Patent Publication Number: US-11031988-B2

Title: Performance-based antenna selection for user devices

Description:
RELATED APPLICATION 
     This application claims priority to, and is a continuation of, U.S. Utility patent application Ser. No. 15/844,358, filed on Dec. 15, 2017, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Computing or electronic devices often communicate with other devices or access resources via wireless networks. Wireless networks are typically provided and administered by base stations of the network with which a device establishes a connection to receive or transmit information. At a physical level, this information is communicated as signals transmitted or received through an antenna of the device. Performance of the antenna, however, can be degraded due to proximity or contact with objects, such as a hand or head of a user. To mitigate these conditions, some devices include multiple antennas that a radio of the device can switch between when a connection to the base station is impaired. 
     Switching from one antenna of the device to another, however, may not improve the connection with the base station. For example, a user holding a phone in a particular fashion may partially detune first antenna and completely obscure or detune a second antenna. If the device switches from the first antenna having marginal performance to the second antenna with little or no reception, the connection with the base station may be severely impaired or lost completely. For real-time or latency sensitive applications, such as voice calls or media streams, further impairment or loss of the connection with the base station can affect performance of the application or impact user experience. In some cases, the application may freeze or crash, forcing a user to restart the application once the device returns to the first antenna. As such, switching the radio between antennas of a device may further impair communication performance and negatively affect various device operations. 
     SUMMARY 
     The present disclosure describes apparatuses and methods of performance-based antenna selection for user devices. In some aspects, a method couples a transceiver of a device to a first antenna to enable communication via the first antenna. The method may also couple a second receiver (e.g., diversity receiver) of the device to a second antenna to enable reception via the second antenna. A third receiver (e.g., a multiple-input receiver) of the device is coupled to a third antenna to enable monitoring of performance of the third antenna. The method then compares the performance of the third antenna to performance of the first antenna and selects, based on the comparison, the first antenna or the third antenna by which to communicate. The transceiver of the device is then coupled to the antenna that is selected based on performance for subsequent communication. 
     In other aspects, an apparatus for communicating over a wireless network comprises at least three antennas that include a first antenna, a second antenna, and a third antenna. The apparatus also includes a transceiver having a transmitter and a first receiver, as well as a second receiver, a third receiver, and a diversity controller. The diversity controller is configured to couple the transceiver to the first antenna to enable communication via the first antenna and couple the second receiver to the second antenna to enable reception via the second antenna. The diversity controller couples the third receiver to the third antenna to enable monitoring of performance of the third antenna. The diversity controller then compares the performance of the third antenna to performance of the first antenna and selects, based on the comparison, the first antenna or the third antenna by which to communicate. For subsequent communication, the diversity controller couples the transceiver to the selected antenna such that the transceiver communicates via the antenna selected based on performance. 
     In yet other aspects, a system-on-chip comprises a transceiver module that includes a transmitter module and a first receiver module, as well as a second receiver module and a third receiver module. The system-on-chip also includes at least one output configured to control radio-frequency (RF) switch circuitry, a processor core, and a hardware-based memory having instructions that, responsive to execution by the processor core, implement a diversity controller. The diversity controller is implemented to cause coupling of the transceiver module to a first antenna to enable communication via the first antenna and cause coupling of the second receiver module to a second antenna to enable reception via the second antenna. The diversity controller also causes coupling of the third receiver module to a third antenna to enable monitoring of performance at the third antenna. Performance of the third antenna is compared by the diversity controller to performance of the first antenna, and the diversity controller selects, based on the comparison, the first antenna or the third antenna by which to communicate. The diversity controller then causes coupling of the transceiver module to the selected antenna to enable the transceiver to communicate via the selected antenna. 
     The details of one or more implementations are set forth in the accompanying drawings and the following description. Other features and advantages will be apparent from the description and drawings, and from the claims. This summary is provided to introduce subject matter that is further described in the Detailed Description and Drawings. Accordingly, this summary should not be considered to describe essential features nor used to limit the scope of the subject matter of the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The details of one or more aspects of performance-based antenna selection are described with reference to the following drawings. The use of same or similar reference numbers throughout the description and the figures may indicate like features or components: 
         FIG. 1  illustrates an example operating environment that includes a user device having multiple antennas and capable of implementing one or more aspects of performance-based antennas selection. 
         FIG. 2  illustrates an example network environment in which the user device can communicate via a wireless network provided by a base station. 
         FIG. 3  illustrates an example configuration of a radio-frequency (RF) circuit capable of implementing aspects of performance-based antenna selection. 
         FIG. 4  illustrates another example of an RF circuit capable of implementing aspects of performance-based antenna selection. 
         FIG. 5  illustrates an example method for selecting an antenna to use for communication based on performance. 
         FIG. 6  illustrates an example method for monitoring antenna performance and selecting an antenna based on the monitored performance. 
         FIG. 7  illustrates an example method for coupling multiple antennas to respective communication modules based on antenna performance. 
