Wireless communication device and wireless communication method

Abstract

The invention provides a wireless communication device and a wireless communication method. The wireless communication device comprises an encoder circuit and a wireless communication circuit. The encoder circuit is configured to encode the same input data to generate and output a plurality of frames having different encoding qualities. The wireless communication circuit is configured to receive the plurality of frames from the encoder circuit and transmit at least one frame selected from the plurality of frames to another wireless communication device over a wireless link.

Description

Technical Field

[0001] This invention relates to wireless communication, and more particularly to a wireless communication device and related wireless communication method with packet-level adaptive bitrate (ABR) control. Background Technology

[0002] Lossless audio is the optimal form of audio because it does not degrade sound quality, and the audio file does not experience quality degradation during compression. The lossless audio heard by the user is of the same high quality as the original audio. However, lossless audio playback requires high data rates to transmit the lossless compressed audio bitstream from the source device to the sink device. To meet the high data rate requirements, the physical layer (PHY) throughput must be high, which necessitates a wider PHY bandwidth. However, in noisy environments, maintaining audio stability with a wider PHY bandwidth is difficult, leading to audio frame loss and a degradation in lossless audio playback quality.

[0003] Furthermore, the transmission throughput between the source and receiver devices may be limited and may vary over time. Therefore, rate control schemes are typically employed to ensure timely transmission / reception of the bitstream. For example, a typical rate estimation (RE) mechanism can be implemented at either the source or receiver end. There is a response delay in reporting the rate estimation result of the RE mechanism back to the encoder at the source device. Additionally, there is a processing delay when the source encoder actually changes its output bitrate. Considering a scenario where the transmission throughput between the source and receiver devices drops to a low level, this can lead to an increased audio packet loss rate. The receiver may experience audio dropout before the source encoder actually reduces the bitrate using a typical RE-based rate control scheme. In particular, the bitrate control delay (which may include response and processing delays) is a significant problem for low-latency uncompressed / lossless audio applications.

[0004] Therefore, an innovative ABR control scheme is needed that does not use the typical RE mechanism and can meet the requirements of low-latency uncompressed / lossless audio applications. Summary of the Invention

[0005] One of the objectives of this invention is to provide a wireless communication device and related wireless communication method controlled by a data packet level ABR.

[0006] In one embodiment of the present invention, a wireless communication device is disclosed. The wireless communication device includes an encoder circuit and a wireless communication circuit. The encoder circuit is used to encode the same input data to generate and output multiple frames with different encoding qualities. The wireless communication circuit is used to receive the multiple frames from the encoder circuit and transmit at least one selected frame from the multiple frames to another wireless communication device via a wireless link.

[0007] In one embodiment of the present invention, a wireless communication method is disclosed. The wireless communication method includes: performing an encoding operation on the same input data to generate and output multiple frames with different encoding qualities; and transmitting at least one selected frame from the multiple frames to a wireless communication device via a wireless link.

[0008] The packet-level ABR control scheme proposed in this invention enables seamless switching between stability-oriented transmission in noisy environments and quality-oriented transmission in clean environments without audio jitter. Furthermore, since low-quality / bitrate bitstreams have higher transmission priority than high-quality / bitrate bitstreams, the packet error rate of high-quality / bitrate bitstreams (e.g., lossless or uncompressed bitstreams) is no longer a bottleneck. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of an audio codec (encoder-decoder) model with packet layer ABR control proposed in this invention, according to an embodiment of the present invention.

[0010] Figure 2 This is a schematic diagram of a wireless communication device using the data packet level ABR control scheme proposed in this invention, according to an embodiment of the present invention.

[0011] Figure 3 This is a flowchart of a data packet layer ABR control method according to an embodiment of the present invention.

[0012] Figure 4 This is a schematic diagram illustrating the availability of retransmission slots between the transmission of two frames.

[0013] Figure 5 This is a schematic diagram illustrating an operational scenario where a retransmission slot is used to retransmit previously transmitted low-quality / low-bit-rate frames.

[0014] Figure 6 This is a schematic diagram illustrating an operational scenario where retransmission slots are reused to transmit high-quality / bit-rate frames that have not yet been transmitted.

