Patent Publication Number: US-11032766-B2

Title: Wire-free bluetooth communication system with fast pairing

Description:
FIELD OF THE INVENTION 
     The present invention relates to a communications interface for wire-free Bluetooth, where the wireless signal is received by individual earpieces not electrically connected to each other. In particular, the invention relates to a Bluetooth communication system providing balanced power consumption for each earpiece. 
     BACKGROUND OF THE INVENTION 
     The Bluetooth protocol provides a transport layer for data communication using a wireless protocol which draws a small amount of power. The Bluetooth protocol supports many different types of transport protocols, each of which is operative using a frequency and/or phase shift keying modulation method. For delivery of audio, samples are digitized and provided to an encoder/decoder (CODEC), the most popular of which is SubBand Coding (SBC), which may be used with the Advanced Audio Distribution Profile (A2DP) and described in the Bluetooth standard. SBC provides support for audio streams with a maximum bit rate of 342 kbps (kilobits per second) for mono and 345 kbps for stereo, with sampling rates up to 48 Khz and using 16 bit samples. Other encodings which may be used include AAC (Advanced Audio Coding) used by YouTube and Apple, aptX which is proprietary to Qualcomm, and LDAC which is proprietary to Sony. The various encodings interoperate with the Audio Visual Remote Control Profile (AVRCP) or service, which adds the remote signaling for “play”, “pause”, and “skip” functions found on Bluetooth audio devices. 
     In a typical Bluetooth system, and according to the terminology used in the Bluetooth standard, the host system delivering music content is a “master”, and a wearable system receiving the music content is a “slave”, and the two channels (Left and Right, or L and R) are delivered together over the Bluetooth encoded audio stream to a wearable receiver which decodes the L and R music streams, and delivers each of them separately to each earpiece. Although this was fully anticipated in the original Bluetooth protocol, there is not a standard mechanism for separately delivering L and R streams to each earpiece to eliminate the interconnecting wire. Apple Computer has recently popularized the wireless AirPod, which provides wireless separate delivery of L and R streams to each AirPod. 
     In one example wire-free implementation of Bluetooth, a dedicated Bluetooth earpiece receiver terminates the slave end of the Bluetooth connection for one earpiece, and the other earpiece also contains a full Bluetooth receiver which silently “sniffs” Bluetooth packets and delivers the remaining channel to the other earpiece. This approach has the disadvantage of high power consumption of fully functional Bluetooth for both earpieces, and the possibility of loss of loss of packets with the “sniffed” channel (such as L) when the received RF signal is attenuated, as re-transmission requests only occur with the non-sniffing fully Bluetooth terminated earpiece (R in this example). 
     Another example prior art system terminates both L and R channels with a Bluetooth device, transmits one of the audio stream directly into one ear, and modulates the other audio stream using Near Field Communication (NFC), which may be directly modulated low frequency RF, since RF does not propagate well through human tissue. 
     It is desired to provide a system for reliable and low-power delivery of audio streams to wire-free earpieces. It is also desired to provide an RF apparatus and method for delivery of multiple audio streams to wire-free earpieces which provides a substantially uniform battery life for each earpiece. 
     Objects of the Invention 
     A first object of the invention is a Bluetooth device having a Bluetooth (BT) transceiver and a local sidelink transceiver, the Bluetooth device having a first mode of operation and a second mode of operation, during the first mode of operation, the BT transceiver receiving at least two streams of audio, the BT transceiver forwarding one of the streams to the local sidelink transceiver for transmission and presenting the other stream to a local output, and during the second mode of operation, the local BT transceiver receives a single stream of audio from a remote sidelink transceiver and presents the received audio stream from the local sidelink transceiver as a local output stream of audio, the first mode of operation and second mode of operation being cyclically alternated. 
     A second object of the invention is a Bluetooth (BT) transceiver having a first mode of operation and a second mode of operation, the first mode of operation enabling power to the BT transceiver and also a sidelink transceiver (such as by use of the BLE physical modulation method or physical layer only), the second mode of operation enabling power to only the sidelink transceiver, the first mode of operation operative to receive from the BT transceiver a data stream having at least two audio streams where one of the audio streams is directed to the sidelink transceiver for transmission over a sidelink transceiver such as a BLE modulation physical layer to a remote device and the other presented locally, the second mode of operation receiving an audio stream from the sidelink transceiver and presenting it as a local audio output. 
