Patent Publication Number: US-2021176811-A1

Title: True wireless stereo system and method

Description:
CROSS REFERENCE 
     This application claims priority from U.S. provisional patent Ser. No. 62/935,089 filing date Nov. 14, 2020. 
    
    
     BACKGROUND 
     True Wireless Stereo (TWS) Technology enables to transmit audio stream from a master device (also referred to as master or audio source) into two or more slave devices (such as wireless transceivers), so that audio is played in synchronization on all slave devices. This technology becomes common on Bluetooth enabled devices such as wireless headphones/earbuds or wireless speakers, in which the headphones, the earbuds and the speakers are not connected. 
     An inquiring Bluetooth enabled device may perform multiple repetitions of the following steps: (a) sending a signal (known as an inquiry of page) using a unique identifier, and (b) listening to responses in order to locate one or more responding Bluetooth enabled devices. A response of may include the frequency hopping synchronization (FHS) packet of the responding device. 
     The inquiring Bluetooth enabled device shares its own FHS packet with the one or more responding Bluetooth enabled devices. 
     The inquiring Bluetooth enabled device may then perform frequency hopping according to the FHS packets exchanged between the Bluetooth enabled devices 
     There is a growing need to perform effective manner for TWS. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which: 
         FIG. 1  is an example of a timing diagram; 
         FIG. 2  is an example of first and second wireless transceivers within a box; 
         FIG. 3  is an example of first and second wireless transceivers within a box; 
         FIG. 4  is an example of an audio source, and the first and second wireless transceivers; 
         FIG. 5  is an example of a timing diagram; 
         FIG. 6  is an example of a timing diagram; 
         FIG. 7  is an example of a timing diagram; and 
         FIG. 8  is an example of a method. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. 
     The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings. 
     It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. 
     Any reference in the specification to a system should be applied mutatis mutandis to a method that can be executed by the system. 
     Because the illustrated at least one embodiment of the present invention may for the most part, be implemented using components and circuits known to those skilled in the art, details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention. 
     Any reference in the specification to a method should be applied mutatis mutandis to a system capable of executing the method. 
     There may be provide a device, a method, a kit and at least one computer readable medium for TWS. 
     For simplicity of explanation it is assumed that there are two wireless transceivers and a master device. It should be noted that there may be more than two wireless transceivers that should receive the audio information from the master device—accordingly—there may be one or more additional sniffers. 
     TWS can be implemented in various ways. 
     Sniffing involves having a first slave device (such as a first wireless transceiver) communicating over a bi-directional wireless link with the master device. Audio information from the master device is sent over the bi-directional wireless link to the first slave device. The first slave device sends to the second slave device (such as a second wireless transceiver) at least one link parameters that allow the second slave device to receive the audio information that was sent over the first wireless link. In a sense the second slave device established a sniffing communication link (which is uni-directional) with the master device. 
     U.S. Pat. No. 8,768,252 illustrates sending the link parameters by a first wireless transceiver, to the second wireless transceiver (and over a second wireless link) only after the establishment of the first wireless link with the master device. 
     The suggested method may involve having the first and second wireless transceivers coupled to each other via a shared link (also referred to as a primary link)—that may be wired or wireless. 
     The first and second wireless transceivers may use a shared link that is wired while within a storing and charging device and may use a shared link that is wireless while outside the storing and charging device. 
     The shared link is used for sharing out of at least some of the link parameters (or at least perform preliminary steps such as clock synchronization), before any of the wireless transceivers establishes, the first wireless link with the master device. The at least some of the link parameters are referred to as sniff enabling information. 
     This schema gives total isolation of the earbuds and allows multiple sniffing device to sniff the link with just few parameters shared between the earbuds. 
     The master device may transmit the audio over a frequency hopping bi-directional wireless link. 
     For Bluetooth (BT) sniffing, the frequency hopping sequence of the master device is characterized by information that is located within an FHS packet. 
     The first and second wireless transceivers (assuming that the second wireless transceiver operates as a sniffer) are clocked synchronized. In order to receive the FHS packet (for example—the accuracy of the clock synchronization may be, for example +/−10 μS). 
     The sniffer needs to scan in Inquiry/paging hopping sequence and once it find ID message it knows the frequency that the FHS will be received in, as depicted in  FIG. 1 . This tasks involves one of the critical timing in the Baseband where each slot is 312 μs. Master timing diagram is denoted  11  and slave timing diagram is denoted  12 . The master transmits identifiers ID then eventually transmits a FHS packet. 
     The clock synchronization may be executed while the first and the second wireless transceivers are located in a storage and charging device such as box  40  (for storing and charging the first and second wireless transceivers) and are coupled to each other by a shared link such as wired communication link  32 . 
     The first and second wireless transceivers may use the wired link for communication and clock synchronization. 
     An example of box  40 , a master device (denoted audio source  40 ), first and second wireless transceivers (also referred to as first and second earbuds)  21  and  22  and a shared link that is wired communication link  32  are illustrated in  FIG. 2 . The figure also illustrates charging unit  31  for charging the first and second wireless transceivers. 
     The charging unit may not be a part of box  30 . 
     The storage and charging device may differ from a box. 
       FIG. 3  differs from  FIG. 2  by illustrating a shared link that is a wireless link  51  between the first and second wireless transceivers—and that wireless link is established even when both first and second transceivers are in the box. 
       FIG. 4  illustrates the first and second wireless transceivers  21  and  22 , the bi-directional wireless communication link  52  between the master device  40  and the first wireless transceiver  21 , and a shared link  51  that is a wireless link that was established between the first and second wireless transceivers to share sniff enabling information  61  and/or exchange commands, status, information, clock synchronization information, and the like. 
     Audio information  62  from the audio source is sent over bi-directional wireless communication link  62  and over a uni-directional sniffing wireless channel  53 . 
     When one of the first and second wireless transceivers is taken out the box (for example the first wireless transceiver), the communication with the second wireless transceiver may stop and the first wireless transceiver may start (immediately or at some delay) to establish the second wireless link with the master device. 
     The second wireless transceiver may start (immediately or at some delay—for example after being outputted from the box) to attempt to sniff. 
     The first and second wireless transceivers may detect that they were outputted from the box in various manners—for example when a charging that occurs in the box stops. Yet another detection methods may be applied—for example detecting a wireless connection loss. 
     Since the sniffer needs to reliably obtain the frequency hopping and timing schema, the first wireless transceiver may query the sniffer for getting the FHS packet of the page response message. In case where the sniffer misses the page response message then the first wireless transceiver may will restart the connection. This will ensure that both earbuds knows the frequency hopping of the master device and can follow the BT link. 
     During connection, while the AFH is active, a FH_channel_map may be sent by the master device to change the frequency hopping schema, in order to adapt to RF environmental changes, and a sniffer should send its acknowledge to the first wireless transceiver, and only when the first wireless transceiver receives acknowledgement from the sniffer (in case of multiple sniffers—from all sniffers) then the first wireless transceiver will acknowledge the AFH command. See, for example, timing diagram  70  of  FIG. 5 . 
     To enable the first and second wireless transceivers to do the pairing (with the master device)—both first and second wireless transceivers may share the same public and private keys. 
     In case of authentication/encryption failure, the BT spec mandate to use different random number. In such case—the first and second wireless transceivers will start the pairing process from scratch. 
     The first and second wireless transceivers may communicate using wired or wireless link before the establishment of the first wireless link (with the master device). 
     Non-limiting example of the link parameters that can be sent to the sniffer (even before the establishment of the first wireless link) are listed below:
         a. Hop sequence parameter: the first wireless transceiver may share this characteristic value with the sniffer and the sniffer may calculate the hop sequence in order to follow the hopping sequence.   b. Random number pair with source: this random number will be used later by the first wireless transceiver to pair with the master device, the first wireless transceiver may share this characteristic value with the second wireless transceiver, such that it can follow the link pairing procedure.       