[0015] [Symbol Explanation]

[0016] 102, 210: Encoder circuit

[0017] 104, 206: Decoder circuit

[0018] 103, 214: Circuit Selection

[0019] 106: Transmission medium

[0020] 200, 202: Wireless communication devices

[0021] 204: Wireless Link

[0022] 212: Wireless communication circuits

[0023] 216: Control Circuit

[0024] 218: TX circuit

[0025] 220: RX circuit

[0026] 222: High-stability PHY circuit

[0027] 224: High-speed PHY circuit

[0028] FL: logo

[0029] ACK: Confirmation

[0030] NAK: Negative Confirmation

[0031] F1: First Frame

[0032] F2: Second Frame

[0033] a, b, au, bu: frame

[0034] S302, S304, S306, S308, S310, S312, S314, S316: Steps Detailed Implementation

[0035] Certain terms are used in the specification and claims to refer to specific elements. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same element. This specification and claims do not distinguish elements based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." Furthermore, the terms "coupled" or "coupled" herein include any direct and indirect electrical connection means. Therefore, if a first device is described as coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices and connection means.

[0036] Figure 1 This is a schematic diagram of an audio codec (encoder-decoder) model with packet layer ABR control proposed in this invention, according to an embodiment of the present invention. The encoder circuit 102 (which is part of the audio codec of the source device) receives uncompressed pulse code modulation (hereinafter referred to as "PCM") audio input and encodes this uncompressed PCM audio input to produce a lossy bitstream (i.e., a bitstream generated by applying lossy compression to the uncompressed PCM audio input) and an uncompressed / lossless bitstream (i.e., a bitstream generated by not applying any compression to the uncompressed PCM audio input, or a bitstream generated by applying lossless compression to the uncompressed PCM audio input). Selection circuit 103 selects at least one of a lossy bitstream and an uncompressed / lossless bitstream for transmission of the audio bitstream via a transmission medium (e.g., a wireless link) 106, where a media access control (MAC) frame is encapsulated in a PHY packet and then transmitted via transmission medium 106. For example, the audio bitstream transmitted via transmission medium 106 may contain a lossy bitstream followed by an uncompressed / lossless bitstream. Alternatively, the audio bitstream transmitted via transmission medium 106 may contain only a lossy bitstream. Decoder circuit 104 (which is part of the audio codec of the receiving device) receives the audio bitstream from the transmission medium (e.g., the wireless link) 106 and decodes the received audio bitstream to produce a PCM audio output for audio playback by the receiving device.

[0037] In this embodiment, the selection circuit 103 is controlled by an acknowledgment (ACK) or negative acknowledgment (NAK) from the receiving device; therefore, packet-level ABR control can be implemented in the source device. Furthermore, typical RE mechanisms are not implemented in either the source or receiving device. Please note that... Figure 1 The audio codec model shown is for illustrative purposes only and is not intended to limit the invention. In fact, any wireless communication device that uses the packet level ABR control scheme proposed in this invention (e.g., a bit rate control scheme that does not use RE (RE-less)) is within the scope of this invention.

[0038] Figure 2 This is a schematic diagram of a wireless communication device using the packet-level ABR control scheme proposed in this invention, according to an embodiment of the present invention. The packet-level ABR control scheme adopted by the wireless communication device 200 is based on... Figure 1 The audio codec model shown specifically illustrates that wireless communication device 200 is a source device with packet-level ABR control, while wireless communication device 202 is a receiving device that communicates with the source device via wireless link 204. In some embodiments of the invention, wireless communication device 200 is a sender, which may be a Bluetooth dongle, a mobile phone, or a laptop computer, while wireless communication device 202 is a receiver, which may be a headphone, a speaker, or earbuds. In some embodiments of the invention, wireless link 204 may be a Bluetooth (BT) link; for example, a BT link may be a Low Energy (LE) Isochronous (ISO) channel.