     SUMMARY OF THE INVENTION 
     A system for wire-free delivery of audio streams to two earpieces has a first and second station, each station having a Bluetooth transceiver and a sidelink transceiver operative as a Low Energy (LE) RF transmitter or receiver. The Bluetooth transceiver may be fully or partially compliant with Bluetooth versions 4.0 or 5.0, and the sidelink transceiver need only communicate a short distance such as from one earpiece to the other earpiece, and the sidelink transceiver may operate using Bluetooth GFSK modulation and/or frequency hopping only at 1 Mbps, 2 Mbps, or 3 Mbps in bursts, and will preferentially draw a fraction of the power consumed by the Bluetooth transceiver of the corresponding station. For a first duration of time in a first mode, Bluetooth packets containing two channels of audio from a master are network terminated by the first BT station, meaning that the Bluetooth transceiver follows the Bluetooth standard for scanning/inquiry, connection, transmission, and acknowledgement of received packets as is well known in the Bluetooth communications protocol. The Bluetooth transceiver is configured to deliver one audio channel to a first earpiece and transmit the other audio channel using its local sidelink station to a second remote sidelink station which receives them. These functions reverse in a second duration of time in a second mode of operation, with the second Bluetooth station terminating the Bluetooth stream from the Bluetooth master, and presenting one channel of audio locally and transmitting the other channel using its sidelink transceiver. The power consumption of the first station in a first mode and power consumption of a second station in a second mode are high compared to the power consumption of a first station in a second mode or the second station in a first mode. Accordingly, alternating the cycles of each station between a first mode and second mode provides approximately equal power consumption between the two earpieces as the roles of a particular earpiece terminating the BT link and transmitting to the sidelink are reversed in each time interval. During the first duration of time, the first BT station (earpiece) has its BT transceiver and sidelink transmitter both enabled, and the second BT station (earpiece) has its sidelink transceiver enabled and BT transceiver disabled. During the second duration of time, the second BT station (earpiece) has its BT transceiver and sidelink transceiver both enabled, and the first station (earpiece) has its sidelink transceiver enabled and BT transceiver disabled. 
     During each first and second interval of time, packets of audio data are sent from a sidelink transmitter of an earpiece station to a sidelink receiver of the remote earpiece based on the buffering capability of the respective receiver, which may be acknowledged to prevent packet loss and to avoid buffer underflow. Because the separation distance between L and R sidelink transceivers of the earpieces is small, the sidelink transmit/receive connections between L and R may optionally use a proprietary data transfer mechanism, the sidelink transceiver including any of Near Field Induction Communication (NFC), or the Bluetooth Low Energy physical layer, in one example by transmitting audio data at standard BLE rates of 1 Mbps, 2 Mbps, or 3 Mbps, or data rates using the BLE physical layer of 4 Mbps or 8 Mbps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of a prior art wired Bluetooth earpiece set. 
         FIG. 2  is block diagram for a Bluetooth receiver suitable for use with the device of  FIG. 1 . 
         FIG. 3  is a diagram of prior art wire-free Bluetooth earpieces. 
         FIG. 4  is a block diagram for a pair of individual R and L wire-free earpiece receivers. 
         FIG. 5  is a block diagram of an example of the present invention. 
         FIGS. 6A and 6B  are block diagrams for the present invention showing data connections during a first and second mode of operation. 
         FIG. 7  is a time progression diagram for delivery of packets according to the present invention. 
         FIG. 8  shows waveforms of power consumption for the example of  FIG. 7 . 
         FIGS. 9A and 9B  show a diagram of a person with a smart watch delivering wireless audio content to an R and L earpiece in an interior and exterior setting. 
         FIG. 10  shows a block diagram of a wireless processor with a Receive Signal Strength Indicator (RSSI) processor. 
         FIG. 11  is a list of RSSI values and example modes for the receiver of  FIG. 10 . 
         FIG. 12  shows a time sequence diagram of Bluetooth connection and sharing of Bluetooth credentials for use by both Left and Right BT devices. 
         FIG. 13  shows a plot of signal strength and first and second modes of a first and second station based on RSSI. 
         FIG. 14  shows a block diagram for a Bluetooth system with a wakeup mechanism and sidelink for passing Bluetooth link parameters. 
         FIGS. 15A and 15B  show a timing diagram for the operation of  FIG. 14  in an example of the invention. 
         FIG. 16  shows an example flowchart for operation of the invention of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a prior art wired Bluetooth (BT) earpiece set  100 . A BT receiver  110  receives a BT audio stream from a master Bluetooth device, decodes the audio stream into Left (L) and Right (R) channels of baseband audio, and delivers them to speakers  104 R and  104 L of earpiece  106 R and  106 L, respectively. 
       FIG. 2  shows a BT receiver  200  suitable for use as a receiver  110  of  FIG. 1  with additional detail. An antenna  202  receives the BT stream, amplifies  204  the RF, and applies the Bluetooth signal RF frequency or phase shift keying (FSK/PSK) to demodulator  206 , thereafter to baseband processor  208 , which converts the phase-modulated frequency hopping patterns into data streams, which are delivered to a Code-Decode (Codec)  210  which separates the audio streams into L  212  and R  214 . Battery  216  provides power to the various functions, and battery management capabilities (not shown) provide that the battery life for a single charge is maximized. 