     Acknowledgement data: the second wireless transceiver may notify the first wireless transceiver about each ACL packets or common packets [DM1, ID, FHS, AFH] received from the master device as an acknowledgement. 
     The acknowledgment will allow the first wireless transceiver to ask for retransmission of the missed packet by the second wireless transceiver. 
     The first wireless transceiver may need to exchange data with the second wireless transceiver over the second wireless link (such as shared link  51 )—that may be a secure connection. Accordingly—the first and second wireless transceivers may pair with each other and generate required security keys. This is illustrated in timing diagram  80  of  FIG. 6 . 
       FIG. 7  depicts an example of a communication between the master device and the first wireless transceiver.  FIG. 7  also depicts the first wireless transceiver shared required details for the second wireless transceiver in order to allow the latter to sniff Bluetooth packets from the master device. 
     Table 1 illustrates that for multiple sniffers—a sniffer may use use proprietary small access code with a TDD schema, if the first wireless transceiver can corelate to it, it will regard as acknowledgement. 
     Each of the sniffed earbuds sends proprietary ACK message after the primary earbud and the all sniffing earbuds complete the reception of the packet. 
     When joining the sniffing, each earbuds gets identifier for being 1 st  2 nd  3 rd  etc. sniffing earbud. 
     The sniffing earbuds uses this number to know exactly when to transmit the proprietary ACK message, such that they will not collide with each other. 
     The primary earbud may use majority vote or consensus method to decide if to ACK the master or to NAK and wait for retransmission 
     In table 1: 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 AC = Access code 
               
