PATENT DOCUMENT

Publication Number: US-11689234-B2
Application Number: US-202117175858-A
Country: US
Kind Code: B2

Title: Techniques for controlling specific absorption rate of radio energy transmission

Abstract:
The disclosure relates to techniques for controlling Specific Absorption Rate (SAR) of radio energy transmission. In particular, the disclosure relates to a radio device and a method for controlling radio energy transmission of a plurality of radio entities to comply with a predefined SAR requirement. Such a radio device includes: a plurality of radio entities configured to transmit radio energy; and a controller configured to control the radio energy transmission of the plurality of radio entities to comply with a predefined Specific Absorption Rate, SAR, requirement, wherein the controller is configured to enable at least two radio entities of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. The disclosure further relates to a method for dynamic management of a SAR budget across multiple radio entities.

Claims:
The invention claimed is: 
     
       1. A radio device, comprising:
 a plurality of radio entities configured to transmit radio energy according to first time quotas and second time quotas based on a predefined requirement for maximum radio frequency (RF) energy absorption by a human body; and 
 a controller communicatively coupled to the plurality of radio entities and configured to
 assign the first time quotas to the plurality of radio entities for a first time window; 
 cause the plurality of radio entities to transmit the radio energy based on the first time quotas, generating a cumulative activity of the plurality of radio entities over the first time window; 
 derive a first cumulative time quota from the cumulative activity of the plurality of radio entities during the first time window; 
 assign the second time quotas to the plurality of radio entities for a second time window different from the first time window based on the first cumulative time quota, where a sum of the second time quotas is equal to the first cumulative time quota; and 
 cause the plurality of radio entities to transmit the radio energy based on the second time quotas. 
 
 
     
     
       2. The radio device of  claim 1 , wherein the predefined requirement comprises a predefined Specific Absorption Rate (SAR) requirement. 
     
     
       3. The radio device of  claim 1 , wherein the controller is configured to enable at least two radio entities of the plurality of radio entities operating concurrently based on a shared transmission power restriction allowing the at least two radio entities to transmit up to a 100% duty cycle without violating the predefined requirement. 
     
     
       4. The radio device of  claim 3 , wherein the shared transmission power restriction is based on a Specific Absorption Rate (SAR) budgeting scheme. 
     
     
       5. The radio device of  claim 1 , wherein the controller is configured to stop an ongoing transmission of at least one radio entity in order to allow at least another radio entity to commence transmitting and still meeting the predefined requirement. 
     
     
       6. The radio device of  claim 1 , further comprising a concurrency detection circuit configured to detect concurrent transmissions of at least two radio entities of the plurality of radio entities and a transmission arbitration circuit configured to disable transmission of at least one radio entity of the at least two radio entities based on a predefined maximum allowed time for concurrent transmission independent of the predefined requirement for maximum radio frequency (RF) energy absorption by a human body. 
     
     
       7. The radio device of  claim 6 , wherein the transmission arbitration circuit is configured to disable the transmission of at least one radio entity of the at least two radio entities based on priorities of the at least two radio entities. 
     
     
       8. A radio device, comprising:
 a plurality of radio entities configured to transmit radio energy; and 
 a controller communicatively coupled to the plurality of radio entities and configured to
 apply a transmission power restriction to the plurality of radio entities that restricts a cumulative transmit power of the plurality of radio entities to a predefined transmission power quota; and 
 control the plurality of radio entities based on the transmission power restriction; and 
 
 a concurrency detection circuit configured to detect concurrent transmissions of at least two radio entities of the plurality of radio entities; and 
 a transmission arbitration circuit configured to disable transmission of at least one radio entity of the at least two radio entities based on a predefined maximum period of time for concurrent transmission independent of the predefined transmission power quota. 
 
     
     
       9. The radio device of  claim 8 , wherein the transmission power restriction is applied to comply with a predefined requirement for maximum radio frequency (RF) energy absorption by a human body. 
     
     
       10. The radio device of  claim 9 , wherein the predefined requirement comprises a predefined Specific Absorption Rate (SAR) requirement. 
     
     
       11. The radio device of  claim 8 , wherein the transmission power restriction is applied the plurality of radio entities over a predefined time window. 
     
     
       12. The radio device of  claim 8 , wherein the controller is configured to estimate the cumulative transmit power of the plurality of radio entities using a moving average filter. 
     
     
       13. The radio device of  claim 12 , wherein the moving average filter comprises an infinite impulse response (IIR) auto-regressive moving average (ARMA) filter or a finite impulse response (FIR) moving average (MA) filter. 
     
     
       14. The radio device of  claim 1 , wherein a time quota assigned to each radio entity of the plurality of radio entities in the first time window is always 100%. 
     
     
       15. A method for wireless communication comprising:
 assigning, by a controller, a first maximum transmit power for a first transmission with a first transmit duration and a second maximum transmit power for a second transmission with a second transmit duration; 
 estimating a moving average of the transmit powers of the first transmission and the second transmission over a time window Tw at multiple measurement intervals Tm, the moving average being based on the first maximum transmit power, the second maximum transmit power, the first transmit duration, and the second transmit duration; 
 assigning, by the controller, a third maximum transmit power for a third transmission over multiple measurement intervals Tm based on a third transmit duration of the third transmission and the estimated moving average of the transmit powers of the first transmission and the second transmission over a time window Tw to comply with a predefined requirement for maximum radio frequency (RF) energy absorption by a human body when using a radio device; and 
 transmitting, by a plurality of radio entities, respective radio energy based on the first maximum transmit power, the second maximum transmit power, and the third maximum transmit power. 
 
     
     
       16. The method of  claim 15 , wherein the predefined requirement comprises a predefined Specific Absorption Rate (SAR) requirement. 
     
