Method and apparatus for synchronization between Bluetooth audio transmitters to avoid collisions

Abstract

A method and apparatus for synchronization between Bluetooth audio transmitters is described. In one example, an audio source includes a synchronous bus. A first audio transmitter is coupled to the audio source and the synchronous bus. The first audio transmitter is configured to evaluate available radio channels, select a set of radio channels, send a transmit command over the synchronous bus to a second audio transmitter, and transmit a first set of audio streams from the audio source to a first set of one or more audio sinks using the selected radio channels. The second audio transmitter is configured to receive the transmit command from the first audio transmitter over the synchronous bus and transmit a second set of audio streams from the audio source to a second set of one or more audio sinks in accordance with the transmit command.

Description

Technical Field

[0001] Relates to an audio device. Background Art

[0002] Radio communication from the Bluetooth Special Interest Group is a standard for wireless communication between electronic devices and always includes an audio profile for microphones and speakers. Although stereo music transmission has been used for many years and is now referred to as traditional audio, the Bluetooth Low Energy (LE) Audio standard extension has extended Bluetooth audio transmission to enable many new use cases. Multi-stream audio allows the transmission of multiple independent and synchronized audio streams between an audio source device and one or more audio sinks. A Low Complexity Communication Codec (LC3) codec has been added for multiple audio streams to provide higher quality audio at lower transmission data rates.

[0003] One such new use case is a home theater that uses a soundbar or receiver as a central audio controller, which is connected to multiple speakers or audio sinks, where each speaker receives a unique, synchronized, and simultaneous audio stream. The same approach can be used to provide spatial audio in conference rooms and virtual reality environments. Another new use case is a conference room or spatial audio environment where multiple microphones are connected to a central controller to provide spatial information to remote locations participating in the conference. Another such use case is to provide multiple broadcasts simultaneously to different listeners in the same space, such as announcements in different languages at airports and train stations. Auracast is being developed TM as a set of technologies for multiple simultaneous audio broadcasts.

[0004] In the case of a home theater, the system has evolved from 5.1 channels (5 audio channels and a subwoofer) to 6.1, to 7.1, to 7.2 (7 audio channels and 2 subwoofer channels) to 9.2, to Dolby Atmos and :X. While, for example, stereo provides a completely independent audio signal or track for each channel, Dolby Atmos in particular provides a single audio signal with metadata to characterize a given sound. An audio decoder can then generate as many different audio signals or tracks as appropriate for the installed system. There are many configurations for different price points, different uses, and different vendors. Summary of the Invention

[0005] Describe a method and device for synchronizing between Bluetooth audio transmitters to avoid conflicts. In one example, an audio device includes: an audio source; a synchronization bus; a first audio transmitter coupled to the audio source and the synchronization bus, the first audio transmitter evaluating available radio channels, selecting a set of radio channels, sending a transmission command to a second audio transmitter via the synchronization bus, and transmitting a first set of audio streams from the audio source to a first set of one or more audio sinks using the selected radio channels; and the second audio transmitter coupled to the audio source and the synchronization bus, the second audio transmitter being configured to receive the transmission command from the first audio transmitter via the synchronization bus and transmit a second set of audio streams from the audio source to a second set of one or more audio sinks according to the transmission command.

[0006] In some embodiments, the second audio transmitter is configured to evaluate available radio channels, generate link quality information based on the evaluation, and send the link quality information to the first audio transmitter via the synchronization bus, wherein the first audio transmitter is configured to select a set of radio channels at least partially based on the link quality information.

[0007] In some embodiments, the first audio transmitter is configured to select a set of radio channels by selecting a first set of radio channels for transmitting the first set of audio streams and a second set of radio channels for transmitting the second set of audio streams, and wherein the transmission command includes an identification of the second set of radio channels.

[0008] In some embodiments, none of the radio channels in the second set of radio channels are included in the first set of radio channels, and none of the radio channels in the first set of radio channels are included in the second set of radio channels.

[0009] In some embodiments, the first set of radio channels is represented as a first channel map and the second set of radio channels is represented as a second channel map, and wherein the first audio transmitter is configured to send the second channel map in the transmission command.

[0010] In some embodiments, the audio stream includes a repeating sequence of sub-events, the audio stream hops at the sub-events according to a frequency hopping sequence, the second audio transmitter is configured to use the synchronization bus to synchronize the transmission of the second set of audio streams with the first audio transmitter, and the second audio transmitter is configured to transmit the second set of audio streams synchronized with the first audio transmitter, wherein the sub-events are offset by an integer number of sub-events relative to the sub-events of the first audio transmitter.

[0011] In some embodiments, the second audio transmitter is configured to transmit the second set of audio streams with an offset of one sub - event of the sub - event sequence.

[0012] In some embodiments, the first audio transmitter is configured to send the channel mapping of the selected set of radio channels to the second audio transmitter via the synchronization bus, and wherein the first audio transmitter is configured to transmit the first set of audio streams based on the channel mapping and the second audio transmitter transmits the second set of audio streams based on the channel mapping.

