BRITISH STANDARD BS EN 50492:2008 +A1:2014 Incorporating corrigendum March 2009 Basic standard for the in-situ measurement of electromagnetic field strength related to human exposure in the vicinity of base stations ICS 13.280; 17.220.20; 33.070.01 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BS EN 50492:2008+A1:2014 National foreword This British Standard is the UK implementation of EN 50492:2008+A1:2014 It supersedes BS EN 50492:2008 which will be withdrawn on January 2017 The start and finish of text introduced or altered by amendment is indicated in the text by tags Tags indicating changes to CENELEC text carry the number of the CENELEC amendment For example, text altered by CENELEC amendment A1 is indicated by !" The UK participation in its preparation was entrusted to Technical Committee GEL/106, Human exposure to low frequency and high frequency electromagnetic radiation A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2009 Amendments/corrigenda issued since publication © The British Standards Institution 2014 Published by BSI Standards Limited 2014 ISBN 978 580 80044 Date Comments 31 March 2009 Correction to poor quality figures 31 May 2014 Implementation of CENELEC amendment A1:2014 EUROPEAN STANDARD EN 50492:2008+A1 NORME EUROPÉENNE EUROPÄISCHE NORM March 2014 ICS 17.220.20; 33.070.01 English version Basic standard for the in-situ measurement of electromagnetic field strength related to human exposure in the vicinity of base stations Norme de base pour la mesure du champ électromagnétique sur site, en relation avec l’exposition du corps humain proximité des stations de base Grundnorm für die Messung der elektromagnetischen Feldstärke am Aufstell- und Betriebsort von Basisstationen in Bezug auf die Sicherheit von in ihrer Nähe befindlichen Personen This European Standard was approved by CENELEC on 2008-09-01 CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member This European Standard exists in three official versions (English, French, German) A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels © 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members Ref No EN 50492:2008 E BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) –2– Foreword This European Standard was prepared by the Technical Committee CENELEC TC 106X, Electromagnetic fields in the human environment The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50492 on 2008-09-01 The following dates were fixed: – latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2009-09-01 – latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2011-09-01 This European Standard has been prepared under Mandate M/305 given to CENELEC by the European Commission and the European Free Trade Association and covers essential requirements of EC Directive RTTED (1999/5/EC) Foreword to amendment A1 This document (EN 50492:2008/A1:2014) has "Electromagnetic fields in the human environment" been prepared by CLC/TC 106X, The following dates are fixed: • • latest date by which this document h as to be implemented at national level by publication of an identical national standard or by endorsement latest date by which the national standards conflicting with this document have to be withdrawn (dop) 2015-01-06 (dow) 2017-01-06 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CENELEC [and/or CEN] shall not be held responsible for identifying any or all such patent rights –3– BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) Contents Scope Normative references Terms and definitions Physical quantities, units and constants 10 4.1 4.2 Quantities 10 Constants 10 General process 10 Site analysis and case determination 12 6.1 6.2 6.3 Introduction 12 RF sources to be considered 12 Case determination 12 Determination of field quantity to measure in relation to the distance to source antennas 13 Requirements of measurement systems 13 8.1 8.2 General 13 Technical requirements of measurement systems 14 Measurement procedures .16 9.1 9.2 General requirements 16 Field strength assessment 16 10 Assessment of the field strength at maximum traffic of a cellular network .18 11 Uncertainty .19 11.1 Requirement for expanded uncertainty 19 11.2 Uncertainty estimation 19 12 Presentation of results 22 Annex A (informative) Main services operating RF 23 Annex B (informative) Sweeping method .24 B.1 B.2 B.3 B.4 Measurement setup .24 Measurement method .24 Discussion on advantages and disadvantages of the method 24 References 25 Annex C (informative) Example of broadband equipment use 26 C.1 C.2 General 26 Locating the point of maximum exposure .26 Annex D (informative) Spectrum analyser settings 28 D.1 D.2 D.3 D.4 Introduction 28 Detection algorithms 28 Resolution bandwidth and channel power processing 29 