       FIG. 3  shows prior art wire-free Bluetooth earbuds  300 , where the wire between the earbuds is not present, and each earbud  106 R and  106 L with respective speaker  104 R and  104 R has a separate Bluetooth receiver  302 R and  302 L. 
       FIG. 4  shows example Bluetooth receivers  400 R and  400 L which may be used with the wire-free earpieces of  FIG. 3 . Examining the Right channel  400 R, BT signals are received at antenna  402 R, amplified  404 R, demodulated  406 R, and applied to a baseband processor  408 R which delivers the data stream to CODEC  410 R which separates the channel into R channel  412 R. Left channel  302 L operates in the same manner, with the codec  410 L configured to separate the Left channel rather than the Right of Codec  410 R. L and R suffix references in the present application are understood to perform the same functions for their respective audio channels, as previously described. 
       FIG. 5  shows an example of the present invention, and will be described with respect to first Bluetooth device  502 R (such as a first earpiece receiver), which has a first Bluetooth transceiver  542 R and a sidelink transceiver  526 R. The Bluetooth transceiver  524 R includes an antenna  504 R, RF amplifier  506 R, demodulator  508 R, baseband processor  510 R and codec  512 R which directs one channel to switch  428 R and the other to sidelink transceiver  520 R for transmission. In the first mode of operation, Bluetooth transceiver  524 R is enabled, its codec  512 R generates a first audio stream (such as R), which can be delivered as an output  514 R when switch  528 R is set to select first BT transceiver  524  output. The second audio stream (such as L) is delivered to the low power sidelink transceiver  520 R for transmission via antenna  516 R. The sidelink transceiver  526 R may use any low power protocol compared to the power requirement of BT transceiver  524 R, such as near field induction communications (NFC), or the physical layer of Bluetooth Low Energy at standard data rates or proprietary data rates of 4 Mbps or 8 Mbps. Since the sidelink transceivers  526 R and  526 L need not interoperate with other communication protocols, they need only provide fidelity of audio transmission and low power consumption. The audio data is transferred in bursts, so higher data rates result in lower total power consumption associated with the shorter bursts of received or transmitted data. In one example of the invention, the sidelink transceiver  526 R may use the BLE frequency/phase shift keying modulation method only, preferably at higher than BLE standard data rates to shorten the time the sidelink transceiver is enabled, with buffering of the audio stream from the transmitting channel so that the modulated RF audio packets may be received in a few bursts and buffered to provide continuous audio content. Because the Bluetooth transceiver  524 R supports the entire Bluetooth stack for interoperability with the master host, it will necessarily have higher power consumption than the sidelink transceiver  526 R. In one example of the invention where the sidelink transceiver  526  is burst transmission of audio packets using BLE modulation, the power consumption of the sidelink transceiver  526 R is roughly ⅓ of the BT transceiver  524 R. For this example, in the first mode of operation, the current consumption from the Bluetooth radio  524 R is approximately 3 ma, and the current consumption from the example BLE sidelink transceiver  526 R is approximately 1 mA. The total current consumption for the first station in the first mode of operation (or the second station in the second mode of operation) is accordingly approximately 4 ma. 
     In a second mode of operation, Bluetooth transceiver  524 R is disabled and side band transceiver  526 R (such as an example of a BLE sidelink transceiver) remains enabled, receiving a remote stream of BLE audio packets from second device  502 L sidelink transceiver  526 L, directing the stream of audio to switch  528 R, which is set to select the stream from the example sidelink transceiver  526 R in the second mode of operation. The current consumption for the example first station sidelink transceiver in the second mode of operation (or second station  502 L in the first mode of operation) is approximately 1 ma. 
     In the second mode of operation, with switch  528 R selecting the sidelink transceiver  526 R output, the output  514 R outputs the Right channel audio stream from the sidelink transceiver  526 R while the BT transceiver  524 L is receiving the Bluetooth stream from the master, the BT transceiver  524 L receiving both L and R audio streams, delivering the Left audio stream via switch  514 L selecting the output of codec  512 L, and the sidelink transceiver  526 L transmitting the R stream for reception by first station sidelink transceiver  526 R. The sidelink transceivers  526 R and  526 L may operate using an acknowledgement and re-transmission protocol to ensure that all transmitted packets are received, or the sidelink transceivers  526 R and  526 L may operate in a unicast manner without retransmission. In a unicast sidelink transceiver mode without retransmission or acknowledgement, the sidelink transceiver  520 R operates primarily as a transmitter in the first mode of operation and as a receiver in the second mode of operation, whereas sidelink transceiver  526 L operates primarily as a receiver in the first mode of operation and as a transmitter in the second mode of operation. A configuration mode of operation which precedes the first and second mode of operation enables the communication of Bluetooth parameters by the terminating Bluetooth transceiver ( 524 R or  524 L) to exchange the Bluetooth parameters, including public and optionally private keys established during initial pairing. Alternatively, the private keys used in pairing may be identical between L and R stations for security and to remove the need for private key exchanges between sidelink transceivers. The sharing of these pairing parameters allows either of the Bluetooth transceivers  524 R and  524 L to receive and acknowledge Bluetooth packets interchangeably. 