[0013] In some embodiments, the audio streams include a repeating sequence of sub - events, the audio streams hop at sub - events according to a frequency - hopping sequence, the second audio transmitter is configured to synchronize the transmission of the second set of audio streams with the first audio transmitter using the synchronization bus, and the second audio transmitter is configured to transmit the second set of audio streams synchronized with the first audio transmitter with the frequency - hopping sequence and an offset relative to the frequency - hopping sequence.

[0014] In some embodiments, the offset includes a channel index offset.

[0015] In some embodiments, the offset includes a frequency offset.

[0016] In some embodiments, the second audio transmitter is configured to receive input parameters for the frequency - hopping sequence from the first audio transmitter via the synchronization bus, and wherein the second audio transmitter is configured to generate the frequency - hopping sequence for transmitting the second set of audio streams seeded by the input parameters.

[0017] In one embodiment, a method includes: evaluating available radio channels at a first audio transmitter; selecting a set of radio channels; transmitting a first set of audio streams received from an audio source to a first set of one or more audio sinks using the selected radio channels; sending a transmission command to a second audio transmitter via a synchronization bus; and transmitting a second set of audio streams from the audio source to a second set of one or more audio sinks according to the transmission command.

[0018] Some embodiments include: evaluating available radio channels at the second audio transmitter; generating link quality information based on the evaluation; and sending the link quality information to the first audio transmitter via the synchronization bus, wherein selecting a set of radio channels includes selecting a set of radio channels at least in part based on the link quality information.

[0019] In some embodiments, the audio stream includes a repeating sequence of sub-events, wherein the audio stream hops at the sub-events according to a frequency hopping sequence, and the method further comprises: the second audio transmitter using the synchronization bus to synchronize the transmission of the second set of audio streams with the first audio transmitter and to offset the transmission of the second set of audio streams by an integer number of sub-events relative to the sub-events of the first audio transmitter.

[0020] In some embodiments, the offset is one sub-event of the sub-event sequence.

[0021] Some embodiments include sending a channel map of the selected set of radio channels to the second audio transmitter via the synchronization bus, wherein transmitting the first set of audio streams includes transmitting the first set of audio streams based on the channel map, and wherein transmitting the second set of audio streams includes transmitting the second set of audio streams based on the channel map.

[0022] In some embodiments, the audio stream includes a repeating sequence of sub-events, wherein the audio stream hops at the sub-events according to a frequency hopping sequence, and the method comprises using the synchronization bus to synchronize the transmission of the second set of audio streams with the first audio transmitter, and wherein transmitting the second set of audio streams includes transmitting the second set of audio streams synchronized with the first audio transmitter with the frequency hopping sequence and an offset of one hop relative to the frequency hopping sequence.

[0023] In some embodiments, the offset includes a channel index offset.

[0024] In an embodiment, a device comprises: means for evaluating available radio channels at a first audio transmitter; means for selecting a set of radio channels; means for transmitting a first set of audio streams received from an audio source to a first set of one or more audio sinks using the selected radio channels; means for sending a transmission command to a second audio transmitter via a synchronization bus; and means for transmitting a second set of audio streams from the audio source to a second set of one or more audio sinks according to the transmission command. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a block diagram of a home entertainment system.

[0026] Figure 2 is suitable for use with Figure 1 a home entertainment system and is a block diagram of a transmitter portion of a soundbar.

[0027] Figure 3 is a process flow diagram of operations performed by an audio device according to embodiments herein.

[0028] Figure 4 is a signal diagram of a first audio stream along a first timeline and a second audio stream along a second timeline according to an embodiment herein.

[0029] Figure 5 is a second signal diagram of a first audio stream along a first timeline and a second audio stream along a second timeline according to an embodiment herein.

[0030] Figure 6 is a third signal diagram of a first audio stream along a first timeline and a second audio stream along a second timeline according to an embodiment herein.

[0031] Figure 7 is a block diagram of an audio transmitter suitable for use as a leading device or a following device according to an embodiment herein. DETAILED DESCRIPTION

[0032] Embodiments are described in the context of a multi-speaker audio system (e.g., a home theater device). However, the principles described herein can be applied outside of home theater and to multiple microphones in addition to or instead of speakers. Examples are presented in the context of 7 speakers, e.g., a 6.1 or 7.0 sound system. However, alternatively or additionally, other numbers of speakers can be used.

[0033] Figure 1 A multi-speaker audio system 100 in the context of a home theater system is shown. This multi-speaker system is shown as an example, and many modifications and variations can be made to suit different uses and purposes, including microphone capture, multiple rooms, etc. As shown, the soundbar 102 is coupled to the television 104. The soundbar can provide video to the television 104, or the television can provide audio to the soundbar 102. In the example shown, the television can be considered to receive a broadcast video signal from terrestrial, cable, or satellite broadcasts, display the video on the screen of the television, and provide the audio to the soundbar. The soundbar can be incorporated into the television, or the soundbar can represent an audio-only device without a television.