Integration per service 31 Annex E (informative) Measuring and evaluating different broadcast signals in respect to EMF 32 E.1 E.2 E.3 E.4 FM radio 32 DAB (Digital Audio Broadcasting; Digitalradio) .32 Long wave, medium wave and short wave service .32 DRM (Digital Radio Mondial) 33 BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) E.5 E.6 –4– Analog (PAL and SECAM modulation) 33 DVB-T 34 Annex F (informative) WCDMA measurement and calibration using a code domain analyser 35 F.1 F.2 F.3 F.4 General 35 Requirements for the code domain analyser 35 Antenna factor 36 Calibration .37 Annex G (informative) Influence of human body on probe measurements of the electrical field strength 40 G.1 G.2 G.3 Simulations of the influence of human body on probe measurements based on the method of moments (surface equivalence principle) 40 Comparison with measurements 41 Conclusions .42 Annex H (informative) Spatial averaging 43 H.1 H.2 H.3 H.4 H.5 H.6 H.7 Introduction 43 Small-scale fading variations 44 Error on the estimation of local average power density 44 Characterization of environment statistical properties 45 Characterisation of different averaging schemes 45 Example of uncertainty assessment .49 References 49 Annex I (informative) Maximum traffic estimation of cellular network contribution 50 I.1 I.2 I.3 I.4 I.5 General 50 GSM and estimation of the exposure at maximum traffic .50 UMTS and estimation of the exposure at maximum traffic .51 Influence of traffic in real operating network 51 Maximum traffic estimation for TETRA and TETRAPOL PMR cellular network contribution 52 Annex J (informative) WiFi measurements 55 J.1 J.2 J.3 J.4 J.5 J.6 General 55 Integration time for reproducible measurements 55 Channel occupation .56 Some considerations .56 Scalability by channel occupation 57 Influence of the application layers 57 Annex K (informative) Examples of implementation of this standard in the context of Council Recommendation 1999/519/EC 58 K.1 K.2 K.3 K.4 Purpose 58 General considerations 58 Evaluation of broadband results 58 Evaluation of frequency selective results 59 !Annex L (informative) FDD LTE measurements 60 General 60 L.2 Maximum LTE exposure 61 L.1 L.2.1 Introduction 61 L.2.2 Method using a dedicated decoder 61 L.2.3 Method using a basic spectrum analyser 62 L.3 Instantaneous LTE exposure measurements 64 " Bibliography 65 –5– BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) Figures Figure – Alternative routes to determine in-situ the electromagnetic field for human exposure assessment 11 Figure – Location of measurement points for spatial averaging 17 Figure D.1 – Spectral occupancy for GMSK 29 Figure D.2 – Spectral occupancy for WCDMA 30 Figure F.1 – Channel allocation 35 Figure F.2 – Decoder power range versus antenna factor and cable losses for satisfying selective measurement requirements 37 Figure G.1 – Simulation arrangement 40 Figure G.2 – Body influence .41 Figure G.3 – Simulation arrangement 42 Figure H.1 – Physical model of small-scale fading variations 43 Figure H.2 – Example of field strength variations in line of sight of an antenna operating at 2,2 GHz 43 Figure H.3 – Error at 95 % on average power estimation 45 Figure H.4 – 343 measurement positions building a cube (centre) and different templates consisting of a different number of positions 46 Figure H.5 – Moving a template (Line 3) through the CUBE 47 Figure H.6 – Standard deviations for GSM 900, DCS 800 and UMTS 48 Figure I.1 – Time variation over 24 h of the exposure induced by GSM 800 MHz (left) and FM (right) 52 Figure J.1 – Example of WiFi frames .55 Figure J.2 – Channel occupation versus the integration time 55 Figure J.3 – Channel occupation versus nominal throughput rate 56 Figure J.4 – WiFi spectrum trace snapshot 56 !Figure L.1 – LTE time-frequency plan .60 Figure L.2 – Illustration of the boosting factor BF, specific to each network operator 62 Figure L.3 – LTE spectrum: PBCH power higher than RS power 63" BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) –6– Tables Table – Quantities to measure at different distances from radio-stations .13 Table – Broadband measurement system requirements 15 Table – Frequency selective measurement systems requirements 15 Table – Uncertainty assessment in controlled environment 20 Table – Uncertainty assessment in-situ .21 Table A.1 – Main services 23 Table D.1 – Example of spectrum analyser settings for an integration per service 31 Table F.1 – WCDMA decoder requirements 36 Table F.2 – Signals configuration .37 Table F – WCDMA generator setting for power linearity .38 Table F.4 – WCDMA generator setting for decoder calibration 38 Table F.5 – WCDMA generator setting for reflection coefficient measurement .39 Table G.1 – Maximum simulated