     
       17. The method of  claim 15 , wherein the first transmission is configured to transmit at a first predefined duty cycle and wherein the second transmission is configured to transmit at a second predefined duty cycle. 
     
     
       18. The method of  claim 15 , wherein the third maximum transmit power is derived from a difference between the predefined requirement for maximum RF energy absorption by a human body and a highest transmit power of the moving average of the transmit powers of the first transmission and the second transmission. 
     
     
       19. The radio device of  claim 1 , wherein the second time quotas are assigned before the second time window. 
     
     
       20. The radio device of  claim 1 , wherein the second time quotas are allocated to the plurality of radio entities based on an amount of activity individual radio entities contributed to the cumulative activity during the first time window.

Description:
This application is a Continuation of U.S. patent application Ser. No. 16/381,554 filed Apr. 11, 2019, entitled TECHNIQUES FOR CONTROLLING SPECIFIC ABSORPTION RATE OF RADIO ENERGY TRANSMISSION, which claims priority to European Patent Application 18171855.2 filed May 11, 2018 and is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     The disclosure relates to techniques for controlling Specific Absorption Rate (SAR) of radio energy transmission. In particular, the disclosure relates to a radio device and a method for controlling radio energy transmission of a plurality of radio entities to comply with a predefined SAR requirement. The disclosure further relates to a method for dynamic management of a SAR budget across multiple radio entities. 
     BACKGROUND 
     SAR—Specific Absorption Rate, is a measure of the amount of RF energy absorbed by the body when using a mobile device such a phone or a tablet. In order to comply with SAR requirements a restriction (e.g. a backoff or another kind of reduction) shall be applied on the maximal TX power permitted for a specific radio of the device. Note that the SAR requirement is for the maximum allowed transmission (Tx) power; a backoff is one way to relate to this restriction in the context of backoff from maximum (HW supported) Tx power. Other ways to relate to this restriction are applicable as well. When the device has an antenna capable of transmitting concurrently at multiple frequency bands or if it has multiple radios that emit energy in close physical proximity such that the SAR restriction is applied on all of them together an additional backoff must be taken on the TX power of each radio entity. The resulting TX power from all applied backoffs degrades the wireless performance for each participating radio. The disclosure presents a solution to the above described problem. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain principles of embodiments. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. 
         FIG.  1    is a schematic diagram illustrating RF energy absorption by a human body  101  and a SAR restriction  112 . 
         FIG.  2    is a block diagram illustrating a radio device  200  with a plurality of radio entities  201 ,  202 ,  203  according to the disclosure. 
         FIG.  3    is a schematic diagram illustrating a first method  300  for managing the SAR budget according to the disclosure. 
         FIG.  4    is a schematic diagram illustrating a second method  400  for managing the SAR budget according to the disclosure. 
         FIG.  5    is a time diagram  500  illustrating measurement points used in a third method for managing the SAR budget according to the disclosure. 
         FIG.  6    is a block diagram illustrating a hardware circuit  600  for controlling concurrent radio energy transmissions according to the disclosure. 
         FIG.  7    is a schematic diagram illustrating a method  700  for controlling radio energy transmissions according to the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the invention may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. 
     The following terms, abbreviations and notations will be used herein:
     SAR: Specific Absorption Rate   TX: Transmission   AQ: Assigned Quota   UQ: Unused Quota   CQ: Cumulative Quota   LQ: Link Quality   SA: Stand-Alone mode   SH: Shared Transmission mode   AP: Activity Percentage   AF: Activity Factor   CDB: Concurrent Dual Band   MA: Moving Average   RF: Radio Frequency   

