icnirp statement · the americas the global system for mobile communi-cations (gsm) system is...

INTERNATIONAL COMMISSION ON NON‐IONIZING RADIATION PROTECTION

ICNIRP PUBLICATION – 2008

ICNIRP STATEMENT ON EMF‐EMITTING NEW TECHNOLOGIES PUBLISHED IN: HEALTH PHYSICS 94(4):376‐392; 2008

ICNIRP Statement

ICNIRP STATEMENT ON EMF-EMITTINGNEW TECHNOLOGIES

The International Commission on Non-Ionizing Radiation Protection*

INTRODUCTION

RECENT DEVELOPMENTS in telecommunication and wirelesstechnology have led to increasing numbers of newdevices and systems that emit radio frequency (RF)electromagnetic (EM) energy. Implementing these devel-opments has resulted in large numbers of individuals atthe workplace or in the general public being exposed toRF-EMFs.

The guidelines of the International Commission onNon-Ionizing Radiation Protection (ICNIRP 1998) pro-vide advice for permissible exposure levels that cover theentire spectrum of non ionizing radiation (NIR), includ-ing the RFs used in new technologies. However, there arequestions being posed about health effects associatedwith exposure to these new systems and devices, whichhave not been tested per se in terms of health risks. Theymay have signal characteristics that are unique anddifferent from the currently used technologies, and theymay also cause the total level of exposure to rise becauseof the superposition of electromagnetic fields (EMFs)emitted by new and existing sources.

The aim of this Statement is to compile a list of thenew technologies under development, soon-to-be or re-cently deployed, which could lead to increased levels ofexposure to NIR at the workplace or in daily life, and toassess the need for further research to evaluate their NIRsafety and health implications. However, the technolo-gies that are included in this Statement are not limited tomobile or wireless communications; they encompass allEMF-emitting devices. Given the technological, regulatoryand marketing challenges, the timing of the introduction ordeployment of any of the products is somewhat uncer-tain. It should be noted that experience of the cellularmobile telephone industry indicates that once the new

technology is deployed, the adoption rate could easilyexplode. While it takes advanced technology to developa product, the availability of low-price, high-quality, andhigh-performance components from around the worldwould push the price of the new product down throughlarge-scale production. See the Appendix for lists oftechnical and organizational acronyms.

MOBILE COMMUNICATION ANDWIRELESS TECHNOLOGIES

While the present document focuses on new mobilecommunication and wireless technologies, the motiva-tion comes from the rapid growth of the cellular mobiletelephone industry and the pervasive use of wirelessdevices in all walks of life. We will therefore begin witha brief discussion on the evolution of cellular mobilecommunication technologies, although the distinctionamong various generations of mobile communications isblurring. Note that a description of the earlier generationsis useful, especially for epidemiological studies of cellphone exposures.

Generations of Mobile Communications

1G systemsThe first generation (1G) mobile telephones were

analog systems—typically operating at 450 MHz usingfrequency modulation. The analog systems deployed invarious parts of the world were slightly different:namely, Nordic Mobile Telephony (NMT) mainly in theNorth European countries, American Mobile Phone Ser-vice (AMPS) in the U.S., and the Nippon Telegraph andTelephone (NTT) system in Japan. The radiated powersof the 1G systems are typically 600 mW. At present,these services have either stopped or are running at a lowlevel of traffic in most parts of the world. Apart frommobile handsets and base stations, analog systems arealso used for cordless telephones. These 1G devices areimportant for the epidemiological studies of long-termexposures or any effect associated with long latency.

* ICNIRP, c/o BfS, G. Ziegelberger, Ingolstaedter Landstr. 1,85764 Oberschleissheim, Germany.

For correspondence contact G. Ziegelberger at the above address, oremail at [email protected].

(Manuscript accepted 3 December 2007)0017-9078/08/0Copyright © 2008 Health Physics Society

376

2G systemsThe major breakthrough in mobile communications

began with the second generation (2G) digital systems.These have become the dominant service with more thanone billion users worldwide. However, the 2G systemsdiffer around the world. In Europe and parts of Asia andthe Americas the Global System for Mobile Communi-cations (GSM) system is dominating. It features carrierfrequencies at 900 and 1,800 MHz (1,900 MHz in U.S.).The bandwidth is around 250 kHz with a 9.6 kbit/s datarate. It uses a Time Division Multiple Access (TDMA)technique—each user is “on” for 4.615/8 � 0.58 ms,then comes back periodically at a frequency of 217 Hz.The remaining 7/8 of the time is used for other users.Thus, from the RF power point of view it uses bursts fortransmission. Apart from the access frequency of 217 Hzand its harmonics, there are various control and systemsignals giving rise to power variations at the frequenciesof 2 and 8 Hz.

The information (voice or data) is carried by the RFsignal in a continuous phase-only manner, so as long asthe user is “on,” the power is constant. This is also calledconstant-envelope modulation. As will be seen later,most other evolving systems do not have this property ofconstant envelope.

IS-95. The IS-95 is the North American version ofthe Code Division Multiple Access (CDMA) standardknown as cdmaOne. The CDMA standard is significantlydifferent from the GSM standard. The IS-95 is a so-calleddirect-sequence spread spectrum system where the users are“on” simultaneously, but separated by different codes,which are “spread” on the carrier to a wider band-width than dictated by the un-spread scheme. The speed ofthe spreading is known as the chiprate, which for IS-95 is1.2288 Mchip/s in a bandwidth of 1.25 MHz. One imme-diate consequence is the lack of the pulsing characteristiccommon in TDMA systems. Further discussion of theCDMA technique is deferred to the 3G systems.

PDC. The Personal Digital Cellular (PDC) system isa TDMA system operating in the 800 MHz and 1.5 GHzbands and is used primarily in Japan. The system also haspacket transmission capability, named the Personal Dig-ital Cellular-Packet (PDC-P) system, which was intro-duced in 1997. As the PDC-P is based on the PDCsystem, the radio characteristics are very similar, i.e.,using 3-channel TDMA. With a single TDMA time slot,PDC-P can provide 9.6 kbit/s packet access and 28.8kbit/s with three time slots. Moreover, i-mode service isavailable on PDC-P channels.

2.5G systemsThe popularity of the Internet and personal comput-

ers created a need for higher data rates on wireless

networks than available with 2G systems, which weredesigned mainly for voice applications. The term “2.5G”is used to denote an enhanced GSM system with highspeed data services.

GPRS. In an effort to increase the data rate withinexisting systems while waiting for the 3G systems todeploy, a General Packet Radio Service (GPRS) evolved.GPRS supports a much better data rate (up to a maximumof 140.8 kbit/s) and is packet-based rather thanconnection-oriented. It is deployed in many places whereGSM is used. GPRS achieves the higher data rates bycombining several timeslots, in practice 2–3. There isalso a circuit-switched version of combining time slots—High-Speed Circuit Switched Data (HSCSD)—as aGSM-enhancement technology. HSCSD bumps up thebit rate and allows the system to combine TDMA“timeslots,” delivering data speeds up to six times fasterthan standard GSM systems.

It is generally assumed that there is a greater needfor downloading than transmitting, so the capabilitiesare asymmetric; for example, 14 kbit/s in the uplink(one timeslot) and 28 – 64 kbit/s in the downlink. Sincethe system is packet-based with the user always on, itis more the amount of data transmitted and receivedthan the time elapsed that counts. It should be stressedthat the exposure may be quite different for the datatransmission applications, since the mobile phone mayno longer be held near the ear. Because the specificabsorption rate (SAR) falls off with distance, thisreduces considerably the actual exposure to the head.

EDGE. There is also another evolution path from2G—known as Enhanced Data rate for GSM Evolution(EDGE)—which uses higher order modulations. How-ever, the signal power in EDGE may vary from symbolto symbol, i.e., it is not constant-envelope modulation. Itrequires a good radio connection, so adaptive techniquesare used to control power variations when possible. Theinformation-bearing high data rate-related power is notconstant, and is from a biological point of view a trulyamplitude-modulated signal. It could offer wireless mul-timedia internet protocol (IP)-based services and appli-cations at theoretical maximum speeds of 384 kbit/s witha bit rate of 48 kbit/s per timeslot and up to 69.2 kbit/sper timeslot, under good radio conditions. Power controlschemes also introduce power variations.