         FIG. 8  illustrates an exemplary configuration of an electronic device in which techniques of performance-based antenna selection may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     Conventional techniques for antenna switch diversity in devices with three or more antennas typically implement switching without characterization or knowledge of a previously-inactive antenna&#39;s performance. In other words, when a conventional communication controller detects that performance of one antenna is impaired, the communication controller blindly switches a transceiver interface to other antennas of the device until performance improves. Blindly switching to the other antenna, however, may not improve performance as described above when a user or other object has detuned or blocked the other antenna worse than the antenna currently in use. As such, conventional communication controllers often cause further degradation or impairment of communications with a base station when blindly switching through different antennas of the device. 
     By way of example, consider a device that implements a conventional type of antenna switch diversity with three antennas. Typically, such a device will have a transceiver with a first receiver and a second receiver for diversity reception. In a default state, the transceiver is connected to a first antenna and the second receiver is connected to a second antenna, with the third antenna left unconnected from either receiver. To implement conventional antenna diversity switching, the communication controller sets diversity switches of the device such that the third antenna is connected to the transceiver and the first antenna is disconnected from the transceiver. With the third antenna connected to the transceiver, the communication controller measures performance of the third antenna. If the performance of the third antenna is better than that of the first antenna, then the communication controller leaves the setting of the diversity switches. Alternately, if performance of the third antenna is not better than that of the first antenna, the communication controller restores previous settings of the diversity switches to the default state. 
     As noted, this conventional antenna diversity switch scheme can be problematic because the third antenna must be connected to the transceiver in order to measure the performance of the third antenna. For example, if a user&#39;s hand is positioned against or over the third antenna such that performance is poor (e.g., worse than that of the first antenna), the transceiver is coupled to a poorly performing antenna for the duration of the diversity switch and measurement operations. This may result in the loss of transmit and receive signals of the transceiver, causing a loss of data or interruption of service. For latency sensitive applications, such as voice calls or media streaming, this data loss may cause a voice call to be dropped or freeze a video streaming application. 
     The present disclosure describes aspects of performance-based antenna selection for user devices. One or more of the described aspects may be implemented to monitor or measure performance of an antenna before the antenna is coupled to a transceiver (e.g., primary transceiver) of a user device. For example, in user devices with three antennas, a third antenna not currently being used for communication can be coupled to a third receiver of the device before diversity switching operations are implemented. In some cases, the third receiver is embodied as part of a multiple-input receiver module or a multiple-input multiple-output (MIMO) receiver module that is idle or not in use while a primary transceiver of the device operates. By monitoring or measuring respective performance of the antennas before the switching operations are implemented, a best-performing antenna can be coupled to the primary transceiver of the device, which may ensure that communication link quality is improved (or at least maintained) through the diversity switch operations. 
     In some aspects, a multi-antenna user device includes a transceiver having a transmitter and first receiver (e.g., primary receiver), as well as a second receiver and third receiver. In some cases, the third receiver is embodied as part of a multiple-input receiver or MIMO receiver module of the device. The multi-antenna user device also includes at least three antennas and radio-frequency (RF) switching circuitry that enables the antennas to be coupled to two or more of the receivers. A diversity controller of the device couples transceiver to the first antenna to enable communication via the first antenna and couples the second receiver to the second antenna to enable reception via the second antenna. While the first antenna and second antenna may be used to communicate, the third receiver is coupled to a third antenna to enable monitoring of performance of the third antenna. Based on a comparison of respective performance of the first antenna and the third antenna, the first antenna or third antenna is coupled the transceiver to enable subsequent communication. By monitoring and comparing respective performance of the antennas before an antenna switch is implemented, a better-performing antenna of the two antennas can be selected for coupling to the transceiver without impacting communication performance. 
     The following discussion describes an operating environment, techniques that may be employed in the operating environment, and an electronic device in which components of the operating environment can be embodied. In the context of the present disclosure, reference is made to the operating environment by way of example only. 
     Operating Environment 
       FIG. 1  illustrates a user device  102  in which performance-based antenna selection can be implemented. The user device  102  is illustrated as a non-limiting example device and is shown here as a smart-phone. Although illustrated as a smart-phone, the user device  102  may be implemented as any suitable type of device, such as a tablet computer, laptop computer, gaming system, smart-glasses, smart-watch, multimedia dongle, set-top box, vehicle-based computing system, navigation device, home automation device, security system controller, or the like. Note that the user device can be wearable, non-wearable but mobile, or relatively immobile (e.g., broadband router and smart-appliances). 
     The user device  102  includes one or more computer processors  104  and computer-readable media  106 , which may include memory media or storage media. The processor  104  may be implemented as a general-purpose processor (e.g., of a multicore central-processing unit (CPU) or application processor (AP)), an application-specific integrated circuit (ASIC), or a system-on-chip (SoC) with other components of the user device  102  integrated therein. The computer-readable media  106  can include any suitable type of memory media or storage media, such as read-only memory (ROM), programmable ROM (PROM), random access memory (RAM), dynamic RAM (DRAM), static RAM (SRAM), or Flash memory. In the context of this discussion, the computer-readable media  106  is implemented as at least one hardware-based or physical storage device, which does not include transitory signals or carrier waves. Applications, firmware, and/or an operating system (not shown) of the user device  102  can be embodied on the computer-readable media  106  as processor-executable instructions, which may be executed by the processor  104  to provide various functionalities described herein. In this example, the computer-readable media  106  also includes a diversity controller  108  and performance monitor  110 , which are described throughout the disclosure. 