     It is understood that comments made in connection with a described method may also hold true for a corresponding device configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such a unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise. 
     The techniques described herein may be implemented in wireless communication networks, in particular communication networks based on mobile communication standards such as LTE, in particular LTE-A and/or OFDM and successor standards such as 5G. The methods are also applicable for high speed communication standards from the IEEE 802.11 family, e.g. 802.11ac, ax, ad and future IEEE 802.11 amendments. The methods are further applicable to on-device radio transmitters compliant to or designed in accordance with other wireless standards such as IEEE 802.15, the Bluetooth Special Interest Group, or even proprietary wireless transmitter specifications. The methods and devices described below may be implemented in electronic devices such as cellular handsets, Tablets, Laptops, and mobile or wireless devices. Note that SAR is particularly relevant for devices held in proximity to the body such as cellular handsets, Tablets, Laptops, and mobile or wireless devices but less relevant to infrastructure devices such as access points or base stations as they are not held in proximity to the body. The described devices may include integrated circuits and/or passives and may be manufactured according to various technologies. For example, the circuits may be designed as logic integrated circuits, analog integrated circuits, mixed signal integrated circuits, optical circuits, memory circuits and/or integrated passives. 
     In the following, radio frequency (RF) signals and transmission of radio energy are described. Radio signals may be or may include radio frequency signals radiated by a radio transmitting device (referred hereinafter as a radio device or a radio entity) with a radio frequency lying in a range of about 3 kHz to about 300 GHz. The frequency range may correspond to frequencies of alternating current electrical signals used to produce and detect radio waves. 
     In the following, embodiments are described with reference to the drawings, wherein like reference numerals are generally utilized to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects of embodiments. However, it may be evident to a person skilled in the art that one or more aspects of the embodiments may be practiced with a lesser degree of these specific details. The following description is therefore not to be taken in a limiting sense. 
     The various aspects summarized may be embodied in various forms. The following description shows by way of illustration various combinations and configurations in which the aspects may be practiced. It is understood that the described aspects and/or embodiments are merely examples, and that other aspects and/or embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present disclosure. 
       FIG.  1    is a schematic diagram  100  illustrating RF energy absorption by a human body  101  and a SAR restriction  112 . SAR—Specific Absorption Rate, is a measure of the amount of RF energy  111  absorbed by the body  101  when using a mobile device  110  such as a phone or a tablet. In order to comply with SAR requirements a restriction  112  (backoff) shall be applied on the maximal TX power permitted for a specific radio of the device  110 . Note that the SAR requirement is for the maximum allowed transmission (Tx) power; a backoff is one way to relate to this restriction in the context of backoff from maximum (HW supported) Tx power. Other ways to relate to this restriction are applicable as well. When the device  110  has an antenna capable of transmitting concurrently at multiple frequency bands or if it has multiple radios that emit energy  111  in close physical proximity such that the SAR restriction  112  is applied on all of them together an additional backoff must be taken on the TX power of each radio entity. The resulting TX power from all applied backoffs yields a poor wireless performance for each participating radio. 
     Existing SAR solutions derive a fixed worst-case backoff value per each radio/band where that backoff needs to account for the case where all radios are transmitting concurrently. Alternatively, existing solutions shall forbid any concurrency between multiple radio technologies under SAR constraints. 
     Since the worst-case backoff will be applied by the radio entity regardless of the level of activity of other wireless technologies, this may result in an unnecessarily poor wireless performance. As an example, if a radio is permitted to transmit at 19 dBm, and needs to reduce its TX power to 15 dBm under SAR constraint  112 , then if that radio could also participate in a Concurrent Dual Band (CDB) scenario it would need to apply an additional backoff of up to 3 dB resulting in TX power of 12 dBm applied on all its transmissions—this may cause a severe range problem. Alternatively, if TX concurrency between multiple radios is prohibited severe degradation in user experience may result. 
       FIG.  2    is a block diagram illustrating a radio device  200  with a plurality of radio entities  201 ,  202 ,  203  according to the disclosure. 
     The radio device  200  comprises a plurality of radio entities  201 ,  202 ,  203  configured to transmit radio energy  211 ,  212 ,  213 . The radio device  200  further comprises a controller  210  that is configured to control the radio energy  211 ,  212 ,  213  transmission of the plurality of radio entities  201 ,  202 ,  203  to comply with a predefined Specific Absorption Rate, SAR, requirement. The controller  210  is further configured to enable at least two radio entities (e.g.  201 ,  202 ) of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, e.g. at 100% duty cycle, without violating the SAR requirement. 
     The controller  210  may further be configured to enable at least one radio entity (e.g.  201 ) of the plurality of radio entities operating in stand-alone mode based on a stand-alone SAR transmission power restriction which allows the at least one radio entity transmitting at a predefined duty cycle, e.g. at 100% duty cycle, without violating the SAR requirement. 
     Thus, the radio device may operate in a first mode where two or more radio entities operate concurrently and where the shared SAR transmission power restriction is fulfilled; and the radio device may operate in a second mode where each radio entity operates in stand-alone mode where the stand-alone SAR transmission power restriction is fulfilled for each radio entity. 
     The shared SAR transmission power restriction may be based on a SAR budgeting scheme. The shared SAR transmission power restriction may be configured to restrict transmission times of the at least two radio entities within a specific time window to predefined quotas, e.g. as described below with respect to  FIGS.  3  to  5    in more detail. The predefined quotas may be specified as percentage values of the specific time window. The specific time window may be less than a period over which the SAR requirement is defined. 
     The controller  210  may be configured to assign time quotas to the plurality of radio entities over a single time window, e.g. as described below with respect to  FIGS.  3  to  5    in more detail. Alternatively, the controller  210  may be configured to assign time quotas to the plurality of radio entities over multiple time windows, e.g. as described below with respect to  FIGS.  3  to  5    in more detail. 
     Alternatively, the controller  210  may be configured to assign transmission power quotas to the plurality of radio entities  201 ,  202 ,  203 , e.g. as described below with respect to  FIG.  5    in more detail. The controller  210  may be configured to assign the transmission power quotas based on a moving average filter, e.g. as described below with respect to  FIG.  5    in more detail. 
     The controller  210  may be configured to apply a strict duty cycling scheme in which within a specific period each transmission is followed by a quiet period to guarantee the predefined duty cycle. 
     The controller  210  may be configured to apply a flexible quota scheme in which for a given time window and a given quota a cumulative transmission time within the time window shall not exceed a threshold. The threshold may be a function of the quota and the time window, in particular a product of the quota and the time window, e.g. as described below with respect to  FIGS.  3  to  5    in more detail. 