error due to the influence of a human body on the measurement values of an omni-directional probe .41 Table G.2 – Measured influence of a human body on omni-directional probe measurements 42 Table H.1 – Uncertainty a 95 % for different fading models 45 Table H.2 – Correlation coefficients for GSM 900 and DCS 800 47 Table H.3 – Variations of the standard deviations for the GSM 900, DCS 800 and UMTS frequency band .48 Table H.4 – Examples of total uncertainty calculation 49 Table K.1 – Example of a results table for broadband measurements of the electric field strength at one measurement point including an evaluation of compliance with exposure limits 59 Table K.2 – Example of a results table for frequency selective measurements of the electric field strength at one measurement point including an evaluation of compliance with exposure limits .59 !Table L.1 – Theoretical extrapolation factor, nRS as function of the bandwidth, assuming all subcarriers are at the same power level 62 " –7– BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) Scope This European Standard specifies in the vicinity of base station as defined in 3.2 the measurement methods, the measurement systems and the post processing that shall be used to determine in-situ the electromagnetic field for human exposure assessment in the frequency range 100 kHz to 300 GHz Normative references The following referenced documents are indispensable for the application of this document For dated references, only the edition cited applies For undated references, the latest edition of the referenced document (including any amendments) applies EN 50383, Basic standard for the calculation and measurement of electromagnetic field strength and SAR related to human exposure from radio base stations and fixed terminal stations for wireless telecommunication systems (110 MHz - 40 GHz) EN 50400, Basic standard to demonstrate the compliance of fixed equipment for radio transmission (110 MHz – 40 GHz) intended for use in wireless telecommunication networks with the basic restrictions or the reference levels related to general public exposure to radio frequency electromagnetic fields, when put into service Terms and definitions For the purposes of this document, the following terms and definitions apply 3.1 antenna device that serves as a transducer between a guided wave (e.g coaxial cable) and a free space wave, or vice versa In the present standard, if not mentioned, the term antenna is used only for emitting antenna(s) 3.2 base station (BS) fixed equipment for radio transmission intended for use in wireless telecommunications networks, such as those used in cellular communication, Wireless Local Area Networks, point-to-point communication and point-to-multipoint communication according to ITU-R Recommendation F.592-3 Point to point and point to multi point communication equipment listed in “The European table of frequency allocations and utilisations covering the frequency range kHz to 275 GHz” (ERC report 25) (see example in Annex A) are considered For the purpose of this standard, the term “base station” includes the radio station and the antenna 3.3 average (temporal) power (Pavg) the time-averaged rate of energy transfer defined by: _ Pavg t = P(t)dt t − t1 ∫t1 where t1 and t2 are the start and stop time of the measurement The period t2 - t1 is the exposure duration time 3.4 averaging time (tavg) appropriate time over which exposure is averaged for purposes of determining compliance with the limits BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) –8– 3.5 electric field strength (E) magnitude of a field vector at a point that represents the force (F) on a small test charge (q) divided by the charge r r F E= q The electric field strength is expressed in units of volt per metre (V/m) 3.6 intrinsic impedance ratio of the electric field strength to the magnetic field strength of a propagating electromagnetic wave The intrinsic impedance of a plane wave in free space is 377 ohm 3.7 hemispherical isotropy maximum deviation of the field strength when rotating the probe around its major axis with the probe exposed to a reference wave, having varying incidence angles relative to the axis of the probe, incident from the half space in front of the probe 3.8 probe isotropy degree to which the response of an electric field or magnetic field probe is independent of the polarization and direction of propagation of the incident wave 3.9 axial isotropy maximum deviation of the field strength when rotating around the major axis of the probe housing while the probe is exposed to a reference wave impinging from a direction along the probe major axis 3.10 linearity maximum deviation over the measurement range of the measured