It should be noted that i-mode was the first servicethat enabled cellular telephones to access and navigatethe Web. It was an overlay on the Japanese PDCsystem with packet transmission. Thus, unlike voicecalls which are circuit-switched and only functionafter dial-up, i-mode communications are “always-on”provided you are in an area where i-mode signals are

377ICNIRP Statement on EMF-emitting new technologies ● ICNIRP

present. It gives the user instant access to text mes-saging, email, and other Internet-based information,entertainment and multimedia content via high-speedGPRS technology.

3G systemsWhile the intention of the International Telecom-

munications Union (ITU) was to establish a truly globalsystem, commercial factors prevented this from hap-pening. There are common features though, in thesense that spread spectrum (like in IS-95) is a domi-nant access scheme for multiple users. It was again thedrive to higher data rates, in general 384 kbit/s and upto 2 Mbit/s in indoor environments, that was the maingoal (Etoh 2005). At the same time, new frequencybands around 2 GHz were released for the new service.

CDMA2000. CDMA2000 is the North Americanversion of the 3G CDMA network. It differs fromW-CDMA mainly in the network architecture. Thereare some differences in the frequency allocations andthe chiprate (Vanghi et al. 2004).

W-CDMA (Universal Mobile Telecommunica-tions System, UMTS). The global standard for thirdgeneration (3G) wireless communications, IMT-2000, isa family of 3G standards, which includes W-CDMA andUMTS. When combined, W-CDMA and UMTS arereferred to as UTRA. W-CDMA is the underlying stan-dard and W-CDMA functions as the air interface forUMTS. The specific frequency bands originally definedare 1,885–2,025 MHz and 2,110–2,200 MHz for uplink(from user to base station) and downlink, respectively.W-CDMA uses a pair of 5-MHz channels, one in the1,900 MHz range for uplink and one in the 2,100 MHzrange for downlink. In contrast, CDMA-2000 uses one ormore arbitrary 1.25 MHz channels for each direction oftransmission. Thus, W-CDMA has a wider bandwidthrequirement. W-CDMA supports up to 2 Mbit/s datatransfer rates, although typical users can expect perfor-mance of around 64 kbit/s in a heavily-loaded real-worldsystem. However, this is still much greater than the 14.4kbit/s of a single GSM error-corrected data channel ormultiple 14.4 kbit/s channels in HSCSD, and offers theprospect of practical inexpensive access to the WorldWide Web on a mobile device and general use of aMultimedia Messaging Service (MMS).

Two different modes are in use: frequency divi-sion duplex (FDD), where the uplink and downlinkcommunications are separated in different frequencybands, and time division duplex (TDD), where thesame frequencies are used both ways, but separated indifferent time slots. This allows for the further advan-tage of having asymmetric transmission, such as usingrelatively more timeslots for downlink than uplink.

The following frequencies have been allocated toW-CDMA:

● FDD Mode: Uplink 1,920–1,980 MHz and 1,850–1,910 MHz; Downlink 2,110–2,170 MHz and 1,930–1,990 MHz;

● TDD Mode: Downlink and Uplink 1,900–1,920 and2,010–2,025 MHz; and Downlink and Uplink 1,850–1,910 and 1,930–1,990 MHz.

The most commonly applied access mode is FDD.Users are separated by different codes, a high data ratemodulation on top of the information. This means thatthe actual bandwidth is much higher than needed for thebasic information rates; in the present system around 5MHz. The basic rate for the codes is called the chiprate,and for W-CDMA the chiprate is 3.84 Mbit/s. The 60MHz FDD frequency bands are divided into 5 MHzbands, which may be used by one operator or by differentoperators, depending on the regulations in the specificregion or country. This fact should be considered whenevaluating the total radiation from base station antennas.

A requirement for the correct use of a CDMAsystem is that signals from all users arrive at the basestation with the same power level, otherwise interferencebetween the users will render it useless. Thus, strict andfast power control is enforced at a rate of 1,500 Hz withsteps as small as 1 dB. This means that the powerradiated from a handset (and thus the SAR) will have a1,500 Hz component. An additional factor contributingto power fluctuations (or discrete frequencies) is thenon-constant-envelope feature. In contrast to GSM, thehigh data rates are seen in the spectrum of the power witha spectral peak at 3.84 MHz and a continuous spectrumbelow that. An example is shown in Fig. 1.

Fig. 1. A typical spectrum of the power variations in a W-CDMAhandset signal (Bach Andersen et al. 2001).

378 Health Physics April 2008, Volume 94, Number 4

The maximum power radiated from a handset isgoverned by different classes. The most common is class4 with a maximum radiated mean power of 125 mW:note that this is a factor of 2 less than the maximum meanpower for GSM. In practice the power radiated may bemuch less if the distance to the base station is small, as inGSM. Fig. 2 shows a distribution of handset powers fora small urban cell, with a mean value of �6 dBm (6 dBbelow 1 mW, i.e., 0.25 mW). For a larger rural cell amuch higher fraction of the powers would be near themaximum value. Nevertheless, the SARs are expected tofall within the ICNIRP basic restrictions. However, moreinformation may be needed for the different chiprates andthe higher rates of power fluctuations associated with theautomatic power level control feature (APC).

Another reason for the small powers is the so-calledprocessing gain, which is equal to the ratio between thesystem bandwidth and the information bandwidth. Forspeech this ratio is large, for heavy data transmission itmay be close to one, and the benefit disappears.

HSDPA. Compared to fixed networks the data rate of384 kbit/s is rather small, so efforts have been made toincrease the maximum data rates of W-CDMA by usingadaptive modulation and coding under favorable conditions.Also, the burst natures of packet transmissions are utilized soother users can utilize the channel when one user has a pause.The system is called High Speed Downlink Packet Access(HSDPA) and allows transmission of up to 14 Mbit/s over a 5MHz channel bandwidth. Naturally, this gives even higher ratepower fluctuations than basic W-CDMA.

Beyond 3GThe quest for higher data rates is continuing, and the

International Telecommunications Union (ITU) has set as

goals 100 Mbit/s for general environments and 1 Gbit/s(1,000 Mbit/s) for indoors. This would require higherbandwidths and higher carrier frequencies, as well asadvanced antenna technologies and adaptive modulations,as for 3G. It is difficult to predict exactly which technolo-gies and access schemes will be applied, but one likelycandidate is the Orthogonal Frequency Division Multiplex-ing (OFDM) system. OFDM is essentially a multi-carriersystem where the wide bandwidth is divided into a largenumber of narrowband carriers, and thus avoids theinter-symbol-interference characteristic of wide band-width systems. Like the other systems mentioned, thissuffers from power fluctuations, often stated as a peak-to-mean ratio. The carrier frequencies will typically bebelow 6 GHz, since it is difficult to accept the Dopplerfrequencies for higher carrier frequencies (Etoh 2005).

In mobile telephony the development is moving fromtransmitting voice mostly to transmitting voice and dataservices built in, whereas in computing the developmentaltrend is from transmitting data to transmitting data andvoice services built in. Both developments would likelyconverge to bring about new applications and technologicalchallenges. It is becoming increasingly apparent that themajor cellular mobile systems will evolve into a 4G envi-ronment with higher bandwidth, shorter latency, and all-IPnetworks. In all cases, existing air interfaces will be re-placed using Orthogonal Frequency Division Multiple Ac-cess (OFDMA) for the downlink and OFDM for the uplink,similar to WiMAX (see later text). A combination of smartantenna technologies and Scalable OFDM (SOFDMA) willenhance the effective spectral efficiency through spectrumreuse and smart networking schemes. The use of frequencydomain techniques will enable designs using Multiple-InputMultiple-Output (MIMO) algorithms for more effectivesystems.