     The controller  210  may be configured to enable a radio entity of the plurality of radio entities  201 ,  202 ,  203  increasing its transmission power to a power level above a given stand-alone SAR transmission power restriction when the radio entity is correspondingly decreasing its transmission power thereafter to fulfill the standalone SAR transmission power restriction within a given time window. The power level may correspond to the standalone SAR transmission power restriction divided by an activity percentage of the radio entity within the time window, e.g. as described below with respect to  FIGS.  3  to  5    in more detail. 
     The controller  210  may be configured to control the energy transmission of the plurality of radio entities  201 ,  202 ,  203  based on averaging over activities of the plurality of radio entities within a measurement window, e.g. as described below with respect to  FIGS.  3  to  5    in more detail. 
     The controller  210  may be configured to allow overlapping activities of the at least two radio entities as long as a cumulative activity across all radio entities  201 ,  202 ,  203  of the plurality of radio entities is below a threshold within a measurement window. 
     In the following an exemplary solution implemented by the controller  210  is described in more detail. The solution is based on allocating a quota of TX activity for each participating radio (entity)  201 ,  202 ,  203  that is applicable within a specific time window. A quota defines an energy budget (Power×Time) for the radio  201 ,  202 ,  203  over that window. Using smart management of quota allocation over consecutive windows and or sliding windows allows achieving an optimal solution that does not sacrifice TX power while still fully complying with SAR requirements. 
     The solution allows customers to operate multiple radio technologies concurrently over the same SAR antenna without requiring an additional backoff on the TX power of each radio due to this concurrency and without severe restrictions on the timing of TX operations. This becomes possible by leveraging the sporadic nature of TX traffic as well as the method in which SAR is being measured. Note that the SAR requirement is for the maximum allowed transmission (Tx) power; a backoff is one way to relate to this restriction in the context of backoff from maximum (HW supported) Tx power. Other ways to relate to this restriction are applicable as well. 
     Such capability is of special interest for SAR-constrained CDB (Concurrent Dual Band) solutions as well as WLAN+LAA sharing solutions which shall become important technologies to support in wireless products in the next years. 
     Depending on the Device Form-Factor SAR measurement and budgeting is either performed on each antenna separately or on multiple antennas together. The solution is applicable to both cases. An example for single antenna is when WIFI 2.4 GHz Band and WIFI 5 GHz Band are transmitting over the same antenna. An example for more than one antenna is when multiple antennas on the device are in close physical proximity such that a single SAR constraint is applicable to all. Other examples are WIFI 5 GHz and LAA (License Assisted Access—i.e. LTE within 5 GHz Band) radios that may share the same antenna or WIFI 2.4 GHz and Bluetooth. 
     In order to participate in SAR budgeting scheme each radio entity  201 ,  202 ,  203  shall support a method to restrict its transmission time and or power within a specific time window to a pre-defined quota specified as a percentage of that window. In order to comply with the allocated quota, the radio entity  201 ,  202 ,  203  may deploy either a strict duty cycling scheme in which within a specific period each transmission is followed by a quiet period that guarantees a predefined duty cycle (e.g. N msec of TX is followed by 2N msec of quiet time to guarantee a duty cycle of N/(N+2N)=33.3%) or it may be able to deploy a more flexible quota scheme based on a TX counter in which for any given quota (e.g. Q=30%) and a Time Window (e.g. T=100 ms) the cumulative transmission time of the radio within that time window shall not exceed Q*T (30 ms). 
     In general, each radio (entity)  201 ,  202 ,  203  shall be assigned with a SAR TX power restriction that is applicable when the radio is operating in Stand-Alone mode (SA_SAR_POWER) and another Shared SAR TX power restriction that is applicable when all radio-entities are operating concurrently (SH_SAR_POWER). 
     The SA_SAR_POWER restriction allows a single radio (e.g.  201 ) to transmit at 100% duty-cycle without violating SAR. Like-wise, the SH_SAR_POWER restriction allows all radio entities  201 ,  202 ,  203  to transmit concurrently at 100% duty-cycle without violating SAR. 
     By leveraging the physical nature of SAR and the way it is measured it can be observed that a radio may increase its TX power beyond SA_SAR_POWER and still comply with SAR as long it proportionally decreases its activity time within the measurement window. In other words, let AP be the Activity Percentage within a window with values in the range [0 . . . 1], then a radio may transmit at a Power value of SA_SAR_POWER/AP within that window without violating SAR—as long as the window size is small enough (i.e. significantly smaller than the SAR measurement period). 
     This idea can be scaled for multiple radios case by averaging the activity of multiple radios within a measurement window. Since any radio has an SA_SAR_POWER that guarantee SAR compliancy with 100% duty cycle also any superposition of radio activities (Radio A is active for X msec then radio B is active for Y msec) is compliant with SAR. Due to the physical nature of SAR it can also be claimed that the activity periods of the multiple radio can overlap without violating SAR as long as the cumulative activity across all radios  201 ,  202 ,  203  within the window is below or equal to 100%. Such an overlap may create a temporal crossing of the maximum allowed cumulative TX power, however since SAR is measured over a period which is longer than the time window in practice no SAR violation occurs. 
     Several mechanisms are introduced in the following with respect to  FIGS.  3  to  7    to leverage the above observations. Using centralized radio management (central controller  210 ) a method can be formed that allows optimizing the TX power of all radio entities  201 ,  202 ,  203  based on their specific requirements while complying with the overall SAR budget of the system. 
     The central controller  210  can track TX activity  211 ,  212 ,  213  of each radio  201 ,  202 ,  203  as well as the Link Quality of each radio  201 ,  202 ,  203  and make allocation decisions based on that information. Link Quality can be defined either as the success rate for sending TX packets over a period of time as tracked by the packet acknowledge rate or as using another approximation such as the MCS that the radio is using (lower MCS indicates lower link quality). 
     The controller  210  can use one of the methods described in the following with respect to  FIGS.  3  to  5    to manage the SAR budget. 
       FIG.  3    is a schematic diagram illustrating a first method  300  for managing the SAR budget according to the disclosure. This first method is related to managing Time Quota over single window. An exemplary number of two radio entities (denoted A and B, e.g. corresponding to  201  and  202  in  FIG.  2   ) is illustrated which produce Radio A activity  301  and Radio B activity  302 . A and B may also specify different frequency bands in which two radio entities transmit radio energy.  FIG.  3    depicts Radio A activity  301 , Radio B activity  302 , Cumulative Activity  303 , Radio A Quota  304 , Radio B Quota  305  in different time intervals (or time windows)  310 ,  320 ,  330 ,  340 . 
     In this method  300  each radio entity is assigned with a Quota Qi (see Radio A Quota  304  and Radio B Quota  305  in  FIG.  3   ) for performing transmissions within a time window, specified as a percentage of the Window&#39;s Time duration WT. The radio can manage the budget by initializing a counter to the value Qi*WT when the window starts then decrementing the counter by the TX Time TT of each packet. Packet transmission is permissible only if counter value is bigger than TT. The radio may either exhaust all its quota or only a portion of it. At the end of the window the central controller (e.g. controller  210  depicted in  FIG.  2   ) will capture the remaining budget in all counters of all radios and adjust the Quota for next window according to the algorithm specified below. 
     An example algorithm that may be used by the central controller to allocate Quota: 
     
