PATENT DOCUMENT

Publication Number: US-9781687-B2
Application Number: US-201414282326-A
Country: US
Kind Code: B2

Title: Controlling radio transmission power in a multi-radio wireless communication device

Abstract:
A method for controlling transmission power in accordance with a total transmission power limit in a multi-radio wireless communication device including a master radio and a slave radio is provided. The method can include the wireless communication device determining, at the master radio, a transmission power of the master radio. The method can further include the wireless communication device providing information indicative of the transmission power of the master radio from the master radio to the slave radio. The method can additionally include determining, at the slave radio, an allowable transmission power for the slave radio. A sum of the allowable transmission power and the transmission power of the master radio may not exceed the total transmission power limit.

Claims:
What is claimed is: 
     
       1. A method comprising:
 in a wireless communication device including a cellular radio and a wireless local area network (WLAN) radio:
 determining, at the cellular radio, instantaneous transmission power values of the cellular radio over a period of time; 
 providing information indicative of the instantaneous transmission power values of the cellular radio for the period of time from the cellular radio to the WLAN radio via a direct interface between the cellular radio and the WLAN radio; and 
 determining, at the WLAN radio, an allowable transmission power for the WLAN radio based at least in part on the information, wherein:
 a sum of the allowable transmission power for the WLAN radio and the transmission power of the cellular radio does not exceed a total transmission power limit, and 
 the allowable transmission power for the WLAN radio is determined based at least in part on an integer number N of distinct time instances that the instantaneous transmission power values of the cellular radio exceeds a transmission power threshold over the period of time when N&gt;1, 
 
 
 wherein the direct interface:
 is dedicated to communication between the cellular radio and the WLAN radio, and 
 
 operates at a lower latency than communication interfaces between either the cellular radio or the WLAN radio and processing circuitry of the wireless communication device. 
 
     
     
       2. The method of  claim 1 , wherein:
 the information indicative of the instantaneous transmission power values of the cellular radio comprises an indication of whether the integer number N of distinct time instances over the period of time that the instantaneous transmission power of the cellular radio exceeded the transmission power threshold exceeds a positive integer threshold number T≧2 of instances; and 
 determining the allowable transmission power for the WLAN radio comprises the WLAN radio reducing its transmission power in at least one instance in which the instantaneous transmission power of the cellular radio exceeds the transmission power threshold at least the positive integer threshold number T of instances over the period of time. 
 
     
     
       3. The method of  claim 1 , further comprising:
 determining a transmission power of a future transmission by the cellular radio; and 
 providing information indicative of the transmission power of the future transmission by the cellular radio via the direct interface between the cellular radio and the WLAN radio. 
 
     
     
       4. The method of  claim 3 , wherein the transmission power of the future transmission by the cellular radio comprises a transmission power configured by a serving cellular base station for the wireless communication device. 
     
     
       5. The method of  claim 3 , wherein the method further comprises:
 determining whether the transmission power of the future transmission exceeds a first transmission power threshold; and 
 in an instance in which it is determined that the transmission power of the future transmission exceeds the first transmission power threshold, providing information indicative of the transmission power of the future transmission by the cellular radio comprises providing an instruction in advance of the future transmission by the cellular radio to the WLAN radio to apply a WLAN transmission power cap. 
 
     
     
       6. The method of  claim 1 , wherein the total transmission power limit is defined based at least in part on a regulation restricting radio frequency emissions by the wireless communication device. 
     
     
       7. The method of  claim 1 , wherein the direct interface between the cellular radio and the WLAN radio comprises a wireless coexistence interface (WCI) directly coupling the cellular radio with the WLAN radio and configured to support exchanging state information of the cellular radio and of the WLAN radio usable to support in-device wireless coexistence between the cellular radio and the WLAN radio. 
     
     
       8. The method of  claim 2 , wherein the period of time comprises a first period of time and the transmission power threshold comprises a first transmission power threshold, the method further comprising:
 determining, at the cellular radio, instantaneous transmission power values of the cellular radio over a second period of time that follows the first period of time; 
 providing second information indicative of the instantaneous transmission power values of the cellular radio for the second period of time from the cellular radio to the WLAN radio via the direct interface between the cellular radio and the WLAN radio; and 
 determining, at the WLAN radio, the allowable transmission power for the WLAN radio based at least in part on the second information, wherein:
 the allowable transmission power for the WLAN radio is determined based at least in part on the number of distinct time instances that the instantaneous transmission power values of the cellular radio exceeds a second transmission power threshold over the second period of time, and 
 the second transmission power threshold is less than the first transmission power threshold. 
 
 
     
     
       9. The method of  claim 8 , wherein:
 the transmission power for the WLAN radio is reduced when the number of distinct time instances that the instantaneous transmission power of the cellular radio exceeds the transmission power threshold over the first period of time exceeds a first positive integer threshold number of instances; and 
 the transmission power for the WLAN radio is allowed to increase after a previous reduction when the number of distinct time instances that the instantaneous transmission power values of the cellular radio exceeds the second transmission power threshold over the second period of time falls below a second positive integer threshold number of instances. 
 
     
     
       10. A wireless communication device comprising:
 a master radio; 
 a slave radio communicatively coupled with the master radio via a direct interface between the master radio and the slave radio; and 
 processing circuitry, wherein the processing circuitry is configured to cause the wireless communication device to at least:
 determine, at the master radio, instantaneous transmission power values of the master radio over a period of time; 
 provide information indicative of the instantaneous transmission power values of the master radio for the period of time from the master radio to the slave radio via the direct interface between the master radio and the slave radio; and 
 determine, at the slave radio, an allowable transmission power for the slave radio based at least in part on the information, wherein:
 a sum of the allowable transmission power for the slave radio and the transmission power of the master radio does not exceed a total transmission power limit, and 
 the allowable transmission power for the slave radio is determined based at least in part on an integer number N of distinct time instances that the instantaneous transmission power values of the master radio exceeds a transmission power threshold over the period of time when N&gt;1, 
 
 
 wherein the direct interface:
 is dedicated to communication between the master radio and the slave radio, and 
 operates at a lower latency than communication interfaces between either the master radio or the slave radio and host processing circuitry of the wireless communication device. 
 
 
     
     
       11. The wireless communication device of  claim 10 , wherein the master radio comprises a cellular radio, and wherein the slave radio comprises a wireless local area network (WLAN) radio. 
     
     
       12. The wireless communication device of  claim 10 , wherein:
 the information indicative of the instantaneous transmission power values of the master radio comprises an indication of whether the integer number N of distinct time instances over the period of time that the instantaneous transmission power of the master radio exceeded the transmission power threshold exceeds a positive integer threshold number T≧2 of instances; and 
 determine the allowable transmission power for the slave radio at least in part by causing the slave radio to reduce its transmission power in at least one instance in which the instantaneous transmission power of the master radio exceeds the transmission power threshold at least the positive integer threshold number of instances T over the period of time. 
 
     
     
       13. The wireless communication device of  claim 10 , wherein the processing circuitry is further configured to cause the wireless communication device to:
 determine a transmission power of a future transmission by the master radio; and 
 provide the slave radio with information indicative of the transmission power of the future transmission by the master radio via the direct interface between the master radio and the slave radio. 
 
     
     
       14. The wireless communication device of  claim 10 , wherein the master radio is implemented on a first chipset and the slave radio is implemented on a second chipset, and wherein the first chipset and the second chipset are communicatively coupled via the direct interface. 
     
     
       15. The wireless communication device of  claim 10 , wherein the master radio, the slave radio, and the host processing circuitry are implemented on a single chipset. 
     
     
       16. The wireless communication device of  claim 10 , wherein the total transmission power limit comprises a specific absorption rate (SAR) limit. 
     
     
       17. The wireless communication device of  claim 12 , wherein the period of time comprises a first period of time and the transmission power threshold comprises a first transmission power threshold, the processing circuitry further configured to cause the wireless communication device to:
 determine, at the master radio, instantaneous transmission power values of the master radio over a second period of time that follows the first period of time; 
 provide second information indicative of the instantaneous transmission power values of the master radio for the second period of time from the master radio to the slave radio via the direct interface between the master radio and the slave radio; and 
 determine, at the slave radio, the allowable transmission power for the slave radio based at least in part on the second information, wherein:
 the allowable transmission power for the slave radio is determined based at least in part on the number of distinct time instances that the instantaneous transmission power values of the master radio exceeds a second transmission power threshold over the second period of time, and 
 the second transmission power threshold is less than the first transmission power threshold. 
 
 
     
     
       18. The wireless communication device of  claim 17 , wherein:
 the transmission power for the slave radio is reduced when the number of distinct time instances that the instantaneous transmission power of the master radio exceeds the transmission power threshold over the first period of time exceeds a positive integer threshold number of instances; and 
 the transmission power for the slave radio is allowed to increase after a previous reduction when the number of distinct time instances that the instantaneous transmission power values of the master radio exceeds the second transmission power threshold over the second period of time falls below a second positive integer threshold number of instances. 
 
     
     
       19. A non-transitory computer readable storage medium storing instructions that, when executed by one or more processors implemented on a multi-radio wireless communication device including a master radio and a slave radio, cause the wireless communication device to perform a method comprising:
 determining, at the master radio, instantaneous transmission power values of the master radio over a period of time; 
 providing information indicative of the instantaneous transmission power values of the master radio for the period of time from the master radio to the slave radio via a direct interface between the master radio and the slave radio; and 
 determining, at the slave radio, an allowable transmission power for the slave radio based at least in part on the information, wherein:
 a sum of the allowable transmission power for the slave radio and the transmission power of the master radio does not exceed a total transmission power limit, and 
 the allowable transmission power for the slave radio is determined based at least in part on an integer number N of distinct time instances that the instantaneous transmission power values of the master radio exceeds a transmission power threshold over the period of time when N&gt;1, 
 
 wherein the direct interface:
 is dedicated to communication between the master radio and the slave radio, and 
 operates at a lower latency than communication interfaces between either the master radio or the slave radio and host processing circuitry of the wireless communication device. 
 