There are millimeter frequencies under consider-ation for various specific applications, but no mobilesystems at the present time.

Non-Mobile Wireless Communications

Wireless LANsSimultaneous with cellular mobile communication,

significant developments have taken place in the area ofWireless Local Area Networks (WLAN), with rathershort-range communication between an access point (abase station) and one or several users. The differencefrom the various generations of cellular mobile systemsdiscussed above is the lack of overall network infrastruc-ture, mobility, and handover between access points.WLANs are ad-hoc systems set up in homes, hotels,cafes, office buildings, airports, city parks, and corporateand university campuses as hotspots, and usually are

Fig. 2. Distribution of handset power in a small urban cell for aW-CDMA system (Bach Andersen et al. 2001).


connected to the Internet through the backbone connec-tion of the access point, as an extension to wired LANs.It allows mobility of terminals in a well-defined area. Asthe popularity of portable devices such as laptop com-puters and personal digital assistants (PDAs) grows,WLAN has become the communication infrastructure ofchoice.

WLANs have been standardized through the Insti-tute of Electrical and Electronic Engineers (IEEE) Stan-dard Organization (IEEE 802.11 Standard, IEEE 1999).The IEEE C standard is a complex family of standards,allowing operation at higher speeds and in additionalfrequency bands (Riezenman 2002). The main features ofthe different extensions of the IEEE 802.11 Standard,commonly identified by letters of the alphabet, aresummarized in Table 1.

The trademark Wi-Fi (acronym stands for WirelessFidelity) was originally used to certify IEEE 802.11bcompliant devices to ensure their interoperability. How-ever, it is now used by the Wi-Fi Alliance to certify allIEEE 802.11 compliant devices, independent of theparticular standard extension used (a, b, g, or h) (Ferroand Potortı̀ 2005). Note that the ISM (Industrial, Scien-tific, and Medical) bands are used for license freecommunications, in contrast to the prices paid for theuse of the 3G spectrum in most countries. This is alsothe case for the popular Bluetooth (http://www.bluetooth.com/)short-range cable replacement system, operating in the2.4 GHz band.

The IEEE 802.11 standard does not impose any limiton the maximum radiated power, because such limits,together with the available frequency bands, are decidedby different regulatory bodies, such as the FCC (FederalCommunications Commission 2005) in the U.S. and

CEPT (European Conference of Postal and Telecommu-nications Administrations 2002, 2004) in Europe. Theassigned frequency bands and allowed maximum radi-ated powers [also expressed in terms of Effective Isotro-pically Radiated Power (EIRP) for USA and Europe] aresummarized in Table 2. The majority of Wi-Fi systemsavailable on the market are IEEE 802.11b devices oper-ating with a maximum EIRP of 100 mW (20 dBm). Themodulation schemes employed by WLANs include fre-quency hopping and direct sequence spread spectrum inthe 2.4 GHz band and OFDM in the 5 GHz band. WLANtransmissions are intermittent, which leads to powerfluctuations at the data rates or higher. Therefore, time-averaged powers are lower and depend on the quantity ofdata being transmitted.

WiMAXThe name WiMAX was introduced in 2001 as the

air interface technology for wireless data transmissionover long distances. It is the acronym for WorldwideInteroperability for Microwave Access and is based onthe IEEE 802.16 standard. It provides connectivity frompoint-to-point links to full cellular mobile type access. Itenables, for example, wireless browsing of the Interneton a laptop computer. WiMAX provides the technologyfor delivery of last mile broadband wireless access as analternative to cable. In many ways, it is closer to Wi-Fithan 3G cellular mobile technologies.

The 802.16d and 16e standards are the most widelyemployed WiMAX standards, covering the 2 to 11 GHzfrequency range (IEEE 2005). IEEE 802.16e uses theSOFDMA instead of the OFDM version with 256 sub-channels in 802.16d. The updated version 802.16e alsomakes use of multiple antenna support through MIMO

Table 1. The main features of the different extensions of the IEEE 802.11 Standard.

Standard DescriptionFrequency

(GHz)Data rate(Mbit/s) Year

IEEE 802.11 Original standard, exploiting the ISM band 2.4 2 1997IEEE 802.11b Enhanced data rate in the ISM band 2.4 11 1999IEEE 802.11a Fastest version of the standard, exploiting the UNII band 5.7 54 1999IEEE 802.11g Same 802.11a speed, but in the ISM band 2.4 54 2003IEEE 802.11h Modification of 802.11a to ensure usability in Europe 5.7 54 2003

Table 2. Assigned frequency bands and allowed maximum radiated powers.

Frequency band(MHz)

USA (FCC) Europe (CEPT)

Radiated power (dBm) EIRP (dBm) Radiated power EIRP (dBm)

2,400−2,483.5 30 36 — 205,150−5,250 17 23 — 235,250−5,350 24 30 — 235,470−5,725 24 30 — 305,725−5,850 30 36 Unavailable frequency band


communication and signal processing technology. Thereis no globally agreed spectrum for WiMAX althougheconomy of scale is driving it toward 2.3 GHz, 2.5 GHzand 3.5 GHz, for mobile phones and laptop computers.The typical channel width is between 3.5 MHz and 10MHz. Under ideal operating conditions, symmetricaluplink and downlink speeds of 70 Mbit/s could beachieved. However, the speeds deliverable in practice areabout 10 Mbit/s at 10 km. One of the significantadvantages of WiMAX is spectral efficiency. Thus,exposure to RF fields is expected to be at or belowexposure limits in 3G applications.

BluetoothShort-range wireless connectivity is achieved using

the Bluetooth cable replacement system, which operatesaround 2.45 GHz. Devices incorporating Bluetooth wire-less technology include mobile phone headsets andcomputer accessories such as printers, keyboards, miceand PDAs. This technology is being increasingly used inbusiness and in the home. The Bluetooth SpecialistInterest Group (Bluetooth SIG), which is a trade associ-ation, lists over 500 products using Bluetooth technol-ogy; some representative products are given in Table 3.

The technology can support small networks, knownas piconets, with a point-to-multipoint configuration. Thecommunication is normally over very short ranges, froma few meters to tens of meters. Devices for theseapplications have very low output powers of only a fewmW, about one hundred times lower than mobile phones.Power requirements are given as power levels at theantenna connector and three power classes are defined(see Table 4). The nominal output power of devices in

Class 2 or 3 is about 1 mW, although reduction of poweris possible through optional power control. Power controldown to �4 dBm is mandatory for Class 1 devices andthe step size is in the range 2–8 dB. Control to lowerpowers for optimizing power consumption and minimiz-ing overall interference is optional for Class 1 devices.Power control is also an option for Class 2 and 3 devices.A lower power limit of less than �30 dBm is suggestedfor all power classes but is not mandatory. Bluetoothdevices in these classes are intended to communicateover short ranges. The low power outputs will give rise tocorrespondingly low exposures, well below guidelinelevels.

DECTDigital Enhanced Cordless Telecommunication

(DECT) is a digital technology which originated inEurope, and is now being adopted worldwide. DECTtechnology is a flexible digital cordless access system forcommunications in home, office and public environ-ments. DECT is mainly known for high quality voicecommunications, but it has widespread applications likeInternet access and internetworking with other fixed orwireless services. Indeed, devices with DECT-basedtransmission have been introduced for on-demand ser-vices. The DECT standard uses a radio spectrum forwireless communication in the 1,880 to 1,900 MHz band

Table 3. Representative products.

Product category Product category

Access point Keyboard and mouseAudio and visual MedicalAutomotive Mobile phoneComponent MusicGaming Office equipmentGPS Personal computerHandheld PrinterHeadset Services and toolsHome environment Unique products

Table 4. Power requirements.

Item Power Class 1 Power Class 2 Power Class 3

Maximum output power (Pmax) 100 mW (20 dBm) 2.5 mW (4 dBm) 1 mW (0 dBm)Nominal output power n/a 1 mW (0 dBm) n/aMinimum output power at

maximum power setting1 mW (0 dBm) 0.25 mW (�6 dBm) n/a

Range of mandatory power control �4 dBm to Pmax n/a n/a

Table 5. The DECT standard.