     The second Bluetooth Device  502 L operations in the identical manner as  502 R, but in opposite mode of operation, such that device  502 L operates in a second mode when device  502 L operates in first mode, and vice versa. During a first interval, Bluetooth transceiver  524 R is enabled and outputting the R channel to switch  528 R, with sidelink transceiver  526 R transmitting the remaining audio channel to the other station  502 L and with Bluetooth transceiver  524 L disabled to reduce power consumption, and  502 L receiving the transmitted signal from its sidelink  526 L transceiver. During a second interval, the operation reverses, and Bluetooth transceiver  524 L is enabled (with example BLE  526 L transmitting the R audio channel to the other station  502 R sidelink transceiver  526 R), during which time BT transceiver  524 R is disabled, the station  502 R receiving the transmitted signal from its sidelink transceiver  526 R. The controllers  530 R and  530 L communicate with each other using their respective sidelink station interfaces  526 R and  526 L to ensure that the Bluetooth receivers  524 R and  524 L are synchronized with each other for first and second mode such that exactly one Bluetooth transceiver ( 524 R or  524 L) is receiving the audio stream from the remote master device (not shown), as well as communicating Bluetooth pairing credentials from the initially pairing transceiver to the other, thereby allowing either to act as a terminating station for the Bluetooth stream from the remote master device. Without careful synchronization, the L and R channels may incur phase or time delays with respect to each other. The controllers  530 R and  530 L also buffer and synchronize the delivery of audio such that the L and R streams are output  514 R and  514 L at the same time and without L to R phase delay. This may be done by including timestamps in the data stream sent with the audio stream over the sidelink to ensure the L and R audio as delivered to the earpieces are identically matched in time as in the original codec stream. 
     Each Bluetooth device  502 R and  502 L maintain synchronization to the Bluetooth stream, such that renegotiation is not necessary when a master BT transmission is received by either  502 R to  502 L as a slave device occurs, and the master device is spoofed into recognizing the same single Bluetooth device  502 R and  502 L during transitions from first mode to second mode. Whichever Bluetooth transceiver of a station is enabled during its respective mode to receive the BT frames ( 502 R during first mode and  502 L during second mode) responds as if they were a single BT station, as only one BT system responds at a time, and each are possessed of the pairing credentials and timeslot information. In this manner, the communications from BT master to BT slave can be performed in a series of alternating bursts, with one station receiving as a fully featured Bluetooth device a burst of frames and forwarding the remote channel audio to the remote earpiece using a sidelink such as BLE transceivers, and then the roles reverse for each station or device  502 L and  502 R during a subsequent interval. In this manner, the inherently asymmetrical battery load (and battery lifetime) of a single mode of operation of the prior art can be equalized between the L and R channel. 
       FIG. 6A  shows a top level of operation of the system during a first mode, and  FIG. 6B  shows the operation during a second mode. Typically, the first mode and second mode alternate in substantially uniform intervals of time. Substantially uniform or substantially equal are understood in the present application to be intervals of time resulting in battery drain less than 20% of equal to each other, such that the L and R batteries exhaust at the same time. First mode  FIG. 6A  shows a Bluetooth master  604  such as a Bluetooth watch streaming music, or a mobile phone streaming music, with the Bluetooth stream  606  received and acknowledged by first BT device  524 R, sending the R channel to output  514 R, and the Left channel being directed via stream  620  to sidelink device  526 R. During the interval of the first mode, first device  502 R consumes 4 ma of current, and second device  502 L consumes 1 ma. 
       FIG. 6B  shows operation during the second mode of operation, where the Bluetooth stream  606  is received and acknowledged by second device  502 L using Bluetooth transceiver  524 L, which uses its sidelink transceiver  526 L to send the R output  620  to sidelink transceiver  502 R which outputs it at  514 R, with  502 R drawing 1 ma of power while  502 L draws 4 ma (3 ma for BT transceiver  524 L and 1 ma for sidelink transceiver  526 L). 