         
         
           
             1. Assigned Quotas for all radios (AQi) is always allocated such that Σ(AQi)=&lt;100%. 
             2. Initially Quota is split evenly among the radios (e.g. AQ1=50%, AQ2=50%) 
             3. After one window is over the controller will collect the following information from each radio:
           a. Unused Quota (UQ)—the remaining quota upon end of window   b. Link Quality—as defined above   
         
             4. If ΣUQi&gt;0:
           a. If all radios have UQi&gt;0—no change in quotas.   b. If some radios (e.g. radio 1) have UQi=0 and other radios (e.g. radio 2) have UQi&gt;0: decrease the quota of radio 2 by 50%*UQ2 and increase the quota of radio 1 by the same amount.   
         
             5. Otherwise (ΣUQi=0)
           a. the controller will check if current quotas should be adjusted using the following algorithm:
               i. If there is a radio with AQi&lt;(100%/num_of_radios) and LQ&lt;Thresh set AQi=(100%/num_of_radios) for that radio and decrease the AQ of all other radios accordingly.   ii. The above will allow radios that are not getting a fair share of the quota and suffer from low Link Quality to gain back their share.   
               
         
             6. Repeat 
           
         
       
    
     Using Method1 all radios can continue transmitting using SA_SAR_POWER and need not suffer the additional power backoff implied by SH_SAR_POWER. 
     The diagram in  FIG.  3    depicts a sequence in which Method 1 is applied to manage the quota of two Bands. Since Band B does not use its quota the central controller gradually increases the allocated quota for Radio A. 
       FIG.  4    is a schematic diagram illustrating a second method  400  for managing the SAR budget according to the disclosure. This second method is related to managing Time Quota over multiple windows. An exemplary number of two radio entities (denoted A and B, e.g. corresponding to  201  and  202  in  FIG.  2   ) is illustrated which produce Radio A activity  301  and Radio B activity  302 . A and B may also specify different frequency bands in which two radio entities transmit radio energy.  FIG.  4    depicts Radio A activity  401 , Radio B activity  402 , Cumulative Activity  403 , Band A Limit  404 , Band B Limit  405  in different time intervals (or time windows)  410 ,  420 ,  430 ,  440 ,  450 ,  460 . 
     Method 2 describes an optimized version of Method 1 (shown in  FIG.  3   ) working in window-pairs—where on the first window  410  each radio shall be assigned with an “unrestricted quota” of 100% and on the next window  420  an adjustment is done to compensate for any budget violations occurring on previous window  410 . The advantage of this version is that it does not restrict in advance the quota of each radio while still complying with the overall SAR budget measured across the two windows. 
     The diagram shown in  FIG.  4    depicts the flow when Method 2 is used. As can be seen on the first window  410  each band is assigned with a quota of 100%. During the window period the cumulative activity  403  of both bands is 150%—in order to compensate for that, on the second window  420  the cumulative budget  403  is dropped to 50% (split evenly among the two bands) hence no violation is observed when measuring SAR over the two windows  410 ,  420 . On the next window  430  the budget is again 100% per band—and since each band uses its entire budget it drops to 0% on the next window  440 . 
     In practice this method allows both bands to transmit freely within each window with no quota enforcement as long as their cumulative activity  403  does not cross 100%. 
     With Method 2, the central controller (e.g. controller  210 ) can use the following exemplary algorithm to allocate quotas for each window:
         1. For window1:
           a. Assign a quota of 100% for each radio   b. After window1 is over collect the following information from each radio:
               i. Link Quality (LQ)—as defined above   ii. Activity Factor (AF)—this is the activity rate during window 1—calculated as TX Time/Window Time   
               
           2. For window2:
           a. Calculate Cumulative Quota (CQ) for window2 as: CQ=200%−ΣAFi   b. Allocate an Activity Quota for each radio under the constraint that Σ(AQi)=CQ using one of the following methods:
               i. Symmetric allocation—the remaining quota is split evenly among the radios: AQi=(1/num_of_radios)*CQ   ii. Proportional allocation—the remaining quota is split such that radios with higher activity receive higher quota on next window: AQi=(AFi/ΣAFi)*CQ   iii. Link Quality based allocation—the remaining quota shall be split such that radios with a lower Link Quality shall receive a higher quota while keeping the constraint that Σ(AQi)=CQ.   
               
           3. Repeat       

     An optimization that can be applied to Method 2 is for the algorithm to perform the averaging over more than 2 windows in order to smooth the traffic pattern. For example, averaging over 3 windows will guarantee that there is never a single window during which no TX is allowed. 
       FIG.  5    is a time diagram  500  illustrating measurement points used in a third method for managing the SAR budget according to the disclosure. This third method is related to managing TX Power Quota using Moving Average Filter. An exemplary number of two radio entities (denoted Radio 1 and Radio 2, e.g. corresponding to  201  and  202  in  FIG.  2   ) is illustrated.  FIG.  4    depicts TX time  510  for Radio 1 and TX time  520  for Radio 2. For Radio 2 different exemplary measurement samples  501 ,  502 ,  503 ,  504 ,  505  are illustrated during a requested TX duration  521  for which TX power shall be defined by the highest measurement sample. 
     Method 3 describes a different method to ensure that the total average TX power over any window of length t w  does not surpass the SAR budget. This method is based on tracking the Moving Average (MA) of the cumulative TX power of all participating radios over a window of size t w . 
     Method 3 applies the dynamic SAR restriction on the TX power rather than the transmission time. Tracking the cumulative TX power of all radios over a relevancy window is done using an MA (Moving Average) filter that estimates the effective SAR due to the radio transmissions over time. In this scheme, the controller (e.g. controller  210  depicted in  FIG.  2   ) measures the TX power of each radio during short time intervals (t m —measurement interval, e.g. 100 uSec) and continuously calculates the effective SAR using a Moving Average filter such as:
 