DECT parameters Range

Frequency band 1,880−1,900 MHzCarrier spacing 1.728 MHzModulation GFSKRadio access FDMA TDMA TDDNumber of time slots 12Number of carriers 10Total duplex channels 120Bit rate 1.15 Mbit/sMaximum data rate 552 kbit/sFrame duration 10 msError detection CRCSpeech coding 32 kbit/s ADPCMChannel assignment Dynamic channel selectionMobility speed 20 km/hPeak power (average) 250 mWAverage power 10 mWDECT range 300 m


using Gaussian Frequency Shift Keying (GFSK) modu-lation (Table 5). DECT is designed to be compatible withany type of telecommunication network. DECT applica-tions include residential, Public Switched TelephoneNetwork (PSTN), Integrated Services Digital Network(ISDN), GSM, voice, fax, modem, e-mail, Internet, andothers.

A simple DECT system consists of a fixed partcommonly known as a base set and a portable part knownas a cordless handset, which is common in a householdsystem capable of making a voice communication. TheDECT base set is continuously transmitting on at leastone channel to provide a beacon for DECT phones. Thehandsets in the coverage area of the base set will verifytheir identity and lock on to the base set. This transmis-sion can be part of the active transmission or a dummybearer transmission. The base set’s beacon transmissioncarries broadcast information in multi-frame, multi-plexed structure on base set identity, system capabilities,Radio Fixed Parts (RFP) status and paging informationfor incoming call set-up. The DECT band is divided into10 equal sub-bands. Within a frequency channel, trans-mit and receive channels are separated by time slotsthrough a TDMA scheme.

RFID technologiesRadio Frequency Identification (RFID) technology is

being applied to a variety of applications such as logisticsand inventory management in many industries includingretail, manufacturing, aerospace, automotive, pharmaceuti-cal, transportation, medical/healthcare, and informationtechnology. A major incentive is to use the wireless auto-matic identification technology to streamline enterpriseoperations.

Advantages of RFID compared to other automaticidentification systems are that they are stable, mobile,non-contact, rewritable, in small and thin shapes, ambienttemperature resistant, and capable of coating, multiple-reading, and individual identification.

RFID systems consist of RF tags and RF readers orinterrogators (Finkenzeller 1999). RF tags are attached orimplanted in the objects to be detected or tracked by RFreaders. Active RF tags with batteries radiate higher-strength RF signals, which are mainly used in largespaces, e.g., factories or container parks. Passive RF tagsare transponders which have no battery but operate withRF power transmitted from an RF reader without anycontact. The convenience of passive RF tag systems hasrendered it the technology of choice for applications thatrequire large numbers of IDs or lower cost compared toactive RF tag systems. Therefore, the description isfocused on the passive RF tag systems.

Many types of passive RF tags have been developed.The card type RF tags are very popular in automaticticket gates, in railway stations for example. Other typesinclude the heat-resistant type for dry cleaning facilities,the glass-case implantable type for animals, outdoortypes for transportation containers, and the adhesion-sheet type for apparels and for books in libraries.

Tunnel or gate type RF readers have been developedfor use in manufacturing facilities. Gate types are alsoused for Electronic Article Surveillance (EAS) in retailstores and libraries. Hand-held type RF readers are usedin cases where long-distance communication is not re-quired, e.g., logistic, inventory, and customer manage-ment. The panel type RF readers are installed in countersin libraries or checkouts in cafeterias for objects embed-ded with an RF tag.

Most RFID systems operate at frequencies from 100kHz to 2.45 GHz or higher (e.g., 5.8 GHz). Differentwireless communication methods are used for the lowerand higher frequencies:

1. Inductive coupling is used at 13.56 MHz or lowerfrequencies. The EMF from a coil or coils in an RFreader couples with a loop or coil antenna in the RFtag. The received RF energy changes the load of theantenna in the RF tag and the RF reader senses thischange. This method is most suited for relatively shortcommunication ranges (up to 1 m) and it is capable offast processing with multi-reading and anti-collisionfunctions. The capacity of this method would deteri-orate if an RF tag is attached to a metal object;

2. Propagation coupling is used at higher frequencies,especially around 1 GHz (referred to as UHF) and2.45 GHz. In operation, the RF reader transmits anEM wave. The RF tag captures the RF energy of theEM wave from the RF reader. The RF tag generatesand emits an EM wave, using the absorbed energy,which is received by the RF reader. This methodaffords a longer communication range (1–5 m). How-ever, the communication range can deteriorate due towater/vapor absorption and electromagnetic interfer-ence (EMI) from other equipment.

The specifications of RFID have been standardizedinternationally in several International Organization forStandardization (ISO) and ISO/International Electrotech-nical Commission (IEC) documents (ISO 11785, ISO14223-1, ISO/IEC 10536-2, ISO/IEC 1443-2, -3, -4,ISO/IEC 15693-2, -3, ISO 10374, ISO/IEC 18000) (ISO2007). Electromagnetic fields from RFID devices used inthe public environment are generally lower than theICNIRP guidelines. Electromagnetic fields in the prox-imity of RF reader antennas can however be locallyhigher than the ICNIRP reference level. For example, the


operation level of the magnetic field for the card type RFtag is specified from 0.15–5 A m�1 at 13.56 MHz inISO/IEC 15693-2, while the corresponding ICNIRP ref-erence level at 13.56 MHz is 0.073 A m�1 for the generalpublic. Because EMFs from RFID rapidly decrease withdistance and are emitted intermittently, spatial and tem-poral averaging should be applied when evaluating theEM exposure. Note that a detailed numerical simulationhas shown that the induced current density in a humanbody in a gate type RF reader (EAS) is lower than theICNIRP basic restriction (Gandhi and Kang 2001). Theimpact of the inductive coupling type RFID system aswell as EAS and security systems have been described inanother statement (ICNIRP 2004a).

The output power of RF readers ranges from several100 mW to several watts, which is significantly lowerthan that of a typical base station antenna but higher thanthat of a cellular phone. Local SAR evaluation may berequired for comparison with the ICNIRP basic restric-tion if an RF reader is located in proximity to a humanbody.

As more RFID systems are implemented in variousbusiness processes, human exposure to EMFs due toRFID will increase significantly. Exposure levels fromeach device are very small while the number of simul-taneous exposures can be very large and the locations ofthe sources are unknown. This exposure scenario is verydifferent from many other RF equipment. Practical meth-ods for evaluation of human-body exposure to EMFsfrom RFID devices may therefore be necessary.

UWB technologyUltra-wide-band (UWB) technology is mainly used

in imaging, sensing, and communication systems (Kaiseret al. 2007). Examples of imaging and sensing systemsinclude vehicular radar, ground penetrating radars(GPRs), through-wall sensing, and medical imaging,while communications systems include hand-held trans-ceivers, sensor networks, Wireless Personal Area Net-works (WPAN), etc.

The FCC defines a UWB device as any devicewhere the fractional bandwidth is greater than 0.20 oroccupies 0.5 GHz of spectrum (FCC 2002). The effect ofthis definition is that UWB systems with a centerfrequency greater than 2.5 GHz need to have a �10 dBbandwidth of at least 500 MHz, while UWB systemsoperating with a center frequency below 2.5 GHz need tohave a fractional bandwidth of at least 0.20. FCC basedits definition of an UWB device on the �10 dB band-width, rather than the �20 dB bandwidth used earlier,because UWB devices operate so close to the noise floorthat in many cases it may not be possible to measure the�20 dB bandwidth. FCC also proposed that the band-width be determined using the antenna that is designed tobe used with the UWB device.