quantity from the closest linear reference curve defined over a given interval 3.11 magnetic flux density (B) vector field quantity B which exerts on any charged particle having velocity v a force F equal to the product of the vector product r r v × B and the electric charge q of the particle: r r r F = qv × B where r F q r v r B is the vector force acting on the particle in newtons is the charge on the particle in coulombs is the velocity of the particle in metres per second is the magnetic flux density in teslas BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 54 – Emcch denotes measured electric field from MCCH only To get the MCCH frequency and/or the information about the number of transmitters: – information from the respective operator or local authority; – spectrum; – visual and expertise; – hold / max hold analysis To get more information about TETRAPOL technology, you can consult the website www.tetrapol.com – 55 – BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) Annex J (informative) WiFi measurements J.1 General The WiFi signal is a spread-frequency signal emitted with random backoff (Figure J.1) Therefore measurement has to be carried out carefully since the signal is noise-like and not permanent Moreover, most spectrum analysers are not able to record the entire trace Figure J.1 ± Example of WiFi frames The assessment of the real exposure to a WiFi system implies the knowledge of the real emitted power by the device In most commercial 802.11 devices, the access to the medium is done by a CSMA/CA (Carrier Sense Multiple Access) protocol completed by a random waiting time before retrial, known as back-off time Even if the maximum output power is constant and known and no power control is performed, the random back-off time makes it impossible to retrieve the emitted power shape over the time for most existing spectrum analysers J.2 Integration time for reproducible measurements The random duration of the back-off time, integrated within the inter-packet delay, makes a deterministic calculation of the channel occupation impossible Moreover, a sequence of random inter-packet delays will introduce a needed minimum integration time on the random duty cycle or channel occupation A set of random back-off time values will converge after a minimum observation time has passed by Figure J.2 ± Channel occupation versus the integration time BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) J.3 – 56 – Channel occupation The packet transmission is done by encapsulating the IP packets into the MAC layer frames These IP packets carry the application data and transport details from the upper layers and their size is not deterministic Moreover, the size of the IP packets is usually not known a priori unless a controlled traffic generator is used Our interest is to calculate the emission time over a full observation time Operating at a fixed maximum throughput, the length of the packets sent into the MAC layer will be an important parameter to be determined This length will provide the variable time in which the channel is occupied Figure J.3 ± Channel occupation versus nominal throughput rate J.4 Some considerations Figure J.4 ± WiFi spectrum trace snapshot A spectrum analyser is not able to plot the entire trace of a WiFi 802.11 signal even using the channel power process because of the insufficient resolution bandwidth The definition of the analyser parameters can enhance the plotting However, due to the random separation between emissions, or packets, and the minimum sweeping time of the analyser, the plotted trace will have discontinuities while performing a measurement Yet, the resolution bandwidth of the conventional equipment is an inverse function of the sweep time An agreement between the 22 MHz minimum needed resolution bandwidth and the minimum sweep time to integrate the full emitted power is not possible – 57 – J.5 BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) Scalability by channel occupation The maximum output power can be measured either with a sensitive power meter or taking as reference the max-hold power trace This trace would be escalated by the occupation factor in order to get close to the real emitted power J.6 Influence of the application layers In ad-hoc networks the traffic can be raised up to the maximum by streaming data packets from one computer to another using the UDP protocol The reason is that UDP offers a higher channel occupation than TCP by eliminating the error control and acknowledgement delays from the transport layer BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 58 – Annex K (informative) Examples of implementation of this standard in the context of Council Recommendation 1999/519/EC K.1 Purpose