DECT-based high-density wireless audio system

Abstract

A wireless communication method and protocol for wireless RF transmission of audio data from multiple wireless RF devices (PPs) to a wireless RF receiving device (FP) using the full-slot DECT protocol. The FP broadcasts multiplexed control information to multiple PPs in each frame. The multiple PPs receive the multiplexed control information and extract the control information targeted for their respective PPs from the multiplexed control information. Preferably, the multiple PPs are synchronized to transmit audio data spanning both the first and second time slots of the frame in each of the time slots. This allows both the normal uplink and downlink portions of the DECT frame to be used for audio data transmission, thereby enabling multiple PPs to connect to a single FP with high audio quality and low latency. This allows the method to be used in a telephone conference system consisting of multiple wireless microphone devices, a wireless microphone and / or musical instrument audio system for live performances, or the like.

Description

[Technical Field]

[0001] The present invention relates to the field of wireless transmission of audio, such as one-way wireless audio streaming. In particular, the present invention proposes a DECT-based high density wireless system that conveys multiple audio streams, such as by utilizing DECT full slots. [Background technology]

[0002] For applications such as wireless microphones for live performances, transmitters for musical instruments, and wireless microphones in teleconferencing systems, simple, high-quality multi-channel wireless audio transmission with low latency (delay) is important.

[0003] Traditional wireless DECT technology is based on a star network topology, typically suitable for two-way communication between multiple portable parts (PPs) and a base station (fixed part, FP). The FP typically controls all communication to multiple PPs, and typically provides slot and frame timing information in a master-slave configuration. Multiple PPs are precisely synchronized to the FP's timing.

[0004] However, in the case of simultaneous streaming of high quality audio from multiple PPs to an FP, such DECT-based protocols limit the number of PPs that can exist simultaneously and / or the available audio quality and / or the resulting latency. Summary of the Invention

[0005] In light of the above, it is therefore an object of the present invention to provide a method for wireless RF communication of low latency, high quality audio streaming from multiple simultaneous RF transmitting devices.

[0006] In a first aspect, the present invention provides a method for wireless RF one-way communication of audio data, the method comprising: providing a plurality of handset devices, each configured to transmit audio data represented in frames in a wireless RF signal including a plurality of time slots according to a DECT compatible protocol; providing a base unit configured to receive the wireless RF signals from a plurality of mobile devices and to reproduce respective audio data represented therein; broadcasting, by a parent device, multiplexed control information in each DECT-compatible frame to a plurality of child devices; receiving the multiplexed control information by each of the slave devices; -extracting control information for each slave device from the multiplexed control information; Includes:

[0007] Such a method provides a high-capacity wireless RF system that uses the DECT protocol to allow a single base station or base station to operate multiple slave devices, such as microphones in a teleconferencing system. This is possible by common broadcast of control information from the base station to all slave devices. This allows both the uplink and downlink portions of the DECT frame to be used for transmitting audio data from the slave devices to the base station, thereby increasing audio transmission capacity. This can be used to increase the number of slave devices connected to a single base station and / or ensure higher audio quality for the same number of master devices. Furthermore, this method enables multi-channel audio transmission to achieve low latency, an important parameter for live audio streaming.

[0008] To accommodate voice transmissions from a large number of portable base stations, a system can be used that includes several separate base station receivers (base stations) operating in synchronization, thus providing, for example, up to 80-100 or even more voice channels.

[0009] The DECT protocol exists in many regional or country-specific variants, but the present invention is compatible with and therefore can be utilized across most of these specific DECT variants.

[0010] The following expressions are used and explained: -Time Division Multiple Access (TDMA) -Digital Enhanced Radio Telecommunications (DECT) - Cyclic Redundancy Check (CRC) for error checking A single radio event, such as a transmission or reception, is represented as a slot or timeslot. A repeating sequence of slots (TDMA frame) containing slots for interference scanning is denoted a frame.

[0011] Preferred embodiments and features are described below.

[0012] The DECT compatible frame is preferably a full slot DECT frame, thus enabling high quality audio quality with a large number of handsets. Alternatively, the DECT frame may be a long slot frame, a double slot frame, or a half slot frame.

