WO2011111049A1

WO2011111049A1 - Method for real time specific absorption rate estimation in mobile devices

Info

Publication number: WO2011111049A1
Application number: PCT/IL2011/000234
Authority: WO
Inventors: Joseph Maoz; Arie Engel
Original assignee: In4Tel Ltd.
Priority date: 2010-03-10
Filing date: 2011-03-10
Publication date: 2011-09-15

Abstract

A method for evaluating actual real-time SAR level of a mobile device transmitting, either constant, device or network controlled electromagnetic RF power.

Description

METHOD FOR REAL TIME SPECIFIC ABSORPTION RATE ESTIMATION IN

MOBILE DEVICES

FIELD AND BACKGROUND OF THE INVENTION

The following invention presents a method for estimating Real-Time Specific Absorption Rate (SAR) level in mobile devices during use, voice or video call, data session (device usage) or in idle time.

The wide use of cellular phones and other mobile devices is accompanied with vast concerns on health issues - the effect of electromagnetic radiation on human tissues. More specifically, the exposure of human body to Radio Frequency (RF) and microwave radiation and its influence on the human tissues are debated. Detailed descriptions on the requirements, methods, equipment and procedures on how to measure SAR are given by official regulations. Further, regulators set the maximum SAR level allowed for each type of mobile device used adjacent to human body. Accordingly, mobile device manufactures are obliged to declare maximum SAR level of each model and to present a warranty regarding the accompanied risks in the brochure attached to each device.

Note that the official SAR is measured and given at maximum allowed transmitted power (maximum Tx). In practice, the transmission power levels of mobile device vary and are not fixed. This phenomenon affects the actual real-time absorbed power level (actual real-time SAR).

Generally speaking, SAR is mainly a function of handset's structure design (e.g. housings, PCB, wires, antenna, speakers, camera, materials, etc.) and the power level transmitted by the device. For a given device, actual SAR level is a function of the transmitted power (Tx). As above-mentioned, the official SAR as used for certification is given for maximum radiated power (Tx) and the actual SAR level is reduced proportional to actual Tx level.

With cellular phones and the likes, the real-time radiated power of mobile phone is controlled by the wireless (cellular or other) network and depends on usable band, distance between handset and base station, connection type (single / multi slot, etc.), operational mode (e.g. GSM, CDMA, WCDMA, BlueTooth, WiFi, WiMax, LTE, UWB etc.), operational band (e.g. DCS, PCS, etc.), network capacity, network load, neighbors, area structure (e.g. urban, etc.), noise, etc. Therefore, actual real-time SAR level, either during device usage or in Idle mode (call off), remains unknown to the user.

THE PRIOR ART

Numerous articles and publications describe methods and systems monitoring real-time Tx power of the mobile devices.

For some wireless technologies and standards, the devices transmit fixed constant power, but for others, the Tx power is controlled by a Network according to various device and network parameters. The device parameters include parameters it reports to the Network such as Rx level, Rx quality, RSSI, RSCP, EC/10, etc... Network parameters include operating modes and Bands (GSM850, GSM900, DCS, PCS, UMTS, CDMA, BT, Wi-Fi, etc.), operational channels, neighboring cells, number of slots used, noise parameters, network load, capacity, distance from the wireless network or network cells (e.g. WiMax, LTE, cellular etc.,), etc. The outcome of all these variables is the Network's determined Tx level command for the device. Usually, the network data as well as the device data are hidden and not available to the users, though experts can sometimes discover them. In some devices, there is an option (either official or non-officially disclosed) to enter a field test mode and see some of the device and network data.

The Tx level, among other parameters (e.g., channel, cell etc.), is continuously changed according to the momentarily conditions and behavior of all these variables.

Wireless network operators (e.g. cellular, WiMax, LTE, etc.) spend huge amounts of resources (time, money, human resources, etc.) to develop efficient network and controlling procedures in order to maximize traffic and network efficiency. This is partially done in control centers by monitoring the overall network traffic, but in addition to above mentioned actions, operators perform routine field tests continuously to improve their network monitoring.