SAR_POWER[ n ]=(1−α)SAR_POWER[ n− 1]+αΣ TXi [ n ];
 
with α set to be t m /t w , where t n  is the measurement interval, and t w  is the time window. Σ TXi[n] is the sum of average TX power of all radios during current the current (n−y) t n  measurement window.
 
     While the filter equation above is a 1 st  order ARMA (IIR) filter, the SAR POWER value can be calculated using as a FIR MA filter or as an IIR ARMA filter. 
     The device shall restrict the power of new transmissions to comply with the SAR budget across t w  as follows: For any new transmission request, the controller shall set the allowed TX power for it in a way that guarantees that the resulting SAR in any time window of length t w  containing the transmission does not surpass the allowed quota. 
     The central controller shall maintain a list of all active transmitting radios, with their specific max TX power, TX start time and TX duration and will calculate the allocated TX power for a new transmission that starts at time to using the following formula:
 
Let ESTIMATED_SAR( t ) be SAR_POWER( t ), where  t  is a number in the range { t   0   ,t   0 +min( t   w ,requested_ tx _duration}, in increments of  t   m .
 
     Then max TX power allowed for the new transmission will be calculated as:
 
MAX_TX_POWER=Min{ t  as defined above,(MAX_SAR−ESTIMATED_SAR( t ))},
 
where MAX_SAR is the maximal allowed cumulative TX Power for all participating radios that guarantees no violation of the SAR budget.
 