       FIG. 7  shows a timing sequence for canonical data transmission, where a Bluetooth master such as a tablet, watch, or mobile phone  702  operates as BT master  604  of  FIG. 6 , Right station  704  operates as  502 R of  FIG. 6A , and Left station  706  operates as  502 L of  FIG. 6A . During a first mode of operation for the sequence  716  and  720 , the tablet  702  transmits audio data for both channels to Right station  705 , which acks the data if necessary, shown as the data/acq pair  724 . Right station  704  uses the sidelink transceiver to forward the L audio to Left station  706 , which acks each data packet if required, shown as the pair  726 . The response acknowledgement of  726  and  730  of the sidelink transceiver and  724  and  728  of the Bluetooth transceiver is shown for completeness, as other Bluetooth protocols may not provide acknowledgement for received data, and the sidelink protocol may ack, simply receive unicast data without acknowledgement, or in the case of certain near field induction protocols, may transmit continuously as modulated low frequency RF. After an interval of time  716 , such as at the end of the duration of an audio track as indicated by the AVRCP protocol/profile, the Right station  704  changes from first mode of operation to second mode of operation, and Left station  706  changes from second mode of operation to first mode of operation. During time interval  718 , the master  702  Bluetooth packets are received by Left station  706 , which separates the Left audio stream and sends the Right audio stream over the sidelink transceiver to Right station  704 . A pair of data/ack packets is shown as  728  from Master BT station  702  to Left station  706 , which results in the Right audio being extracted and sent via the sidelink channel to Right station  704 , where the data/ack pair is shown as  730 . 
       FIG. 8  shows a plot of power consumption during operation, intervals  716  and  720  represent Right station and Left station power consumption for the first mode where Right Ear  802  receiver is running Bluetooth plus a sidelink protocol such as BLE physical encoding, and Left Ear  804  is running on the sidelink protocol only. The present examples are for the case where a Bluetooth transceiver consumes 3 ma (receiving both L and R streams, and transmitting L or R only) and a BLE transceiver consumes 1 ma (receiving only L or R stream), and are shown only for illustrative purposes. The time allocations for each of first and second mode of operation may vary greatly, it is preferable that the duty cycle be 50% in each of first and second mode of operation over the charge life of a battery, but preferably the first and second cumulative interval times are adjusted so that the battery consumption from each Left and Right earpiece are equalized over each battery state of charge, so that both stations respective battery preferably exhausts at the same moment in time. This may be accomplished by changing modes between audio tracks, or during pauses in the audio stream, or at times when the rate of Bluetooth packet reception from the master is reduced. In another example of the invention, the Left and Right earpieces communicate with each other as to the relative state of charge, and adjust the duty cycle  716 / 720  to  718 / 722  such that the available charge in Left and Right earpieces is taken to the end of the battery capability for Left and Right earpieces at the same time. 
       FIGS. 9A and 9B  show additional embodiments of the invention for a problem that occurs in the outdoor usage case of  FIG. 9B  compared to the indoor case of  FIG. 9A  where the RF couples from a wearable BT master such as a watch  904  with antenna  902  to the earpieces  908 L and  908 R with respective antennas  906 L and  906 R. Alternative embodiments of the present invention may address a problem which occurs with a wearable Bluetooth device (shown as watch  904 ) streaming data to earpieces  908 L/ 908 R. In the indoor case of  FIG. 9A , there exists a direct RF path  924  from BT master  904  to antenna  906 R. Several multipath reflections from master  904  to  908 L are available, including path  920  with reflective surface  910 A, path  922  with reflective surface  910 B, and path  926  with reflective surface  910 C. Similarly, many indoor reflective paths  921  (including multipath reflections) exist between earpiece  908 L and  908 R for use by the sidelink transceivers. Any of the surrounding reflective surfaces  910 A,  910 B, or  910 C may provide a single or multi-reflection path from Bluetooth master  904  to earpieces  908 R and  908 L, or between  908 R and  908 L. 
     The outdoor coupling shown in  FIG. 9B  is more challenging, as there are not multi-path couplings available for RF, although the coupling from master  904  to antenna  906 R is unchanged from the indoor case of  FIG. 9A . Because the earpieces are positioned in the ear canal, and the RF-conductive pinnae of the ear surround the earpieces, coupling from one earpiece antenna  906 R to  906 L is problematic, and from master  902  antenna  904  to far earpiece  908 L antenna  906 L is even more problematic, with typical path attenuations in excess of 100 dB, although the shorter link from  906 R to  906 L may still be usable for RF communications such as BLE. In the case of the master being a watch is on a wearer&#39;s L or R wrist, it may occur that a Bluetooth earpiece  908 R with antenna  906 R has a direct coupling path to the Bluetooth watch master  902  with antenna  905  and has a stronger Received Signal Strength Indicator (RSSI) from the watch  902 / 904  than the earpiece  908 L with antenna  906 L on the opposite side of the head from the watch  902 / 904 . RSSI may be measured and stored using any prior art method of signal strength at an antenna, and in  FIG. 11  is shown with the signal strength unit dBm, which is the absolute signal strength in decibels compared to 1 milliwatt (1 mw). The earpiece position with respect to the watch is typically not a configured earpiece parameter, and may change over time of with different wearers or positions in the outdoor environment (reflective surface vs absorptive surface for RF). It is desirable for the system of  FIG. 5  to adaptively select mode  1  for the earpiece with the strongest signal and select mode  2  for the earpiece with the weakest signal, and optionally to use an alternative sidelink transmission method (such as near field induction) rather than the physical layer of BLE with lower power consumption but greater attenuation from  906 R to  906 L. The stronger signal link also provides reduced power consumption by allowing faster data rates, reducing transmit and receive times and resumption of a sleep state in the associated transmitter and receiver. 