Note that real-time Tx power is nowadays more a network dependent rather than device dependent. But at the same time, the device Tx level does not give any estimation of the actual real-time SAR level, or of the maximum SAR level, which behavior is device dependent. Hence, two different devices with identical Tx level may have totally different maximum SAR level since SAR is mainly function of the particular device structure and varies from one device to another device (either models, manufacturers, etc.).

Many publications in prior art describe methods for evaluation of the Tx level based on data collected from the mobile device, usually based on the reception (Rx) and noise levels. This data is then used for building polynomials or otherwise functions, which present the predicted Tx as function of the Rx, noise and /or other parameters. Such evaluations sometimes even distinguish between different areas of operation, such as inside buildings, in and outside urban areas, etc., for better evaluation, by having different formulas for each scenario.

All prior art, although providing real-time Tx level estimates, do not provide any indication of the absorbed radiation into the user body / head, i.e. SAR values - either maximum SAR level or actual real-time SAR level. Such SAR information can be used in order to provide vital data regarding health risks in terms of electromagnetic RF/microwave power exposure and as bases for actions taken by either network operators, users or regulators.

OBJECTS AND BRIEF SUMMARY OF THE PRESENT INVENTION

An object of the present invention is to provide a method for estimating the realtime actual SAR, either during device usage or in idle mode, enabling operators, users and the likes to monitor human tissues exposure to RF power. Another object of the invention is to provide a tool for researchers to get real-time evaluation of the absorbed radiation. Yet another object of the invention is to provide tool for a user of a mobile device to determine whether to continue or stop a voice, video or data call, to take the mobile device away from his head or body or any other action. As a further object of the invention, such data may enable operators such as wireless networks' operators to monitor and control such exposure by adjusting the transmitted power level and to add the evaluation of the actual SAR to the other variables affecting the network control.

According to present invention, the task is divided into 2 parts:

1. Measuring device's SAR levels (per model) in Laboratory:

1.1 Maximum SAR values are measured per each model in certain

Channels (either all channels or sampled channels), at the device's operational bands and modes, while the device operates at its maximum allowed power (Max. Tx). Alternatively, these values may be given by the device manufacturer.

1.2 According to present invention, each device model is measured in Laboratory with SAR Test Equipment and SAR levels are recorded per Band, Channel for various Tx level (maximum to minimum or vice versa). These detailed measurements give better description of SAR behavior. The recorded data can be arranged either in tables, as formulas or in any other way.

2. Calculating Actual Real-Time SAR level:

Establishing actual real-time Tx can be done as described above (prior art) or any other way. With the known real-time Tx level, Band and Channel, the actual real-time SAR level can be pulled out/calculated from the tables or formulas measured in above paragraph (1.).

According to a broad aspect of the present invention, there is provided a mobile device, and also a method of estimating, in a real-time manner, the actual SAR absorbed by a body during the operation of the mobile device, comprising:

Initially operating the mobile device at one or more Tx levels for one mode, band and channel;

measuring the SAR at each initially operated Tx;

repeating the above procedure for all or sampled channels at all operational bands and modes;

establishing a relationship (table or equation) between the SAR and the Tx levels for the particular mobile device at said mode, band and channel;

in real-time, operating the mobile device at a specific mode, band and channel with specific Tx level (where Tx is either estimated or read from the mobile device or the network); and

utilizing the established relationship to determine the SAR for the specific mode, band and channel for that specific Tx level at which the mobile device is operated. BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a pictorial illustration illustrating the set-up for measuring and recording the SAR absorbed by a body during the operating of a particular mobile device at particular mode, band and channel for the desired Tx level;

FIG. 2 is a flow diagram illustrating the manner in which the actual SAR is estimated, in a real-time manner, during the operation of the mobile device; and

FIG. 3 presents the measured and estimated SAR max vs. channel for GSM850 band, as detailed below.

FIG. 4 presents the normalized SAR vs. Tx level, as described in detail below.

DESCRIPTION OF PREFERRED EMBODIMENTS

The method of the present invention can be used with respect to any mobile device having a specific structure and unique SAR characteristics wherein the mobile device transmits electromagnetic power at predetermined power level; and the electromagnetic power is characterized by specific standard, mode, band and channel (frequency); the method being characterized in that the actual real-time SAR level is evaluated by using parameters from said mobile device.