[0039] The wireless communication device 200 may include an encoder circuit (which is part of the audio codec of the source device) 210 and a wireless communication circuit 212. The wireless communication circuit 212 may include a selection circuit 214, a control circuit 216, a transmission circuit (labeled "TX circuit") 218, and a receiving circuit (labeled "RX circuit") 220. Note that... Figure 2 Only elements relevant to this invention are shown; in practice, the wireless communication device 200 may include other elements to achieve the specified functions.

[0040] Encoder circuit 210 encodes the same input data D_IN to generate and output multiple frames with different encoding qualities. In this embodiment, encoder circuit 210 supports different compression modes, including lossy compression, lossless compression, and no compression. Wireless communication circuit 212 receives the multiple frames (generated by encoding the same input data D_IN) from encoder circuit 210 and transmits at least one selected frame from the received multiple frames to wireless communication device 202 via wireless link 204. For example, wireless communication circuit 212 can sequentially transmit all frames with different encoding qualities (e.g., different bit rates) to wireless communication device 202, thereby achieving high-quality audio playback on the receiving device. Alternatively, wireless communication circuit 212 can transmit only a subset of frames with different encoding qualities (e.g., different bit rates) to wireless communication device 202, thereby achieving high-stability audio playback on the receiving device.

[0041] To better understand the technical features of the present invention, it is assumed that multiple frames with different coding qualities (generated by encoding the same input data D_IN) may include a first frame F1 with low coding quality (e.g., low bit rate) and a second frame F2 with high coding quality (e.g., high bit rate). Control circuitry 216 may include a TX scheduler (not shown) for scheduling the transmission of the first frame (e.g., low quality / bit rate frame) F1 and the second frame (e.g., high quality / bit rate frame) F2, wherein whether or not the second frame F2 is transmitted may depend on the current channel state of wireless link 204 and / or the setting of flag FL. Decoder circuitry 206 (which is part of the audio codec of the receiving device) receives an audio bitstream from wireless link 204 (which may contain PHY data packets carrying the first frame F1, or may contain PHY data packets carrying the first frame F1 and subsequent PHY data packets carrying the second frame F2), and decodes the received audio bitstream to generate a PCM audio output for audio playback by the receiving device. If the audio bitstream does not contain a PHY packet carrying the second frame F2, the PCM audio output can be generated by decoding the PHY packet carrying the first frame F1. If the audio bitstream contains a PHY packet carrying the first frame F1 and a subsequent PHY packet carrying the second frame F2, the PCM audio output can be generated by decoding the PHY packet carrying the second frame F2.

[0042] In some embodiments of the present invention, the encoding operation performed on the same input data D_IN may include lossy compression with a first compression setting and lossy compression with a second compression setting. Therefore, the first frame (e.g., a low quality / bitrate frame) F1 may be a lossy compressed frame, and the second frame (e.g., a high quality / bitrate frame) F2 may also be a lossy compressed frame.

[0043] In some embodiments of the present invention, the encoding operation performed on the same input data D_IN may include lossy compression and lossless compression. Therefore, the first frame (e.g., a low-quality / bitrate frame) F1 may be a lossy compressed frame, while the second frame (e.g., a high-quality / bitrate frame) F2 may be a lossless compressed frame. For example, the second frame (e.g., a high-quality / bitrate frame) F2 may be a lossless compressed frame containing only lossless compressed data. As another example, the second frame (e.g., a high-quality / bitrate frame) F2 may be a lossless compressed frame containing multiple subframes, wherein the multiple subframes may include an uncompressed subframe and a lossless compressed subframe. Therefore, the decoder circuit 206 of the wireless communication device 202 can perform partial lossless decoding based on the correct subframes.

[0044] In some embodiments of the present invention, the encoding operation performed on the input data D_IN may include lossy compression and no compression. Therefore, the first frame (e.g., a low-quality / bitrate frame) F1 may be a lossy compressed frame, while the second frame (e.g., a high-quality / bitrate frame) F2 may be an uncompressed frame.