 
     
     
       20. The non-transitory computer readable storage medium of  claim 19 , wherein the master radio comprises a cellular radio, and wherein the slave radio comprises a wireless local area network (WLAN) radio.

Description:
FIELD 
     The described embodiments relate generally to wireless communications technology. More particularly, the present embodiments relate to controlling radio transmission power in a multi-radio wireless communication device in accordance with a total transmission power limit. 
     BACKGROUND 
     Many modern wireless communication devices include multiple radios. These multiple radios may be used by the device to concurrently communicate via multiple wireless communication technologies. For example, many wireless communication devices include both a cellular radio for supporting communication over a cellular network and a wireless local area network (WLAN) radio, such as a Wi-Fi radio, for supporting communication over a WLAN. Such devices can accordingly communicate concurrently over both a cellular network and a WLAN. In many instances a device supporting concurrent connections to a cellular network and a WLAN can emit simultaneous transmissions via both the cellular radio and the WLAN radio. 
     Wireless communication devices are often subject to regulations limiting radio frequency (RF) emissions that are issued by government and other regulatory bodies, such as the Federal Communications Commission (FCC). For example, Specific Absorption Rate (SAR) restrictions, such as those issued by the FCC, place limits on the transmission power of wireless communication devices to limit the amount of RF energy radiated when the devices are in proximity to a human body (i.e., a device user). In this regard, SAR can be defined in terms of a measure of the rate at which energy is absorbed by the human body when exposed to an RF electromagnetic field. As such, SAR limits can be imposed that limit the total transmission power of a wireless communication device so as to limit RF absorption by a user of the device. 
     When multiple radios are transmitting concurrently in a multi-radio wireless communication device, the imposition of SAR restrictions and/or other regulations restricting total transmission power impose a requirement to jointly limit the transmission power of the concurrently transmitting radios. Present wireless communication devices generally apply a conservative approach that assumes a maximum transmission power for a higher transmission power radio, such as a cellular radio, and then decides a safe transmission power level for a lower transmission power radio, such as a WLAN radio (i.e., any remaining transmission power within the total transmission power limit after subtracting the maximum cellular transmission power from the total transmission power limit). As a cellular radio does not always transmit at its maximum possible transmission power, the WLAN radio is often penalized by transmitting at an overly conservative transmission power. 
     SUMMARY 
     Some example embodiments provide methods, apparatuses, and computer program products implementing improved techniques for controlling radio transmission power in a multi-radio wireless communication device including at least a first radio and a second radio in accordance with a total transmission power limit. More particularly, some example embodiments provide for adaptive transmission power selection in the second radio, referred to as a slave radio, based on an actual transmission power characteristic of a transmission in the first radio, referred to as a master radio. In this regard, the master radio can select its transmission power and can then provide information indicative of the transmission power (e.g., a prior transmission power and/or a predicted future transmission power) to the slave radio, which can then determine an allowable transmission power within the confines of a total transmission power limit based at least in part on the transmission power of the master radio. Accordingly, rather than always assuming a maximum transmission power of a first radio (e.g., a cellular radio), as in prior wireless communication devices, wireless communication devices in accordance with various example embodiments can dynamically select a transmission power for a second radio (e.g., a WLAN radio) in concurrent transmission scenarios based on an actual transmission power of the first radio. In many circumstances, this dynamic transmission power selection by the second radio can yield a higher transmission power for the second radio and improve second radio performance compared to prior wireless communication devices. 
     This Summary is provided merely for purposes of summarizing some example embodiments so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example embodiments are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other embodiments, aspects, and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG. 1  illustrates an example system in which some example embodiments can be applied; 
         FIG. 2  illustrates a block diagram of an apparatus that can be implemented on a wireless communication device in accordance with some example embodiments; 
         FIG. 3  illustrates an example chip architecture of a wireless communication device including multiple radios in accordance with some example embodiments; 
         FIG. 4  illustrates another example chip architecture of a wireless communication device including multiple radios in accordance with some example embodiments; 
         FIG. 5  illustrates a flowchart according to an example method for controlling radio transmission power in a multi-radio wireless communication device in accordance with a total transmission power limit in accordance with some example embodiments; 
         FIG. 6  illustrates a flowchart according to an example method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on an average transmission power of a master radio in accordance with some example embodiments; 
         FIG. 7  illustrates an example architecture for implementing a method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on an average transmission power of a master radio in accordance with some example embodiments; 
         FIG. 8  illustrates a flowchart according to an example method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on a nonlinear peak power of a master radio in accordance with some example embodiments; 
         FIG. 9  illustrates an example architecture for implementing a method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on a nonlinear peak power of a master radio in accordance with some example embodiments; 
         FIG. 10  illustrates a flowchart according to an example method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on a predicted future transmission power of a master radio in accordance with some example embodiments; and 
         FIG. 11  illustrates an example architecture and a corresponding flowchart according to an example method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on a predicted future transmission power of a master radio in accordance with some example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     When multiple radios are transmitting concurrently in a multi-radio wireless communication device subject to SAR restrictions and/or other regulation restricting total transmission power, the transmission power of the concurrently transmitting radios must be jointly limited such that the total sum of the transmission power of the radios complies with the total transmission power limit imposed by the regulation. Present wireless communication devices generally apply a conservative approach that assumes a maximum transmission power for a first radio, such as a cellular radio, and then decides a safe transmission power level for a second radio, such as a WLAN radio (i.e., any remaining transmission power within the total transmission power limit after subtracting the maximum cellular transmission power from the total transmission power limit). 
     For example, given a maximum cellular radio transmission power of 23 dBm and a maximum WLAN radio transmission power of 18 dBm with an example 23.63 dBm SAR limit, prior art WLAN radios can always back off their transmission power to 15 dBm when transmitting concurrently with a cellular radio even when the cellular radio is not transmitting at its full 23 dBm capability. As a cellular radio frequently does not transmit at its maximum possible transmission power, the WLAN radio is often penalized by transmitting at an overly conservative transmission power. Moreover, the overly conservative WLAN back off applied by present wireless communication devices during concurrent transmission with a cellular radio can reduce an effective range of the WLAN radio, thus reducing radio performance. Moreover, due to the reduced radio performance, WLAN data throughput can be reduced as the lower radio link performance can result in an increase in dropped packets on the WLAN. 
     Some example embodiments provide methods, apparatuses, and computer program products implementing improved techniques for controlling radio transmission power in a multi-radio wireless communication device including at least a first radio and a second radio in accordance with a total transmission power limit. More particularly, some example embodiments provide for adaptive transmission power selection in the second radio, referred to as a slave radio, based on an actual transmission power characteristic of a transmission in the first radio, referred to as a master radio. In this regard, the master radio can select its transmission power and can then provide information indicative of the transmission power (e.g., a prior transmission power and/or a predicted future transmission power) to the slave radio, which can then determine an allowable transmission power within the confines of a total transmission power limit based at least in part on the transmission power of the master radio. Accordingly, rather than always assuming a maximum transmission power of a first radio, such as a cellular radio, as in prior wireless communication devices, wireless communication devices in accordance with various example embodiments can dynamically select a transmission power for a second radio, such as a WLAN radio, in concurrent transmission scenarios based on an actual transmission power of the first radio. In many circumstances, this dynamic transmission power selection by the second radio can yield a higher transmission power for the second radio and improve second radio performance through an increased effective transmission range and increased data throughput compared to prior wireless communication devices. 
       FIG. 1  illustrates an example system  100  in which some example embodiments can be applied. The system  100  can include a wireless communication device  102 , which can, for example, be embodied as a cellular phone, such as various mobile communication devices, such as a smart phone device, a tablet computing device, a smart watch or other wearable computing device, and/or the like; a personal computing device, such as a laptop computing device; a cellular hotspot device; and/or other computing device that can be subject to a restriction on total transmission power and that can include multiple radios that may transit concurrently. 
     The wireless communication device  102  can include a cellular radio, and can be configured to engage in cellular communications, which can be supported by a base station  104 . The base station  104  can be any type of cellular base station dependent on a type of radio access technology (RAT) supported by the base station  104 . By way of non-limiting example, the base station  104  can be a base station (BS), base transceiver station (BTS), node B, evolved Node B (eNB), some combination thereof, and/or other type of cellular base station. 
     The cellular radio of the wireless communication device  102  can be configured to support communication via any cellular RAT that can be supported by both the wireless communication device  102  and the base station  104 . In some example embodiments, the wireless communication device  102  can be a multi-mode device capable of supporting multiple cellular RATs. By way of non-limiting example, the wireless communication device  102  and base station  104  can use a Long Term Evolution (LTE) RAT, such as various releases of the LTE standard specified by the Third Generation Partnership Project (3GPP), including various releases of LTE, LTE-Advanced (LTE-A), and/or other present or future releases using LTE technology. As another example, the wireless communication device  102  and base station  104  can communicate via a third generation (3G) cellular RAT, such as Wideband Code Division Multiple Access (WCDMA) or other Universal Mobile Telecommunications System (UMTS) RAT, such as Time Division Synchronous Code Division Multiple Access (TD-SCDMA); CDMA2000; 1 xRTT; and/or the like. As another example, the wireless communication device  102  and base station  104  can communicate via a second generation (2G) cellular RAT, such as a Global System for Mobile Communications (GSM) RAT. It will be appreciated that the foregoing RATs are provided by way of example, and not by way of limitation. In this regard, the wireless communication device  102  and base station  104  can be configured to communicate via any present or future developed cellular RAT, including, for example, various fifth generation (5G) RATs now in development. 