The pictorial diagram in Fig. 1 presents the set-up for SAR measurement:

A base station emulator (e.g. Agilent 8960), designated 2, wirelessly controls the handset, designated 1, to engage a call at certain mode, band and channel and at certain Tx level. The handset, 1, is placed on SAR test equipment (i.e. SPEAG Dasy) designated 3, and the SAR level is recorded on the computer, designated 4. The same procedure applies to all modes, bands, channels and Tx levels.

Fig. 2 is a schematic diagram illustrating the basic operations in the method of the present invention.

Thus, as shown in Fig. 2, the mobile device 1 is operated at one or more Tx levels for one mode, band and channel (block 10); and the SAR at each of said one or more Tx levels is measured (block 11) for said mode, band and channel; and the above two steps are then repeated per all or sampled channels for all operational modes and bands (block 12).A relationship (table or equation) is established between the SAR and the Tx (block 13) for said mode, band and channel.

At any time thereafter, when the mobile device is operated in a real-time manner, the specific real-time Tx level (where Tx is either estimated or read from the mobile device or the network) (block 14); and the relationship established in operation 13 are utilized to determined the SAR (block 15).

Establishing device's real-time transmit power (Tx) can be achieved in two ways:

A. Reading the Network determined Tx level for the device. This is usually hidden, but for some devices the Tx may be shown by the device or being received from the wireless network (e.g. cellular, WiMax and LTE operators, etc.).

B. Estimating Tx based on known parameters. This estimation formula is function of above variables (device and Network) and its accuracy depends on amount of known variables. Good prediction can be achieved based on device parameters such as Rx and noise parameters as well as operational mode, band and used channel (Network) which are most often available.

Fig. 3 shows the maximum SAR values (measured and estimated) as function of the channel for a particular case (i.e. mode 2G and GSM850 band), and is more detailed in example 2 below.

Fig. 4 shows the normalized SAR values as a function of the Tx level for a particular case (i.e., mode 2G and GSM 850 band), as more detailed in example 2 below. The normalized SAR is referred to as SAR_factor-

According to a preferred embodiment of the invention, a mobile device is first measured with standard SAR equipment (e.g. Dasy system from Schmid & Partner Engineering AG) while the device is controlled by a wireless network emulator (e.g. Agilent 8960). The output is maximum SAR level for maximum transmission power level and "actual" SAR level for all or sampled Tx levels allowed by the particular standard. The SAR level values are collected and the above-mentioned procedure is then repeated for all or sampled channels in all operational modes and bands with said Tx levels (either all or sampled). These SAR values are then saved, e.g. as a single table or several tables of SAR vs. Tx level, channel, band and mode. Those tables can be saved either in the device or on the network (e.g. on a computer, server, etc.), depends on the application.

These tables are then used in conjunction with any real-time Tx prediction method or with available Tx (given either from the device or from the network) to predict the actual real-time SAR as a function of the actual real-time Tx, the operational mode and band and the used channel data.

Thus the actual SAR is recalled from the above tables such that:

SAR _RT = ^SARtabi®_[moAerband)[ Chim&ex > TXRT) Wherein the database includes all parameters per each mobile device type/model; the SARRT is the actual real-time SAR; Mode, band and channel define the "operational point"; and TX_RT is the actual real-time Tx.

According to another preferred embodiment of the invention, the SAR is measured only at maximum Tx level allowed for the used technology and standard at all or at sampled channels for all operational modes and bands to obtain the maximum SAR levels. These maximum SAR values are then manipulated, being represented by a function of the channel in all modes and bands. The ratio of the actual Tx level (either given by the device or predicted) and the maximum Tx level, and the maximum SAR at same operational mode and band are also taken as parameters in the above mentioned function to estimate the actual real-time SAR at the operational mode, band and channel. Thus the actual SAR is calculated from the following function:

SAR_RT = ^R_maX[mgde ^[€h_index} - SAR_factortmoie^_an£)(Tx_RT}

Wherein SARRT is the actual real-time SAR at specific mode, band and the operating channel for the real-time actual Tx; SAR_MAX is function of the mode, band and the operating channel {mode, band, chi„dex} presenting the maximum SAR for said specific mode and band for the psrticular channel; and SAR_factor presents the SAR variations as

TXRT changes for given mode and band. ¹

Fig. 4 shows a graph of the SARf_actor for the particular case of example 2 below, where the mode is 2G and band is GSM850. This method helps reducing the amount of information required to evaluate the actual real-time SAR, as only a simple formula of the maximum SAR level as function of the Tx, channel at the operational mode and band is needed. If such a program is to be installed in a mobile device aimed at evaluating the actual SAR - the size of the code resulted from this method will be significantly smaller and much more efficient than the code generated by previous preferred embodiment.

