ECCElectronic Communications Committee

CE

PT Revision 1 to ECC PT1(17)235rev1

ECC PT1#57

ETSI, Sophia Antipolis, 11-15 December 2017

Date issued: 13 December 2017

Source: Germany

Subject: Initial compatibility studies of IMT-2020 and automotive radar in the frequency band 76-81 GHz for AI 1.13

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Summary:

This paper presents initial compatibility studies of IMT-2020 operating in the frequency band 71-76 GHz and 81-86 GHz into Automotive radar operating in the frequency band 76-81 GHz in Annex 1. In particular, the impact of the IMT-2020 base station spurious emission of -13 dBm/1 MHz is investigated in this study.

IMT-2020 in the frequency bands 71-76 GHz and 81-86 GHz can only be identified for IMT-2020 if studies show that automotive radar in the 76-81 GHz band are protected.

It is intended to further update the study, should further information become available, e.g. how to use the composite pattern for adjacent band studies, normalization factor of the antenna etc.

Proposal:

ECC PT1 is invited to consider the study in Annex 1 for a possible submission to TG5/1 so that this study can be considered in the sharing/compatibilty studies related to the identification of frequency bands for the future development of International Mobile Telecommunications (IMT), including possible additional allocations to the mobile service on a primary basis, in accordance with Resolution 238 (WRC-15)

ECC PT1 is invited to discuss the matter, of how to deal with a base station loading less than 100% for otherwise static parameters as described in Annex 2

Background:

N

WRC-19 Agenda Item 1.13 – IMT-2020, considers identification of frequency bands for the future development of International Mobile Telecommunications (IMT), including possible additional allocations to the mobile service on a primary basis, in accordance with Resolution 238 (WRC-15).

In particular, the potential development for IMT above 24.25 GHz considers the operation of IMT-2020 in the frequency band 71-76 GHz and 81-86 GHz.

Annex 1

Initial compatibility studies of IMT-2020 and automotive radar in the frequency band 76-81 GHz

1. Introduction

This paper presents initial compatibility studies of IMT-2020 operating in the frequency band 71-76 GHz and 81-86 GHz versus Automotive radar operating in the frequency band 76-81 GHz. In particular, the impact of the IMT spurious emission of -13 dBm/1 MHz is investigated.

Figure 1 presents an overview of the frequency bands considered in this study and the situation for automotive radars operating in the band 76-81 GHz.

Figure 1: Situation for automotive radars operating in the band 76-81 GHz

This study will focus on the adjacent band impact of IMT bases station (BS) into automotive long range radar (LRR). Automotive LRR are deployed in vehicles for adaptive cruise control or the emergency brake assistant in the lower range of the band i.e. 76-77 GHz. In this part of the band automotive radar

operates with a 1 GHz bandwidth. In the 77-81 GHz, radars with reference bandwidth of 4 GHz can be deployed.

This basic study provides an estimate of the impact of an IMT BS into an automotive radar and the importance of the effect of the proposed spurious proposed by IMT technology. Results of impact of the spurious emission in automotive radars of 1 GHz bandwidth will be shown in this study.

2. Current regulatory framework

Since the WRC-15, automotive radars can claim protection as application of radiolocation service in the entire frequency band 76-81 GHz as sown in Table 1.

Table 1: Radiolocation Service allocation in the 76-81 GHz according to the Radio Regulation (WRC-15)

3. Interference scenario

Based on the information available in WP5D and TG5/1 documents, it can be assumed that IMT2020 components operating in the 71-76 GHz and 81-86 GHz band will be deployed in urban environment in both mobile and fixed scenarios. Figure 2 illustrates a basic sketch of the interference scenario.

Figure 2: Interference scenario between IMT-2020 BS and UE and the automotive radars operating in the band 76-81 GHz

The interference from IMT-2020, from both the BS or the UE, will have significant impact on the performance of automotive radars. The out of band and spurious emissions of the IMT-2020 components will lead to a range reduction of automotive radar sensors as illustrated in Figure 3.