     The wireless communication device  102  can further include a radio(s) configured to support communication over a WLAN and/or a personal area network (PAN), such as the WLAN/PAN  106 . The WLAN/PAN  106  can comprise any type of WLAN and/or PAN, such as, by way of non-limiting example, a WLAN implementing Wi-Fi or other Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology (e.g., 802.11 a/b/g/n/ac/ad/af/ah/aj/ax and/or other present or future developed 802.11 technology); a WLAN implementing a Z-wave technology, a PAN implementing an IEEE 802.15 technology, such as Bluetooth, Zigbee, an/or the like; and/or other present or future developed WLAN and/or PAN technology. As such, the wireless communication device  102  can include one or more WLAN radios, such as one or more WLAN radios configured to communicate via an IEEE 802.11 technology; a Bluetooth radio, a Zigbee radio, some combination thereof, and/or other radio(s) that may be configured to support a WLAN and/or PAN communication technology. The WLAN/PAN  106  and supporting radio(s) of the wireless communication device  102  can, for example, use an unlicensed band(s), such as an Industrial, Scientific, and Medical (ISM) band(s). 
     The wireless communication device  102  can engage in wireless communications with a device  108  via the WLAN/PAN  106 . For example, in some embodiments in which the WLAN/PAN  106  is a structured WLAN, the device  108  can comprise a wireless router and/or other access point for the WLAN. As a further example, in embodiments in which the WLAN/PAN  106  comprises a Bluetooth network, the device  108  can be a Bluetooth headset or other Bluetooth device that can be interfaced with a wireless communication device. 
     While the wireless communication device  102  has been described and illustrated as having a combination of a cellular radio and one or more WLAN and/or PAN radios, it will be appreciated that the illustration of  FIG. 1  and attendant description is provided solely by way of example to illustrate an example context in which various embodiments can be applied. In this regard, the wireless communication device  102  can include any combination of two or more radios, including, for example, multiple cellular radios (e.g., a first cellular radio supporting a first cellular RAT and a second cellular radio supporting a second cellular RAT), multiple WLAN radios (e.g., a first WLAN radio supporting communication in a first band and a second WLAN radio supporting communication in a second band), and/or other combination of radios that can transmit concurrently. 
     The wireless communication device  102  of some example embodiments can be subject to a regulation(s) restricting total transmission power by the wireless communication device  102 , such as when the wireless communication device is within proximity of a human body. By way of non-limiting example, the wireless communication device  202  can be subject to SAR regulations, such as can be issued by the United States Federal Communications Commission (FCC), The European Committee for Electrotechnical Standardization (CENELEC), and/or other government or other regulatory body that can regulate radio frequency emissions by a wireless communication device when the device is within proximity of a human. In embodiments in which the wireless communication device  102  can be subject to a SAR and/or other transmission power regulation when within proximity of a human body, the wireless communication device  102  can include a proximity sensor, such as proximity sensor  223  illustrated in and discussed below with respect to  FIG. 2 , which can be configured to detect when the wireless communication device  102  is within proximity of a human body, such as if the wireless communication device  102  is held close to a user&#39;s head to enable the user to talk into the device and participate in a voice call. 
     When the wireless communication device  102  is concurrently transmitting via multiple radios, such as if the wireless communication device  102  is sending a cellular transmission to the base station  104  via a cellular radio while sending a transmission to the device  108  via a WLAN/PAN radio, while subject to a regulation limiting the device&#39;s total transmission power, the transmission power of the concurrently transmitting radios can be jointly limited such that the total sum of the transmission power of the radios complies with the total transmission power limit imposed by the regulation. 
     In accordance with some example embodiments, a first radio of the wireless communication device  102 , such as by way of non-limiting example, the cellular radio, can be designated as a master radio. A second radio, such as by way of non-limiting example, a WLAN and/or PAN radio, can be designated as a slave radio. The master radio determine its transmission power and can then provide information indicative of the transmission power of the master radio to the slave radio. The slave radio can then determine its allowable transmission power in accordance with the total transmission power limit. In this regard, the allowable transmission power of the slave radio can be determined in accordance with various embodiments such that a sum of the allowable transmission power of the slave radio and the indicated transmission power of the master radio does not exceed the total transmission power limit. Thus, for example, in the example system  100 , the cellular radio of the wireless communication device  102  can indicate an actual (e.g., an actual observed and/or predicted future) transmission power used for a transmission to the base station  104  to the WLAN/PAN radio supporting the connection to the WLAN/PAN  106 . The WLAN/PAN radio can then determine its allowable transmission power for transmissions to the WLAN/PAN  106  based on the total transmission power limit and the indicated transmission power of the cellular radio. 
       FIG. 2  illustrates a block diagram of an apparatus  200  that can be implemented on a wireless communication device, such as wireless communication device  102 , in accordance with some example embodiments. It will be appreciated that the components, devices or elements illustrated in and described with respect to  FIG. 2  below may not be mandatory and thus some may be omitted in certain embodiments. Additionally, some embodiments can include further or different components, devices or elements beyond those illustrated in and described with respect to  FIG. 2 . 
     In some example embodiments, the apparatus  200  can include processing circuitry  210  that is configurable to perform actions in accordance with one or more example embodiments disclosed herein. In this regard, the processing circuitry  210  can be configured to perform and/or control performance of one or more functionalities of a wireless communication device, such as wireless communication device  102 , in accordance with various example embodiments, and thus can provide means for performing functionalities of the wireless communication device in accordance with various example embodiments. The processing circuitry  210  can be configured to perform data processing, application execution and/or other processing and management services according to one or more example embodiments. In some embodiments, the apparatus  200  or a portion(s) or component(s) thereof, such as the processing circuitry  210 , can include one or more chipsets, which can each include one or more chips. The processing circuitry  210  and/or one or more further components of the apparatus  200  can therefore, in some instances, be configured to implement an embodiment on a single chip or chipset. 
     In some example embodiments, the processing circuitry  210  can include a processor  212  and, in some embodiments, such as that illustrated in  FIG. 2 , can further include memory  214 . The processing circuitry  210  can be in communication with or otherwise control a transmission power manager  216  and two or more radios that can be implemented on the apparatus  200 , including a master radio  218  and slave radio  220 . In some example embodiments, the apparatus  200  can further include a proximity sensor  224 , which can also be in communication with or otherwise controlled by the processing circuitry  210 . 
     The processor  212  can be embodied in a variety of forms. For example, the processor  212  can be embodied as various hardware-based processing means such as a microprocessor, a coprocessor, a controller or various other computing or processing devices including integrated circuits such as, for example, an ASIC (application specific integrated circuit), an FPGA (field programmable gate array), some combination thereof, or the like. The processor  212  of some example embodiments can comprise a host processor configured to serve as a host for controlling or otherwise facilitating operation of two or more device radios, such as the master radio  218  and slave radio  220 . In some example embodiments, the processor  212  can comprise an application processor, which can be configured to support execution of various applications that can be implemented on a wireless communication device. Although illustrated as a single processor, it will be appreciated that the processor  212  can comprise a plurality of processors. The plurality of processors can be in operative communication with each other and can be collectively configured to perform one or more functionalities of the apparatus  200  as described herein. In some example embodiments, the processor  212  can be configured to execute instructions that can be stored in the memory  214  or that can be otherwise accessible to the processor  212 . As such, whether configured by hardware or by a combination of hardware and software, the processor  212  capable of performing operations according to various embodiments while configured accordingly. 
     In some example embodiments, the memory  214  can include one or more memory devices. Memory  214  can include fixed and/or removable memory devices. In some embodiments, the memory  214  can provide a non-transitory computer-readable storage medium that can store computer program instructions that can be executed by the processor  212 . In this regard, the memory  214  can be configured to store information, data, applications, instructions and/or the like for enabling the apparatus  200  to carry out various functions in accordance with one or more example embodiments. In some embodiments, the memory  214  can be in communication with one or more of the processor  212 , transmission power manager  216 , master radio  218 , slave radio  220 , or proximity sensor  224  via one or more buses for passing information among components of the apparatus  200 . 
     The apparatus  200  can further include transmission power manager  216 , which can be embodied as various means, such as circuitry, hardware, a computer program product comprising a computer readable medium (for example, the memory  214 ) storing computer readable program instructions executable by a processing device (for example, the processor  212 ), or some combination thereof. In some embodiments, the processor  212  (or the processing circuitry  210 ) can include, or otherwise control the transmission power manager  216 . The transmission power manager  216  can be configured to control and/or otherwise support the control of the transmission power of a radio, such as the master radio  218  and slave radio  220 , on a multi-radio wireless communication device in accordance with an applicable total transmission power limit in accordance with various example embodiments. 
     The apparatus  200  can include a plurality of co-located radios. Two such radios—the master radio  218  and slave radio  220 —are illustrated by way of example in  FIG. 2 . It will be appreciated, however, that the apparatus  200 , and thus, the wireless communication device  102  and/or other wireless communication device implementing the apparatus  200 , can include one or more further radios in some example embodiments. 
     The radios implemented on the apparatus  200  can each implement any respective wireless communication technology. For example, in some example embodiments, one or more radios on the apparatus  200 , such as one or more of the master radio  218  or slave radio  220 , can implement a cellular communication technology, such as a Long Term Evolution (LTE) cellular communication technology, a Universal Mobile Telecommunications System (UMTS) cellular communication technology, a Global System for Mobile Communications (GSM) cellular communication technology, a Code Division Multiple Access (CDMA) cellular communication technology, or a CDMA 2000 cellular communication technology, and/or the like. As a further example, in some example embodiments, one or more radios on the apparatus  200 , such as one or more of the master radio  218  or slave radio  220 , can be a connectivity radio, such as Bluetooth, Zigbee, or other wireless PAN radio; a Wi-Fi or other wireless local area network (WLAN) radio; or other connectivity radio. As still a further example, the apparatus  200  of some example embodiments can include a global navigation satellite system (GNSS) radio, such as a Global Positioning System (GPS) radio, Russian GLONASS system radio, Doppler Orbitography and Radio-positioning Integrated by Satellite (DORIS) radio, Chinese Compass system radio, Galileo positioning system radio, and/or other GNSS radio. It will be appreciated, however, that the foregoing example radio technologies are provided by way of example, and not by way of limitation, as various example embodiments support in-device coexistence between any two (or more) radios that use disparate wireless communication technologies. 