This annex describes how to evaluate the compliance of the measured electric and magnetic field strengths or the equivalent power density levels with the reference levels specified in the Council Recommendation 1999/519/EC (non-compliance with these reference levels does not necessarily imply non-compliance with the basic restrictions) For simplicity, only electric field strength levels are considered in this annex K.2 General considerations The measurement value, or the extrapolated value if extrapolation is used, should be compared directly with the appropriate reference levels To evaluate the compliance of simultaneous exposure in multiple frequency bands the exposure ratio (ER) for all measured frequencies or frequency bands is defined according to: ER = ∑ f Ef E L, f E L, f 87 V/m (0,1 MHz ≤ f < MHz) 87 f V/m (1 MHz ≤ f < 10 MHz) = 28 V/m (10 MHz ≤ f < 400 MHz) 1,375 f V/m (400 MHz ≤ f < 000 MHz) 61 V/m (f ≥ 000 MHz) (K.1) where Ef is the electric field strength at frequency f and EL,f is the electric field strength limit as specified in the Council Recommendation If the total ER is below or equal to the exposure at the measurement point meets the requirements specified in the Council Recommendation NOTE The listed reference levels are applicable for public exposure NOTE The relation between the reference levels for the electric and the magnetic field strength is not equal to the free space impedance at frequencies below 10 MHz K.3 Evaluation of broadband results When broadband equipment is used the measured value should be compared with the lowest reference level in the frequency range covered by the probe If several probes have been used to cover a wide frequency range, the total exposure should be evaluated by summing the exposure ratios determined using Equation (K.1) NOTE If the measured equivalent power density exceeds the threshold used in 6.3.2, measurements shall be performed with frequency selective equipment as specified in 8.2.2 and according to the procedures described in Clause BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 59 – Table K.1 ± Example of a results table for broadband measurements of the electric field strength at one measurement point including an evaluation of compliance with exposure limits Measurement point Frequency Height MHz m 0,1 - 000 Measured value V/m Reference level V/m Exposure ratio 1,1 2,1 28 0,006 1,5 2,0 28 0,005 1,7 1,8 28 0,004 Average K.4 0,005 Evaluation of frequency selective results Measurement values assessed by frequency selective equipment should be compared with the limits on a sample basis, i.e values corresponding to the frequency range defined by the radio band width (RBW) at a specific frequency should be compared with the exposure limit at that frequency Alternatively, if a measurement value is obtained by integration over a wider frequency band, e.g a GSM downlink band, the lowest exposure limit in that band should be used The total exposure in the measured frequency range should be evaluated by summing the exposure ratios determined using Equation (K.1) Table K.2 ± Example of a results table for frequency selective measurements of the electric field strength at one measurement point including an evaluation of compliance with exposure limits Measurement point Band Frequency MHz FM broadcast GSM 900 88 - 108 925 - 960 Reference level V/m 28 42 GSM 800 WCDMA/3G 805 - 910 110 - 170 58 61 Height m Measured value V/m Exposure ratio 1,1 0,061 0,000 004 1,5 0,052 0,000 003 1,7 0,065 0,000 005 Average 0,000 004 1,1 0,52 0,000 15 1,5 0,71 0,000 29 1,7 0,73 0,000 30 Average 0,000 25 1,1 0,63 0,000 12 1,5 0,28 0,000 023 1,7 0,45 0,000 060 Average 0,000 067 1,1 0,47 0,000 059 1,5 0,4 0,000 043 1,7 0,4 0,000 043 Average 0,000 049 Sum 0,000 37 BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 60 – Annex L (informative) ! FDD LTE measurements L.1 General Annex L describes methods to measure and extrapolate LTE (MIMO 2x2 and MIMO 2x1) exposure level (FDD LTE [1]) This annex is not an exhaustive summary of existing methods, and other measurement methods for LTE have been published [2] The proposed methods require classical radiofrequency (RF) measurement instruments: a basic spectrum analyser or a dedicated decoder and an isotropic antenna LTE emissions consist of specific signals at specific time-frequency allocations [3] [4] This kind of dynamic time-frequency allocation is known as Orthogonal Frequency Division Multiple Access (OFDMA) See Figure L.1 Figure L.1 - LTE time-frequency plan As for other telecommunication signals, LTE signals are subject to time variations because of traffic variations and random fluctuations of the propagation medium The extrapolation to the maximum traffic should be