Figure 3: Example of the impact of IMT-2020 on the operating range of automotive radar sensors

4. Technical characteristics

4.1 IMT technology

The characteristics of terrestrial IMT systems for frequency sharing/interference analyses in the frequency range between 24.25 GHz and 86 GHz used in this study are summarized in Table 2. These characteristics are extracted from document TG 5-1/36 provided by WP 5D [1].

Table 2: Characteristics of terrestrial BS IMT systems

Parameter IMT-2020 (Base station)Band of operation 71-76 GHzAdjacent frequency studied 76.5 GHzSpurious emissions As a basis –13 dBm/MHz Total Radiated Power (Note 1).

The feasibility of more stringent spurious domain emission limits is under investigation by 3GPPA range between -10 dBm and -30 dBm is analysed

Antenna Height (OutdoorSuburban hotspot)

6 m (above ground level)

Antenna pattern ITU-R REC M.2101 [2] (see Figure 4)Antenna peak gain 5 dB Antenna normalization factor 4.8 dB [3]Horizontal/vertical 3 dB beamwidth of single element

65 degree

Horizontal/vertical front-to-back ratio

30 dB

Antenna downtilt 10 degreeBase station loading factor (note 2)

For studies involving only a single IMT base station/cell, a high value of 50% for BS/network loading may be used

Note 1: Unwanted emissions requirements are defined in terms of Total Radiated Power (TRP). The relative emission levels to be used for sharing studies will need to be calculated based on the above emission mask information and relevant deployment parameters below. These calculations have been performed to obtain the information in the Appendix to assist and inform Task Group 5/1.

Note 2: For this study, we are interested to know the impact of the IMT-2020 signal transmitted from the BS (i.e. the BS is active). When the BS does not transmit (i.e. BS is inactive), it will not interfere to the automotive radar. Therefore, all the events simulated consider an active BS. (see also Annex 2)

For the antenna pattern, ITU-R REC M.2101 [2] recommends that in an adjacent frequency band situation with IMT as the interferer system when adjacent channel interference is calculated, the antenna pattern can be assumed to have a similar antenna pattern as a single antenna element. The antenna radiation pattern is presented in Figure 4.

Figure 4: Antenna pattern for the (a) horizontal and (b) vertical plan to emulate IMT BS antenna pattern

(a) (b)

4.2 Automotive radar

Automotive radar characteristics in the frequency band 76-81 GHz used in this study are summarized in Table 3. These characteristics are extracted from ITU-R REC M. 2057 [4].

This study will focus on the category Radar A that are automotive radar mounted on the front of the vehicle for e.g. for adaptive cruise control.

Table 3: Automotive radar characteristics in the frequency band 76-81 GHz

Parameter Radar AFrequency 76-77 GHzBandwidth 1 GHzNoise -69 dBAntenna height 0.7 mAntenna pattern - Implementation of an actual radar (See Figure 5)

- Radar A of ITU-R M.2057[4] (see Figure 6)Antenna peak gain (actual radar) 25 dBiAntenna peak gain (Radar A) Typical 30 dBi

(Maximum 45 dBi)Antenna azimuth 3dB beamwidth ± 5 degreesAntenna elevation 3dB beamwidth ± 3 degreesNoise = RX sens (1 GHz) in dBm +RX-noise figure 15 dB (note 2)

-69 dBm (=-84 dBm +15)

Cross-polarisation loss 0 dB Worse case scenario to be considered as the polarization used for the automotive radar is manufacturer dependent.

Note 2: The RX sensitivity values for automotive RX are referenced to the antenna port with regards to a bandwidth of 1 GHz.

Figure 5: Automotive radar antenna pattern for the (a) horizontal and (b) vertical plan

(a) (b)

Figure 6: Radar A [4] antenna pattern for the (a) horizontal and (b) vertical plan with peak gain 30 dBi

(a) (b)

4.3 Propagation model

Based on Document 5-1/38 [5], we used the ITU-R REC P.452 [6] without the clutter effect as shown in Table 4.

Table 4: Propagation model summary guidance for AI.13 sharing studies [5]

Figure 7 presents the path loss calculated for a distance from 10 m to 500 m using the ITU-R REC P.452 (in blue) using SEAMCAT [7]. It is drawn in the same graph as the free space propagation model (in red) as a reference. Note that these values are calculated assuming a frequency of 76.5 GHz.