     It will be appreciated that the master radio  218  and slave radio  220  support any combination of RATs. For example, in some embodiments both the master radio  218  and slave radio  220  can each support communication via the same RAT, such as a WLAN technology, but can operate in different frequency bands (e.g., a 2.4 GHz radio and a 5 GHz radio). As another example, in some embodiments, one of the master radio  218  and slave radio  220  can support communication via a first RAT, such as a cellular RAT, and the other of the master radio  218  and slave radio  220  can support communication via a second RAT, such as an IEEE 802.11 and/or other WLAN technology. 
     Each radio, including the master radio  218  and slave radio  220 , implemented on the apparatus  200  can include appropriate circuitry for supporting radio frequency communication via a RAT supported by the radio. For example, each radio implemented on the apparatus  200  can include one or more transceivers. In some example embodiments, a radio, such as master radio  218  and/or slave radio  220  can be implemented on a chipset, which when implemented on a computing device, such as wireless communication device  102 , can be configured to enable the computing device to support wireless communication via one or more RATs. In some such example embodiments, at least a portion of processing circuitry  210  and/or transmission power manager  216  can be implemented on the chipset to support transmission power control in accordance with various example embodiments. 
     An interface  222  can be used to interface (e.g., communicatively couple) two or more radios, such as the master radio  218  and slave radio  220 , on the apparatus  200 . The interface  22  can be separate from an interface(s) that may be used to interface the master radio  218  and slave radio  220  with a host application processor, such as can be provided by the processor  212 . The interface  222  can be a higher speed interface than the interface(s) between the radios and processor  212 , which can offer low latency to allow (e.g., on the order of microseconds) for communication of real time state information between radios. For example, the interface  222  can be a real time, or near-real time interface. The interface  222  of some example embodiments can be an interface dedicated to the exchange of information between radios, which may not be used for communication of information to or from non-radio components of the apparatus  200 . In some example embodiments, the interface  222  can be a direct interface linking the master radio  218  and slave radio  220  (and potentially one or more further radios). In some example embodiments, the interface  222  can comprise a coexistence interface, such as a Wireless Coexistence Interface (WCI) (e.g., a WCI-2 interface, WCI-1 interface, or other type of WCI), that can be configured to support exchange of state information usable to support in-device coexistence. It will be appreciated, however, that WCI interface types are provided as one non-limiting example of an interface that can be used to facilitate communication of state information between radios, and any appropriate interface that can be used to interface two or more radios to support the exchange of state information between radios can be used in addition to or in lieu of an WCI interface to provide the interface  222  in accordance with some example embodiments. As described further herein below, the interface  222  can be used by the master radio  218  of some example embodiments to provide information indicative of the transmission power of the master radio  218  so as to enable the slave radio  220  to determine its allowable transmission power. 
     The apparatus  200  can further include proximity sensor  224 . The proximity sensor  224  can be configured to sense proximity between a wireless communication device, such as wireless communication device  102 , and another object, such as a human body. For example, in some embodiments, the proximity sensor  224  can be configured to sense when the wireless communication device  202  is positioned within sufficient proximity of a human body to trigger a restriction on total transmission power (e.g., in compliance with a SAR regulation and/or other regulation that can apply to a wireless communication device). The proximity sensor  224  of such example embodiments can be configured provide output indicating that the wireless communication device is within proximity to a human body when proximity to the human body is detected. As such, the transmission power manager  216 , master radio  218 , and slave radio  220  of some example embodiments can be configured to selectively implement techniques for controlling the total transmission power of the radio based on whether the proximity sensor  224  detects that the wireless communication device is sufficiently proximate to a human body to trigger implementation of a restriction limiting the total transmission power. The proximity sensor  224  can be in communication with one or more of processing circuitry  210 , processor  212 , memory  214 , transmission power manager  216 , master radio  218 , or slave radio  220  via one or more buses for passing information among components of the apparatus  200 . 
     As described further herein, in various embodiments, the master radio  218  can determine its transmission power (e.g., within total transmission power limits) without regard to the transmission power of the slave radio  220 . In this regard, the master radio  218  can have priority over the slave radio  220  in choosing its transmission power. The master radio  218  can provide information indicative of its transmission power (e.g., an actual prior/current transmission power and/or a predicted future transmission power) to the slave radio  220 , such as via interface  222 . The slave radio  220  can determine an allowable transmission power based at least in part on the information. In this regard, the slave radio  220  can determine an allowable transmission power such that a sum of the allowable transmission power and the transmission power of the master radio does not exceed the applicable total transmission power limit. For example, the allowable transmission power of the slave radio  220  can be defined as: Allowable Slave Tx Power=Total Transmission Power Limit−Transmission Power of Master Radio. 
     In some example embodiments the slave radio  220  can further factor, a buffer, Δ, which can function as a safety margin reduce the chance of exceeding the total transmission power limit. In some such example embodiments, the slave radio  220  can calculate its allowable transmission power as: Allowable Slave Tx Power=Total Transmission Power Limit−Transmission Power of Master Radio−Δ. 
     In some example embodiments, the total transmission power limit can be a static transmission power limit that can be applied regardless of the operating scenario. Alternatively, in some example embodiments, the total transmission power limit can be dynamically determined by the transmission power manager  216  based at least in part on observed operating conditions. For example, the total transmission power limit can be determined based at least in part on factors such as a frequency band being used for transmission by a radio, a frequency or frequencies within a band being used for transmission by a radio, a RAT(s) used by the radios, device antenna configurations (e.g., placement of antennas within the device, an antenna being used for transmission when multiple antennas are available, and/or other antenna configuration qualities), a proxy state, a multiple-input and multiple-output (MIMO) mode being used by a radio (if applicable), and/or other factors. In this regard, any factor that can affect the amount and/or rate of RF absorption by a device user at a given transmission power can be considered when determining the total transmission power limit in embodiments in which the total transmission power limit can be dynamically determined. In some embodiments, the transmission power manager  216  and/or one or both of the master radio  218  and slave radio  220  can be configured to access a table or other data structure that defines applicable total transmission power limits for various conditions. Accordingly, the data structure can be used to determine the applicable total transmission power limit given an observed operating condition(s). 
     A person having ordinary skill in the art will understand that the components of the apparatus  200  can be implemented via any of a variety of architectures. As such, it will be appreciated that, in some example embodiments, the components of the apparatus  200  can be arranged and/or distributed across multiple chips (e.g., multiple dies, integrated circuits, and/or the like). In some such embodiments, aspects of one or more component&#39;s of the apparatus  200 , such as processing circuitry  210  and/or transmission power manager  216 , can be distributed across the multiple chips. An example architecture implementing multiple chips is illustrated in and described below with respect to  FIG. 3 . Alternatively, in some example embodiments, each component of the apparatus  200 , or at least those components implemented in a given embodiment, can be implemented on a single chip (e.g., a single die, integrated circuit, and/or the like), such as a system on a chip. An example architecture implementing each component on a single chip is illustrated in and described below with respect to  FIG. 4 . 
       FIG. 3  illustrates an example chip architecture  300  of a wireless communication device, such as wireless communication device  102 , including multiple radios in accordance with some example embodiments in which the radios can be implemented on separate chips that can be interfaced with a host processor. The architecture  300  can include a master radio chip  302  and a slave radio chip  312 , which can comprise embodiments of the master radio  218  and slave radio  220 , respectively. It will be appreciated, however, that the architecture  300  can be extended to include further radio chips. 
     The master radio chip  302  can include appropriate circuitry for supporting communication via a RAT(s) supported by the master radio chip  302 . For example, the master radio chip  302  can include a master radio transceiver(s)  304  that can be configured to send and receive wireless signals in accordance with a RAT(s) supported by the master radio chip  302 . The master radio chip  302  can further include master radio control circuitry  306  that can be configured to implement at least some on-chip functionality for controlling the master radio chip  302 . In some example embodiments, the master radio control circuitry  306  can comprise a portion of processing circuitry  210 , and can be configured to perform at least some functionality of the transmission power manager  216 . The master radio control circuitry  306  can, for example, be configured to determine a transmission power (e.g., an actual and/or a predicted future transmission power) of the master radio transceiver  304 , and can provide information indicative of the transmission power to the slave radio chip  312  to enable the slave radio chip  312  to determine its allowable transmission power in accordance with various example embodiments. The master radio chip  302  can further include interface component  308 , which can be configured to support connection to a further radio chip, such as slave radio chip  312 , via an interface, such as interface  322  described below. 
     The slave radio chip  312  can include appropriate circuitry for supporting communication via a RAT(s) supported by the slave radio chip  312 . For example, the slave radio chip  312  can include a slave radio transceiver(s)  314  that can be configured to send and receive wireless signals in accordance with a RAT. The slave radio chip  312  can further include slave radio control circuitry  316  that can be configured to implement at least some on-chip functionality for controlling the slave radio chip  312 . In some example embodiments, the slave radio control circuitry  316  can comprise a portion of processing circuitry  210 , and can be configured to perform at least some functionality of the transmission power manager  216 . For example, the slave radio control circuitry  316  can be configured to receive information that can be provided by the master radio chip  302  regarding a transmission power of the master radio chip  302 , and can be configured to use the information to determine an allowable transmission power for the slave radio transceiver  314  in accordance with various example embodiments. The slave radio control circuitry  316  can be further configured to regulate the transmission power of the slave radio transceiver  314  in accordance with the allowable transmission power. The slave radio chip  312  can further include interface component  318 , which can be configured to support connection to a further radio chip, such as master radio chip  302 , via an interface, such as interface  322 . 