     The user device  102  also includes transmitters  112  and receivers  114 , which may be implemented separately or combined as one or more transceivers that are capable of implementing both signal-receiving and -transmitting functions. The transmitters  112  and receivers  114  may be configured to communicate via any suitable type of wireless network, such as a local-area-network (LAN), a wireless local-area-network (WLAN), a personal-area-network (PAN), a wide-area-network (WAN), cellular network, a peer-to-peer network, point-to-point network, a mesh network, and so on. In some aspects, one or more of the transmitters  112  and receivers  114  are configurable to communicate in accordance with a Global System for Mobile Communications (GSM) standard, Third Generation (3G) standard, Worldwide Interoperability for Microwave Access (WiMax) protocol, High Speed Packet Access (HSPA) protocol, Evolved HSPA (HSPA+) protocol, Long-Term Evolution (LTE) standard, LTE Advanced standard, Fifth Generation (5G) standard, or the like. 
     An RF front end  116  of the user device  102  includes signal conditioning and switching circuitry that enables coupling of various ones of the transmitters  112  and receivers  114  to, or with, antennas  118  of the user device. The RF front end may include any suitable combination of circuitry, such as filters, amplifiers, diplexers, switches, multiplexers, baluns, or the like. The antennas  118  may include any number or type of antennas, which may be positioned on or proximate an outer surface of the user device  102 . In this example, the antennas  118  are shown as four separate antennas  118 - 1  through  118 - 4  that are located proximate edges and/or corners of the user device  102 . Any or all of the antennas  118 - 1  through  118 - 4  may be tuned for a single frequency band or multiple frequency bands. For example, one of the antennas  118  may be tuned for multiple frequency bands that range from approximately 700 MHz to 960 MHz, 1.4 GHz to 1.5 GHz, 1.7 GHz to 2.2 GHz, 2.3 GHz to 2.7 GHz, 3.4 GHz to 3.6 GHz, and so on. 
       FIG. 2  illustrates an example network environment  200  in which the user device  102  can communicate via a wireless network provided by a base station  202 , such as an enhanced Node B of an LTE network. Generally, the user device  102  communicates with the base station  202  via a wireless link  204  established or managed in accordance with various networking protocols or standards. The wireless link  204  may include an uplink  206  by which the user device  102  transmits data or control information to the base station  202  and a downlink  208  by which the base station  202  transmits data or control information to the user device  102 . As noted, the wireless link  204  may be implemented in accordance with at least one suitable protocol or standard, such as a GSM standard, a WiMAX standard, an HSPA protocol, an Evolved HSPA protocol, an LTE standard, an LTE-A standard, a 5G standard, any standard promulgated or supported by the 3rd Generation Partnership Project (3GPP), and so forth. Although the wireless link  204  is shown or described with reference to a separate uplink  206  or downlink  208 , various types of communications between the user device  102  and the base station  202  may also be referred to as a wireless communication, a wireless connection, a wireless association, a frame exchange, a communication link, or the like. 
     With reference to the user device  102  and as indicated by the directionality of the uplink  206  and downlink  208 , the uplink  206  may include signals transmitted from the user device  102  to the base station  202 . Alternately, the downlink  208  may include signals transmitted by the base station  202  for reception by the user device  102 . In some aspects, the base station  202  or another base station may transmit downlink signals in a frequency band for which multiple antennas  118  of the user device  102  are configured to operate. As such, the diversity controller  108  of the user device  108  may connect a receiver  114  of the user device  102  to the antenna  118  with optimal reception to improve quality of the wireless link  204  or communication performance. Alternately or additionally, multiple receivers  114  (e.g., primary and diversity receivers) of the user device may be connected to multiple respective antennas  118  such that the multiple receivers  118  can receive a downlink signal. 
     Generally, the wireless link  204  enables the user device  102  to access resources, other networks, or other devices through the base station  202 . As shown in  FIG. 2 , the base station  202  can provide access to a network  210  (e.g., the Internet) that is connected to the base station via a backhaul link  212  (e.g., a fiber network). As such, applications or functions of the user device  102  may request or access data from the network  210  (e.g., video or voice content), which is received via signals of the downlink  208 . With respect to a multi-cell wireless network, the base station  202  may be implemented to realize or manage one cell of the wireless network that includes multiple other base stations that each realize other respective cells of the wireless network. As such, the base station  202  may communicate with a network management entity or other base stations to coordinate connectivity or hand-offs of user devices within or across the cells of the wireless network. 