[0045] The control circuit 216 includes a TX scheduler for controlling the transmission of the first frame F1 and the second frame F2 to achieve packet hierarchical ABR control. Figure 3 This is a flowchart of a packet-level ABR control method according to an embodiment of the present invention. The packet-level ABR control method can be adopted by a wireless communication device 200. The steps do not necessarily need to be exactly the same, as long as the results are substantially the same. Figure 3The operations are performed sequentially as shown. In step S302, encoder circuit 210 receives input data D_IN. In step S304, encoder circuit 210 performs an encoding operation on the same input data D_IN to generate and output a first frame (e.g., a low-quality / bitrate frame) F1 and a second frame (e.g., a high-quality / bitrate frame) F2. In step S306, wireless communication circuit 212 (in particular, selection circuit 214 of wireless communication circuit 212) receives the first frame F1 and the second frame F2 generated and output by encoder circuit 210. Furthermore, wireless communication circuit 212 (in particular, control circuit 216 of wireless communication circuit 212) instructs selection circuit 214 to output the first frame F1 to TX circuit 218, and instructs TX circuit 218 to transmit the first frame F1 to wireless communication device 202 via wireless link 204. Please note that regardless of whether the transmission of the second frame (e.g., a high-quality / bitrate frame) F2 is permitted, the wireless communication device 200 will always transmit the first frame (e.g., a low-quality / bitrate frame) F1 to the wireless communication device 202. When the input data D_IN is audio data, the transmission of the first frame (e.g., a low-quality / bitrate frame) F1 can provide audio dropout protection for the wireless communication device 202.

[0046] In this embodiment, the TX circuit 218 may have multiple individual PHY circuits, including a high-stability PHY circuit (labeled "PHY1") 222 and a high-speed PHY circuit (labeled "PHY2") 224. The high-stability PHY circuit 222 is used to transmit low-quality / bit-rate frames to the wireless communication device 202. The high-speed PHY circuit 224 is used to transmit high-quality / bit-rate frames to the wireless communication device 202. Therefore, in step S306, the high-stability PHY circuit 222 is enabled to transmit the first frame F1 under a narrower PHY bandwidth to achieve high-stability transmission.

[0047] In step S308, the control circuit 216 determines whether the multiple retransmission time slots should be used for their original purpose (i.e., retransmission of the first frame F1) or reused for the transmission of the second frame F2. Specifically, the use of the retransmission time slots depends on whether the previously transmitted first frame F1 was successfully received by the wireless communication device 202. NAK is used to indicate which expected frame was not successfully received by the receiver. ACK is used to indicate which frame has been successfully received by the receiver.

[0048] Consider the case where RX circuit 220 receives an ACK (step S308) from wireless communication device 202, indicating that wireless communication device 202 has received the previously transmitted first frame (e.g., a low-quality / bitrate frame) F1. The process proceeds to step S310. In step S310, control circuit 216 checks the setting of flag FL. The setting of flag FL controls whether the transmission of the second frame F2 should be skipped in the retransmission slot. Figure 4 This diagram illustrates the availability of retransmission slots between the transmission of two frames, a and b. A Bluetooth adapter (e.g., wireless communication device 200) can transmit frames a / b to a Bluetooth headset (e.g., wireless communication device 202). Considering that frames a / b are transmitted in a clean environment, no data packet loss occurs, and the Bluetooth headset (e.g., wireless communication device 202) does not request data packet retransmission, these retransmission slots originally defined for data packet retransmission are unused (free). According to the packet hierarchy ABR control scheme proposed according to the present invention, these unused retransmission slots can be reused to transmit the second frame F2. However, the Bluetooth adapter (e.g., wireless communication device 200) may also use these unused retransmission slots to transmit other data (e.g., non-audio data) to the Bluetooth headset (e.g., wireless communication device 202). When the flag FL is set to the first logic value (e.g., FL=1), it indicates that the packet level ABR control scheme proposed in this invention should be deactivated, thereby allowing unused retransmission time slots to be reused to transmit other data (e.g., non-audio data) to Bluetooth headsets (e.g., wireless communication device 202). Therefore, the operation of transmitting the second frame F2 in the retransmission time slot will be skipped (step S312).