Figure 7: Path loss (in dB) calculated for a distance from 10 m to 500 m using the ITU-R REC P.452 [6] and free space

4.4 Interference criteria

A protection criterion I/N of -6 dB, as recommended in ITU-R REC M.2057 [4], is considered in this study.

5. Simulation Methodology

5.1 Spurious emission consideration

For the initial study, we are only considering the spurious domain limits (i.e. considering a sharp edge to the emission limit). Using the spectrum mask would provide worse results as there are -5 dBm over 20 MHz to consider as shown in the table below [1]. However, since other values for the spurious emission limit are considered as well in this study the results are independent of the BS in-band output power.

In this study the spurious emission of -13 dBm/1 MHz acts as a transmit power into a 1 GHz radar bandwidth. This is equivalent to a transmit power of -13 dBm/1 MHz + 10*log10(1000) = 17 dBm/1 GHz.

Another aspect to take into account is that IMT-2020 is intended to operate in the frequency bands below and above the 76-81 GHz frequency bands, from a spurious emission point of view this is equivalent to double the energy. Therefore, the total emission power to consider for this study is -13 dBm/1 MHz + 3 dB = -10 dBm/1 MHz.

5.2 Simulation topology

An initial SEAMCAT [7] simulation scenario was prepared for adjacent channel compatibility study. SEAMCAT proposes existing implemented modules of propagation models (i.e. ITU-R REC P.452) and antenna models (i.e. ITU-R REC M.2101 IMT).

This initial study focuses on a single IMT-2020 BS that could interfere with an automotive radar. Therefore, the characteristics of the IMT-2020 BS are somewhat static, like the spurious emission level, antenna pattern, antenna down tilt. The only parameters that are not constant are the geographical position of the automotive radar mounted on a vehicle.The simulation considers a vehicle traveling over 500 m away from an IMT BS positioned at 4 m from it in a straight trajectory. This is illustrated in Figure 8, where the yellow lines represent the vehicle trajectory (actually it is 20000 positions of the vehicle, i.e. the victim, on a straight line) and where the red dot (bottom/left corner) represents the IMT BS (i.e. the interferer). The red dot is 4 m from the yellow line. The yellow line is 500 m long. Figure 8 also illustrates how the antenna pattern of the transmit BS and the receive radar are pointed.

Figure 8: Simulation topology (yellow line = 20000 victim positions; red dot= interfering IMT BS)

5.3 Interference calculation

SEAMCAT proposes a flexible and generic interference calculation tool. The graphical interface provides easy topology setup as shown in Figure 7. Since the protection criterion is I/N, we will only focus on the “I” component since the noise “N” is an input to the tool.

The interference “I” is calculated as follows:

I = Tx + Gradar + GIMT_BS - PL

Where:

I is the received interference level at the victim (i.e. radar) in dBm

Tx is the transmit power in dBm for 1 GHz Gradar is the antenna gain for the victim radar. The gain is calculated for each of the simulated

event according to the azimuth and elevation angle of arrival of the interfering signal in dB. GIMT_BS is the antenna gain for the interfering IMT-2020 BS. The gain is calculated for each of the

simulated event according to the azimuth and elevation angle of departure of the interfering signal in dB.

PL path loss in dB

In SEAMCAT, for each event the interference is calculated for each of the position of the victim. For this study, 20000 events are simulated.

Eventually, the 20000 calculated “I” are compared to “N”. If the ratio I/N fulfills the protection criterion, the radar is not interfered. In the case where the ratio I/N does not fulfill the protection criterion, this means that the radar is interfered.

6. Results

Results of the initial study for I/N = -6 dB are reported in the table 5 and table 6 for various spurious emission level using an actual automotive radar and radar A [4] respectively.

The results extracted from SEAMCAT indicate the probability of interference P(%) for a protection criterion of -6 dB. This means that for a percentage P of the 20000 generated positions of the victim the I/N was not respected For instance, with the proposed spurious emission of -13 dBm/1 MHz (for both bands it is equivalent to -10 dBm/1 MHz), 40.3 % of the simulated links the I/N of -6 dB could not be respected for a radar A with an antenna peak gain of 30 dBi.