It is noted that if the actual real-time Tx is calculated from other parameters, e.g. Rx, the above function may change to include the Rx or the relevant parameter instead or in addition to the actual real-time Tx.

According to a further preferred embodiment of the invention, any combination of the above embodiments may occur. Hence, part of the data may be stored e.g. in tables and another part may be formulated in a function.

According to another preferred embodiment of the invention, the SAR can be evaluated from the derivative of the temperature if temperature sensors are available. In such a case, the SAR is calculated as follows:

Whereas c denotes a specific measurement of tissue heat c.

Thus, if temperature data is available from sensors around the RF amplifier, the SAR can be calculated directly. The c value can be found by either measuring the tissue heat directly (e.g. the liquid used for SAR system) or easily calculating it from measurements of the SAR, for any given mobile device.

For any embodiment, the calculation may be performed either by the device or the wireless network (e.g. a computers or servers on the network, etc.) or by any combination thereof to obtain the actual real-time SAR level. '

According to one preferred use of the present invention, the evaluated actual real-time SAR can be used by wireless network operators as one of the various parameters for setting the Tx level of the mobile device. The latter may be important as the users are very much aware of the health issues caused by electromagnetic radiation absorbed into human tissues. Hence, wireless network operators can use the invention to limit and /or reduce the power level radiated in scenarios where the SAR might be too high. The latter might even be an added value service either given free or paid for. The term "too high" might have wide range of interpretations and means:

It might be absolute to be set by the wireless network operator or relative per user, allowing users to limit the SAR value of their mobile devices to their desired level. The term "too high" may also represent the accumulated exposure of a user to electromagnetic radiation over time, even if the momentary actual real-time SAR is reasonable.

According to another application of the present invention, the evaluated actual real-time SAR can be used by wireless network operators or the mobile device to warn the user from having high actual real-time SAR values (either absolute, relative, pre-set etc.) and set various actions, such as disconnecting the mobile device from the network, warn the user either with audio, video or written warning or with any other suitable message. Said actions may include preset or set actions, taken by either the user or the wireless network, or a combination thereof.

It will enable, for instance, to set various levels - one level for protecting children and another level for protecting adults from exposure to high values of SAR. In such a case, the choice of a child or an adult will be probably set by the user, while the limit level and actions might be set by the wireless network.

EXAMPLES

Following examples provide two possible implementations of presenting SAR vs. Tx (transmit power) characteristics of two particular handsets.

Measurements were made according to regulations with the set-up as illustrated in Fig. 1.

Although the following examples present the above methods and shown for specific modes and bands, it is clear that same procedures apply to all other modes and bands.

Example 1: SAR Table [2G, EGSM900]

1.1 The SAR values (10 g for this band) were measures for three sampled channels (note that measuring more or all channels is possible, too) at all transmit levels. Following SAR_table (∞, EGSM9oo₎{ch_index , Tx_RT} present measured results for three channels (start, mid and end channels):

1.2 Once the actual real-time Tx level (TXR_T) (either estimated or read from the device/network) and the operating channel (for the known mode and band) are known, the SAR_tabi_e (₂G, EGSM900){ch_index, Tx_RT} table is then approached to pullout (or interpolate) the real-time SAR (SARRT) level.