[0034] The soundbar 102 generates an audio stream and transmits the stream via a first transmitter 106 coupled to a first antenna 107 of the soundbar or a second transmitter 108 coupled to a second antenna 109. The components are referred to as transmitters 106, 108 because it is their primary function as described herein. In an expected implementation, transmitters 106, 108 are transceivers with two-way capabilities. The soundbar uses the first transmitter 106 to implement a single LE audio radio to serve as the center for transmitting the first four streams. The second transmitter 108 implements another single LE audio radio to serve as the second center for transmitting the last three streams. Different audio streams are received at each of a plurality of audio sinks. In fact, each audio sink may be capable of receiving all audio streams, but only decodes one stream addressed to that audio sink via the audio streaming radio protocol. As shown, the first transmitter sends different audio streams to each of the first four audio sinks, namely speaker 1, 111, speaker 2, 112, speaker 3, 113, and speaker 4, 114. The second transmitter 108 sends different audio streams to each of the next three audio sinks, namely speaker 5, 115, speaker 6, 116, and speaker 7, 117. Each speaker 111, 112, 113, 114, 115, 116, 117 includes a corresponding receiver 121, 122, 123, 124, 125, 126, 127 in each device as a single LE audio device to serve as the peripheral for receiving its corresponding stream. The components are referred to as receivers because it is their primary function as described herein. In an expected implementation, the receivers are transceivers with two-way capabilities. In some embodiments, a different one of the seven different streams is provided for each speaker. Each speaker is capable of receiving a unique stream and producing a unique audio output. The soundbar 102 has a central role in this example. The center will establish and maintain an isochronous stream (or CIS) with each peripheral device. In this example, there will be a total of seven CISs.

[0035] The soundbar 102 represents any one of a variety of different audio sources and can be replaced by any one of a variety of audio transmitters. In some embodiments, an audio / video receiver, a set-top box, a conferencing station, or a virtual reality controller is used in place of the soundbar. The soundbar may have integrated speakers for regenerating one or more audio channels, additional wired speakers, including those of the television 104 for some of the audio channels, or may not have speakers and rely on external speakers.

[0036] Any one or more audio sources (not shown) may be provided to the soundbar, e.g., an Internet interface, a Bluetooth radio interface, a broadcast interface, a disk player, a turntable, a media server, a television 104, etc., to receive audio in one or more channels. The soundbar or another component receives audio data in any suitable format and generates seven streams using suitable audio processing resources. The audio may contain seven discrete audio channels, or the audio may be converted into seven different streams or another number of streams, depending on the configuration of the audio system 100. The configuration, structure, and content of the original audio received by the soundbar may be adapted for different uses and configurations.

[0037] Speakers 111, 112, 113, 114, 115, 116, 117 represent any one of a variety of different audio sinks, and devices of different types having an audio receiver may replace the speakers. One or more of the speakers may be part of a headset, a headphone, earbuds, or a virtual reality headset. The audio sinks may be adapted for suitable different uses. One or more of the audio sinks may be full-range speakers, effect speakers, subwoofers, placed in another room or location for a multi-room system. In a multi-broadcast system, each speaker may represent a different broadcast listener, e.g., an English-speaking airport visitor, a Flemish-speaking airport visitor, a Dutch-speaking airport visitor, etc., and there may be multiple receivers of each type, such as for Auracast TM as shown in the embodiment.

[0038] In an alternative configuration, each speaker contains a microphone that generates an audio stream to send back to the soundbar, or each speaker may represent a microphone instead of a speaker. The specific nature of the source and sink may be adapted for suitable different sources and configurations. The speakers represent audio sinks in any one of a variety of different configurations. Receivers 121, 122, 123, 124, 125, 126, 127 may be integrated into the same housing as the audio transducer that converts an electrical signal into sound. Each speaker may contain multiple discrete components or be manufactured as a single device. Each speaker may contain additional features and capabilities not discussed herein.

[0039] LE Audio allows for individual isochronous (ISO) streams (CIS) to each peripheral device. Auracast allows for individual broadcast isochronous streams (BIS) to each group or broadcast receiver. A scheduling algorithm at the leading device, shown as the first transmitter 106 of the soundbar 102, generates a schedule for transmitting and receiving audio packets. A scheduler within the soundbar allocates a certain number of time slots, called sub-events (SEs), for exchanging one or more audio packets, including the option for retransmission. The schedule is repeated for each ISO event interval such that the sub-events act as time slots within a repeating frame defined as the ISO event interval. Each stream is sent as a different packet within the assigned sub-events of the ISO event interval. Thus, the bandwidth of the ISO event interval determines the amount of audio data that can be transmitted. This bandwidth can be allocated in different ways. In the case of two streams or channels, higher-definition audio can be transmitted. If all seven streams are sent from a single transmitter out of the transmitters 106, 108 of Figure 1 then lower-quality audio will be sent than what is possible with the two-transmitter system shown.