       FIG. 3  illustrates an example configuration of an RF circuit  300  that is capable of implementing aspects of performance-based antenna selection. The components and architecture of RF circuit  300  are presented as a non-limiting example of ways in which performance-based antenna selection can be implemented. As such, the aspects described herein may be applied or extended to any suitable RF circuit to implement various features of performance-based antenna selection. Further any coupling or connection between various components may be direct or indirect, such as made through one or more intervening components. For visual brevity and/or clarity, some unrelated or redundant components (e.g., filters or amplifiers) or circuitry may also be omitted from this or other circuit diagrams. Such an omission is not to be construed as limiting, but rather one example of the many ways in which various aspects of the described circuitry may be used or applied to implement performance-based antenna selection. In other words, the aspects (e.g., circuitry) described herein may also be implemented with any suitable number or combination of filters, amplifiers, and/or additional or separate RF switches. 
     In this example, a device is implemented with three communication modules that include a primary transceiver  302 , a diversity receiver  304 , and a multiple-input multiple-output (MIMO) receiver  306 , which are coupled to antennas  118  by the RF front end  116 . The communication modules may be implemented as separate hardware- or software-based modules, such as blocks or modules of one or more software-defined radios (SDRs). As such, any of the structure or functionality described herein may be provided by or configurable (e.g., for different communication standards or protocols) through execution of firmware or instructions by a processor core of a communication module. Alternately or additionally, each communication module may include, for each port or connection, a respective transmit chain or receive chain and/or additional front end circuitry to process various communication signals (e.g., transmit signals or receive signals). 
     The primary transceiver  302  includes a first transmitter  308  and a first receiver  310  for communicating data of the device. The primary transceiver  302  can be configured to communicate in multiple frequency bands, and includes a low-band port  312 , a mid-band port  314 , and a high-band port  316  for transmitting. In some cases, the ports also support reception of a complimentary band such that two of the ports permit the primary transceiver to communicate bi-directionally over a similar or same frequency band. For example, port  314  may also support high-band reception and port  316  may also support mid-band reception. 
     The diversity receiver  304  includes a second receiver  318  of the device for receiving signals. In some cases, signals or information provided by the diversity receiver  304  are used to enhance or improve reception performance of the primary transceiver  302 . As such, the diversity receiver  304  may also be configured for multiband operation and include a low-band port  320 , a mid-band/high-band port  322 , and a high-band/mid-band port  324 . Alternately or additionally, the diversity receiver  304  may include other types of receiver modules, such as a Global Positioning System (GPS) receiver to provide navigational or position data. 
     To support MIMO communication, the device also includes the MIMO receiver  306  that is implemented as a third receiver  326 . The MIMO receiver  306  may support reception of any suitable number of spatial streams, and in this example includes four ports  328  through  334  to receive four respective spatial streams. In aspects of performance-based antenna selection, the MIMO receiver  306  can also be used to monitor or measure performance of an antenna that is not coupled or connected to another receiver. For example, the performance monitor  110  may query the MIMO receiver  306  for an indication of performance for one the antennas  118 - 1  through  118 - 4  that is not connected to the primary transceiver  302  or the diversity receiver  304 . The MIMO receiver  306  or another receiver may provide or indicate antenna performance with any suitable metric or measurement, such as a received signal strength, receive signal quality, carrier-to-interference ratio, signal-to-noise ratio, bit-error rate, packet-error rate, or the like. Alternately or additionally, the performance monitor  110  may query or poll any or all of the receivers to determine performance indicators or metrics for one or more of the antennas  118 . 
     In some aspects, the MIMO receiver  306  can be enabled or used as a measurement receiver for a minimal amount of time, such as an amount of time that corresponds to detecting a change in user interaction (e.g., a few milliseconds to a few seconds). For example, the MIMO receiver  306  can be used to detect a hand or head of a user moving into or out of near-proximity of one of the antennas  118  that is not connected to the primary receiver  302  or diversity receiver  304 . When not employed for MIMO operation or as a measurement receiver, MIMO receiver  306  can be turned off or placed in a low-power state to reduce power consumption. 
     Generally, the RF front end  116  enables coupling of one or more of the antennas  118  to a respective one of the primary transceiver  302 , diversity receiver  304 , or MIMO receiver  306 . In this example, the RF front end  116  includes double-pole double-throw (DPDT) RF switches  336  and  338 , which can be controlled or managed by the diversity controller  108  to implement aspects of performance-based antenna selection. In some cases, the RF switch  336  is configured to couple (or switch) low-band receiver ports between the antennas  118  and the RF switch  338  is configured to couple mid-band and/or high-band receiver ports between the antennas  118 . To enable routing of communication signals in or based on different frequency bands, the RF front end  116  includes diplexers  340  through  350  as shown in  FIG. 3 . In some aspects, the diplexers  340  through  346  are coupled to a respective one of the antennas  118 - 1  through  118 - 4  such that high-band or ultra-high-band communication signals are routed to ports  328  through  334  of the MIMO receiver  306 . As such, the MIMO receiver  306  may monitor or measure performance of an antenna in a frequency that is different from a frequency for which the antenna is selected for communication. The diplexers  348  and  350  can also be coupled to the RF switches  336  and  338  such that low-band signals communicated through the antennas  118 - 1  and  118 - 2  are routable to the primary transceiver  302  and the diversity receiver  304 . 