Specifically, for UWB applications, FCC allows theuse of the frequency range below 0.96 GHz, between1.99 and 10.6 GHz, and between 22 and 29 GHz in theU.S. In particular, FCC has stipulated the followingdefinitions: low frequency imaging systems are thosewhose �10 dB bandwidth is contained below 960 MHz;mid-frequency imaging, consisting of through-wall im-aging systems and surveillance systems, that operate withthe �10 dB bandwidth within the frequency band 1,990–10,600 MHz; and high frequency imaging systems,equipment that operates exclusively indoors, and hand-held UWB devices that may operate anywhere, includingoutdoors and for peer-to-peer applications, that operatewith a �10 dB bandwidth within the frequency band of3,100–10,600 MHz. Vehicular radar systems operatewith the �10 dB bandwidth within the frequency band of22–29 GHz and with a carrier frequency greater than24.075 GHz.

The average emission limits for UWB systems, interms of EIRP measured in dBm with 1 MHz resolutionbandwidth, are given in Table 6. It must be noted that thehighest value in the table is �41.3 dBm/MHz, whichcorresponds to 75 nW/MHz.

Like most UWB systems, the average emissionsfrom vehicular radar systems in driver assistance systems

Table 6. The average emission limits for UWB systems.

Frequency band(MHz)

Imagingbelow

960 MHz

Imagingmid

frequency

Imaginghigh

frequencyIndoor

applications

Hand heldincludingoutdoor

Vehicularradar

0.009−960 �41.3 �41.3 �41.3 �41.3 �41.3 �41.3960−1,610 �65.3 �53.3 �65.3 �75.3 �75.3 �75.31,610−1,990 �53.3 �51.3 �53.3 �53.3 �63.3 �61.31,990−3,100 �51.3 �41.3 �51.3 �51.3 �61.3 �61.33,100−10,600 �51.3 �41.3 �41.3 �41.3 �41.3 �61.310,600−22,000 �51.3 �51.3 �51.3 �51.3 �61.3 �61.322,000−29,000 �51.3 �51.3 �51.3 �51.3 �61.3 �41.3Above 29,000 �51.3 �51.3 �51.3 �51.3 �61.3 �51.3


are low, but widespread adoption and associated hightraffic density in many urban environments could poten-tially lead to an increased ambient RF power level.

With regard to imaging systems, UWB signals areappealing due to their low probability of interception,non-interfering signal waveform, precision ranging, andlocalization (Taylor 1995). In this application, UWBradar has the possibility to probe the motion of theinternal organs of the human body with a remote non-contact approach (McEwan 1994). For example, anUWB radar was able to detect, non-invasively, themovements of the heart wall. In practice, vocal cords,vessels, bowels, heart, lung, chest, bladder, and fetus, andany body part of adequate size can be monitored by anUWB radar. Recently, UWB systems have also beenused for breast tumor detection (Fear et al. 2002).

As for communication systems, UWB communica-tion is a transmission technology promising less complexhardware. Transmission takes place in baseband, i.e., nohardware is required for mixers and RF oscillators, aswould be necessary in narrowband systems. In this areaUWB signals are used for applications requiring eitherhigh bit rates over short ranges or low bit rates overmedium-to-long ranges (Di Benedetto and Giancola2004). The high bit rate/short range case includes WPANfor multimedia traffic, cable replacement such as wire-less USB, and wearable devices, e.g., wireless head-phones. The low bit rate/medium-to-long range caseapplies to long-range sensor networks such as indoor/outdoor distributed surveillance systems, non-real-timedata applications, e.g., e-mail and instant messaging, andin general all data transfers compatible with a transmis-sion rate in the order of 1 Mbit/s over several tens ofmeters.

In UWB systems, a radiating antenna could beplaced very close to the human body (hand-held radio,wireless headphones, etc.) at the same time anotherradiating antenna could be broadcasting. Thus, in prin-ciple, both near-field and far-field human exposurecan take place. Since the fields radiated by UWBsystems are broadband or multiple frequency, accord-ing to ICNIRP guidelines, the exposure assessment isbased on the summation formula in the frequencyrange of UWB systems, where the relevant dosimetricparameter is the SAR.

Finally, an aspect of UWB to be taken intoaccount is that it is a form of broadband EM radiation,which can increase the level of noise floor for radio-communication services or block receiver front ends.Communication systems such as cellular phones,WLANs, etc., often employ adaptive power control.When such systems find the quality of service is degrad-ing, they ramp up their transmitter power to compensate.

Thus, it is conceivable that an indirect consequence ofUWB systems could be a rise in average SAR as cellularphones, etc., are caused to use increased powers.

Digital video broadcastingDigital video broadcasting (DVB) systems transmit

programs through different techniques, such as satellite(DVB-S), terrestrial antennas (DVB-T), and terrestrialtelevision for hand-helds (DVB-H). It replaces analogbroadcasting with digital systems. In the case of DVB-T,the conventional analog signals characterized by ampli-tude modulation are replaced with integrated digitalpulses and repetitive transients modulations similar toWLAN spread over many individual frequencies.

The modulation schemes used vary with differentservices; for example, DVB-S uses Quadrature Phase ShiftKeying (QPSK), and DVB-T uses QPSK in combinationwith OFDM and hierarchical modulation to allow moreefficient use of available frequencies. Therefore, frequen-cies for conventional analog broadcasting are made avail-able for additional broadcasting and other services. Indeed,DVB-H mobile TV has become a reality in some locationsalong with the availability of hand-held receivers.

TelemedicineTelemedicine involves the use of wireless commu-

nication technologies for medical diagnosis, treatment,and patient care. Current aims of telemedicine are toprovide remote access to medically relevant data andexpert-based health care to remote sites through modemtelecommunication and information technologies. Atpresent, the number of telemedicine sites and variety ofclinical applications are increasing. Potentially, telemedi-cine could involve large numbers of people with body-worn sensors and transmitters. Present development in-volves a combination of some of the wirelesscommunication technologies (e.g., GSM, WLAN, WPAN,and Bluetooth) to acquire physiological data, monitorpatients and manage diseases in a cost-effective manner.This may be done by applying sensors to the patient andsampling them on demand or on a regular basis withinhospitals using WLAN or after discharge via mobile tele-communication in their homes. Thus, it could take placeeither in real time or the data could be stored and thenforwarded for subsequent examination. In contrast to theconventional use of medical devices, the wireless sensorsare body-worn and can be used intermittently over a longperiod of time for large numbers of people (e.g., patients).

Other Non-Communication Uses

Ground penetrating radarGround penetrating radar (GPR), surface penetrating

radar, or subsurface radar are all names that refer to the


same technique used to locate objects and (or) interfacessituated in a region not penetrable by the eyes. GPR issimilar to the conventional free-space radar used to detectbackscattered radiation from a target to evaluate itsposition and velocity. GPR systems are made of atransmitting part (source and antenna) which transmitsEM power to the region under investigation, and areceiving part which collects the reflected power and,through signal processing techniques, elaborates it toextract the requested information. The presence of theinterface between the air where the antenna is located andthe region under investigation, and its influence on thereflected signal, are the fundamental differences betweenGPR and conventional radar.

GPR is used as an alternative technique to seismicmethods, sonar, or other specific techniques, its mainadvantage over those techniques being the general pur-pose principles of operation and the use of remote,non-contacting transducers to radiate and receive the EMenergy. Moreover, it has the highest resolution in sub-surface imaging of any geophysical method, approachingcentimeters under the right conditions (Leon et al. 1994).

The design of GPR systems is largely applications-oriented and the overall design philosophy, as well as thedetails, depends on the target type and the backgroundmedium. The bandwidth of the received signal is directlylinked to the number of features (geological strata orburied objects) that will be resolved. Since penetrationdepth decreases with frequency, usually GPR systemswork with frequencies less than 1 GHz. In long-rangeinvestigations, frequencies as low as a few tens of MHzhave also been used. On the other hand, resolution ishigher for higher frequencies. Consequently, low fre-quency antennas (10–120 MHz) radiate long wavelengthEMFs that can penetrate up to 50 m or more in certainconditions, but are capable of resolving only very largesubsurface features. In contrast, the penetration depth ofa 900 MHz EMF is about 1 m, and often less in typicalground conditions, but the generated reflections canresolve features down to a few centimeters in diameter(Carin 2001; Daniels 1996).