     The diagram shown in  FIG.  5    illustrates an example of the measurement points  501 ,  502 ,  503 ,  504 ,  505  that will be used for resolving the Max TX power in method 3. 
     Method 1 (shown in  FIG.  3   ) and Method 2 (shown in  FIG.  4   ) imply that there are periods during which both radios transmit concurrently using their SA_POWER rather than their SH_POWER. While this temporal violation is compensated over the measurement window, some regulatory bodies may require a restriction on the maximal period where such concurrency is permitted. The HW circuit  600  shown in  FIG.  6    can be used for restricting the maximal amount of concurrency within a given measurement window. 
       FIG.  6    is a block diagram illustrating a hardware circuit  600  for controlling concurrent radio energy transmissions according to the disclosure. The hardware circuit  600  can be used for Quota allocation with hardware restriction of maximal concurrency. 
     The hardware circuit  600  comprises an exemplary number of two radio entities (Radio A  610  and Radio B  620 ). The hardware circuit  600  comprises a concurrency detection circuit  620  in which a concurrency counter  632  is implemented which counts concurrent transmissions of radio A and Radio B. A maximum allowed concurrency value  634  can be loaded  633  to counter  632  which forms a threshold for the counter  632 . An AND gate  631  passes concurrent transmissions of both radios  610 ,  620  to the counter  632 . The transmissions of each radio  610 ,  620  are measured after the MAC  612 ,  622  of each radio entity  610 ,  620  and before transmitter  611 ,  621 . If counter  632  is greater zero, concurrency is allowed  635  which is signaled to TX arbitration circuit  640 . TX arbitration circuit includes a concurrency control block  642  which detects if both bands are transmitting and concurrency is not allowed. If this condition is fulfilled, the transmission of the band with lower priority is killed. Priorities are determined by band priority block  641 . 
     The hardware circuit  600  can be implemented in a radio device, e.g. a radio device  200  described above with respect to  FIG.  2   . The radio device comprises a plurality of radio entities  610 ,  620  (e.g. corresponding to entities  201 ,  202 ,  203  in  FIG.  2   ) configured to transmit radio energy, e.g. as described above with respect to  FIGS.  1  to  5   . The radio device includes a concurrency detection circuit  620  configured to detect concurrent transmissions of at least two radio entities of the plurality of radio entities  610 ,  620 . The radio device further includes a transmission arbitration circuit  640  configured to disable transmission of at least one radio entity of the at least two concurrently transmitting radio entities based on a concurrency criterion  642 . 
     The concurrency criterion  642  may be based on a Specific Absorption Rate, SAR, requirement. The concurrency detection circuit  620  may be configured to count concurrent transmissions of the at least two radio entities  610 ,  620  within a measurement interval. The concurrency detection circuit  620  may be configured to indicate a concurrency allowance  635  to the transmission arbitration circuit  640  if the counted concurrent transmissions are below a threshold. 
     The transmission arbitration circuit  640  may be configured to disable transmission of the at least one radio entity of the at least two concurrently transmitting radio entities if the concurrency detection circuit  620  stops indicating concurrency allowance  635 . 
     The transmission arbitration circuit  640  may be configured to disable transmission of the at least one radio entity of the at least two concurrently transmitting radio entities based on priorities  641  of the at least two concurrently transmitting radio entities  610 ,  620 . The priorities  641  may be based on strict priority to one of the radio entities  610 ,  620 , strict priority based on access category and/or Round Robin between the radio entities  610 ,  620 . 
     In the following a functionality of the hardware circuit  600  is described in more detail. At the beginning of each window a counter  632  is initialized to the max time allowed for concurrent transmission within that window (MAX_ALLOWED_CONCURRENCY). During the window, counter  632  is decremented whenever both radios  610 ,  620  are transmitting in each tick. Once counter  632  is reaching zero an arbitration logic  640  is armed. The arbitration logic  640  will kill the transmission of the radio with the lower priority whenever the other radio is active. The priority  641  can be defined as either strict priority to one of the bands, strict priority based on Access Category or Round Robin with between the two bands per TX packet. 
     By controlling the value of MAX_ALLOWED_CONCURRENCY the behavior is tuned to be either a real-TDM between the radios (zero concurrency), full concurrency or a hybrid mode of operation in which quotas are enforced within the window while the overall concurrency time is restricted. 
     Since Method 3 (described above with respect to  FIG.  5   ) makes TX power decisions one at a time, it may be that a high priority TX request may require a TX power higher than permitted by the method. In this case, the central controller may use the HW circuit  600  described above to “kill” a lower priority TX activity such that its power budget may then be assigned to the high priority TX request. It should be noted that for Method 3, the central controller may be provided in advance the inputs regarding any pre-assigned Tx activity on any of the radios, to allow for a “forecasting” calculation of allowed Tx powers, to comply with the SAR requirements. 
       FIG.  7    is a schematic diagram illustrating a method  700  for controlling radio energy transmissions according to the disclosure. 
     The method  100  allows controlling radio energy transmission of a plurality of radio entities, e.g. entities  201 ,  202 ,  203  as shown in  FIG.  2    or entities  610 ,  620  as shown in  FIG.  6   , to comply with a predefined Specific Absorption Rate, SAR, requirement. The method  700  comprises: enabling  701  at least two radio entities of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     The method  700  may further comprise: enabling at least one radio entity of the plurality of radio entities operating in stand-alone mode based on a stand-alone SAR transmission power restriction which allows the at least one radio entity transmitting at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     The shared SAR transmission power restriction may be based on a SAR budgeting scheme. 
     The method  700  may further comprise: restricting transmission times of the at least two radio entities within a specific time window to predefined quotas. The predefined quotas may be specified as percentage values of the specific time window. The specific time window may be less than a period over which the SAR requirement is defined. 
     The method  100  may further comprise: assigning time quotas to the plurality of radio entities over a single time window, e.g. as described above with respect to  FIG.  3   . Alternatively, the method  700  may comprise: assigning time quotas to the plurality of radio entities over multiple time windows, e.g. as described above with respect to  FIG.  4   . 
     The devices and systems described in this disclosure may be implemented as Digital Signal Processors (DSP), micro-controllers or any other side-processor or hardware circuit on a chip or an application specific integrated circuit (ASIC). 
     Embodiments described in this disclosure can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations thereof, e.g. in available hardware of mobile devices or in new hardware dedicated for processing the methods described herein. 
     The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing blocks described herein, in particular the methods  300 ,  400 ,  500 ,  700  described above with respect to  FIGS.  3  to  5  and  7    and the computing blocks described above with respect to  FIGS.  2  and  6   . Such a computer program product may include a non-transient readable storage medium storing program code thereon for use by a processor, the program code comprising instructions for performing the methods or the computing blocks as described above. 
     EXAMPLES 
     The following examples pertain to further embodiments. Example 1 is a radio device, comprising: a plurality of radio entities configured to transmit radio energy; and a controller configured to control the radio energy transmission of the plurality of radio entities to comply with a predefined Specific Absorption Rate, SAR, requirement, wherein the controller is configured to enable at least two radio entities of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     In Example 2, the subject matter of Example 1 can optionally include that the controller is further configured to enable at least one radio entity of the plurality of radio entities operating in stand-alone mode based on a stand-alone SAR transmission power restriction which allows the at least one radio entity transmitting at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     In Example 3, the subject matter of any one of Examples 1-2 can optionally include that the shared SAR transmission power restriction is based on a SAR budgeting scheme. 
     In Example 4, the subject matter of any one of Examples 1-2 can optionally include that the shared SAR transmission power restriction is configured to restrict transmission times of the at least two radio entities within a specific time window to predefined quotas. 
     In Example 5, the subject matter of Example 4 can optionally include that the predefined quotas are specified as percentage values of the specific time window. 
     In Example 6, the subject matter of Example 4 can optionally include that the specific time window is less than a period over which the SAR requirement is defined. 
