Hengxuan Technology TWS Headphones LBRT Technology

With the release of Airpods by Apple, TWS Bluetooth headsets became famous overnight. This new form of headset solution has been loved by consumers, but due to Apple's patent monopoly, it has become more difficult for other manufacturers to enter this field. However, Hengxuan Technology has successfully entered this market by relying on its technical patents.

The technical barrier lies in how to maintain communication between the mobile phone and the two Bluetooth headsets. One solution is that the smart device and the master headset transmit data via Bluetooth, and then the master headset forwards the data to the slave headset. In this way, the master headset has high power consumption and needs to send and receive more data, which will also affect the transmission performance.

Another solution is for the smart device to establish Bluetooth connections with the left and right earphones for data transmission, but most existing smart devices do not have the function of establishing multiple Bluetooth connections at the same time, so this solution is not very reliable. In addition, the frequency hopping information between the master earphone and the smart device is independent of the frequency hopping information between the master and slave earphones, and needs to be maintained and updated separately, which increases the complexity of binaural wireless headset communication, reduces the data transmission rate, occupies more channels, and causes more interference to other devices.

To this end, Hengxin Technology applied for an invention patent entitled "A Bluetooth audio hybrid communication solution for Bluetooth headsets" on March 21, 2018 (application number: 201810235920.X), an invention patent entitled "High-reliability Bluetooth headset wireless communication solution" on June 22, 2018 (application number: 201810648005.3), and an invention patent entitled "Wireless headset and communication method for wireless headset" on September 5, 2019 (application number: 201910834578.X). The applicant is Hengxin Technology (Shanghai) Co., Ltd.

Based on the currently disclosed information of these patents, let us take a look at Hengxuan Technology's TWS Bluetooth headset solution.

As shown in the figure above, it is a schematic diagram of the structure of audio data transmission between the smart device and the master earphone and the slave earphone in the patent. A Bluetooth connection is established between the smart device 10 and the master earphone 20, and a Bluetooth connection is also established between the master earphone and the slave earphone 30. When playing music, the smart device plays stereo music and sends the audio data packet to the master earphone through the Bluetooth connection. The master earphone receives the audio data packet and sends the audio data packet to the slave earphone, so that the master earphone and the slave earphone can play music at the same time.

In this process, the smart device sends audio data packets of left and right channels to the master earphone, and the slave earphone monitors and receives the audio data packets sent by the smart device to the master earphone, where ACK packet indicates response and NACK indicates negative response. This packet information is used to establish a connection between the master earphone and the slave earphone.

The specific process is: the slave earphone monitors and receives the audio data packet sent by the smart device to the master earphone. When the slave earphone receives the audio data packet from the smart device, it sends an ACK packet to the master earphone; when the slave earphone does not receive the audio data packet from the smart device, it sends a NACK packet to the master earphone.

The flowchart of the slave earphone monitoring and receiving the audio data packets sent by the smart device to the master earphone is shown in the figure above. The master earphone needs to obtain the Bluetooth address information of the smart device, digitally modulate the Bluetooth address information, and perform carrier modulation after adding the synchronization header. The modulated Bluetooth address information is sent to the slave earphone through the audio sending device of the master earphone.

The Bluetooth address information is received from the headset through the audio receiving device for carrier demodulation and information synchronization. In addition, the synchronization header of the Bluetooth address information needs to be removed and digital demodulation needs to be performed. The audio data packets sent by the smart device are monitored based on the Bluetooth address information of the smart device.

In this solution, a communication link is established between the master and slave earphones to achieve data transmission. In another patent of Hengxuan, this method of using ACK packets and NACK packets for data transmission is also introduced. The specific flow chart is as follows:

The smart device sends the maximum number of retransmissions N1 of the audio data packet to the main headset, that is, the mobile phone is preset to send the audio data packet N1 times to the main headset. According to the A2DP protocol, the smart device can retransmit the data packet countless times.

The first (N-1) times that the smart device sends an audio data packet to the main headset, the main headset will reply a NACK packet to the smart device, and regardless of whether the main headset receives the audio data packet, it needs to return a NACK signal, thereby forcing the smart device to repeat the transmission of the audio data packet, and reply an ACK packet to the smart device after the main headset receives the audio data packet. In this way, the main headset can avoid missing audio data packets, so that the audio quality received by the headset is better.

As shown in the figure above, it is a communication diagram for data transmission between a wireless headset and a mobile phone. The wireless headset includes two headsets 102 and 103, 104 is a first connection and uses Bluetooth for communication. When the master headset communicates with the mobile phone, the relevant communication parameters will also be sent to the slave headset. These parameters ensure that the slave headset can directly receive the Bluetooth signal sent by the mobile phone without performing pairing and establishment of the Bluetooth link.

The first connection 104 also involves a link management protocol, through which information can be exchanged between the mobile phone and the master headset. In order to determine whether the master and slave headsets support the FM mode, the mobile phone can also initiate a query to the slave headset. The information in the format of the link management protocol contains the minimum number of channels that can be used by both parties. These connections need to be updated periodically to ensure the anti-interference effect of the FM operation.

The above is the TWS Bluetooth headset invented by Hengxuan Technology. On the one hand, this solution only requires the mobile phone to establish a Bluetooth connection with the master headset to realize the communication between the two headsets and the mobile phone, and the master and slave headsets do not need to forward audio data packets via Bluetooth, thus effectively reducing the power consumption of the master headset. On the other hand, since the information transmission between the two headsets can follow the master headset, it reduces the occupation of other channels and reduces interference with other devices.