     In some cases, the diplexers  344  and  350  are coupled to the RF switch  338  such that mid-band and/or high-band signal communicated through either of the antennas  118 - 1  and  118 - 3  are routable to the primary transceiver  302 . By so doing, the MIMO receiver  306  may be used by the diversity controller  108  and/or the performance monitor  110  to monitor performance of antenna  118 - 1  or  118 - 3  while the other of the antennas is coupled to or being used by the primary transceiver  302 . This may enable the diversity controller  110  to monitor performance of an antenna before diversity switch operations are implemented, thereby ensuring that communication performance can be maintained or improved by a diversity switch operation based on antenna performance. 
       FIG. 4  illustrates another example of an RF circuit  400  that is capable of implementing aspects of performance-based antenna selection. In this example, antenna diversity switching is enabled by a triple-pole triple-throw (TPTT) RF switch  402 , which is managed or controlled by the diversity controller  108 . Although shown in association with entities described with reference to  FIG. 1  or  FIG. 3 , the RF circuit  400  may be implemented with any suitable number and/or combination of components, such as antennas or receivers. As shown in  FIG. 4 , the RF switch  402  is coupled to the primary transceiver  302  at a port  404 , the diversity receiver  304  at a port  406 , and the MIMO receiver  306  at a port  408 . Each of the ports  404  through  408  may represent a port of a given receiver that is configured to operate over one or more particular frequency bands, such as approximately 700 MHz to 960 MHz, 1.4 GHz to 1.5 GHz, 1.7 GHz to 2.2 GHz, 2.3 GHz to 2.7 GHz, 3.4 GHz to 3.6 GHz, and so on. 
     In some aspects, the RF switch  402  of the RF circuit  400  enables the diversity controller  108  to couple any of the antennas  118 - 1  through  118 - 3  to the primary transceiver  302 , the diversity receiver  304 , or the MIMO receiver  306 . The RF circuit  400  also includes a performance monitor  110  to measure performance of the antenna  118 - 1 , antenna  118 - 2 , and/or antenna  118 - 3 . For example, the performance monitor  110  can monitor a performance of the antenna  118 - 3  while the primary transceiver  302  is coupled to the antenna  118 - 1  and the diversity receiver  304  is coupled to the antenna  118 - 2 . The performance monitor  110  may also query or poll the primary transceiver  302  or the diversity receiver  304  for performance indicators associated with the antenna  118 - 1  or  118 - 2 . To implement performance-based antenna selection, the diversity controller  108  can compare the respective performance of each of the antennas  118 - 1  through  118 - 3  and select the antenna  118  with the best performance for coupling to the primary transceiver  302 . Alternately or additionally, the diversity controller  108  can couple the antenna  118  with the next best performance to the diversity receiver  304 , and couple the antenna  118  with the lowest performance to the MIMO receiver  306 . By so doing, antenna switch diversity can be implemented based on antenna performance to improve communication link quality, such as when one antenna becomes impaired, blocked, detuned, or the like. 
     Example Methods of Performance-Based Antenna Selection 
       FIGS. 5-7  depict example methods of performance-based antenna selection for user devices. These methods are shown as sets of blocks that specify operations performed but are not necessarily limited to the order or combinations shown for performing the operations by the respective blocks. For example, operations of different methods may be combined, in any order, to implement alternate methods without departing from the concepts described herein. In portions of the following discussion, the methods (or techniques) may be described with reference to various entities of  FIGS. 1-4  or  FIG. 8 , reference to which is made by way example only. The methods or techniques are not limited to performance by one entity or multiple entities operating on one device, or those described with reference to the figures. 
       FIG. 5  illustrates an example method  500  for selecting an antenna to use for communication based on performance, including operations performed by the diversity controller  108  and/or performance controller  110 . In some aspects, operations of the method  500  may be implemented by a multi-antenna user device to improve quality of a communication link with a base station. 
     At  502 , a transceiver of a device is coupled to a first antenna to enable communication via the first antenna. The transceiver includes a transmitter and a first receiver of the device, and may be implemented as a multiband transceiver module or SDR. In some cases, the transceiver of the device is a primary transceiver that is configured to communicate in accordance with one or more wireless networking standards or protocols. Communication via the first antenna may include the transmission of signals as part of an uplink or the reception of other signals as part of a downlink. 
     At  504 , a second receiver of the device is coupled to a second antenna to enable reception via the second antenna. The second receiver may be a diversity or secondary receiver of the device configured to receive downlink signals in coordination with a first receiver or primary transceiver of the device. In some cases, the second receiver is configured to receive downlink signals in a same or similar frequency band to that of the first receiver. Alternately or additionally, the second receiver may be configured as part of a transceiver or MIMO receiver of the device. 
     At  506 , a third receiver of the device is coupled to a third antenna to enable monitoring of performance of the third antenna. The third receiver may be coupled to the third antenna via a diplexer or RF switch. The third receiver can be implemented as a MIMO receiver that is capable of receiving multiple spatial streams of information. In some cases, the third antenna is coupled to a port of the third receiver that is configured to operate in a frequency band that is different from frequency bands in which another transceiver or receiver of the device is configured to operate. Alternately, the third antenna may be coupled to a port of the third receiver that is configured to operation in a same or similar frequency band as another transceiver or receiver of the device. 