[0040] The quality of a pulse code modulation (PCM) digital audio signal can be represented by the sampling rate and word length. The Red Book compact disc is specified as 44.1 kHz / 16 bits. For digital streaming sources, 48 kHz / 24 bits is popular. Higher and lower bitrates and word lengths are often used and other coding systems are characterized differently. Signals of either of these two types can be further encoded and compressed in the LE Audio protocol before transmission to reduce the bandwidth required to transmit each audio stream. For 44.1 kHz or 48 kHz streams, approximately 100 kbps is sent for each audio stream, depending on the required audio quality.

[0041] The round-trip time required to send 7 audio streams of 100 kbps with a single sub-event for each stream exceeds the bandwidth typically available to any one transmitter, even without expected control overhead and retransmission. Figure 1 The audio system 100 of

[0042] avoids this problem by using two transmitters 106, 108 such that only 3 or 4 streams are required from each transmitter. More transmitters can be used to support even more streams or higher-bitrate audio streams. However, this introduces a new problem of conflict when the two transmitters transmit simultaneously on the same frequency. LE Audio provides additional robustness to audio streams by allowing retransmission in the case of unsuccessful reception of an audio packet (e.g., a sub-event). Thus, when the packets in a sub-event conflict with packets from another transmitter, both transmitters can retransmit their respective packets. As described herein, the transmission of audio streams can be configured to minimize conflicts and thus minimize retransmissions. In some embodiments, this can allow for more channels or higher bitrates.

[0043] Figure 2 It is a block diagram of a transmitter part 200 of a soundbar, and the soundbar is, for example, Figure 1 the soundbar 102 of or a similar component. The transmitter part 200 includes an audio source 202, which provides a selected audio stream to a first LE audio transmitter 204 having a first transmitting antenna 208 and a second LE audio transmitter 210 having a second transmitting antenna 212.

[0044] A single audio bus 206, such as a time-division multiplexing (TDM) audio bus, is connected from the audio source 202 to the two LE audio transmitters 204, 210 in the soundbar. The LE audio protocol will ensure that all audio streams will have the same end-to-end audio latency on the two or more LE audio networks. Each LE audio network is a path from the audio source to the corresponding transmitter to each corresponding audio sink coupled to the transmitter. The two networks will generate their own independent time-division multiple access (TDMA) schedules, as well as a frequency allocation table for the audio streams from the corresponding transmitters 204, 210 to the associated audio sinks. As a center, the transmitters 204, 210 are both capable of independently performing channel evaluations to optimize the use of LE audio channels depending on interference from other devices. This results in an acceptable flight time and low latency.

[0045] However, placing the two transmitters within their respective wireless ranges allows for strong interference in the case where they transmit simultaneously on the same frequency. This can affect link robustness. This can occur during a sub-event (SE) at the same or very close frequencies when both transmitters are transmitting or even when one transmitter is receiving and the other transmitter is receiving. These and other conflicts cause packet loss and reduced link robustness. If the two transmitters are not synchronized, the conflicts are uncontrolled and their impact on another LE audio network may be minimal or maximal. The corresponding TDMA scheme, the actual transmit and receive timings, and the frequency allocation table may overlap and cause conflicts. Over time, the timings may also drift relative to each other. To solve these and other problems, a synchronization bus 214 is provided between the two transmitters.

[0046] The synchronization bus 214 allows the two transmitters to align their transmit and receive timings. Additionally, the synchronization bus 214 can be used to coordinate the LE audio TDMA schedules between one or more transmitters. The synchronization bus 214 can be used to coordinate the frequency channel mapping and frequency use between the two or more transmitters. The mapping can use non-overlapping frequencies or frequency hopping offsets for the same mapping. The synchronization bus 214 can also be used to offset the channel indices between isochronous streams (CIS) of two different channels.

[0047] The synchronous bus 214 can be a wired connection between the two or more radio devices using a Universal Asynchronous Receiver-Transmitter (UART), Serial Peripheral Interface (SPI), or another chip-to-chip interface, such as the LE audio transmitters 204, 210. The synchronous bus can include additional timing signals to achieve accurate synchronization between the two transmitters. In the example described, one device, such as the first transmitter 204, acts as a leading device, and another device, such as the second transmitter 210, acts as a following device. The leading device gives instructions to the following device regarding which frequency bands to use and / or which TDMA timing to use, such as transmit commands. There may be one or more following devices, and the following devices can contribute to the optimal selection by providing information about the link quality they measure on the available radio channels to the leading device.