     In Example 7, the subject matter of Example 4 can optionally include that the controller is configured to assign time quotas to the plurality of radio entities over a single time window. 
     In Example 8, the subject matter of Example 4 can optionally include that the controller is configured to assign time quotas to the plurality of radio entities over multiple time windows. 
     In Example 9, the subject matter of Example 4 can optionally include that the controller is configured to assign transmission power quotas to the plurality of radio entities. 
     In Example 10, the subject matter of Example 9 can optionally include that the controller is configured to assign the transmission power quotas based on a moving average filter. 
     In Example 11, the subject matter of any one of Examples 1-2 can optionally include that the controller is configured to apply a strict duty cycling scheme in which within a specific period each transmission is followed by a quiet period to guarantee the predefined duty cycle. 
     In Example 12, the subject matter of any one of Examples 1-2 can optionally include that the controller is configured to apply a flexible quota scheme in which for a given time window and a given quota a cumulative transmission time within the time window shall not exceed a threshold. 
     In Example 13, the subject matter of Example 12 can optionally include that the threshold is a function of the quota and the time window, in particular a product of the quota and the time window. 
     In Example 14, the subject matter of any one of Examples 1-2 can optionally include that the controller is configured to enable a radio entity of the plurality of radio entities increasing its transmission power to a power level above a given stand-alone SAR transmission power restriction when the radio entity is correspondingly decreasing its transmission power thereafter to fulfill the standalone SAR transmission power restriction within a given time window. 
     In Example 15, the subject matter of Example 14 can optionally include that the power level corresponds to the standalone SAR transmission power restriction divided by an activity percentage of the radio entity within the time window. 
     In Example 16, the subject matter of any one of Examples 1-2 can optionally include that the controller is configured to control the energy transmission of the plurality of radio entities based on averaging over activities of the plurality of radio entities within a measurement window. 
     In Example 17, the subject matter of any one of Examples 1-2 can optionally include that the controller is configured to allow overlapping activities of the at least two radio entities as long as a cumulative activity across all radio entities of the plurality of radio entities is below a threshold within a measurement window. 
     In Example 18, the subject matter of any one of Examples 1-2 can optionally include that the controller is configured to stop an ongoing transmission of at least one radio entity in order to allow at least another radio entity to commence transmitting and still meeting the SAR requirement. 
     Example 19 is a radio device, comprising: a plurality of radio entities configured to transmit radio energy; a concurrency detection circuit configured to detect concurrent transmissions of at least two radio entities of the plurality of radio entities; and a transmission arbitration circuit configured to disable transmission of at least one radio entity of the at least two concurrently transmitting radio entities based on a concurrency criterion. 
     In Example 20, the subject matter of Example 19 can optionally include that the concurrency criterion is based on a Specific Absorption Rate, SAR, requirement. 
     In Example 21, the subject matter of any one of Examples 19-20 can optionally include that the concurrency detection circuit is configured to count concurrent transmissions of the at least two radio entities within a measurement interval. 
     In Example 22, the subject matter of any one of Examples 19-20 can optionally include that the concurrency detection circuit is configured to relate to a Tx power weighted list of concurrent transmissions of the at least two radio entities within a measurement interval. 
     In Example 23, the subject matter of Example 21 can optionally include that the concurrency detection circuit is configured to indicate a concurrency allowance to the transmission arbitration circuit if the counted concurrent transmissions are below a threshold. 
     In Example 24, the subject matter of Example 23 can optionally include that the transmission arbitration circuit is configured to disable transmission of the at least one radio entity of the at least two concurrently transmitting radio entities if the concurrency detection circuit stops indicating concurrency allowance. 
     In Example 25, the subject matter of any one of Examples 19-20 can optionally include that the transmission arbitration circuit is configured to disable transmission of the at least one radio entity of the at least two concurrently transmitting radio entities based on priorities of the at least two concurrently transmitting radio entities. 
     In Example 26, the subject matter of Example 25 can optionally include that the priorities are based on strict priority to one of the radio entities, strict priority based on access category and/or Round Robin between the radio entities. 
     Example 27 is a method for controlling radio energy transmission of a plurality of radio entities to comply with a predefined Specific Absorption Rate, SAR, requirement, the method comprising: enabling at least two radio entities of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     In Example 28, the subject matter of Example 27 can optionally include: enabling at least one radio entity of the plurality of radio entities operating in stand-alone mode based on a stand-alone SAR transmission power restriction which allows the at least one radio entity transmitting at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     In Example 29, the subject matter of any one of Examples 27-28 can optionally include that the shared SAR transmission power restriction is based on a SAR budgeting scheme. 
     In Example 30, the subject matter of any one of Examples 27-28 can optionally include: restricting transmission times of the at least two radio entities within a specific time window to predefined quotas. 
     In Example 31, the subject matter of Example 30 can optionally include that the predefined quotas are specified as percentage values of the specific time window. 
     In Example 32, the subject matter of Example 30 can optionally include that the specific time window is less than a period over which the SAR requirement is defined. 
     In Example 33, the subject matter of Example 30 can optionally include: assigning time quotas to the plurality of radio entities over a single time window. 
     In Example 34, the subject matter of Example 30 can optionally include: assigning time quotas to the plurality of radio entities over multiple time windows. 
     Example 35 is a device for controlling radio energy transmission of a plurality of radio entities to comply with a predefined Specific Absorption Rate, SAR, requirement, the device comprising: means for enabling at least two radio entities of the plurality of radio entities operating concurrently based on a shared SAR transmission power restriction which allows the at least two radio entities transmitting concurrently at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     In Example 36, the subject matter of Example 35 can optionally include: means for enabling at least one radio entity of the plurality of radio entities operating in stand-alone mode based on a stand-alone SAR transmission power restriction which allows the at least one radio entity transmitting at a predefined duty cycle, in particular at 100% duty cycle, without violating the SAR requirement. 
     Example 37 is a radio system, comprising: a plurality of radio entities configured to transmit radio energy; a concurrency detection circuit configured to detect concurrent transmissions of at least two radio entities of the plurality of radio entities; and a transmission arbitration circuit configured to disable transmission of at least one radio entity of the at least two concurrently transmitting radio entities based on a concurrency criterion. 
     In Example 38, the subject matter of Example 37 can optionally include that the concurrency criterion is based on a Specific Absorption Rate, SAR, requirement. 
     Example 39 is a computer readable non-transitory medium on which computer instructions are stored which when executed by a computer cause the computer to perform the method of any one of Examples 27 to 34. 
     In addition, while a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms “include”, “have”, “with”, or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term “comprise”. Furthermore, it is understood that aspects of the disclosure may be implemented in discrete circuits, partially integrated circuits or fully integrated circuits or programming means. Also, the terms “exemplary”, “for example” and “e.g.” are merely meant as an example, rather than the best or optimal. 
     Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein. 
     Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Metadata:
Filing Date: 20210215
Publication Date: 20230627
Grant Date: 20230627
Priority Date: 20180511
Inventors: KAIDAR, OREN
RESHEF, EHUD
BALABAN, NIR
D'ANGELO, WILFRID
Elad, Yuval
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B1/3838", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/44", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04B1/3838", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/146", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/241", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/30", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 62196343