     At  508 , the performance of the third antenna is compared to performance of the first antenna. The performance of the third antenna or the first antenna may be monitored, measured, or received from the third receiver or the first receiver. In some cases, an indication of the performance of the third antenna or the first antenna is received from a performance monitor implemented by the device or a communication module thereof. Alternately or additionally, the performance of the third antenna or the first antenna can be compared with a performance of the second antenna. 
     At  510 , the first antenna or third antenna is selected to use for communication based on the comparison of respective performance. By comparing respective antenna performance, a diversity controller can select the antenna with better performance for subsequent communication. In aspects of performance-based antenna selection, an antenna can be selected for diversity switching before a primary transceiver of a device is disconnected from an antenna. This can be effective to prevent loss of reception due to connecting a transceiver to an antenna with worse performance, which is a common issue with conventional antenna diversity switching. 
     At  512 , the transceiver of the device is coupled to the selected antenna to enable subsequent communication via the selected antenna. The transceiver may be coupled to the selected antenna via any suitable type of circuit or switch, such as a DPDT RF switch or TPTT RF switch. In some cases, coupling the transceiver to the selected antenna is effective to improve quality of a communication link or wireless link. In such cases, improving the quality of the communication link can prevent disruption of data or voice services, thereby enabling user applications or device functions to continue when one antenna of a device is blocked or impaired. 
       FIG. 6  illustrates an example method  600  for monitoring antenna performance and selecting an antenna based on the monitored performance, including operations performed by the diversity controller  108  and/or performance controller  110 . In some aspects, operations of method  600  may be implemented to adaptively connect a primary transceiver of a user device to a best-performing antenna as reception conditions vary. 
     At  602 , signals are communicated via a transceiver of a device that is coupled to a first antenna of the device. The transceiver of the device includes a transmitter and a first receiver of the device, which may be configured as a multiband transceiver for communication in multiple frequency bands. In some cases, the signal communicated include downlink signals and/or uplink signals of a communication link with a base station of a cellular network. Alternately or additionally, the transceiver may measure or characterize performance of the first antenna based on the signals received through the first antenna. 
     At  604 , signals are received via a second receiver of the device that is coupled to a second antenna of the device. The signals received via the second antenna may be the same or part of the signals received via the first antenna. In other words, the second receiver can be implemented as a diversity receiver for communications of a primary transceiver to improve communicative performance of the device. Alternately or additionally, the second receiver may be implemented as part of another transceiver or a MIMO receiver of the device. 
     At  606 , performance of a third antenna is monitored via a third receiver of the device that is coupled to the third antennas and not communicating. In some communication configurations, the third antenna and/or the third receiver are not actively involved in the transmission or reception of signals. For example, a device use the transceiver and second receiver to communicate with a base station while the third antenna, or diplexer output associated with the third antenna, is not connected to transceiver or second receiver. In such cases, the third receiver can be used to monitor or measure performance of the third antenna, such as before diversity switch operations are to occur. During other times, such as when not monitoring or measuring, the third receiver can be turned off, disabled, or placed in a reduced-power state (e.g., idle or sleep state) to conserve power. Alternately or additionally, the third receiver may be implemented as part of another transceiver (e.g., with a transmitter) or a MIMO receiver of the device. 
     At  608 , performance of the third antenna is compared to performance of the first antenna. The performance of the third antenna or the first antenna may be monitored, measured, or received from the third receiver or the first receiver. In some cases, an indication of the performance of the third antenna or the first antenna is received from a performance monitor implemented by the device or a communication module thereof. Alternately or additionally, the performance of the third antenna or the first antenna can be compared with a performance of the second antenna. In some aspects, the operations of  608  and  606  are repeated to implement a hysteresis type of measurement. For example, the first antenna may be preferred or favored over the inactive third antenna when respective performance is approximately the same or similar. In such cases, antenna switching may be implemented when a delta in respective performance exceeds a predefined threshold, which can be effective to prevent excessive antenna switching operations. 
     Optionally at  610 , the method  600  leaves the transceiver coupled to the first antenna based on the comparison of respective antenna performance. When the performance of the first antenna is better than the performance of the third antenna, leaving the transceiver coupled to the first antenna may prevent further degradation or disruption of a wireless connection. From operation  610 , the method  600  may return to operation  606  to continue to monitor the performance of the third antenna with the third receiver, such as until performance of the third antenna exceeds that of the first antenna. 
     Optionally at  612 , the transceiver of the user device is coupled to the third antenna based on the comparison of respective antenna performance. When the performance of the third antenna equals or exceeds the performance of the first antenna, coupling the transceiver to the third antenna may improve quality of a wireless connection with a base station. From operation  612 , the method  600  may proceed to  614 , at which performance of the first antenna is monitored via the third receiver of the device. While the transceiver is coupled to the third antenna, the third receiver may be used to monitor the performance of the first antenna, such as until the performance of the first antenna exceeds that of the third antenna. From operation  614 , the method  600  may return to operation  608  to compare respective performance of the third antenna coupled to the transceiver and the first antenna coupled to the third receiver. 