[0048] Figure 3 is a process flow diagram of operations performed by an audio device as described herein, such as a soundbar, receiver, set-top box, virtual reality (VR) controller, broadcaster. Block 302 is to evaluate available radio channels at a first audio transmitter, such as the first transmitter 204 of the audio device Figure 2 . Block 304 is to select a set of radio channels. This can be done using the evaluation of the available radio channels in block 302 and also using the channel evaluation from the second audio transmitter 210. As discussed above, although these components are referred to as transmitters herein, they will typically be transceivers capable of both transmitting and receiving. For such an evaluation, the transmitters 204, 210 act as receivers and measure the RF energy at the available radio channels. The available radio channels may be in an unlicensed band but subject to interference from other wireless sources, including other radio transmitters, electrical interference, and environmental conditions that affect signal propagation in the available radio channels. Block 306 is to transmit a first set of audio streams received from an audio source, such as the audio source 202, to a first set of one or more audio sinks, such as the speakers 111, 112, 113, 114 Figure 1 .

[0049] Block 308 is to send a transmit command to a second audio transmitter, such as the second audio transmitter 210, via a synchronous bus, such as the synchronous bus 214. As described in more detail below, the transmit command can include frequency allocation, frequency mapping hopping sequences, transmit parameters, and other transmit commands. Additionally, the synchronous bus can be used to synchronize the timing of the second audio transmitter to the timing of the first audio transmitter. Block 310 is to transmit a second set of audio streams from the audio source to a second set of one or more audio sinks, such as the speakers 115, 116, 117, according to the transmit command.

[0050] UsingFigure 3 The method can avoid interference between the first audio transmitter and the second audio transmitter by using transmit commands via a synchronous bus to assign different transmit frequencies to each audio transmitter. For example, the preamble device of the first audio transmitter can perform channel assessment, select a set of frequency bands that can be optimally used, and divide the selected frequency bands into two non-overlapping channel maps. The preamble device will use the first channel map and will instruct the follower device, such as the second audio transmitter, to use the second channel map.

[0051] In addition, the follower device can also perform channel assessment and provide information to the preamble device. The channel assessment can be used alone or in combination with the channel assessment of the preamble device. In this example, the preamble device can generate the two non-overlapping channel maps based on information from both devices. This prevents any conflicts caused by the two audio transmitters transmitting simultaneously on the same frequency, thereby eliminating packet loss caused by other audio transmitters.

[0052] This technique may cause twice as many frequency bands to be occupied. For a system with multiple follower devices, even more frequency bands are used. In other words, for a fixed number of suitable radio channels, half of the radio channels can be used for each audio transmitter. For example, LE Audio of other Bluetooth communication protocols uses frequency hopping to reduce conflicts with external interference sources. In LE Audio, each audio stream is assigned a CIS index and is placed in a time series as an individual sub-event. The audio stream hops at each sub-event according to a frequency hopping sequence. The sequence number of the frequency hopping sequence changes after each sub-event, but the pseudo-random sequence can repeat a certain frequency a certain number of times and then change the frequency. Therefore, the frequency may not change after each sub-event. One effect of this method is that if a packet of a stream is sent on a frequency blocked by an interference source, the next opportunity to retransmit the packet will be at a different frequency. This can avoid interference at the first frequency. Dividing the radio channels into two discrete groups reduces the number of radio channels available for a particular transmitter. This can cause the overall solution of splitting the available radio channels between two transmitters to be more sensitive to interference from other sources because the total number of available frequency bands for each LE Audio network is reduced by half.

[0053] To ensure that both audio transmitters can use the complete complement of available radio channels, the transmission can be coordinated via a synchronous bus in several different ways. Generally speaking, for LE Audio, the frequency hopping algorithm determines that frequency hopping occurs at each sub-event. When the physical link parameters that result in the same input seed entering the frequency hopping algorithm are selected and when the link start times are synchronized, the two audio transmitters will hop simultaneously and in the same way. Coordinated synchronous transmission can be used so that the two audio transmitters can transmit simultaneously without frequency overlap.

[0054] In this example, the leading audio transmitter selects a first set of radio channels for transmitting a first set of audio streams and a second set of radio channels for transmitting a second set of audio streams. The transmission command includes an identification of the second set of radio channels for use by the following audio transmitter. The first or leading audio transmitter transmits the first set of audio streams using the first set of radio channels, and the following audio transmitter transmits the second set of audio streams on the second set of radio channels. In this example, the first set of radio channels does not include any of the radio channels in the second set of radio channels, and the second set of radio channels does not include any of the radio channels in the first set of radio channels.

[0055] Figure 4 is a signal diagram of a first audio stream along a first timeline 402 that can be transmitted by a first audio transmitter and a second audio stream along a second timeline 430 that can be transmitted by a second audio transmitter. The audio streams have a similar structure, but the packets carry different data. The first timeline 402 is for the leading audio transmitter. The packets are included within a repeating ISO event interval 404. The ISO event interval 404 has first sub-events 406, second sub-events 408, and third sub-events 410 that each correspond to different audio streams. The three sub-events 406, 408, 410 constitute a first CIS 412 of sub-events, which repeats with the next CIS for the same three audio streams. Although three are shown, any other number can be used. As indicated, the first sub-event 406 is labeled SE1, CIS1, and frequency F n . The second sub-event 408 is labeled SE2, CIS1, F n+1 . The third sub-event 410 is labeled SE3, CIS1, F n+2 . The next CIS again starts with a new first sub-event 420 SE1 for CIS2 and another frequency F m . As shown, the third sub-event 422 of the second audio stream on the second timeline 430 is offset by one sub-event from the third sub-event 420 of the first audio stream on the first timeline 402. This offset continues through the second timeline and avoids conflicts.