Table 5: Probability that an automotive radar is interfered for various spurious emission level using an actual automotive radar peak gain G = 25 dBi

Spurious emission level (dBm/1MHz)

Probability of interference P(%)

Probability of interference P(%)(with 4.8 dB antenna normalization factor [3])

-10 (double side bands effect) 23.7 33.2-13 (single band effect) 15.9 27.7-20 4.3 10.8-25 0 4.2-30 0 0

Table 6: Probability that an automotive radar is interfered for various spurious emission level using radar A [4] with typical peak gain G = 30 dBi.

Spurious emission level (dBm/1MHz)

Probability of interference P(%)

Probability of interference P(%)(with 4.8 dB antenna normalization factor [3])

-10 (double side bands effect) 32.9 40.3-13 (single band effect) 27.6 36-20 8.4 21.3-25 0.1 8-30 0 0

7. Conclusion

This initial study presents the effect of the spurious emission level on automotive radar (BW=1 GHz). It shows that the proposed spurious emission -13 dBm/1 MHz from IMT-2020 will lead to a significant interference (40.3 %) to the automotive radar.

Based on the information we have about the deployment scenarios for the IMT-2020 components, we can assume that automotive radars would face the main impact in urban areas. In urban areas the radar based functions are a key element for autonomous driving vehicles as well as for current driver assistance functions and emergency braking systems.

This study only presents the impact of the spurious emission. In fact, the out of band emissions would be even worse, but the study already shows that spurious of -13dBm/MHz would interfere automotive radars.

This study only considers the impact of the spurious emission in automotive radars of 1 GHz bandwidth.

In order to protect radar across the band (76-81 GHz), IMT-2020 needs to respect a spurious emission limit of -30 dBm/1 MHz. Also, in order to sufficiently protect the automotive radar from IMT-2020, the implementation of guard bands in the frequency bands 71-76 GHz and 81-86 GHz could be a possible method to achieve that.

8. References

[1] document TG 5-1/36: LS from WP 5D to TG 5/1 - Spectrum needs andcharacteristics for the terrestrial component of IMT in the frequency range between 24.25 GHz and 86 GHz[2] ITU-R REC M.2101-0: Modelling and simulation of IMT networks and systems for use in sharing and compatibility studies[3] document TG 5-1/174: LS from WP 5D to TG 5/1 - Total integrated gain for the active antenna system (AAS) antenna pattern[4] ITU-R REC M. 2057-1: Systems characteristics of automotive radars operating in the frequency band 76-81 GHz for intelligent transport systems applications.[5] Document TG 5-1/38: Guidance on the use of ITU-R P-Series Recommendations for interference prediction and sharing studies under WRC-19 agenda item 1.13

[6] ITU-R REC P.452: Prediction procedure for the evaluation of interference between stations on the surface of the Earth at frequencies above about 0.1 GHz[7] SEAMCAT: https://cept.org/eco/eco-tools-and-services/seamcat-spectrum-engineering-advanced-monte-carlo-analysis-tool

Annex 2

Effect of the base station loading factor

Footnote 10 of document 5-1/36:This represents a typical/average value for the loading of base stations within a network. In order to provide adequate quality of service, IMT networks are dimensioned such that, across the cells within a network, most of the cells will be relatively lightly loaded most of the time, with only a small percentage of cells being heavily loaded. For studies involving only a single IMT base station/cell, a high value of 50% for BS/network loading may be used.

For studies that involve the aggregation of multiple base stations, the temporal variation of each single base station can be approximated by a simple loading factor.

For studies that involve only the impact of a single base station, its impact will depend strongly on the characteristics of the signal of the base station. The information provided by WP5D, however, does not provide any information in this respect. 50% loading could be understood as transmitting fully loaded for 10s and being off for the next 10s, or as transmitting for 100ns and being off for the next 100ns. The impact to the interfered with system will, however, be very different.

Therefore clarification is sought about the characteristics of the emissions, in particular for the out-of-band case.