     The interface  322  can be any interface that can be used to support communication between radios on a wireless communication device. The interface  322  can, for example, be an interface offering low latency to allow (e.g., on the order of microseconds) for communication of real time state information between radios. For example, the interface  322  can be a real time, or near-real time interface. The interface  322  of some example embodiments can be an interface dedicated to the exchange of information between radios, which may not be used for communication of information to or from non-radio components of the architecture  300 . In some example embodiments, the interface  322  can be an embodiment of the interface  222 . 
     The architecture  300  can further include host processing circuitry  324 , which can be interfaced with each of the master radio chip  302  and the slave radio chip  312 . In some example embodiments, the host processing circuitry  324  can be interfaced with the master radio chip  302  and slave radio chip  312  via an interface(s) that is separate from the interface  322  used to convey information between the radio chips  302  and  312 . The host processing circuitry  324  can, for example, comprise an application or system processor that can be configured to execute and perform applications and/or other system level functionalities of a wireless communization device, such as wireless communication device  102 . In some example embodiments, host processing circuitry  324  can comprise a portion of processing circuitry  210 , and can be configured to perform at least some functionality of the transmission power manager  216 . 
       FIG. 4  illustrates another example chip architecture of a wireless communication device, such as wireless communication device  102 , including multiple radios in accordance with some example embodiments. More particularly, the architecture illustrated in  FIG. 4  is an example architecture in which multiple radios and host processing circuitry can be implemented on a single chip  400  as a system on a chip. The chip  400  can accordingly include circuitry for each radio implemented on the chip  400 , including master radio circuitry  418  and slave radio circuitry  420 , which can comprise embodiments of the master radio  218  and slave radio  220 , respectively. The master radio circuitry  418  and slave radio circuitry  420  can be interfaced via the interface  422 , which can, for example, comprise an embodiment of the interface  222 . The master radio circuitry  418  and slave radio circuitry  420  can be further interfaced with processing circuitry  410 , which can, for example, comprise an embodiment of processing circuitry  210 , or portion thereof. Aspects of the transmission power manager  216  can be distributed among the processing circuitry  410 , master radio circuitry  418 , and slave radio circuitry  420 . 
     It will be appreciated that the example architectures illustrated in  FIGS. 3 and 4  are provided by way of example, and not by way of limitation. In this regard, a person having ordinary skill in the art will realize that other architectures are contemplated within the scope of the disclosure. For example, in some embodiments, the master radio  218  and slave radio  220  can be implemented on a first chip, which can be interfaced with a second chip that can include a host or application processor. 
     In some example embodiments, a first radio implemented on a wireless communication device can be permanently configured as the master radio  218 , and a second radio can be permanently configured as the slave radio. The configuration of such permanent master and slave radio slave designations can, for example, be defined based on a the RATs implemented by the respective radios and/or general transmission powers associated therewith, respective radio priorities in terms of desired quality of service, and/or other factors. For example, in some embodiments, a cellular radio can be defined as a permanent master radio and a lower powered connectivity radio(s), such as a WLAN radio, PAN radio, and/or the like, can be defined as the slave radio(s). In some such embodiments, a PAN radio, such as a Bluetooth radio can function as a slave radio to a WLAN radio and/or as a second slave radio to a cellular radio in a device including a cellular radio, WLAN radio, and a Bluetooth or other PAN radio. 
     In some example embodiments, the roles of master and slave radio can be dynamically assigned and can be switched in operation. In some such example embodiments, the transmission power manager  216  can be configured to assign master and slave roles and to provide the master/slave designations to the device radios. For example, if a higher priority application is using and/or a high priority task is being performed via a WLAN connection, the transmission power manager  216  can at least temporarily assign a WLAN radio a master radio designation with the cellular radio being at least temporarily assigned a slave radio designation. Additionally or alternatively, in some example embodiments, a first radio that typically operates as a slave radio can signal a second radio that typically operates as a master radio (e.g., via interface  222 ) that the first radio is performing and/or about to perform a high priority transmission and that the second radio should function as the slave radio and adjust its transmission power to accommodate the desired transmission power of the first radio during the transmission. For example, in some such embodiments, a WLAN radio can signal a cellular radio that the WLAN radio is going to operate as a master radio when performing a WiFi association procedure for associating with a WLAN. 
       FIG. 5  illustrates a flowchart according to an example method for controlling radio transmission power in a multi-radio wireless communication device, such as wireless communication device  102 , in accordance with a total transmission power limit in accordance with some example embodiments. The method of  FIG. 5  can, for example, be performed by components of the apparatus  200 , architecture  300 , and/or architecture  400 . Thus, for example, one or more of processing circuitry  210 , processor  212 , memory  214 , transmission power manager  216 , proximity sensor  224 , master radio  218 , or slave radio  220  can provide means for performing one or more of the operations illustrated in and described with respect to  FIG. 5 . 
     Operation  500  can, for example, include the master radio  218  determining a transmission power of the master radio  218 . The determined transmission power can, for example, comprise one or more actual instantaneous transmission powers of the master radio  218  and/or can comprise a predicted future transmission power of the master radio  218 . In some example embodiments in which the master radio  218  is a cellular radio, the determined transmission power can be a transmission power configured and/or otherwise specified by a serving cellular base station, such as base station  104 . 
     Operation  510  can include the master radio  218  providing information indicative of the transmission power determined in operation  500  to the slave radio  220 . In some example embodiments, the information can be provided to the slave radio  220  via the interface  222 . However, in some example embodiments, the master radio  218  can communicate the information to the slave radio  220  via an alternative interface(s), such as via the processing circuitry  210  or portion thereof. 
     The information can be received by the slave radio  220 , and operation  520  can include the slave radio  220  determining an allowable transmission power for the slave radio  220  based at least in part on the information. For example, the slave radio  220  of some example embodiments can calculate the allowable transmission power as a function of the total transmission power limit and the transmission power of the master radio  218 : Allowable Slave Tx Power=Total Transmission Power Limit−Transmission Power of Master Radio  218 . In embodiments in which a buffer, Δ, is also factored, the allowable transmission power can be calculated as: Allowable Slave Tx Power=Total Transmission Power Limit−Transmission Power of Master Radio−Δ. As such, the slave radio  220  can dynamically determine its allowable transmission power and, thus the amount of back off from its maximum possible transmission power, within the confines of any applicable total transmission power limit that can be jointly applied to the master radio  218  and the slave radio  220  based on the transmission power of the master radio  218 . 
     The slave radio  220  can use a transmission power up to the determined allowable transmission power to support a transmission. The operations of  FIG. 5  can be repeated, such that the slave radio  220  can dynamically determine the allowable transmission power and adjust its transmission power in response to changes in the transmission power of the master radio  218 . 
     In instances in which it is determined in operation  520  that the allowable transmission power is less than a transmission power being used by the slave radio  220 , the slave radio  220  can be configured to reduce its transmission power in compliance with the allowable transmission power immediately or at least within a relatively short delay tolerance, such as, by way of non-limiting example, within 10 milliseconds. If, however, the allowable transmission power calculation of operation  520  indicates that a transmission power being used by the slave radio  220  is less than the allowable transmission power such that an increase in transmission power is permitted, the slave radio  220  can be configured to wait at least a delay period, such as, by way of non-limiting example, 500 milliseconds, before increasing its transmission power to verify that any decrease in transmission power of the master radio  218  resulting in the increased allowable transmission power is not transient. In this regard, waiting for the delay period before increasing the transmission power of the slave radio  220  can enable the wireless communication device to avoid exceeding the total transmission power limit in the event that a decrease in master radio  218  transmission power is transient and can provide a hysteresis condition to reduce the incidence of the slave radio  220  ping ponging between transmission power levels in response to transient changes in the transmission power of the master radio  218 . 
     In some example embodiments, the method of  FIG. 5  can be selectively performed based on the output of the proximity sensor  224 . For example, in some such embodiments, if the proximity sensor  224  does not detect that the wireless communication device is proximate to a human body, each radio can transmit at up to its maximum transmission power capabilities irrespective of the transmission power used by the other radio. However, if the proximity sensor  224  detects that the wireless communication device is proximate to a human body such that a total transmission power limit is jointly applied to the master radio  218  and the slave radio  220 , the method of  FIG. 5  can be performed so as to control the transmission power of the slave radio  220  within its allowable transmission power based on the transmission power of the master radio  218 . 
     In some example embodiments, the information that can be provided to the slave radio  220  in operation  510  can include a transmission power characteristic of one or more instantaneous transmission powers of the master radio  218 . In this regard, the master radio  218  of some example embodiments can be configured to determine a transmission power characteristic of one or more instantaneous transmission powers of the master radio  218  that is usable by the slave radio  220  to determine an allowable transmission power in addition to or in lieu of a raw observed instantaneous and/or predicted future transmission power of the master radio  218 . The transmission power characteristic can provide an indication of the transmission power of the master radio  218  over a period of time that can be a more accurate representation on which to base slave radio  220  transmission power than a single instantaneous transmission power value. 