       FIG. 10  shows a modified version of  FIG. 5 , with Bluetooth transceiver  1012 R with RSSI processor  1010 R which maintains at least one pair of RSSI readings for the local receiver ( 1012 R as shown, such as the position of  908 R of  FIG. 9B ) and the remote receiver ( 1012 L not shown, such as in the position of  908 L of  FIG. 9A ), each RSSI for the Bluetooth signal strength with respect to the Bluetooth master  902 / 904 . 
       FIG. 11  shows example RSSI measurements as may be maintained by the RSSI processor  1010 R, where the remote RSSI measurement from the other station  1002 L (not shown) is transmitted to the local station ( 1002 R in this example) using a BLE interface ( 526 R in this example), and vice versa so that both earpieces  1002 R and  1002 L (not shown) have the values of the RSSI table of  FIG. 11 . In this manner, each device  1002 R and  1002 L (not shown) is able to examine its respective RSSI processor table  1010 R and  1010 L to determine which station should switch to the first mode for reception of BT master signal based on strongest comparative RSSI to master station, and which station should be in second mode based on weaker comparative RSSI. In this manner, the L and R Bluetooth transceivers  1012 R and  1012 L may determine which earpiece should operate to terminate the BT signal from master watch  902  of  FIG. 9 , adaptively changing which station terminates the BT master as needed by spoofing each other as a single station response for each data exchange or group of data exchanges. Left and Right earpieces  908 L and  908 R typically have a uniform attenuation when transmitting in either direction, and also typically less attenuation than from the master to far earpiece of the previous example. In one measurement, the link budget may be 100 dB from transmit antenna to receive antenna for reliable operation, and in the example, the link from antenna  904  to near earpiece antenna  906 R is in the range −35 dB to −85 dB, well within link budget, but the link loss from master antenna  904  to earpiece antenna  906 L may approach or exceed 110 dB, so that earpiece  908 L is unable to function. Alternatively, using BLE physical layer modulation (without BT stack or retransmission protocols), the path loss from  906 R to  906 L may be less than 90 dB or above an RSSI threshold required for a reliable link, and sufficient for reliable operation. In one example of the invention, the earpiece with strongest RSSI is used for the Bluetooth termination to the master, and the earpiece with the weaker RSSI to the master becomes the sidelink receiver from the station terminating the Bluetooth signal, as long as the earpiece with the weakest RSSI is below the RSSI threshold required for a reliable link. In this manner, the system may operate to cause the batteries in each earpiece to drain uniformly, as long as the RSSI for the weaker earpiece is above the threshold for reliable communication, such as a threshold of −90 dbm, or a threshold between −80 dbm and −95 dbm. The present invention of  FIG. 10  thereby provides flexibility in where the Bluetooth master is positioned on the body, as well as changes in environment (moving outdoors to indoors), where the power consumption equalization previously described may resume. In another example, the device may operate seamlessly between a battery life equalizing mode, where the first mode and second mode alternate with a duty cycle which equalizes the load to remaining battery life for each battery, to cause the first earpiece battery and second earpiece battery to reach exhaustion at the same time, and when it is not possible to operate in this preferred mode because the weakest RSSI is below the threshold required for reliable communications, the device may operate in a safety mode to preferably link the earpiece with strongest RSSI to the BT master, reverting to battery life equalizing mode when the earpiece with the weakest RSSI is above the threshold required for reliable communications. 