[0056] In one example, each sub-event 416 of the following audio transmitter uses an equal length and is aligned with the sub-events of the leading audio transmitter, as shown by the synchronization line 414. However, the first sub-event 416 of the synchronized ISO event interval 418 has an offset of one sub-event. This allows the two audio transmitters to use the full range of available radio channels and reduces the number of possible conflicts by three times. Only the overlapping sub-events between different corresponding CIS streams may still have different frequencies and cause packet loss. Compared with other technologies, the offset of one sub-event provides a significant reduction in conflicts. The second audio transmitter uses a synchronization bus to synchronize the transmission of the second set of audio streams with the first audio transmitter and offsets the transmission of the second set of audio streams by an integer number of sub-events relative to the sub-events of the first audio transmitter.

[0057] To implement this offset, a Figure 3 procedure can be used, and the offset can be sent as part of the transmit command. A specific offset can be configured to suit different channel conditions and system configurations. The offset can be one or another number of sub-events. The synchronization bus can also be used to send channel mappings to the following audio transmitter.

[0058] In another alternative, the frequency mapping is the same between the first audio transmitter and the second audio transmitter, and the offset is one or more hops of the frequency hopping sequence. By not aligning the first SE 516 of the following device as Figure 4 with the second SE 408 of the leading device, but as Figure 5 with the first SE 506 of the leading device, there is complete frequency overlap at each SE. This is avoided by extending the LE audio channel frequency hopping sequence for the following audio transmitter by a hopping offset compared to the starting frequency when the CIS is created. This ensures zero overlap because each following frequency band selection will have a configurable offset of the following channel mapping index to the leading frequency.

[0059] Figure 5 is a signal diagram of the first audio stream along the first timeline 502 that can be transmitted by the first audio transmitter and the second audio stream along the second timeline 530 that can be transmitted by the second audio transmitter. The audio streams have a similar structure, but each packet carries different data. The first timeline 502 is for the leading audio transmitter. The packets are contained within the repeating ISO event interval 504. As in the Figure 4 example, the ISO event interval 504 has a first sub-event 506 and subsequent sub-events. As indicated, the first sub-event 506 is labeled SE1, CIS1, and frequency F n . The first sub-event 516 of the second timeline 530 is labeled SE1, CIS1, and frequency F n+1This frequency indicates a frequency hopping offset from the frequency of the first sub - event 506 of the first timeline 502.

[0060] The follow - up sub - event is aligned with the corresponding leading sub - event based on the synchronization line 514. The sub - events can also be from the same CIS, as shown. Because there are always differences due to offsets of one or more sub - events in, for example, the channel index of F n、 F n+1 a frequency mismatch between the two audio streams is maintained. This avoids packet loss between the central devices. This offset can be implemented with only a small modification to the existing LE audio protocol.

[0061] In another example, the offset can be expressed in terms of a frequency offset. Although Figure 4 in, the offset is one or more SEs, and in Figure 5 in, the offset is one or more frequency hops, but in Figure 6 in, the offset is presented as a frequency offset, such as a specific number of kHz. Alternatively, a numerical offset can be added to the channel index modulo the number of channels. The specific value for the frequency offset can be selected based on the available radio channels and the nature of the transmitters and receivers in a radio environment suitable for ensuring no significant interference. In this example, the same basic frequency hopping sequence can be used, but the leading frequency or the follow - up frequency can be changed by, for example, adding the offset to the channel index. The channel index is the position of the radio frequency (RF) frequency in the active channel. If multiple LE audio follow - up devices are connected to a single LE audio leading device, each follow - up device can have a different offset.

[0062] The frequency for each LE audio follow - up device can be calculated using any suitable formula. In one example, the formula can be expressed as:

[0063] Ci_follower=(Ci_leader + Foffset_follower) mod channel_map_length

[0064] where Ci_follower is the channel index of the follow - up device sub - event, Ci_leader is the channel index of the leading device, Foffset_follower is the frequency offset applied to the sub - event of the follow - up device, and the channel map length is the number of hops in the channel hopping sequence before the channel hopping sequence repeats.

[0065] Figure 6602 is a signal diagram of a first audio stream along a first timeline 602 that may be transmitted by a first audio transmitter and a second audio stream along a second timeline 630 that may be transmitted by a second audio transmitter. The audio streams have a similar structure, but the packets carry different data. The first timeline 602 is for the leading audio transmitter. The packets are contained within a repeating ISO event interval 604. Figure 4 In the example of FIG. 6 , ISO event interval 604 has a first sub-event 606 and subsequent sub-events.