               
                 HD = header 
               
               
                 SW = Switch from RX to TX + move to GFSK 
               
               
                 GF = Move to GFSK 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Hop sequence 
                 k 
                 k 
                 k 
                 k 
                 k 
                 k 
                 k 
                 k 
                 k 
                 k + 1 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                   
                 AC 
                 HD 
                 DH5/2DH5/3DH5 
                   
                   
                   
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Master 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Primary 
                 GF 
                 RX 
                 EDR 
                 RX 
                   
                   
                 GF 
                 RX 
                 SW 
                 ACK 
               
               
                 earbud 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Sniffing 
                   
                   
                   
                   
                   
                 SW 
                 AC 
                   
                   
                   
               
               
                 earbud1 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Sniffing 
                   
                   
                   
                   
                   
                 SW 
                   
                 AC 
                   
                   
               
               
                 earbud2 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Sniffing 
                   
                   
                   
                   
                   
                 SW 
                   
                   
                 AC 
                   
               
               
                 earbud3 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Sniffing 
                   
                   
                   
                   
                   
                 SW 
                   
                   
                   
                 AC 
               
               
                 earbud4 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 time μSec 
                 68 
                 54 
                   
                 2712 
                   
                   
                   
                 291 
               
               
                   
               
            
           
         
       
     
       FIG. 7  illustrates an example of a method  700 . 
     Method  700  may start by initialization step  710 . 
     The initialization step  710  may include at least one of the following:
         a. Sharing sniff enabling information between the first and second wireless transceivers, over a shared link. The sharing occurs before an establishment of a bi-directional wireless link between an audio source and a first wireless transceiver. (Step  712 ).   b. Sharing the sniff enabling information while the first and second wireless transceivers are being charged.   c. Performing clock synchronization between the first and second wireless transceivers while the first and second wireless transceivers are being charged.   d. Sharing, by the first and second wireless transceivers private and public keys.   e. Sharing of the sniff enabling information while the first and second wireless transceivers are positioned in a storage and charging device.   f. Detecting, by each of the first and second wireless transceivers, an exit from the storage and charging device.   g. Stopping, by the first wireless transceiver, to communicate with the second wireless transceiver, following a detection of an exit of the first wireless transceiver from the storage and charging device.   h. Resuming a communication between the first and second wireless transceivers, following a detection of an exit of each one of the first wireless transceiver and second wireless transceiver from the storage and charging device.   i. Performing clock synchronization between the first and second wireless transceivers while the first and second wireless transceivers are positioned in the storage and charging device.       

     Step  710  may be followed by steps  720 ,  730  and  740 . 
     Step  720  may include receiving, by a first wireless transceiver, audio information from the audio source over the bi-directional wireless link. 
     Step  720  may include establishing the bi-directional wireless link. 
     Step  730  may include sniffing, by a second wireless transceiver, audio information sent over the bi-directional wireless link. 
     The shared link may be a wired link or a wireless link. 
     Method  400  may also include step  740  of communicating between the first and second wireless transceivers. The communication may be executed during the reception of the audio information. 
     Step  740  may include:
         a. Informing, by the first wireless transceiver, the second wireless transceiver about a future change in the sniff enabling information.   b. Determining by the first wireless transceiver, whether the second wireless transceiver received the sniff enabling information.   c. Re-establishing communication with the second wireless transceiver when determining that the second wireless transceiver did not receive the sniff enabling information.       

     Any of the figures may or may not be in scale. 
     Any reference to any of the terms “comprise”, “comprises”, “comprising” “including”, “may include” and “includes” may be applied to any of the terms “consists”, “consisting”, “and consisting essentially of”. 
     In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims. 
     Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. It is understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. 
     Those skilled in the art will recognize that the boundaries between elements are merely illustrative and that alternative embodiments may merge elements or impose an alternate decomposition of functionality upon various elements. Thus, it is to be understood that the architectures depicted herein are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. 
     Any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “operably connected,” or “operably coupled,” to each other to achieve the desired functionality. 
     Furthermore, those skilled in the art will recognize that boundaries between the above described operations are merely illustrative. The multiple operations may be combined into a single operation, a single operation may be distributed in additional operations and operations may be executed at least partially overlapping in time. Moreover, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be altered in various other embodiments. 
     Also for example, in one embodiment, the illustrated examples may be implemented as circuitry located on a single device. Alternatively, the examples may be implemented as any number of separate devices or separate devices interconnected with each other in a suitable manner. However, other modifications, variations and alternatives are also possible. The specifications and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense. 
     In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word ‘comprising’ does not exclude the presence of other elements or steps then those listed in a claim. Furthermore, the terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. 
     While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.