Example 2: SAR prediction [2G, GSM850]

2.1 Only maximum SAR values (lg for this case due to being used in the US) for sampled channels at maximum transmit power (maximum Tx) were measured. The following table presents the results in the sampled channels:

Channel lg SAR [W/Kg]

128 0.469

133 0.474

138 0.480

143 0.486

148 0.492

153 0.505

158 0.512

163 0.520 168 0.522

173 0.534

178 0.542

183 0.552

188 0.560

193 0.569

198 0.576

203 0.585

208 0.594

213 0.605

218 0.615

223 0.626

228 0.636

233 0.647

238 0.659

243 0.668

248 0.680

251 0.685

The maximum SAR values were manipulated to form a function of the channel number - polynomial representation in this example. The following formula gives a good estimation of the above measured SAR values for the entire band, i.e. for all channels in that band (and mode):

SAR _max .ri = 3.922e→ -

+ 0. 68

(aftfiSMSSS)

Where SAR_max <2G, GSMSSO) is the estimated maximum SAR level at that particular channel (chi_ndex) while the device operates at its maximum power level for that mode and band. A comparison of the measured and estimated maximum SAR levels vs. channel are shown in Fig. 3, where one can see the good matching of the simple estimation formula to the measured data. 3 The SAR value for various Tx level (ranging from maximum to minimum) and normalized the maximum recorded SAR value. The result is presented in Fig. 4 - SAR_factor vs. Tx [dBm] for 2G mode and SM850 band. 2.4 Once the actual real-time Tx level (which, as above mentioned, is either estimated or read from the device or from the network) is known, the actual real-time SAR is then calculated for that particular channel as follows:

SARR = SAR _MSG o [chfnOex) ^"

Wherein:

SAR_RT is the actual real-time SAR level;

TX_RT is the actual real-time Tx value, either predicted, read from the device or obtained from the wireless network;

SAR_MAX(2_G,_GSM850₎{chjndex} - the maximum SAR level, as detailed in paragraph 2.2 above; and

SARf ac or <∞, GSMS50}{ XRT} - the SAR versus Tx level behavior normalized to 1.0 in 2G, GSM850; see paragraph 2.3 above and Fig. 4.

While the invention has been described with respect to several preferred embodiments, it will be appreciated that these are set forth merely for purposes of example, and that many other variations, modifications and applications of the invention may be made.

Claims

WHAT IS CLAIMED IS:

1. A method of estimating, in a real-time manner, the actual SAR absorbed by a body during the operation of a mobile device, comprising:

initially operating the mobile device at one or more transmission power Tx levels for one mode, band and channel;

measuring the SAR at one or more initially operated transmission power Tx levels;

establishing a relationship (table or equation) between the SAR and the transmission power Tx levels for the particular mobile device at said mode, band and channel;

utilizing the established relationship to determine the SAR for the specific mode, band and channel for that specific Tx level at which the mobile device is operated.

2. The method according to claim 1, wherein the actual real-time SAR level is calculated with the use of the mobile device actual real-time transmission power (Tx) level and channel (frequency) at the operational standard, band and mode.

3. The method according to claim 1, whereas the actual real-time SAR level is calculated with the use of the mobile device actual real-time transmission power (Tx) level and operational band at the operational standard and mode.

4. The method according to claim 1, wherein the actual real-time SAR level is calculated with the use of the mobile device actual real-time receiving power (Rx) level and channel (frequency) at the operational standard, band and mode.

5. The method according to Claim 1, wherein said power level is constant.

6. The method according to Claim 1, wherein said power level varies in time.

7. The method according to Claim 1, wherein said power level is controlled by a network, a network cell or network operator.

8. The method according to any of claims 1-7, wherein said mobile device is engaged in a voice or video call.

9. The method according to any of claims 1-7, wherein said mobile device is engaged in a data interaction with a wireless network.

10. The method according to any of claims 1-7, wherein said mobile device is idle and not in a call.

11. The mobile device according to any of claims 1-7, wherein the evaluation of the actual real-time SAR is used as a parameter for determination of an action or recommendation proposed to at least one of the uses of the mobile device, the network, the network cell and network operator.

12. The mobile device according to any of claims 1-7, wherein the evaluation of the actual real-time SAR is used as a parameter for determination of the actual real-time transmission power (Tx) level of the mobile device.

13. The mobile device according to claim 11, wherein said determination limits the actual real-time transmission power (Tx) level of the mobile device.

14. The mobile device according to claim 11, wherein said determination reduces the actual real-time transmission power (Tx) level of the mobile device.

15. The mobile device according to claim 11, wherein said determination is performed by the mobile device.

16. The mobile device according to claim 11, wherein said determination is performed by a network, a network cell or network operator.