Usually, GPR systems use very narrow pulses (e.g.,pulse duration 1 ns) with low mean power (e.g., peakpulse power 50 W, mean pulse power 50 mW) and thereceived power is at least one order of magnitude belowthe transmitted one. It should be noted that GPR systems,on the basis of the FCC classification reported in FCC(2002), belong to the imaging system class; as a conse-quence, their transmitted power should conform to Table6, at least in the U.S.

Since antenna frequency, radiation pattern and radi-ated power strongly depend on the application, it is verydifficult to define general exposure conditions with

reference to GPR systems as a whole. In particular, toevaluate the operator exposure to the GPR EMF, it mustbe considered that the operator will be in the near-field ofthe transmitting antenna, so that the exposure evaluationshould be conducted considering the SAR according tothe formula for multiple-frequency exposure (ICNIRP1998).

Induction heating (IH) cooking hobsRecently, domestic induction heating (IH) hobs

(stoves or cook tops) have gained popularity in Japan andEuropean countries, even though they were introducedinto the market some time ago.

When electrically-conducting materials are im-mersed in an alternating magnetic field, they can beheated as a result of eddy current losses (Joule effect).This heating technique has been applied mainly forindustrial purposes, such as in metal furnaces. Inductionheating is also used as a cooking tool. Aside fromhigh-power (5–10 kW) equipment for commercial cater-ing use, low-power (1–3 kW) IH hobs are produced asdomestic kitchen appliances. The advantages of IH hobsinclude cleaner operation and the possibility of reducedfire hazards. As many as 300,000 units per year areprojected for sales in Europe alone (Gaspard 1998).

IH hobs operate at the intermediate frequencies of20 to 50 kHz to take advantage of efficient energy usageand to avoid the audible noise created by cookingutensils (pots, pans, and other containers) made of castiron and stainless steel having high magnetic permeabil-ity (ICNIRP 2003; Litvak et al. 2002; Wennberg 2001).More recent developments in IH hobs have enabled theuse of aluminum cookware at higher frequencies (over60 kHz) (Suzuki and Taki 2005).

The strength of the electric field in the vicinity of IHhobs is much lower (a few tens of volts per meter at adistance of 10 cm from the stove edge) than the strengthof the magnetic field (Stuchly and Lecuyer 1987). Atypical waveform of the magnetic field is shown in Fig.3. It consists of a carrier wave (26.1 kHz in the example),amplitude-modulated at a frequency of 100 Hz (for 50 Hzpower) or 120 Hz (for 60 Hz power). In general, theharmonic content is significantly higher, and the operat-ing frequency depends on the output power setting. For agiven power setting, the magnetic field strengths aroundthe hob depend on the material and size of the utensils.The magnetic fields decrease rapidly with distance, andare characterized by the magnetic field distributions of amagnetic dipole or a current loop (Yamazaki et al. 2004).

In practice, the magnetic field strength experiencedby the user depends on the user’s position, i.e., where theoperator is likely to stand (IEC 2005), or whether aperson is leaning over the top of the hob or not (Stuchly


and Lecuyer 1987). Numerical calculations of inducedcurrent showed that only parts of the body of the operator(in particular, the hands) are exposed to magnetic fieldsabove the reference level (Burais 1998). Other reportsindicate that the maximum induced currents averagedover 1 cm2 perpendicular to the current direction arelower than the ICNIRP’s basic restrictions, while themaximum magnetic field may exceed the referencelevels (Suzuki and Taki 2005).

Note that for complex multiple-frequency fields,with complex non-sinusoidal waveforms such as thosegenerated by the IH hob, ICNIRP guidelines provide asummation procedure for the various frequency compo-nents. In addition, the guidelines provide an alternativemethod of assessment based on a weighting function(ICNIRP 2002).

Medical MRI equipmentMagnetic resonance imaging (MRI) is an imaging

technique that employs strong DC magnetic fields, rap-idly switched gradient magnetic fields, and RF EMFs. It canimage soft tissues—unobstructed by bone—with enhancedcontrast, compared to x-ray computed tomography.Moreover, the ability to provide images in numerousfreely selectable planes in terms of number and orienta-tion without requiring the repositioning of the patient,has rendered MRI a very effective and important tool forsoft tissue medical imaging. Indeed, it has become the

radiological modality of choice for a great number ofdiagnostic procedures.

Because of its design, a conventional MRI systemoperating at 1.0 T is unlikely to expose radiological staffto field levels in excess of basic restrictions. Some neweropen 0.7 T MRI systems allow medical personnel toperform interventional procedures on patients under MRIguidance. Despite this success the diagnostic possibilitiesare far from being exhausted. Higher static fields andconsequently higher RF fields offer new possibilities ofimaging target molecules. Therefore, the devices need tobe classified in conventional devices up to 2 T, in deviceswhich may need patient monitoring (�2 T up to 4 T) anddevices where applications need to be governed byethical risk/benefit estimations (�4 T). Depending on theclass, it is no longer assured that basic requirements aremet during occupational exposure, in particular concern-ing partial-body exposure of hands, heads or torsos. It ispossible that hands, heads or torsos exposed under suchconditions may exceed current safety guidelines, espe-cially for gradient fields (ICNIRP 2004b). The gradientfield is lower than the static magnetic field but it is pulsedrapidly in time and is a function of the imaging techniqueand design of the MRI system. It is important to note thatthe time rate of change of the gradient magnetic field isclosely related to the strength of the electric field inducedinside the body.

Fig. 3. Example of measured magnetic field generated by IH hob: (a) and (b) waveforms of magnetic field; (c) and (d)frequency characteristics.


Recently, the demand for increased spatial resolu-tion and high signal-to-noise ratio (SNR) from MRIinstruments and imaging target molecules has promptedthe use of higher and higher magnetic fields (as high as11 T). This development intrinsically requires higher RFsfor MRI, which, in principle, can not only augment theamount of RF power deposition inside the patient’s body,but also increase the EMF exposure for workers usingMRI equipment in the hospital environment and workersemployed in supporting, servicing, developing and man-ufacturing this equipment. There has been particularinterest in the exposure of the head, torso, and limbs tothe gradient fields, which may be substantial undercertain operational environments. Some recent investiga-tions have shown that exposure to the stray magneticfield of whole-body 7 T MRI may affect neurobehavioralperformance such as visual perception and hand-eyecoordination, but there was no effect on working memory(Glover et al. 2007). The effect appears to depend on thedynamic field component generated by head movements(�150–300 mT/s) and not on the static magnetic field.

In the near future it may be necessary to classifyMRI systems, such as classifying conventional systemsas scanners with magnetic fields up to 2 T, scannerswhich need patient monitoring (�2 T up to 4 T), andscanners where their application needs to be governed byethical risk/benefit estimations (�4 T). Depending on theclass and use, the basic restrictions may not be metduring occupational exposures, especially with regard topartial-body exposure of hands, heads, or torsos.

Electrified trains and magnetically levitated vehicles(MAGLEVs)

High-speed ground transport systems for intercitypassenger and long distance travel have been in activedevelopment ever since limitations of existing transportmodes became apparent. At present, several of thehigh-speed electric transportation systems (including theelectrified train and the magnetically levitated vehicle)have been put into commercial operation in various partsof the world. These high-speed electric transportationsystems generate complex electric and magnetic fields(EMFs) with various frequency components and have acomplex spatial distribution. Because of their uniquecharacter, it is difficult to describe the entire environ-mental electric and magnetic fields from these systems.Therefore, in this section, examples from commercialsystems are shown together with a description of theMAGLEV systems as advanced guided ground transpor-tation systems.