     The transmission power characteristic can be defined at various levels of granularity depending on the characteristic used and/or the time period over which the characteristic is determined such that the slave radio  220  can be tuned to various tolerance levels of compliance with a total transmission power limit. For example, if better performance of the slave radio  220  is desired such that the slave radio  220  is given more opportunity to transmit at a higher transmission power at the expense of briefly exceeding the total transmission power limit on occasion, a transmission power characteristic can be selected that can allow compliance with the total transmission power limit on average, but that may allow some momentary moments at which the total transmission power of the master radio  218  and the slave radio  220  can exceed the total transmission power limit. Some example embodiments of such an averaging power concept are illustrated in and described below with respect to  FIGS. 6 and 7 . However, if more conservative approach yielding more consistent compliance with the total transmission power limit is desired at the expense of potentially reduced performance of the slave radio  220 , a nonlinear peak power approach can be adopted to reduce the incidence of exceeding the total transmission power limit compared to the averaging power approach. Examples of the nonlinear peak power approach in accordance with some example embodiments are illustrated in and described below with respect to  FIGS. 8 and 9 . 
       FIG. 6  illustrates a flowchart according to an example method for controlling slave radio  220  transmission power in a multi-radio wireless communication device, such as wireless communication device  102 , based at least in part on an average transmission power of the master radio  218  in accordance with some example embodiments. The method of  FIG. 6  can, for example, be performed by components of the apparatus  200 , architecture  300 , and/or architecture  400 . Thus, for example, one or more of processing circuitry  210 , processor  212 , memory  214 , transmission power manager  216 , proximity sensor  224 , master radio  218 , or slave radio  220  can provide means for performing one or more of the operations illustrated in and described with respect to  FIG. 6 . 
     Operation  600  can include determining one or more instantaneous transmission powers of the master radio  218  over a period of time. Operation  600  can, for example, correspond to an embodiment of operation  500 . 
     Operation  610  can include determining an average transmission power of the one or more instantaneous transmission powers. Thus, for example, operation  610  can include determining an average transmission power of the master radio  218  over the period of time. 
     Operation  620  can include the master radio  218  providing an indication of the average transmission power to the slave radio  220 . In some example embodiments, the indication of the average transmission power can comprise an actual average transmission power value. Alternatively, in some example embodiments, the indication can comprise a quantized representation of the average transmission power value into one of a plurality of transmission power ranges, which can then be correlated into a corresponding allowable transmission power for the slave radio  220 . The indication can, for example, be provided to the slave radio  220  via the interface  222 . Operation  620  can accordingly correspond to an embodiment of operation  510 . 
     Operation  630  can include the slave radio  220  determining an allowable transmission power for the slave radio  220  based at least in part on the indication. For example, in some embodiments in which the indication is an actual average transmission power value, the slave radio  220  can calculate the allowable transmission power value as a function of the total transmission power limit, the average transmission power, and optionally a buffer, A. As another example, in some embodiments, such as some embodiments in which a quantized representation of the average transmission power value is provided, which indicates which of a plurality of transmission power value ranges the average transmission power value falls in, the slave radio  220  can reference a lookup table and/or other data structure to determine an allowable transmission power value corresponding to the quantized representation. Operation  630  can accordingly correspond to an embodiment of operation  520 . 
     In instances in which it is determined in operation  630  that the allowable transmission power is less than a transmission power being used by the slave radio  220 , the slave radio  220  can be configured to reduce its transmission power in compliance with the allowable transmission power immediately or at least within a relatively short delay tolerance, such as, by way of non-limiting example, within 10 milliseconds. If, however, the allowable transmission power determination of operation  630  indicates that a transmission power being used by the slave radio  220  is less than the allowable transmission power such that an increase in transmission power is permitted, the slave radio  220  can be configured to wait at least a delay period, such as, by way of non-limiting example, 500 milliseconds, before increasing its transmission power to verify that any decrease in transmission power of the master radio  218  resulting in the increased allowable transmission power is not transient. 
       FIG. 7  illustrates an example architecture  700  for implementing a method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on an average transmission power of a master radio in accordance with some example embodiments. In this regard, the architecture  700  can provide an architecture for performing the method of  FIG. 6  in accordance with some example embodiments. The architecture  700  can include a master radio  702  and slave radio  704 , which can, for example, comprise embodiments of the master radio  218  and slave radio  220 , respectively. The master radio  702  and slave radio  704  can be interfaced via an interface  706 , which can, for example, comprise an embodiment of the interface  222 . 
     The master radio  702  can include an averaging filter  712 . The instantaneous transmission power  710  of the master radio  702  can be provided as an input to the averaging filter  712 . The averaging filter  712  can be configured to determine an average transmission power value of a plurality of instantaneous transmission power value samples (e.g., over a windowed period of time). In this regard, the averaging filter  712  can, for example, be configured to perform operation  610 . It will be appreciated that any appropriate averaging filter can be used to implement the averaging filter  712 . By way of non-limiting example, an infinite impulse response (IIR) filter, a windowed filter, some combination thereof, or the like can be used to implement the averaging filter  712 . 
     The master radio  702  can further include a multi-level quantizer  714 . The output of the averaging filter  712  (e.g., the average transmission power of the master radio  702 ) can be provided as an input to the multi-level quantizer  714 . The multi-level quantizer can be configured to quantize the average transmission power into one of a plurality of levels. 
     Depending on the desired level of granularity, any number of levels can be implemented. For example, in some embodiments, the quantizer  714  can be a 1-bit quantizer, which can be configured to indicate whether the average transmission power is above or below a defined threshold. As another example, in some embodiments, the quantizer  714  can be a 2-bit quantizer that can be configured to quantize the average transmission power into one of four defined transmission power ranges. As a non-limiting example of transmission power ranges that can be applied in order to provide an example of how a 2-bit quantizer can be implemented, a first quantized value can indicate that the average transmission power is in excess of 18 dBm; a second quantized value can indicate that the average transmission power is between 15 dBm and 18 dBm; a third quantized value can indicate that the average transmission power is between 10 dBm and 15 dBm; and a fourth quantized value can indicate that the average transmission power is less than 10 dBm. The concept can be similarly applied using a quantizer providing a 3 or more bit output. Also, the transmission power ranges can be tweaked depending on the general transmission power level of the master radio  702 , such as can vary on a type of RAT implemented by the master radio  702 , and a desired tolerance level with respect to compliance with the applicable total transmission power limit. 
     The output of the multi-level quantizer  714  can be provided to the slave radio  704  via the interface  706 . The slave radio  704  can be configured to lookup the quantized value in a lookup table  716  or other data structure, which can define associations between each possible output of the multi-level quantizer  714  and a respective allowable transmission power value. The result of the lookup can accordingly yield the allowable slave transmission power value  718 , which can be used by the slave radio  704 . In this regard, the lookup table  716  can, for example, be used to perform operation  630 . 
     It will be appreciated that the method illustrated in and described with respect to  FIGS. 6 and 7  is provided by way of example, and not by way of limitation. In this regard, the operations performed to enable implementation of an averaging power concept in accordance with various example embodiments can be distributed among the master radio  218  and slave radio  220  and/or among other components of the apparatus  200  in a different manner than illustrated in  FIGS. 6 and 7 . For example, in some embodiments, the master radio  218  can provide the slave radio  220  with actual instantaneous transmission power values of the master radio  218 , and the slave radio  220  can perform averaging of the instantaneous transmission power values. 
     The averaging power concept, such as illustrated in and described can yield a significant improvement in the transmission power of the slave radio  220  compared to prior art approaches that always assume the worst case scenario in which a radio is transmitting at its maximum capable power. As an example in which the master radio  218  can be embodied as a Long Term Evolution cellular radio, a maximum transmission power of the master radio  218  can be 23 dBm. However, in the case of bursty cellular traffic, such as Voice over LTE (VoLTE) traffic, the cellular radio may only be transmitting at a high power for periodic brief periods of time, such as for only 1 or 2 subframes out of every 20. If the slave radio  220  were to assume a worst case transmission power for the cellular radio, there would be long stretches in which the slave radio  220  would needlessly back off its transmission power even when the cellular radio is not even transmitting due to the bursty nature of the traffic. Thus, by averaging the transmission power of the cellular radio over a period of time and calculating the allowable slave transmission power based on the average, significant gains in transmission power and performance of the slave radio  220  can be gained. However, the total transmission power limit can be exceeded on occasion, such as during the subframes in which the cellular radio can be transmitting the bursty traffic at a high transmission power. 
       FIG. 8  illustrates a flowchart according to an example method for controlling slave radio  220  transmission power in a multi-radio wireless communication device, such as wireless communication device  102 , based at least in part on a nonlinear peak power of a master radio  218  in accordance with some example embodiments. The method of  FIG. 8  can, for example, be performed by components of the apparatus  200 , architecture  300 , and/or architecture  400 . Thus, for example, one or more of processing circuitry  210 , processor  212 , memory  214 , transmission power manager  216 , proximity sensor  224 , master radio  218 , or slave radio  220  can provide means for performing one or more of the operations illustrated in and described with respect to  FIG. 8 . 
     Operation  800  can include determining one or more instantaneous transmission powers of the master radio  218  over a period of time, L 1  (e.g., L 1  seconds). Operation  800  can, for example, correspond to an embodiment of operation  500 . 
     Operation  810  can include determining whether instantaneous transmission power of the master radio  218  exceeded a transmission power threshold, T 1 , at least a threshold number, T 2 , of instances over the period of time, L 1 . In this regard, T 1  can be a power threshold; T 2  can be a counter threshold; and L 1  can be a timer-based threshold. By way of non-limiting example, in some embodiments, such as some embodiments in which the master radio  218  is a cellular radio, T 1  can be defined as 22.25 dBm, L 1  can be defined as 3 seconds, and T 2  can be defined as 1. Thus, operation  810  can include determining whether the number of instances, N, in which the instantaneous transmission power exceeded T 1  over a period of length, L 1 , is greater than or equal to T 2 . 
     The transmission power threshold, T 1 , and the threshold number of instances, T 2 , that can be evaluated in operation  810  can be selected based on factors, such as a desired level of compliance with the applicable total transmission power limit on an instantaneous basis, a desired performance of the slave radio  220 , the RATs used by the master radio  218  and slave radio  220 , and/or other factors. In a simple case, T 2  can be defined as 1. However, if a better performance level of the slave radio  220  (e.g., higher transmission power level) is desired and it is considered acceptable for the total cumulative transmission power of the master radio  218  and slave radio  220  to exceed the total transmission power limit on occasion, T 2  can be defined as a higher threshold (e.g., 2 or more) such that back off of the transmission power of the slave radio  220  may be triggered less frequently in response to a temporary increase in the transmission power of the master radio  218  above T 1 . 