[0049] When the flag FL is set to a second logic value (e.g., FL=0), it indicates that the packet-level ABR control scheme proposed in this invention can be enabled, thereby allowing unused retransmission time slots to be reused for transmitting the second frame F2. Therefore, the process proceeds to step S316. In step S316, the control circuit 216 instructs the selection circuit 214 to output the second frame F2 to the TX circuit 218, and instructs the TX circuit 218 to transmit the second frame F2 to the wireless communication device 202 via the wireless link 204. As described above, the TX circuit 218 may have multiple individual PHY circuits, including a high-stability PHY circuit (labeled "PHY1") 222 and a high-speed PHY circuit (labeled "PHY2") 224. Therefore, in step S316, the high-speed PHY circuit 224 is enabled to transmit the second frame F2 with a wider PHY bandwidth, thereby achieving high-speed transmission.

[0050] In short, the wireless communication circuit 212 (especially the control circuit 216 of the wireless communication circuit 212) is further configured to receive the flag FL and determine whether to skip transmitting the second frame (e.g., a high-quality / bitrate frame) F2 in the retransmission slot based on the setting of the flag FL. Note that the setting of the flag FL at the receiving device (i.e., the wireless communication device 202) is synchronized with the setting of the flag FL at the source device (i.e., the wireless communication device 200). Therefore, the wireless communication device 202 can refer to the setting of the flag FL to skip the function of decoding the second frame F2 in the retransmission slot. However, this is merely illustrative and not intended to limit the invention.

[0051] Consider another scenario where the RX circuit 220 receives a NAK from the wireless communication device 202 (step S308), where the NAK indicates that the wireless communication device 202 did not receive the previously transmitted first frame F1. In response to the NAK indicating a lost data packet, the control circuit 216 instructs the TX circuit 218 to retransmit the first frame F1 in the retransmission time slot (step S314).

[0052] Figure 5 This is a schematic diagram illustrating an operational scenario where a retransmission slot is used to retransmit previously transmitted low-quality / low-bit-rate frames a / b. A Bluetooth adapter (e.g., wireless communication device 200) can transmit frames a / b to a Bluetooth headset (e.g., wireless communication device 202). For example, frames a / b can be transmitted via a high-stability PHY circuit. When frames a / b are transmitted in a noisy environment, data packet loss occurs, so the Bluetooth headset (e.g., wireless communication device 202) requests data packet retransmission. Therefore, the same frames a / b are retransmitted in the retransmission slot.

[0053] Figure 6 This diagram illustrates an operational scenario where retransmission slots are reused to transmit high-quality / bitrate frames that have not yet been transmitted. A Bluetooth adapter (e.g., wireless communication device 200) can transmit frames a / b to a Bluetooth headset (e.g., wireless communication device 202). For example, frames a / b can be transmitted via a high-stability PHY circuit. When frames a / b are transmitted in a clean environment, no data packet loss occurs, and the Bluetooth headset (e.g., wireless communication device 202) does not request data packet retransmission. Therefore, the retransmission slots can be reused to transmit frames au / bu. For instance, since frames au / bu do not affect stability, they can be transmitted via a high-speed PHY circuit to save transmission time. Furthermore, since frames au / bu are transmitted in unused retransmission slots, they do not affect the retransmission of frames a / b.

[0054] According to the packet-level ABR control scheme proposed by the present invention, the source device can encode a single input bitstream (e.g., an uncompressed PCM bitstream) to generate two bitstreams with different qualities / bit rates (e.g., a first lossy bitstream and a second lossy bitstream, or a lossy bitstream and a lossless bitstream, or a lossy bitstream and an uncompressed bitstream). The bitstream with the lower quality / bit rate (e.g., the lossy bitstream) is transmitted first, while the bitstream with the higher quality / bit rate (e.g., the lossy bitstream, the lossless bitstream, or the uncompressed bitstream) is only allowed to be transmitted if the wireless link between the source device and the receiving device has good quality. Therefore, the source device can dynamically switch between operations that transmit only the low-quality / bit-rate bitstream and operations that transmit the low-quality / bit-rate bitstream and the high-quality / bit-rate bitstream sequentially, referring to the availability of unused retransmission slots. Since the bitstream switching is handled in the source device, no rate estimation is required, and the response delay is almost zero. Specifically, the packet-level ABR control scheme proposed in this invention enables seamless switching between stability-oriented transmission in noisy environments and quality-oriented transmission in clean environments without audio jumpiness. Furthermore, since low-quality / bitrate bitstreams have higher transmission priority than high-quality / bitrate bitstreams, the packet error rate (PER) of high-quality / bitrate bitstreams (e.g., lossless or uncompressed bitstreams) is no longer a bottleneck.