Electrified trains (commuter in Japan and TGVin France). In electrified train systems, motors, variable

voltage and variable frequency (VVVF) inverters, induc-tors and other electric devices are the major sources ofEMFs. The EMF sources are located under the floor ofthe train car and generate complex magnetic fields infrequency and in distribution. Moreover, the frequencyand distribution of the magnetic field change dependingon the vehicle condition such as mode of run (accelera-tion, constant speed, deceleration, or free running). Thereare only a few papers describing the distribution of EMFsin electric transportation systems. For example, maxi-mum static magnetic fields in DC electrified trains up to1.5 mT were shown on the floor above the inductor, butthe magnetic field decreased to below 1 mT 20 cm abovethe floor level (Mizuma and Kato 1999). For the time-varying magnetic field, the maximum density is 50 �Ton the floor above a VVVF inverter.

EMFs measured from a commercial TGV vehicleshowed that the spatially averaged static magnetic fielddensity inside the car was 54.5 �T and the maximum was96.2 �T. At 50 to 60 Hz, the average magnetic field was3.05 �T and the maximum was 16.5 �T (U.S. DOT1993).

Advanced Guided Ground Transportation SystemsTransrapid—Transrapid is a German MAGLEV

system that has been operating in Shanghai, China, since2003. EMFs measured in prototype vehicles of Trans-rapid (TR-07) were reported by the U.S. Department ofTransportation (U.S. DOT 1993). In TR-07 cars, theaverage static magnetic field density was 49.8 �T and themaximum was 98.1 �T at a point 175 cm above the floor.Below this height, the static magnetic field exceeded 500�T and no reliable measurement has been reported at thispoint. At 50 to 60 Hz, the average magnetic field was 1.6�T and the maximum was 4.3 �T at a point 12 cm abovethe floor.

Superconducting MAGLEV—SuperconductingMAGLEV systems are currently under development inJapan. While they have been technically approved, thesesystems have not been put into commercial use. They usesuperconducting magnets (SCM) for levitation, guidanceand propulsion of the vehicle. Therefore, a uniquealternating magnetic field in the form of an extremely-low-frequency, intermittent pulsed magnetic field is gen-erated near the tracks by the moving SCMs on thevehicle. A few measurements of MAGLEV have beenconducted so far. One report showed that the magneticfields were between 45 �T (19.3 m from the SCM) and268 �T (7.5 m from the SCM), outside the vehicle. Thefrequency of the magnetic field can be up to 6.4 Hz at500 km h�1 (Sasakawa et al. 1998).

HSST Trains—HSST uses resistive magnets forlevitation and propulsion. The first commercial line,


named “Linimo,” has been in operation since March2005 in Aichi, Japan. There is no report of magnetic fieldmeasurement inside a Linimo vehicle. In a predecessorvehicle (H-200 type), the levels of stray magnetic fieldswere up to 1 �T for the static magnetic field at 10 cmabove floor and 100 �T for 10–20 Hz above its VVVFinverter (Mizuma and Kato 1999).

Note that magnetic field levels across the high-speedground transport systems range over many orders ofmagnitude (from a few �T to several mT). Specificallyfor the system mentioned above, the static magneticfields vary from 1 �T to 1.5 mT, while the AC magneticfields vary from 1 to 100 �T. A comparable observationwas made across the whole range of transportationsystems (Muc 2001). It is important to recognize that theextent and distribution of magnetic fields associated withtransportation systems vary considerably with locationinside or outside the vehicle. Even more important is thatthe extent and distribution of exposure within the body ofthe person receiving the exposure varies considerably.Nevertheless, for members of the general public, therange of EMF exposures in existing and developing highspeed transportation systems is comparable. However,the exposures may be very different with regard to thefrequency contents.

Wireless transport of electrical energyThe concept of wireless-power transmission (WPT)

from solar-power satellites (SPS) envisions the generationof electric power by solar energy in space for use onEarth [NRC 2001; Lin 2002; International ScientificRadio Union (URSI) 2007]. The system would involveplacing a constellation of solar power satellites in geosta-tionary Earth orbits. Each satellite would provide be-tween 1 and 6 GW of power to the ground, using a 2.45or 5.8 GHz microwave beam (see Table 7). The power-receiving rectenna on the ground would be a structuremeasuring 1.0 to 3.4 km in diameter. The higher (5.8GHz) frequency has been proposed since it has a similaratmospheric transparency. Although, in principle, the

higher frequency could involve a reduced size for thetransmitting and receiving antennas, as can be seen fromTable 7 current designs have opted for larger transmittingantennas and smaller rectenna sites, but a larger powerdensity on the ground to conserve land use, especially inJapan.

A joint effort between the Department of Energy(DOE) and the National Aerospace Administration(NASA) in the U.S. extensively investigated the feasi-bility of SPS-WPT during 1976–1980. The effort gener-ated a Reference System Concept for Solar PowerSatellites. The DOE–NASA Reference System involvedplacing a constellation of solar power satellites (5 �10 � 0.5 km deep) in geostationary Earth orbits, each ofwhich would provide 5 GW of power to major cities onthe ground, using a 2.45 GHz microwave beam. TheReference System’s 60 such satellites were contemplatedto deliver a total of 300 GW of generating capacity. Thetransmitting antenna was about 1 km in diameter. Thepower-receiving rectenna on the ground was a 10 � 13km structure.

Japan’s Ministry of Economy, Trade and Industry(METI) announced plans to launch research for a solar-power-generation satellite and to begin operating a giantsolar power station by 2040. This program is expected todesign and operate an SPS-WPT system that wouldensure the microwaves would not interrupt cellular mo-bile telephone and other wireless telecommunicationsservices. The Japan Aerospace Exploration Agency(JAXA) has proposed and evaluated various systemconfigurations for operation at 5.8 GHz (see Table 7).For example, the JAXA-2 model would have a maximumpower density of 1,000 W m�2 on the ground. A smallertransmitting system would have 260 W m�2 at therectenna site on the ground.

The ICNIRP guidelines are 50 or 10 W m�2 foroccupationally exposed persons vs. the general public, ateither 2.45 or 5.8 GHz (ICNIRP 1998). Note that theaverage absorption remains fairly stable for frequenciesabove 2 GHz (Lin and Gandhi 1996; Lin and Bernardi

Table 7. System configurations.

System parameters NASA JAXA JAXA-2

Frequency 2.45 GHz 5.8 GHz 5.8 GHzTotal transmitted power 6.72 GW 1.3 GW 1.3 GWMaximum power density in beam 22,000 W m�2 630 W m�2 1,140 W m�2

Minimum power density 2,200 W m�2 63 W m�2 114 W m�2

Maximum power/element 185 W 0.95 W 1.7 WNumber of antenna elements 97 million 3,450 million 1,950 millionElement spacing 0.75 � 0.75 � 0.75 �Transmit antenna size 1.0 km dia 2.6 km dia 1.93 km diaAmplitude taper 10 dB Gaussian 10 dB Gaussian 10 dB GaussianRectenna size 1.0 km dia 2.0 km dia 2.45 km diaMax power density above rectenna 230 W m�2 1,800 W m�2 1,000 W m�2


2007), except when the frequency becomes much higher,i.e., at 10 GHz, where the skin effect takes over, themaximum tolerable exposure at 5.8 GHz would beessentially the same as for 2.45 GHz.

As can be seen from Table 7 at the center of themicrowave beam, where power densities would be max-imum, the proposed power densities range from 23 to180 mW cm�2 (230 to 1,800 W m�2) above the rectenna.At 2.45 GHz, the power density is projected to be 1.0 Wm�2 at the perimeter of the rectenna. Beyond the peri-meter of the rectenna site or 15 km, the side lobe peakswould be less than 0.1 W m�2. Clearly, beyond the peri-meter of the rectenna, the potential exposure would bewell below that currently permissible to the generalpublic.

The danger of loss of control of highly focusedbeams may be minimized by tightly tuned phased arraytechniques and by automatic beam defocusing to dispersethe power in the event it occurs. Defocusing woulddegrade the beam toward a more isotropic radiationpattern, which would give rise to even lower powerdensity on the ground (Osepchuk 1996).