     Operation  820  can include the master radio  218  providing an indication to the slave radio  220  indicating whether instantaneous transmission power of the master radio  218  exceeded the transmission power threshold, T 1 , at least the threshold number, T 2 , of instances over the period of time, L 1 . In this regard, the nonlinear peak power approach can implement a windowed peak detection algorithm based on the peak (or peaks) instantaneous transmission power of the master radio  218  over the time period. The indication can, for example, be provided to the slave radio  220  via the interface  222 . Operation  820  can accordingly correspond to an embodiment of operation  510 . 
     Operation  830  can include the slave radio  220  determining an allowable transmission power for the slave radio  220  based at least in part on the indication. For example, in some embodiments, the slave radio  220  can reference a lookup table and/or other data structure that can define a first transmission power to use in an instance in which instantaneous transmission power of the master radio  218  exceeded the transmission power threshold, T 1 , at least the threshold number, T 2 , of instances over the period of time, L 1 ; and a second transmission power to use in an instance in which instantaneous transmission power of the master radio  218  did not exceed the transmission power threshold, T 1 , at least the threshold number, T 2 , of instances over the period of time, L 1 . Operation  830  can accordingly correspond to an embodiment of operation  520 . 
     In instances in which it is determined in operation  830  that the allowable transmission power is less than a transmission power being used by the slave radio  220 , the slave radio  220  can be configured to reduce its transmission power in compliance with the allowable transmission power immediately or at least within a relatively short delay tolerance, such as, by way of non-limiting example, within 10 milliseconds. If, however, the allowable transmission power determination of operation  830  indicates that a transmission power being used by the slave radio  220  is less than the allowable transmission power such that an increase in transmission power is permitted, the slave radio  220  can be configured to wait at least a delay period, such as, by way of non-limiting example, 500 milliseconds, before increasing its transmission power to verify that any decrease in transmission power of the master radio  218  resulting in the increased allowable transmission power is not transient. 
     It will be appreciated that in some example embodiments, the method of  FIG. 8  can be extended to consider multiple thresholds for the transmission power of the master radio  218  and/or multiple thresholds for number of instances in which the instantaneous transmission power of the master radio  218  exceed a transmission power threshold. As a non-limiting example, a first transmission power threshold, T 1 _low, and a second transmission power threshold, T 1 _high, can be defined, where T 1 _high&gt;T 1 _low. If there have not been at least T 2  instances in which the instantaneous transmission power exceeded T 1 _low over the last L 1  seconds, a first allowable transmission power can be applied by the slave radio  220 . However, if there have been at least T 2  instances in which the instantaneous transmission power exceeded T 1 _low over the last L 1  seconds, but not T 2  instances in which the instantaneous transmission power exceeded T 1 _high over the last L 1  seconds, a second allowable transmission power can be applied by the slave radio  220 . Finally, if there have been at least T 2  instances in which instantaneous transmission power exceeded T 1 _high over the last L 1  seconds, a third allowable transmission power can be applied by the slave radio  220 . The first allowable transmission power can be greater than the second allowable transmission power, which can, in turn, be greater than the third allowable transmission power. 
     As another example, there can be a different set of thresholds that can be applied for raising the transmission power of the slave radio  220  than for lowering the transmission power of the slave radio  220 , such as to prevent hysteresis. For example, if N≧T 2  for L 1  seconds, the transmission power of the slave radio  220  can be reduced. However, if N&lt;T 3  for and L 2  second period, the allowable transmission power of the slave radio  220  can be increased. The values of T 3  and L 2  can be defined to be equal to T 2  and L 1 , respectively, in some example embodiments. However, in some embodiments, T 3  and L 2  can be tuned so as to prevent hysteresis and/or to reduce the incidence of the total transmission power exceeding the total transmission power limit on an instantaneous basis. For example, L 2  can be defined as a longer time period than L 1  such that transmission conditions can be required to be relatively stable over a longer period of time to increase the transmission power of the slave radio  220  than to decrease the transmission power of the slave radio  220 . Additionally or alternatively, as another example, T 3  can be defined as a lower threshold than T 2  to prevent hysteresis conditions. 
       FIG. 9  illustrates an example architecture  900  for implementing a method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on a nonlinear peak power of a master radio in accordance with some example embodiments. In this regard, the architecture  900  can provide an architecture for performing the method of  FIG. 8  in accordance with some example embodiments. The architecture  900  can include a master radio  902  and slave radio  904 , which can, for example, comprise embodiments of the master radio  218  and slave radio  220 , respectively. The master radio  902  and slave radio  904  can be interfaced via an interface  906 , which can, for example, comprise an embodiment of the interface  222 . 
     The master radio  902  can include a logic block  912 , which can be configured to accept instantaneous transmission power  910  of the master radio  902  as input. The logic block  912  can be implemented as dedicated circuitry, a processor executing program code, a memory storing executable program code, some combination thereof, or the like. In some example embodiments, one or more of processing circuitry  210  or transmission power manger  216  can be configured to implement at least some functionality of the logic block  912 . The logic block  912  can be configured to determine the number of instances, N, over the previous L 1  seconds (e.g., 1 second) that the instantaneous transmission power  910  exceeded a transmission power threshold, T 1 . The logic block  912  can be further configured to determine whether N is greater than or equal to a threshold, T 2 , over the L 1  second period. In this regard, the logic block  912  can, for example, be configured to perform operation  810 . 
     If the logic block  912  determines that N≧T 2  for L 1  seconds, the master radio  902  can indicate this determination (e.g., “YES”) to the slave radio  904 , via interface  906 , which can prompt the slave radio  904  to use a first (e.g., low) transmission power, as described further below. If, however, the logic block  912  determines that N&lt;T 2  for L 1  seconds, the master radio  902  can indicate this determination (e.g., “NO”) to the slave radio  904 , which can prompt the slave radio  904  to use a second (e.g., high) transmission power, as described further below. 
     The slave radio  904  can receive the indication (e.g., “YES/NO” and/or other indication of the determination of the logic block  912 ) that can be provided by the master radio  902 , and can be configured to lookup the indication in a lookup table  916  or other data structure, which can define associations between indications that can be provided by the master radio  902  respective allowable transmission power values. The result of the lookup can accordingly yield the allowable slave transmission power value  918 , which can be used by the slave radio  904 . In this regard, the lookup table  916  can, for example, be used to perform operation  930 . 
     It will be appreciated that the method illustrated in and described with respect to  FIGS. 8 and 9  is provided by way of example, and not by way of limitation. In this regard, the operations performed to enable implementation of a nonlinear peak power concept in accordance with various example embodiments can be distributed among the master radio  218  and slave radio  220  and/or among other components of the apparatus  200  in a different manner than illustrated in and described with respect to  FIGS. 8 and 9 . For example, in some embodiments, the master radio  218  can provide the slave radio  220  with actual instantaneous transmission power values of the master radio  218 , and the slave radio  220  can perform the threshold comparisons, such as determining the number of instances N and determining whether N≧T 2  based on raw instantaneous transmission power values of the master radio  902 , as described with respect to logic block  912  and operation  810 . As another example, in some embodiments, the master radio  218  can provide the slave radio  220  with an indication of when the instantaneous transmission power exceeds a transmission power threshold, and the slave radio can count the number of such instances, N, over a time period, L 1 , and can determine whether N≧T 2 . 
     While the total transmission power of the master radio  218  and slave radio  220  can still exceed total transmission power limit on occasion when using the nonlinear peak power approach discussed with respect to  FIGS. 8 and 9 , the frequency of such instances can be significantly less and, in some scenarios, several orders of magnitude less than the averaging concept discussed with respect to  FIGS. 6 and 7 . However, the transmission power gain in slave radio transmission power compared to prior approaches that assume maximum transmission power of the master radio can be less than when using the averaging concept in some scenarios. 
     In some example embodiments, the master radio  218  can provide the slave radio  220  with an indication of a predicted future transmission power rather than providing information indicative of an actual observed prior and/or current transmission power or characteristic(s) thereof. In such embodiments, the slave radio  220  can determine an allowable transmission power given the predicted future transmission power of the master radio  218  in time to adjust (if appropriate) its transmission power in advance of the transmission by the master radio  218 . Assuming the master radio  218  does not exceed the indicated future transmission power, the slave radio  220  can realize an improved transmission power compared to prior approaches in which the maximum transmission power of the master radio  218  is always assumed by the slave radio  220 , while avoiding instances of exceeding the applicable total transmission power limit on an instantaneous basis as can occur with the approaches discussed with respect to  FIGS. 6-9 . 
       FIG. 10  illustrates a flowchart according to an example method for controlling slave radio transmission power in a multi-radio wireless communication device, such as wireless communication device  102 , based at least in part on a predicted future transmission power of a master radio in accordance with some example embodiments. The method of  FIG. 10  can, for example, be performed by components of the apparatus  200 , architecture  300 , and/or architecture  400 . Thus, for example, one or more of processing circuitry  210 , processor  212 , memory  214 , transmission power manager  216 , proximity sensor  224 , master radio  218 , or slave radio  220  can provide means for performing one or more of the operations illustrated in and described with respect to  FIG. 10 . 
     Operation  1000  can, for example, correspond to an embodiment of operation  500 , and can include the master radio  218  determining a future transmission power of the master radio  218 . In this regard, the master radio  218  of some example embodiments can have advance notice of a predicted future transmission power. For example, in some embodiments, the master radio  218  can autonomously set its transmission power within limits, such as any applicable total transmission power limit on the device and/or a maximum transmission power capability of the master radio  218 , and can determine its transmission power sufficiently in advance of a transmission to alert the slave radio  220 . As another example, in some embodiments, the master radio  218  can be assigned a transmission power in advance of a transmission, such as by a higher layer entity of the wireless communication device and/or by another device or entity with which the wireless communication device can be communicating. For example, in some embodiments in which the slave radio  220  is a cellular radio, a serving cellular base station, such as base station  104 , can configure a transmission power to be used for a given transmission time interval (TTI) in advance of the TTI. For example, in LTE systems, the serving evolved node B can inform a wireless communication device, such as wireless communication device  102 , of a transmission power value to use for a scheduled transmission approximately 4 milliseconds in advance of the transmission. 