[0066] As indicated, the first sub-event 606 is labeled SE1, CIS1, and frequency Fn. The first sub-event 616 of the second timeline 630 is synchronized with the first sub-event 606 of the first audio emitter as shown by the synchronization line 614. Figure 5 The first sub-event 616 of the second timeline 630 is labeled as SE1, CIS1 and frequency F n+Foffset This frequency indicates that this is the added frequency offset F offset The frequency F of the first sub-event of the leading device n The frequency offset may be positive or negative. As in other examples, the frequency offset may be sent over the sync bus. SE is sent at different frequencies between the two transmitters due to the offset. As in other examples, there may be more than one follower audio transmitter. One is shown to simplify the description.

[0067] Figure 7 706 is a block diagram of an audio transmitter suitable for use as a leader or follower in the context of the examples described above. The form factor can be modified to suit different uses and integrated with a variety of different audio devices such as sound bars, receivers, VR controllers, etc. The audio transmitter has an audio interface 706 that is coupled to an audio bus 707 to receive audio from a suitable audio source. The audio interface is coupled to an audio codec 704 to convert the received audio into a format suitable for transmission to an audio sink via an RF system 712. A bus interface 714 is coupled to a synchronization bus 715 to communicate with other audio transmitters as a leader or follower.

[0068] The audio interface 706 and bus interface are further coupled to the processor 708 to provide data that the processor can use and communicate in any suitable manner. The processor is coupled to the memory 710 to store data from the interface and other values ​​determined by the processor or received from other components.

[0069] The processor and memory are also coupled to an RF system 712 that provides communication to an audio sink and other external components, which may include network nodes, user interfaces, and other audio transmitters. The RF system includes one or more antennas 713 to transmit and receive radio signals. The RF system also receives signals on available radio channels to allow the RF system 712 of system 700 to evaluate the available radio channels. In one example of use, system 700 communicates with a smart phone (not shown) via an RF interface to provide information to a user to allow for audio configuration. In another example of use, the system communicates with a cellular or Wi-Fi network node to directly send information to a control device or user interface. In addition to Bluetooth LE Audio and Auracast mentioned herein, the RF interface may also use one or more wireless communication systems and protocols, including Near Field Communication, Wi-Fi, and cellular.

[0070] System 700 may be in the form of a single integrated circuit (IC), or some components may be combined while others are not. Multiple components may be combined into a single package, for example, combined as a multi-chip module (MCM) or system-in-package (SiP) or other physical implementation. Additional components may be added to system 700, and fewer components may be used. Some functions may be provided on modules different from those described herein. More or fewer modules than those shown herein may be provided.

[0071] The boundaries between the operations described above are provided as examples. Multiple operations may be combined into a single operation, a single operation may be dispersed among additional operations, and the execution of operations may at least partially overlap in time. Additionally, alternative embodiments may include multiple instances of a particular operation, and the order of operations may be changed in various other embodiments.

[0072] Although the operations of the methods herein are shown and described in a particular order, the order of operations of each method may be changed such that some operations may be performed in reverse order, or such that some operations may be performed at least partially concurrently with other operations. In another embodiment, the instructions or sub-operations of different operations may be implemented in an intermittent and / or alternating manner.

[0073] It should also be noted that at least some of the operations of the methods described herein may be implemented using software instructions stored on a computer-usable storage medium for execution by a computer. As an example, an embodiment of a computer program product includes a computer-usable storage medium for storing a computer-readable program.

[0074] Alternatively, embodiments of the present invention may be implemented entirely in hardware or in an implementation that includes both hardware elements and software elements. In embodiments using software, the software may include, but is not limited to, firmware, resident software, microcode, etc.

[0075] The connections discussed herein can be any type of connection suitable for including the transmission of signals or power from or to corresponding nodes, units, or devices, including via intermediate devices. Connections can be shown or described as a single connection, multiple connections, unidirectional connections, or bidirectional connections. However, different embodiments can vary the implementation of the connections. For example, separate unidirectional connections can be used instead of bidirectional connections, and vice versa. Additionally, a single connection that transmits multiple signals in a sequential manner or in a time-division multiplexed manner can be used instead of multiple connections. Similarly, a single connection carrying multiple signals can be divided into various different connections carrying subsets of those signals. The term "coupled" or similar language can include direct physical connections or connections through other intermediate components, even when these intermediate components change the form of the coupling from the source to the destination.

[0076] The described examples can be implemented on a single integrated circuit, such as in software in a digital signal processor (DSP) as part of a radio frequency integrated circuit (RFIC). The described examples can also be implemented in hardware in a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), or in other electronic devices. The described examples can be implemented in analog circuitry, digital circuitry, or a combination of analog and digital circuitry. Alternatively, the circuit and / or component examples can be implemented as any number of separate integrated circuits or separate devices interconnected in a suitable manner. Instead, these examples can be implemented, for example, as a software or code representation of a physical circuit system or a logical representation that can be transformed into a physical circuit system in a hardware description language or any other suitable form.