     From operation  608 , the method  600  may then proceed to operation  616  based on the comparison of the performance of the third antenna and performance of the first antenna. For example, if a determination is made that the first antenna coupled to the third receiver has or provides better performance than the third antenna, the transceiver can be coupled to the first antenna. Alternately or additionally, the method  600  can also return to operation  606  to monitor the performance of the third antenna using the third receiver. In some cases, the third receiver is recoupled to the third antenna to enable monitoring of the performance of the third antenna. 
       FIG. 7  illustrates an example method for coupling multiple antennas to respective communication modules based on antenna performance, including operations performed by the diversity controller  108  and/or performance controller  110 . In some aspects, operations of method  700  may be implemented to optimize communication performance of a multi-antenna user device. 
     At  702 , performance of a first antenna coupled to a primary transceiver of a device is measured. The performance of the first antenna may be measured based on a quality or strength of downlink signals received from a base station. In some cases, the primary transceiver is queried or polled for performance metrics associated with the first antenna. For example, a performance monitor or diversity controller of the device may request the performance metrics before initiating diversity antenna switching operations. 
     At  704 , performance of a second antenna coupled to a second receiver of the device is measured. The performance of the second antenna may also be measured based on a quality or strength of downlink signals received from a base station. In some cases, the second receiver is queried or polled for performance metrics associated with the first antenna. 
     At  706 , performance of a third antenna coupled to third receiver of the device is measured. This receiver may be inactive or not actively communicating data, such as a multiple-input receiver or MIMO transceiver that is idle. Alternately, the third receiver may measure or provide an indication of the performance of the third antenna based on MIMO communications received by the third receiver. 
     At  708 , respective performance of the first antenna, second antenna, and/or third antenna is compared. The respective performance of all three antennas may be compared to determine which antenna provides the best performance, which antenna provides the next best performance, and which antenna provides the lowest level of performance. When metrics or an indication of performance is not available for a particular antenna, operation  708  may proceed with a comparison of respective performance for two of the three antennas. Alternately or additionally, operation  708  may omit or skip a comparison of performance for an antenna having lost a wireless link or downlink signal, such as to save time and energy for a known low performance antenna. 
     At  710 , the antenna with the best respective performance is coupled to the primary transceiver of the device. The primary transceiver may be coupled to the selected antenna via any suitable type of circuit or switch, such as a DPDT RF switch or TPTT RF switch. In some cases, coupling the transceiver to the best-performing antenna is effective to improve quality of a communication link or wireless link. In such cases, improving the quality of the communication link can prevent disruption of data or voice services, thereby enabling user applications or device functions to continue when one antenna of a device is blocked or impaired. 
     At  712 , the antenna with the next best respective performance is coupled to the second receiver of the device. The second receiver can be coupled to the next best-performing antenna via any suitable type of circuit or switch, such as a DPDT RF switch or TPTT RF switch. In some cases, coupling the second receiver to the next best-performing antenna is effective to improve diversity reception of the device. 
     At  714 , the antenna with the lowest respective performance is coupled to the third receiver of the device. The antenna with the lowest performance may be coupled to the third receiver via any suitable type of circuit or switch, such as a DPDT RF switch or TPTT RF switch. In some aspects, coupling the antenna to the third receiver, such as a MIMO receiver, enables performance of the antenna to be monitored while other antennas are used for communication. Alternately, the third receiver can be disabled, powered down, or placed in a low-power state to conserve power of the device. From operation  714 , the method  700  may return to operation  702  to continue the various operations of measurement, comparison, and/or coupling for implementing one or more aspects of performance-based antenna selection. 
     Example Electronic Device 
       FIG. 8  illustrates various components of an example electronic device  800  that can implement performance-based antenna selection in accordance with one or more aspects as described with reference to any of the previous  FIGS. 1-7 . The electronic device  800  may be implemented as any one or combination of a fixed or mobile device, in any form of a consumer, computer, portable, user, server, communication, phone, navigation, gaming, audio, camera, messaging, media playback, and/or other type of electronic device or a base station device. For example, the electronic device  800  may be implemented as a smart-phone, phone-tablet (phablet), laptop computer, set-top box, wireless drone, vehicle-based computing system, or wireless broadband router. 
     The electronic device  800  includes communication transceivers  802  that enable wired and/or wireless communication of device data  804 , such as received data, transmitted data, or other information as described above. Example communication transceivers  802  include NFC transceivers, WPAN radios compliant with various IEEE 802.15 (Bluetooth™) standards, WLAN radios compliant with any of the various IEEE 802.11 (WiFi™) standards, WWAN (3GPP-compliant) radios for cellular telephony, wireless metropolitan area network (WMAN) radios compliant with various IEEE 802.16 (WiMAX™) standards, and wired local area network (LAN) Ethernet transceivers. In some aspects, multiple communication transceivers  802  or components thereof are operably coupled with an instance of an RF front end  116  embodied on the electronic device  800 . The RF front end  116  of the electronic device  800  may be implemented similar to or differently from an RF front end  116  as described with reference to  FIGS. 1-7 . 