based on the measurement of a time independent channel or signal Due to the LTE specifications, the power of each time-frequency unitary element [1] (66,7 µs, 15 kHz) in the LTE downlink signal is scalable from one kind of transmitted data to another In addition, LTE downlink spectrum is totally flexible and may vary from 1,4 MHz to 20 MHz, and inside the spectrum, the power level may vary from one channel to another Two types of measurements are specified: the assessment of instantaneous LTE exposure levels and the assessment of maximum LTE exposure by extrapolation For the instantaneous LTE exposure assessment a basic spectrum analyser and suitable measurement probes are used For the maximum LTE exposure two types of reproducible methods of electromagnetic field (EMF) exposure assessment of LTE signals, depending on " – 61 – BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) ! the used measurement instrument, are described: one method, using a dedicated decoder, similar to existing methods that are based on pilot signals (see Clause 8) and another method using a basic spectrum analyser If no frequency information about the present LTE channels is available the LTE downlink bandwidth should first be determined using a spectrum analyser in frequency mode and a peak detector In this way the frequency information and LTE bandwidth can best be determined L.2 Maximum LTE exposure L.2.1 Introduction In L.2, two methods to assess the maximum exposure level are described Both methods are acceptable but, in case of selective fading, the method using dedicated decoder is recommended L.2.2 Method using a dedicated decoder As extrapolation method, the reference signal RS is measured and extrapolated to the maximum value with an extrapolation factor The influence of the traffic load and output power of the base station on in-situ RS, S-SYNC, P-SYNC, PBCH signals [1] are lower than dB for all power and traffic load settings, showing that these signal levels can be used for the extrapolation method For this method, dedicated LTE equipment or LTE analysers are needed To estimate the maximum exposure level (Emax) of the LTE signal at each measurement location, Formula (L.1) is used: nRS Emax = × E RS_PORT1 + E RS_PORT2 BF (L.1) where Emax is maximum exposure level in V/m ERS_PORT1 is the measured electric field values of the reference signal RS for antenna port in V/m, ERS_POR2 is the measured electric field values of the reference signal RS for antenna port in V/m, nRS is the ratio of the maximum total output power at the base station to the power of the reference signal RS at the base station BF is the power boosting factor (see Figure L.2) ERS_ANT1 and ERS_ANT2 are the measured electric field values of the reference signal RS for each antenna port, nRS the ratio of the maximum total output power at the base station to the power of the reference signal RS at the base station and BF is the power boosting factor (see Figure L.2) nRS corresponds to the number of subcarriers and is provided by the network operator or can be calculated theoretically (assuming that the power of the RS subcarriers are at the same power level as the other subcarriers, see Table L.1) " BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 62 – ! Table L.1 - Theoretical extrapolation factor, nRS as function of the bandwidth, assuming that all subcarriers are at the same power level Bandwidth [MHz] 1,4 10 15 20 Total number of resource blocks (12 subcarriers per symbol) 15 25 50 75 100 nRS =Maximum total nRS 72 180 300 600 900 1200 18,57 22,55 24,77 27,78 29,54 30,79 output power/PRS [dB] Figure L.2 - Illustration of the boosting factor BF, specific to each network operator L.2.3 Method using a basic spectrum analyser Using a basic spectrum analyser, the power of the reference signals (RS) cannot be detected since these signals are not permanent signals To overcome this issue and avoid requirements of previous knowledge on band occupation or service characteristics, the broadcast channel (PBCH) [3] power can be measured PBCH is transmitted with same characteristics regardless of configuration or service bandwidth and always spans about MHz over the LTE signal center frequency f (Figure L.3) " – 63 – BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) ! Figure L.3 - LTE spectrum: PBCH power higher than RS power The PBCH power should be measured using the following setup on a spectrum analyser (SA): - - the centre frequency of the spectrum analyser should be equal to the centre frequency of the LTE signal; a frequency span should be set to zero (scope mode) in order to measure the received time signal at the downlink emission frequency; a resolution bandwidth (RBW) should be of MHz to integrate the