       FIG. 12  shows an example Bluetooth session according to an example of the present invention. During a first pairing interval  1208 , Master device  1202  is in a scanning mode (also known as inquiry mode) and receives pairing advertisements (also known as paging)  1230  from one of the BT slave devices (shown as Right device  1204 ). Since Right and Left devices  1206  are in communication with each other using the sidelink transceivers, either device may initiate the Bluetooth advertisement using its BT transceiver, such as on the basis of best signal strength from the BT master, as was indicated in  FIGS. 10 and 11 , or any other mechanism providing advertisements for pairing. During the pairing interval  1210 , public and private keys are exchanged and the pairing is complete. In one example of the invention, the Right device  1204  and Left device  1206  have identical private keys which are unique from any other private keys, allowing each device to share pairing credentials from a single public key during the pairing interval  1210  and either earpiece initiate a connection without other parameters. During the initialization of the sidelink channel  1234 , the pairing device such as  1204  is also able to share the Bluetooth pairing credentials to the other device such as  1206  if needed. During a first mode interval  1214  the Right device  1204  receives L and R audio streams, and transmits the L audio stream  1238  as was previously described. In a subsequent second mode interval  1216 , the Left device  1206  receives and acknowledges packets shown as data/ack  1240 , which continues during interval  1216 . In one example, the Left device  1206  is able to respond using the pairing credentials shown by  1244 . In another example, the sideband channel initialization  1234  is not necessary, and the two BT transceivers are able to communicate with the BT master using local keys, without the key exchange step  1234 . Other exchanges and updates of pairing credentials or Bluetooth link parameters may be performed at other times as required. 
       FIG. 13  shows a time diagram with respect to a Local station, where the “local RSSI”  1304  (signal strength of the BT master measured by a given local BT transceiver) and “Remote RSSI”  1302  (signal strength of the BT master as reported by the remote BT transceiver and transmitted to the local station) are shown along with the first and second mode configuration for the local and remote stations. At point in time  1308 , the local station RSSI becomes stronger, and the local station takes over as terminating the Bluetooth connection from the master in the first mode as previously described, and at time  1310 , the remote device switches to operating in the first mode. 
       FIG. 14  shows another aspect of the invention related to problem of initial pairing of the earpieces to a master, or alternatively, to synchronization of the earpieces to each other using BLE which requires an initial pairing. The latency and delay associate with pairing and re-establishment of an existing Bluetooth connection is related to the frequency hopping sequence of Bluetooth used in the pairing and connection protocols. Bluetooth implements frequency hopping at 1600 hops per second with a corresponding time slot length of 625 μs, where a master may occupy one or more contiguous BT time slots and a slave typically acks in a single timeslot. In the master scan/inquiry process, Bluetooth devices hop through a set of 32 common frequencies. The potential master in an INQUIRY STATE breaks this set into two 16-hop trains, A and B. It hops through the frequencies in each train at twice the normal rate, repeating the train at least 256 times (2.56 s) before switching to the next train. During this process, the device is sending inquiry packets on every frequency. To find all devices in an error-free environment, the length of time a device spends in inquiry, must consist of at least three train switches of 10.24 s. It is desired to shorten the connection time. 
       FIG. 14  shows a block diagram of an example BT master  1470  which is pairing to an example BT first slave  1402 , using a typical pairing sequence shown in  FIG. 15 . During an advertisement interval  1506 , the first slave device such as  1402  sends pairing advertisements on incremental channels, as shown by the sequence  1512 . After a variable interval of scan time by the BT master, the BT master  1504  receives an advertisement leading to a pairing request  1512  on an observed channel and acknowledges the pairing request with connection request  1514  on one of the advertised channels, which includes exchanges of public and private keys during connection interval  1508 . This is followed by a data exchange interval  1510  where the Master transmits frames to the slave on one or more regular slotted time intervals, and the slave responds with any acknowledgements or data it may have to transmit, as shown by the arrows between master  1504  and slave 1  1502  in  FIG. 15A . As shown in event  1210  of  FIG. 12 , during the establishment of the connection, the slave device  1402  of  FIG. 14  is possessed of the pairing credentials to pair with the Bluetooth master  1470 . 
     One aspect of Bluetooth pairing is that there is initially no synchronization between a slave device, which transmits a sequence of advertisement frames on incrementing channels during a matching scanning interval by the master, wherein the master is listening on a sequence of channels until the advertising device and scanning master find themselves on the same channel and the advertisement is received by the master. Because of the long latency of the pairing protocol, and the power consumed during the pairing protocol, an objective of the present invention is to allow the second slave  1442  of  FIG. 14  to join in receiving frames from the master  1470  as early as possible and without consuming power during the comparatively long pairing sequence, or by receiving the credentials over sidelink link  1403  as was described previously in  FIG. 12 . In the present aspect of the invention, after establishment of a Bluetooth connection between Bluetooth master  1470  and first slave  1402  using the typical pairing sequence, the wakeup controller  1416  has the Bluetooth credentials (private and public key) necessary for any other station to substitute for first slave  1402 . In one aspect of the invention, the sidelink transceiver  1420  under control of the wakeup controller transmits an on/off keying (OOK) sequence that contains a wakeup pattern during a first interval of time, the OOK pattern being formed of uniform length packets and uniform length packets to represent each 1 and 0 value, respectively, or by keying a carrier on and off. The wakeup controller  1456  of second slave  1442  receiving this sequence compares the incoming wakeup sequence against a wakeup pattern, such as by cross correlation of the incoming OOK pattern against the wakeup pattern, and when the cross correlation is above a threshold such as 80% or 90% of a complete match, the wakeup controller powers up the functions of the station  1442  for full functionality and readiness to receive and respond to BT master data packets. By synchronizing the transmission of the Bluetooth public/private key pair with a future expected transmit window of the Bluetooth master  1470 , the second slave  1442  may wakeup with the public/private key pair of the first slave  1402  and directly engage in data communications with the BT master  1470  in place of the first slave  1402 . 
