have been compared with ‘standard’ Monte Carlo simulations. General
technical parameters used for the simulations are provided in Annex 1.
Results
The IP calculated for both the ‘standard’ and ‘constrained’ Monte Carlo simulations for
DTT receiver ACS values of 65dB, 70dB and 75 dB are shown in Figure 4.
Discussion
For this rural scenario the ‘standard’ Monte Carlo approach underestimates the
interference probability, when compared with the constrained approach by a factor of 6.
The predicted interference probability for the ‘constrained’ rural example is
comparable to the interference probability for an urban environment modelled using
the ‘standard’ approach.
The distribution of population in the sector will affect the result. In the example chosen
the majority of the population, as would be expected, are located towards the location of
the cell site. This will lead to lower hand set powers, therefore less interference and
hence less of a difference between ‘standard’ and ‘constrained’ predictions.
It is expected that as population density increases and it is more uniformly distributed,
as in the suburban and urban cases, the difference between ‘standard’ and ‘constrained’
predictions of interference will reduce.
Conclusion
The ‘standard’ Monte Carlo simulations, because UE distribution is not independent of
DTT receiver position, can significantly underestimate the interference probability. This
is particularly the case in rural environments. When considering out of band emission
limits for 700 MHz UE due account should be taken of this shortcoming of ‘standard’
Monte Carlo simulations.
Figure 1 : 5km x 5km SW corner of 10km x
10km sample area
© Crown copyright and database rights 2013 Ordnance Survey
100039117
Figure 2: 10km x10km sample area showing rural 8km cell sector
Yellow = Open, Red = close to building, Black = building
Google Maps Image
Figure 3: Cell site used in ‘real world’ simulation
Figure 4: Comparison of a ‘standard’ Monte Carlo simulation with a ‘real world’ simulation for a rural environment
0.10000%
65 dB ACS REAL
70 dB ACS REAL
75 dB ACS REAL
65 dB ACS
70 dB ACS
0.01000%
Interference Probability (IP%)
75 dB ACS
0.00100%
0.00010%
45
50
55
60
65
ACLR (dB)
70
75
80
Annex 1: Technical Parameters
General parameters used in Monte Carlo simulations are provided in Tables A1.1 & A1.2
TABLE A1.1
DTTB system parameters
Parameter
Location variation of DTTB signal
Rx antenna height
Rx antenna pattern
Rx antenna gain (including feeder loss)
DVB-T2 Rx noise floor
Required C/N
ACS
Value
Gaussian random variable with
mean equals to median field
strength and standard deviation
of 5.5 dB
10 m
ITU-R BT.419-3
9.15 dBi
-99.07 dBm
20 dB
various
Source / notes
ITU-R 1546-4
Doc 4-5-6-7/126
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TABLE A1.2
IMT system parameters
Parameter
Channel bandwidth
Base station antenna
height
Base station antenna gain
(excluding feeder loss)
Feeder loss
BS antenna patterns
BS antenna downtilt
Maximum UE Tx power
Minimum UE Tx power
UE antenna gain
Body loss
Propagation model for the
link LTE UE-BS
Value
10 MHz, with lower channel edge at 703
MHz
Source / notes
Doc 4-5-6-7/49.
30 m
Doc 4-5-6-7/49.
15 dBi
Doc 4-5-6-7/49.
3 dB
ITU-R F.1336 with k=0.7
3 degrees
23 dBm
–40 dBm
–3 dB
4 dB
Doc 4-5-6-7/49.
Doc 4-5-6-7/49.
Doc 4-5-6-7/49.
Doc 4-5-6-7/49.
Doc 4-5-6-7/49.
Doc 4-5-6-7/49.
Doc 4-5-6-7/49.
Extended Hata model
ITU-R SM.2028-1
Pt  Pmax
Transmit power control
(TPC)
Simultaneously
transmitting UEs
Number of trials in MC
simulation
Indoor terminal usage
Building entry loss
Cell radius
Reference Cell network



 CL   
   ,
 min 1, max  Rmin , 

 CLx ile   

(all in linear scale)
where Rmin = Pmin/Pmax, CL is the coupling
loss (all propagation effects considered), γ
= 1 and CLx-ile as described in the document
Doc 4-5-6-7/236 (Annex 2)
1
10,000,000
Urban scenario: 70%
Suburban scenario: 70%
Rural scenario: 50%
Gaussian random variable with 11 dB mean
and 6 dB standard deviation
Urban scenario: 1 km
Suburban scenario: 2 km
Rural scenario: 8 km
See Figure A2.1
19 Cell sites (BS), 57 hexagonal Sectors
See Figure A2.1
Doc 4-5-6-7/49
Recommendation
ITU-R P.1812
Doc 4-5-6-7/49
Doc 4-5-6-7/236 (Annex 2)
FIGURE A1.1
IMT Network configuration used in Monte Carlo simulations