     Operation  1010  can include the master radio  218  providing information indicative of the future transmission power of the master radio  218  to the slave radio  220 , such as via the interface  222 . In this regard, operation  1010  can, for example, correspond to an embodiment of operation  510 . In some example embodiments, the information can comprise the actual predicted future transmission power. However, in some embodiments, such as that illustrated in and described below with respect to  FIG. 11 , the master radio  218  can determine whether the future transmission power exceeds a threshold transmission power and, if so, can provide an indication to the slave radio  220  to apply a transmission power cap such that the slave radio  220  backs off its transmission power to comply with a total transmission power limit. 
     Operation  1010  can be performed sufficiently in advance of the future transmission to enable the slave radio  220  to adjust its transmission power, if appropriate. For example, in some embodiments in which the master radio  218  is a cellular radio and receives an indication of the transmission power to use from a serving base station approximately 4 milliseconds in advance of the transmission, it can take approximately 2 milliseconds to process the instruction and the slave radio  220  can be provided with the indication of the future transmission power approximately 2 milliseconds in advance of the transmission by the master radio  218 . 
     Operation  1020  can include the slave radio  220  determining an allowable transmission power for the slave radio  220  based at least in part on the information. In this regard, operation  1020  can correspond to an embodiment of operation  520 . 
       FIG. 11  illustrates an example architecture and a corresponding flowchart according to an example method for controlling slave radio transmission power in a multi-radio wireless communication device based at least in part on a predicted future transmission power of a master radio in accordance with some example embodiments. More particularly,  FIG. 11  illustrates an example embodiment of the method of  FIG. 10  in which a cellular radio  1102  is configured as a master radio and a WLAN radio  1104  is configured as the slave radio, and the cellular radio  1102  instructs the WLAN radio  1104  whether to apply a transmission power cap in advance of a transmission based on a predicted future transmission power of the cellular radio  1102 . 
     The cellular radio  1102  can, for example, be an embodiment of the master radio  218 . The WLAN radio  1104  can similarly be an embodiment of the slave radio  220 . The cellular radio  1102  and WLAN radio  1104  can be interfaced with a transmission power manager  1106 , which can, for example, be an embodiment of transmission power manager  216 . The transmission power manager  1106  can configure the cellular radio  1102  with a transmission power threshold, Pc_Hi. The transmission power manager  1106  can be further configured to configure the WLAN radio  1104  with a transmission power cap, WLAN_Cap to be applied when indicated by the cellular radio  1102 . The values of Pc_Hi and WLAN_Cap can, for example, be defined in some embodiments as a function of factors, such as a frequency band being used for transmission by the cellular radio  1102  and/or by the WLAN radio  1104 , a frequency or frequencies within a band being used for transmission by the cellular radio  1102  and/or by the WLAN radio  1104 , the device antenna configurations (e.g., placement of antennas within the device, an antenna being used for transmission when multiple antennas are available, and/or other antenna configuration qualities), a proxy state, a MIMO mode being used by the cellular radio  1102  and/or by the WLAN radio  1104  (if applicable), and/or other factors that can affect the radio frequency absorption rate, and thus the applicable total transmission power limit. Alternatively, in some embodiments, Pc_Hi and WLAN_Cap can be defined as static values regardless of the actual operating conditions. 
     Pc_Hi and WLAN_Cap can be defined such that if a transmission power level of the cellular radio  1102  is to exceed Pc_Hi, a reduction in transmission power of the WLAN radio  1104  in accordance with the WLAN_Cap value can be required to satisfy the total transmission power limit. However, if the transmission power level of the cellular radio does not exceed Pc_Hi, the WLAN radio  1104  can be permitted to transmit without capping its transmission power. In this regard, Pc_Hi and WLAN_Cap values can be selected in some example embodiments such that the total transmission power limit is never exceeded, even on a transient basis. 
     The cellular radio  1102  can determine a Predicted P_Cell value, which can be the predicted future transmission power, such as can be configured by a serving base station. At operation  1122 , the cellular radio  1102  can determine whether P_Cell is greater than Pc_Hi. If it is determined that P_Cell is greater than Pc_Hi, the method can proceed to operation  1122 , in which the cellular radio  1102  can determine if the last message sent to the WLAN radio  1104  was an instruction to apply the WLAN_Cap (e.g., Apply_WLAN_Cap). If the last message did not indicate to apply the WLAN_Cap, such as if a message to stop applying the WLAN_Cap (e.g., Remove_WLAN_Cap) was the last instruction sent to the WLAN radio  1104 , the method can proceed to operation  1124 , which can include the cellular radio  1102  sending an Apply_WLAN_Cap message to the WLAN radio  1104 . If, however, it is determined at operation  1122  that the last message was Apply_WLAN_Cap, the method can terminate until the next Predicted P_Cell value is received. 
     Returning to operation  1122 , if it is instead determined that P_Cell is not greater than Pc_Hi, the method can proceed to operation  1126 , in which the cellular radio  1102  can determine if there have been L_Low consecutive seconds where P_Cell has been less than a transmission power threshold, Pc_Low. In this regard, operation  1126  can comprise determining whether certain thresholds have been met for removing the WLAN_Cap and/or otherwise permitting an increase in the transmission power of the WLAN radio  1104 . In some embodiments, Pc_Low can be set equal to Pc_Hi. However, in some embodiments, Pc_Low can be set to a lower value than Pc_Hi as a safeguard to reduce the chance of exceeding the total transmission power limit and to prevent hysteresis conditions. L_Low can similarly be set to any desired period so as to avoid increasing the transmission power of the WLAN radio  1104  in response to a transient change in condition. As a non-limiting example, in some embodiments L_Low can be set to 500 milliseconds. 
     If it is determined at operation  1126  that the condition is not satisfied, the method can terminate until the next Predicted P_Cell value is received. However, if it is determined at operation  1126  that the condition is satisfied, the method can proceed to operation  1128 , which can include the cellular radio  1102  determining if the last message sent to the WLAN radio  1104  was an instruction to remove the WLAN Cap (e.g., Remove_WLAN_Cap). If the last message sent to the WLAN radio  1104  did not indicate to remove the WLAN_Cap, such as if a message to apply the WLAN_Cap (e.g., Apply_WLAN_Cap) was the last instruction sent to the WLAN radio  1104 , the method can proceed to operation  1130 , which can include the cellular radio  1102  sending a Remove_WLAN_Cap message to the WLAN radio  1104 . If, however, it is determined at operation  1128  that the last message was Remove_WLAN_Cap, the method can terminate until the next Predicted P_Cell value is received. 
     On the WLAN radio  1104  side, if the WLAN radio  1104  receives an instruction from the cellular radio  1102 , the WLAN radio  1104  can determine whether the message indicates to apply the WLAN_Cap or to remove the WLAN_Cap, as illustrated by operations  1132  and  1134 . If the message indicates that the WLAN_Cap can be removed, the WLAN radio  1104  can cease application of the WLAN_Cap and can transmit at a higher power level, as illustrated in operation  1136 . 
     If, however, the message has instructed the WLAN radio  1104  to apply the WLAN_Cap, the WLAN radio  1104  can determine if there is a packet in progress (e.g., a packet for which transmission will continue into the future transmission of the cellular radio  1102  for which the WLAN_Cap is to be applied), at operation  1138 . Operation  1138  can, for example, include determining if there is a media access control (MAC) protocol data unit (PDU) in progress. If it is determined that there is a packet in progress, the method can include operation  1140 , which can include the WLAN radio  1104  killing the packet within a time limit, such as by way of non-limiting example, within 1 millisecond. Killing the packet can include stopping transmission of the packet before completion to avoid exceeding the total transmission power limit. If, however, there is not such a packet in progress, operation  1140  can be omitted. Operation  1142  can include the WLAN radio  1104  applying the WLAN_Cap. 
     While various example embodiments have been described with respect to two radios, it will be appreciated that the techniques and architectures illustrated and described herein can be applied mutatis mutandis to wireless communication devices including three or more radios that can transmit concurrently and which can be subject to a jointly applied total transmission power limit. In this regard, there can be multiple slave radios, which can, for example, be prioritized such that each slave radio determines its allowable transmission power in priority order based on information received from a master radio and/or a higher priority slave radio. In this regard, a first slave radio having a higher priority than a second slave radio can function as a master radio to the second slave radio. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as a computer readable medium (or mediums) storing computer readable code including instructions that can be performed by one or more computing devices. The computer readable medium may be associated with any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code may be stored and executed in a distributed fashion. 
     In the foregoing detailed description, reference was made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. For example, it will be appreciated that the ordering of operations illustrated in the flowcharts is non-limiting, such that the ordering of two or more operations illustrated in and described with respect to a flowchart can be changed in accordance with some example embodiments. As another example, it will be appreciated that in some embodiments, one or more operations illustrated in and described with respect to a flowchart can be optional, and can be omitted. 
     Further, the foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of specific embodiments are presented for purposes of illustration and description. The description of and examples disclosed with respect to the embodiments presented in the foregoing description are provided solely to add context and aid in the understanding of the described embodiments. The description is not intended to be exhaustive or to limit the described embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications, alternative applications, and variations are possible in view of the above teachings. In this regard, one of ordinary skill in the art will readily appreciate that the described embodiments may be practiced without some or all of these specific details. Further, in some instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments.

Metadata:
Filing Date: 20140520
Publication Date: 20171003
Grant Date: 20171003
Priority Date: 20140520
Inventors: SEN INDRANIL
NARANG MOHIT
JADHAV DIGVIJAY ARJUNRAO
BURCHILL WILLIAM S.
MAJJIGI VINAY R.
FLYNN PAUL V.
ZHAO WEN
SEMERSKY MATTHEW L.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W52/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/346", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W84/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W84/042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W88/06", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/367", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/346", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W84/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/34", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W84/042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/346", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 54557045