     The electronic device  800  may also include one or more data input ports  806  via which any type of data, media content, and/or other inputs can be received, such as user-selectable inputs, messages, applications, music, television content, recorded video content, and any other type of audio, video, and/or image data received from any content and/or data source. The data input ports  806  may include USB ports, coaxial cable ports, and other serial or parallel connectors (including internal connectors) for flash memory, DVDs, CDs, and the like. These data input ports  806  may be used to couple the electronic device to components, peripherals, or accessories such as keyboards, microphones, or cameras. 
     The electronic device  800  of this example includes at least one processor  808  (e.g., one or more application processors, processor cores microprocessors, digital-signal processors (DSPs), controllers, and the like), which can include a combined processor and memory system (e.g., implemented as part of an SoC), that executes computer-executable instructions stored on computer-readable media to control operation or implement functionalities of the device. Generally, a processor or processing system may be implemented at least partially in hardware, which can include components of an integrated circuit or on-chip system, a DSP, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), and other implementations in silicon and/or other hardware. 
     Alternately or additionally, the electronic device  800  can be implemented with any one or combination of electronic circuitry  810 , which may include hardware, fixed logic circuitry, or physical interconnects (e.g., traces or connectors) that are implemented in connection with processing and control circuits. This electronic circuitry  810  can implement executable or hardware-based modules (not shown) through logic circuitry and/or hardware, such as an FPGA or CPLD. Although not shown, the electronic device  800  may also include a system bus, interconnect fabric, crossbar, or data transfer system that couples the various components within the device. A system bus or interconnect fabric can include any one or combination of different bus structures or IP blocks, such as a memory bus, memory controller, a peripheral bus, a universal serial bus, interconnect nodes, and/or a processor or local bus that utilizes any of a variety of bus architectures. 
     The electronic device  800  also includes one or more memory devices  812  that enable data storage, examples of which include random access memory (RAM), non-volatile memory (e.g., read-only memory (ROM), flash memory, EPROM, and EEPROM), and a disk storage device. Any or all the memory devices  812  may enable persistent and/or non-transitory storage of information, data, or code, and thus do not include transitory signals or carrier waves in the general context of this disclosure. For example, the memory device(s)  812  provide data storage mechanisms to store the device data  804  and other types of data (e.g., user data). The memory device  812  may also store an operating system  814 , firmware, and/or device applications  816  of the electronic device as instructions, code, or information. These instructions or code can be executed by the processor  808  to implement various functionalities of the electronic device, such as to provide a user interface, enable data access, or manage connectivity with a wireless network. In this example, the memory device  112  also stores processor-executable code or instructions for providing respective instance of a diversity controller  108  and performance monitor  110 , which may be implemented similar to or differently from the diversity controller and/or performance monitor described with reference to  FIGS. 1-7 . 
     As shown in  FIG. 8 , the electronic device  800  may include an audio and/or video processing system  818  for processing audio data and/or passing through the audio and video data to an audio system  820  and/or to a display system  822  (e.g., a video buffer or device screen). The audio system  820  and/or the display system  822  may include any devices that process, display, and/or otherwise render audio, video, graphical, and/or image data. Display data and audio signals can be communicated to an audio component and/or to a display component via an RF link, S-video link, HDMI (high-definition multimedia interface), Display Port, composite video link, component video link, DVI (digital video interface), analog audio connection, or other similar communication link, such as media data port  824 . In some implementations, the audio system  820  and/or the display system  822  are external or separate components of the electronic device  800 . Alternately, the display system  822  can be an integrated component of the example electronic device  800 , such as part of an integrated display with touch interface. 
     The electronic device  800  also includes antennas  826 - 1 ,  826 - 2 , through  826 - n , where n may be any suitable number of antennas. The antennas  826 - 1  through  826 - n  are coupled to the RF front end  116  of the electronic device  800 , which may include any suitable combination of filters, amplifiers, switches, diplexers, and/or multiplexers to facilitate transmission or reception of signals by the communication transceivers  802  through of the antennas  826 - 1  through  826 - n . In some aspects, the diversity controller  108  or performance monitor  110  may interact with the RF front end  116  and the antennas  826 - 1  through  826 - n  to implement performance-based antenna selection as described herein. Alternately or additionally, the electronic device  800  may represent an example implementation of the user devices  102  as described throughout the present disclosure. Thus, in some cases the processor  808  is an example of the processor  104  (not shown) and/or the memory device  812  is an example of the computer-readable storage medium  106  (not shown) for storing various data, instructions, or code for implementing a diversity controller or other applications. As such, aspects of performance-based antenna selection as described herein can be implemented by, or in conjunction with, the electronic device  800  of  FIG. 8 . 
     Although various implementations of performance-based antenna selection for user devices have been described in language specific to certain features, structures, and/or methods, the subject matter of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example ways in which performance-based antenna selection for user devices can be implemented.