       FIG. 15A  was previously described showing the advertisement interval  1505  matching the scanning interval  1506 , followed by connection interval  1508 , and data exchange interval  1516 .  FIG. 15B  shows the first slave  1550  using sidelink transceiver  1420  of  FIG. 14  to transmit a wakeup sequence  1554 , which results in the second slave  1552  waking up, enabling power to its sidelink transceiver, and either receiving the Bluetooth parameters  1556  transmitted by the first slave  1550 , or beginning communications directly with the BT master in interval  1564 . Alternatively, the Bluetooth communication parameter transfer  1556  may be transmitted by OOK methods to transfer the Bluetooth connection parameters from first slave  1550  to second slave  1552  if necessary. The Bluetooth parameters are either pre-shared or known by both slave stations so that the second slave  1552  can spoof the master  1550  by replying to Bluetooth packets from the master in place of the first slave  1550  as shown in the exchange  1562  and  1564 . The second slave wakeup controller  1456  samples the incoming RF and determines when to power up the rest of the receiver (mixers, baseband processor, anything other than the extremely low power energy detection and sampling circuit sampling the OOK (or alternatively fixed length packets modulated at RF for 1 and the absence of RF for 0). The wakeup sequence  1554  matches the internal wakeup key of wakeup controller  1456  which is sampling the RF envelope, and results in the wakeup controller  1456  powering up with the Bluetooth parameters required for each station to respond seamlessly to the BT master  1474 A or  1474 . The parameters used by connection  1474  of  FIG. 14  may be transmitted by the first slave using its sidelink transceiver  1420  monitored by second slave  1442  over channel  1403 . In one example of the invention, the identical private keys of the first slave and second slave allow the private/public key pair  1554  used by the first slave  1402  in communicating with master  1470  while maintaining the secrecy of the private key during the connection establishment of the sidelink transceiver  1420 . The state of the master  1470  Bluetooth connection is either active or inactive, and may be provided by slave  1402  in the optional parameter transfer  1556  along with timing parameters that indicate when the anchor points of the Bluetooth frame used by the slave to synchronize time slots and frequency hopping pattern. For an inactive connection, upon wakeup, one of the sidelink parameters  1556  identifies anchor points and timing slots to the second slave. For an active connection, the master  1504  transmits data  1562  and second slave  1552  transmits data such as acknowledgements  1564 , each in their respective time slots as defined by the master  1504  and the Bluetooth anchor points transmitted by the BT master, or as received by slave  1442  as Bluetooth connection parameters. 
       FIG. 16  shows a simplified flowchart for the present invention. In step  1602 , a first slave pairs to a master, during which time the first slave acquires the link parameters for slave 1 to the master, which includes connection state, public private key pair, timing information to next BT anchor point and other parameters needed by a second slave responding to the master as if it were the first slave device in a spoofing manner. In step  1604 , an example second Bluetooth master serially transmits a wakeup sequence, connection state (no connection, active, inactive), pairing parameters including public/private key pair of step  1602 , and any other Bluetooth parameters required for directly connecting to the master. In step  1606 , the second slave receives the OOK wakeup sequence, followed by the public/private key pair and any other Bluetooth parameters provided. In step  1608 , if the wakeup sequence matches, the master transmits on master timeslots to the second slave and the second slave transmits on corresponding slave timeslots, exactly as the first slave device would do. In this manner, responses from the first and second slave are treated identically by the master device, thereby allowing an extremely low power pairing process compared to the prior art pairing sequence of Bluetooth. 
     In another example of the invention, the wakeup pattern is a hierarchical wakeup pattern comprising at least a first and second sequence, the first sequence having a lower bit rate than the second sequence, and the first sequence using fewer bits than provide a reliable indication of wakeup, with the second sequence greatly improving the reliability while reducing the power consumption of the wakeup event. An example hierarchical wakeup system and pattern is described in U.S. patent application Ser. No. 13/783,785 filed Mar. 2, 2017, and in Ser. No. 15/811,690 filed Nov. 14, 2017, both of which are incorporated in their entirety by reference. 
     The present examples are provided for illustrative purposes only, and are not intended to limit the invention to only the embodiments shown.