[0077] It will be readily understood that the components of the embodiments generally described herein and illustrated in the figures can be arranged and designed in a variety of different configurations. Accordingly, the more detailed description of the various embodiments represented in the figures is not intended to limit the scope of the present disclosure, but merely to represent the various embodiments. Although various aspects of the embodiments are presented in the figures, the figures are not necessarily drawn to scale unless specifically stated otherwise.

[0078] Without departing from the basic characteristics of the present invention, the present invention can be embodied in other specific forms. The described embodiments are to be considered in all respects only as illustrative and not restrictive. Accordingly, the scope of the present invention is indicated by the appended claims rather than by this detailed description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.

[0079] References throughout this specification to features, advantages, or similar language do not imply that all features and advantages that can be realized by the present invention should be present in or in any single embodiment of the present invention. On the contrary, language referring to features and advantages should be understood to mean that a particular feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, references throughout this specification to features, advantages, and the like may, but do not necessarily, refer to the same embodiment.

[0080] Furthermore, the described features, advantages, and characteristics of the present invention may be combined in any suitable manner in one or more embodiments. Those skilled in the art will recognize that, given the description herein, the present invention may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized that may not be present in all embodiments of the present invention.

[0081] While specific embodiments of the present invention have been described and illustrated, the present invention is not limited to the specific forms or arrangements of components so described and illustrated. The scope of the present invention will be defined by the appended claims and their equivalents.

Claims

1. An audio device, characterized in that: include: Audio source; Synchronous bus; a first audio transmitter coupled to the audio source and the synchronization bus, the first audio transmitter configured to evaluate available radio channels, select a set of radio channels, send a transmit command to a second audio transmitter via the synchronization bus, and transmit a first set of audio streams from the audio source to a first set of one or more audio sinks using the selected radio channels; as well as The second audio transmitter is coupled to the audio source and the synchronization bus, the second audio transmitter being configured to receive the transmit command from the first audio transmitter via the synchronization bus and transmit a second group of audio streams from the audio source to a second group of one or more audio sinks according to the transmit command.

2. The audio device according to claim 1, characterized in that the second audio transmitter being configured to evaluate an available radio channel, generate link quality information based on the evaluation, and send the link quality information to the first audio transmitter via the synchronization bus, Wherein the first audio transmitter is configured to select a set of radio channels based at least in part on the link quality information.

3. The audio device according to claim 1, wherein The first audio transmitter is configured to select a set of radio channels by selecting a first set of radio channels for transmitting the first set of audio streams and selecting a second set of radio channels for transmitting the second set of audio streams, and wherein the transmit command includes an identification of the second set of radio channels.

4. The audio device according to claim 3, characterized in that The first set of radio channels does not include any radio channels in the second set of radio channels, and the second set of radio channels does not include any radio channels in the first set of radio channels.

5. The audio device according to claim 3, characterized in that The first set of radio channels is represented as a first channel map and the second set of radio channels is represented as a second channel map, and wherein the first audio transmitter is configured to send the second channel map in the transmit command.

6. The audio device according to claim 1, characterized in that: wherein the audio stream comprises a repeating sequence of sub-events, wherein the audio stream hops frequency at sub-events according to a frequency hopping sequence, wherein the second audio transmitter is configured to synchronize transmission of the second set of audio streams with the first audio transmitter using the synchronization bus, and Wherein the second audio emitter is configured to emit the second set of audio streams synchronized with the first audio emitter, wherein the sub-events are offset by an integer number of sub-events relative to the sub-events of the first audio emitter.

7. The audio device according to claim 6, characterized in that The second audio transmitter is configured to transmit the second set of audio streams at an offset of a sub-event of the sequence of sub-events.

8. The audio device according to claim 1, characterized in that: wherein the audio stream comprises a repeating sequence of sub-events, wherein the audio stream hops frequency at sub-events according to a frequency hopping sequence, wherein the second audio transmitter is configured to synchronize transmission of the second set of audio streams with the first audio transmitter using the synchronization bus, and The second audio transmitter is configured to transmit the second group of audio streams synchronized with the first audio transmitter using the frequency hopping sequence and an offset relative to the frequency hopping sequence.

9. A method, characterized in that include: evaluating available radio channels at a first audio transmitter; Select a set of radio channels; transmitting a first set of audio streams received from an audio source to a first set of one or more audio sinks using the selected radio channel; sending a transmit command to a second audio transmitter via a synchronization bus; as well as A second set of audio streams is transmitted from the audio source to a second set of one or more audio sinks in accordance with the transmit command.

10. A device, characterized in that: include: means for evaluating available radio channels at a first audio transmitter; A means for selecting a set of radio channels; means for transmitting a first set of audio streams received from an audio source to a first set of one or more audio sinks using the selected radio channel; means for sending a transmit command to a second audio transmitter via a synchronization bus; as well as Means for transmitting a second set of audio streams from the audio source to a second set of one or more audio sinks in accordance with the transmit command.

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