Near the center of the microwave beam, powerdensities would be greater than the ICNIRP occupationalreference levels. Except for maintenance personnel, hu-man exposure would normally not be allowed at thislocation. In the case of occupationally required presence,protective measures such as glasses, gloves and garmentscould be used to reduce the exposure to within guidelinelevels.

CONCLUSION

The cellular mobile communication systems of thefuture will likely continue to have speech as an importantusage as in present systems. However, their functionswill be significantly enlarged by additional services suchas interactive games, new information, and entertainmentservices such as mobile video and television. The expo-sure from future handsets would be lower due to lesspower output than in present systems but would probablylast longer per use.

For non-speech use, the exposure will be even lowerdue to greater distances of separation from the body, butwill probably last longer per use. However, the band-width will increase and with it power fluctuations athigher and higher frequencies. It remains an open ques-tion whether non-constant power variation with time hasany significant biological effect.

The popularity of cellular mobile telephones and theInternet is having a tremendous impact on future wirelesscommunication systems. In addition to voice, Internet-based devices will use the IP and Internet addresses to

establish communications between almost anything ofinterest. This could be communication between machinesfor control purposes, or communication between sensorsin the environment in huge sensor networks for life,safety and environmental monitoring. Since these sensorsare of low power and low energy for a battery-drivensensor to work for years at a time, exposure would bevery low.

In the case of RFID, wireless communications takeplace between an active and a passive device. The trendin wireless communication is toward increased use of theelectromagnetic spectrum, but in general at lower powerlevels and shorter ranges. From a health point of view,the exposures will be of lower level compared with thosefrom the long-range systems discussed under the 2Gmobile systems.

A number of significant other or non-communicationuses of nonionizing EM energy are emerging in thedomains of transportation, energy, household appliances,and health care establishments. In contrast to communi-cations, these applications tend to rely on higher powersand thus generate higher field strengths. However, inmost situations, exposure of humans is generally re-stricted to lower levels. In general, the RF spectrum willbe used and reused more intensively in all frequencybands; previous gaps such as intermediate frequencieswill likely be filled with new applications, and the use isextended upward to even higher RFs.

The experience of the cellular mobile telephoneindustry has demonstrated that once new technology isdeployed, the adoption rate could easily explode throughlarge-scale production and distribution. It is thereforeimportant to be aware of the rapid development of newsources of NIR and to continue the scientific assessmenton the various health aspects related to these innovations.This would include different exposure scenarios withregard to body site, duration of use, target population,and also to simultaneous exposure to complex multiplefrequencies spread over a potentially large frequencyrange.

Acknowledgments—This statement is based on the deliberations of theICNIRP Task Group on New Technologies chaired by James C. Lin. Thefollowing experts participated in the work by the Task Group: StuartAllen, Health Protection Agency, Chilton, UK; James C. Lin, Univer-sity of Illinois, Chicago, U.S.; Jørgen Bach Anderson, Aaborg Univer-sity, Aaborg, Denmark; Howard Bassen, Center for Devices andRadiological Health, Rockville, MD, U.S.; Masateru Ikehata, RailwayTechnical Research Institute, Tokyo, Japan; Norbert Leitgeb, Univer-sity of Graz, Austria; Stefano Pisa, University of Rome “La Sapienza,”Rome, Italy; Soichi Watanabe, National Institute of CommunicationTechnology (NICT), Tokyo, Japan; Kenichi Yamazaki, Central Re-search Institute of Electric Power Industry (CRIEPI), Yokosuka, Japan.The Statement was approved by the Commission in September 2007.

Disclaimer: The designations employed and the presentation of thematerial in this publication do not imply the expression of any opinion


whatsoever on the part of the International Commission on Non-IonizingRadiation Protection concerning the legal status of any country,territory, city or area or of its authorities, or concerning the delimitationof its frontiers or boundaries. The mention of specific companies or ofcertain manufacturers’ products does not imply that they are endorsedor recommended by the International Commission on Non-IonizingRadiation Protection in preference to others of a similar nature that arenot mentioned. All reasonable precautions have been taken by theInternational Commission on Non-Ionizing Radiation Protection toverify the information contained in this publication. However, thepublished material is being distributed without warranty of any kind,either express or implied. The responsibility for the interpretation anduse of the material lies with the reader. In no event shall theInternational Commission on Non-Ionizing Radiation Protection beliable for damages arising from its use.

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LIST OF TECHNICAL ACRONYMS

AC, Alternating CurrentADPCM, Adaptive Differential Pulse Code ModulationAMPS, American Mobile Phone Service in the U.S.APC, Automatic Power ControlCDMA, Code Division Multiple Access schemeCRC, Cyclic Redundancy CodesDVB, Digital Video Broadcasting systemsDVB-H, DVB terrestrial television for hand-heldsDVB-S, DVB by satelliteDVB-T, DVB by terrestrial antennasEAS, Electronic Article SurveillanceEDGE, Enhanced Data rate for GSM EvolutionEIRP, Effective Isotropic Radiated PowerEM, ElectromagneticEMF, Electromagnetic FieldFDD, Frequency Division DuplexGFSK, Gaussian Frequency Shift KeyingGPR, Ground Penetrating RadarsGPRS, General Packet Radio ServiceGSM, Global System for Mobile CommunicationsHSCSD, High-Speed Circuit Switched DataHSDPA, High Speed Downlink Packet AccessHSST, Trains using resistive magnets for levitation andpropulsion in JapanIH, Induction Heating, i-mode, overlay on Japanese PDCsystem to access and navigate the WebIMT-2000, International Mobile Telecommunications-2000IP, Internet ProtocolIS-95, North American version of the Code DivisionMultiple AccessISDN, Integrated Services Digital NetworkISM, Industrial, Scientific, and Medical bandsMAGLEV, Magnetically Levitated VehicleMIMO, Multiple-Input Multiple-OutputMMS, Multimedia Messaging ServiceMRI, Magnetic Resonance ImagingNIR, Non Ionizing RadiationOFDM, Orthogonal Frequency Division MultiplexingOFDMA, Orthogonal Frequency Division Multiple Access


PDA, Personal Digital AssistantPDC, Personal Digital Cellular systemPSTN, Public Switched Telephone NetworkQPSK, Quadrature Phase Shift KeyingRF, Radio FrequencyRFID, Radio Frequency Identification TechnologySAR, Specific Absorption RateSCM, Superconducting MagnetsSOFDMA, Scalable OFDMASNR, Signal-to-Noise RatioSPS, Solar Power SatellitesTDD, Time Division DuplexTDMA, Time Division Multiple Access TechniqueTGV, Electrified trains (in France)UHF, Ultra High Frequency bandUMTS, Universal Mobile Telecommunications SystemUTRA, combined, W-CDMA and UMTSUWB, Ultra-Wide-Band signalsVVVF, Variable Voltage and Variable FrequencyW-CDMA, Wideband Coded Division Multiple AccessWi-Fi, Wireless Fidelity, also a trademark of Wi-FiAllianceWiMAX, Worldwide Interoperability for MicrowaveAccess

WLAN, Wireless Local Area NetworksWPAN, Wireless Personal Area NetworksWPT, Wireless-Power Transmission

LIST OF ORGANIZATIONAL ACRONYMS

CEPT, European Conference of Postal and Telecommu-nications AdministrationsDECT, Digital Enhanced Cordless TelecommunicationDOE, Department of Energy in the U.S.DOT, Department of Transportation in the U.S.FCC, Federal Communications Commission in the U.S.ICNIRP, International Commission on Non-Ionizing Ra-diation ProtectionIEC, International Electrotechnical CommissionIEEE, Institute of Electrical and Electronic EngineersISO, International Organization for StandardizationITU, International Telecommunications UnionJAXA, Japan Aerospace Exploration AgencyMETI, Japan’s Ministry of Economy, Trade and IndustryNASA, National Aerospace Administration in the U.S.NMT, Nordic Mobile TelephonyNTT, Nippon Telegraph and Telephone CorporationURSI, International Scientific Radio Union

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