signal over the PBCH spectral spread; a sweep time should be about equal to the multiplication of number of display points of the SA and the symbol duration of about 70 µs, in order to obtain an integration time close to the symbol duration of each pixel on the screen of the SA, e.g a sweep time of about 70 ms over 1000 display points (or equivalent ratio for instruments with lower resolution); a minimum of 20 s sweep time when using an r.m.s detector to measure the peak power, which will correspond to the estimated PBCH power PˆPBCH In order to use the RMS detector the maximum power shall effectively be allocated to the PBCH channel To estimate the maximum exposure level (Emax) of the LTE signal at each measurement location, Formula (L.2) is used: = Emax nPBCH × EPBCH (L.2) where Emax is maximum exposure level in V/m EPBCH is the electric field value of the PBCH signal in V/m nPBCH is the ratio of the maximum total output power at the base station to the power of the PBCH signal at the base station " BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 64 – ! EPBCH the electric field value of the PBCH signal and nPBCH is the ratio of the maximum total output power at the base station to the power of the PBCH signal at the base station nPBCH is the number of subcarriers divided by 72 and can be provided by the network operator or can be calculated theoretically L.3 Instantaneous LTE exposure measurements L.3 concerns optimal settings for the measurement of momentary or instantaneous LTE exposure A spectrum analyser (SA) and suitable antenna probes are needed The spectrum analyser settings have a huge influence on the measurement results and it is very important to specify these to determine the optimal settings to check compliance of LTE signals with the ICNIRP guidelines The following optimal settings to perform exposure assessment of LTE are proposed in [5]: r.m.s detector, resolution bandwidth RBW = MHz, sweep time SWT = 20 s, and appropriate selection of the frequency span e.g., 50 MHz These settings have been determined and tested in-lab and in-situ [5] " – 65 – BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) ! Bibliography [1] S Sesia, I Toufik and M Baker (2011) LTE-The UMTS Long Term Evolution: from theory to practice United Kingdom: Wiley, second edition, 752 p [2] F Pythoud, B Mühlemann, “Measurement Method for LTE Base Stations”, METASReport 2012-218-808, Bern, May 2012 [3] 3GPP TS36.201, “LTE Physical Layer - General Description” 3GPP TSG RAN, v9.1.0, March 2010 [4] 3GPP T S36.211, "Physical Channels and Modulation," 3GPP TSG RAN, v9.1.0, March 2010 [5] W Joseph, L Verloock, F Goeminne, G Vermeeren, and L Martens, “Assessment of general public exposure to LTE and RF sources present in an urban environment”, Bioelectromagnetics, vol 31, no 7, pp 576-579, 2010." BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) – 66 – Bibliography EN ISO/IEC 17025:2005, General requirements for the competence of testing and calibration laboratories (ISO/IEC 17025:2005 + corr.1:2006) Directive 1999/5/EC of the European Parliament and of the Council of March 1999 on radio equipment and telecommunications terminal equipment and the mutual recognition of their conformity, Official Journal L 91, 7.4.1999, p 10-28 Council Recommendation 1999/519/EC of 12 July 1999 on the limitation of exposure of the general public to electromagnetic fields (0 Hz to 300 GHz), Official Journal L 197 of 30.7.1999, p 59-70 International Commission on Non-Ionizing Radiation Protection (ICNIRP), Guidelines for limiting exposure in time-varying electric, magnetic, and electromagnetic fields (up to 300 GHz) Health physics 74(4), p 494522; 1998 ISO/IEC Guide 98:1995, Guide to the expression of uncertainty in measurement (GUM) ITU-R Recommendation F.592-3:2002, Vocabulary of terms for the fixed service ITU-R Recommendation F.1399-1:2001, Vocabulary of terms for wireless access FCC OET Bulletin 65, Evaluating Compliance with FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, Ed.1, 1997 ERC report 25, The European table of frequency allocations and utilisations covering the frequency range kHz to 275 GHz, 2002-2004 BS EN 50492:2008+A1:2014 EN 50492:2008+A1:2014 (E) This page has been intentionally left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British Standards and other standards-related publications, information and services BSI is incorporated by Royal Charter British Standards and other standardization products are published by BSI Standards Limited About us Revisions We bring together business, industry, government, consumers, innovators and others to shape their combined experience and expertise into standards -based 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