[0055] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be within the scope of the present invention.

Claims

1. A wireless communication device, comprising: An encoder circuit is used to encode the same input data to generate and output multiple frames with different encoding qualities; and A wireless communication circuit is used to receive the plurality of frames from the encoder circuit and transmit at least one selected frame from the plurality of frames to another wireless communication device via a wireless link.

2. The wireless communication apparatus of claim 1, wherein the plurality of frames include a first frame having a first coding quality and a second frame having a second coding quality, the second coding quality being higher than the first coding quality, and the at least one frame includes the first frame.

3. The wireless communication device of claim 2, wherein the wireless communication circuit is further configured to receive a negative acknowledgment indicating that the first frame was not received by the other wireless communication device, and to retransmit the first frame in a retransmission time slot in response to the negative acknowledgment; and the at least one frame does not contain the second frame.

4. The wireless communication device of claim 2, wherein the wireless communication circuit is further configured to receive an acknowledgment indicating that the first frame has been received by the other wireless communication device; and the at least one frame further includes the second frame, wherein the wireless communication circuit transmits the second frame in a retransmission time slot in response to the acknowledgment.

5. The wireless communication device of claim 4, wherein the wireless communication circuit comprises: Multiple separate physical layer circuits, including: The first physical layer circuitry is used to transmit the first frame; and The second physical layer circuit is used to transmit the second frame.

6. The wireless communication device of claim 2, wherein the wireless communication circuit is further configured to receive a flag and, based on the flag, determine whether to transmit the second frame in a slightly over-retransmission time slot.

7. The wireless communication device of claim 2, wherein the first frame is a lossy compressed frame.

8. The wireless communication device of claim 7, wherein the second frame is a lossy compressed frame.

9. The wireless communication device of claim 7, wherein the second frame is a lossless compressed frame.

10. The wireless communication device of claim 9, wherein the lossless compressed frame comprises a plurality of subframes, and the plurality of subframes comprises uncompressed subframes and lossless compressed subframes.

11. The wireless communication device of claim 7, wherein the second frame is an uncompressed frame.

12. The wireless communication device of claim 1, wherein the same input data is uncompressed audio data.

13. The wireless communication device of claim 1, wherein the wireless link is a Bluetooth link.

14. The wireless communication device of claim 13, wherein the Bluetooth link is a low-power synchronization channel.

15. The wireless communication device of claim 13, wherein the wireless communication device is an adapter, a mobile phone, or a laptop computer, and the other wireless communication device is a headset, a speaker, or an earphone.

16. A wireless communication method, comprising: Encoding operations are performed on the same input data to generate and output multiple frames with different encoding qualities; and At least one frame selected from the plurality of frames is transmitted to the wireless communication device via a wireless link.

17. The wireless communication method of claim 16, wherein the plurality of frames includes a first frame having a first coding quality and a second frame having a second coding quality, the second coding quality being higher than the first coding quality, and the at least one frame includes the first frame.

18. The wireless communication method of claim 17, further comprising: The receiver receives a negative acknowledgment indicating that the first frame was not received by the wireless communication device; and The first frame should be retransmitted in the retransmission slot if the confirmation is denied. At least one of the frames does not contain the second frame.

19. The wireless communication method of claim 17, further comprising: The receiver acknowledges that the first frame has been received by the wireless communication device. The at least one frame also includes the second frame, which will be transmitted in the retransmission slot in response to the confirmation.

20. The wireless communication method of claim 16, wherein the first frame is a lossy compressed frame; and the second frame is a lossy compressed frame, a lossless compressed frame, or an uncompressed frame.

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