[0013] Preferably, one or more time slots in each frame are dedicated to the broadcast of the multiplexed control information from the parent device. In particular, two time slots in each half-frame may be dedicated to the broadcast of the multiplexed control information from the parent device. In particular, the first two time slots in each half-frame may be dedicated to the broadcast of the multiplexed control information. However, it will be appreciated that preferably, any one or two time slots in each frame may be dedicated to the broadcast of the multiplexed control information.

[0014] The multiplexed control information is preferably included as an A field multiplexed within a B field of one or more slots, such as one or more full slots. Specifically, a slot, e.g., a full slot, dedicated to the multiplexed control information may include an A field and a B field, with the B field including a header portion, an error checking portion (e.g., CRC), and a portion containing the multiplexed control information.

[0015] Preferably, at least 50% of the time slots in both the first and second halves of each frame are dedicated to transmitting audio data from multiple slave devices, for example, 50% to 80%. In this way, a large amount of the available transmission capacity is utilized for audio data, which still allows connecting multiple PPs to one FP with high quality audio, for example, at a sampling frequency of 48 kHz and with amplitude representation of 16 to 32 bits.

[0016] The multiple slave devices are preferably synchronized to transmit audio data in each of the time slots of each frame. Specifically, more than eight slave devices, e.g., 9-16 slave devices, may be synchronized to transmit audio data in each of the time slots of each frame, e.g., each slave device transmits audio data in one time slot per half frame.

[0017] The base unit is preferably configured to receive a total of at least 64 kbps of audio data.

[0018] It should be understood that each slave device may be a stand-alone device comprising RF receiving and transmitting circuitry configured to operate in accordance with the method defined above. A slave device may comprise an audio data source, e.g., a microphone with an associated analog-to-digital converter, or the slave device may be a dedicated stand-alone audio transmitting device having an analog or digital audio interface for receiving audio signals, e.g., a wireless RF transmitter for transmitting sound from a musical instrument or the like.

[0019] This method is suitable for high quality audio transmission and allows low latency, so the slave device can be, for example, a stage microphone. Another example of a wireless RF device is a teleconferencing microphone.

[0020] Generally, this method is advantageous in wireless voice transmission systems, as it provides a trade-off between 1) the number of slave devices that can be connected to one master device (base station) and 2) sound quality (i.e., bit rate per second) given the limited capacity of the wireless RF transmission channel.

[0021] In particular, the audio data packets may represent digital audio signals sampled at a sampling frequency of 20 kHz or higher, such as 32 kHz, 48 kHz or higher. The digital audio signal may be an encoded digital audio signal, for example encoded according to an ADPCM algorithm or the like.

[0022] In a preferred embodiment, the method is implemented as a DECT compatible protocol that is compatible with the requirements of one or more regional or national DECT compatible variants.

[0023] In some embodiments, the method comprises: broadcasting, by the master device, audio data of at least one time slot, such as two to four time slots, in each DECT-compatible frame to a plurality of slave devices; receiving, by each of the slave devices, audio data of at least one time slot; extracting, by each of the plurality of slave devices, an audio signal in response to the received audio data of at least one time slot; Includes:

[0024] In such an embodiment, another audio feature is added to the one-way audio transmission from multiple handset devices to the base device, i.e., the possibility of broadcasting or multicasting one audio signal to all of the multiple handset devices. In particular, the base device or another device may generate an audio signal, e.g., a combination of the multiple audio signals, in response to multiple audio signals received from the multiple handset devices, which may then be transmitted as feedback to the multiple handset devices. Thus, the base device cannot perform duplex audio communication with multiple handset devices, but may simply transmit or broadcast one common audio signal to all of the multiple handset devices. In particular, two to four time slots in each DECT frame may be dedicated to the broadcast of the audio data from the base device. In particular, two time slots in each half-frame are dedicated to the broadcast of the audio data from the base device. In particular, two consecutive time slots in each half-frame are dedicated to the broadcast of the audio data from the base device. In particular, at least four time slots in each DECT frame are dedicated to the multiplexed control information and at least four time slots in each DECT frame are dedicated to the audio data broadcast by the base device. In particular, at least 16 time slots in each DECT frame are dedicated to the audio data transmitted from multiple child devices. In a particular embodiment, each DECT frame has 16 time slots dedicated to audio data from multiple child devices, 4 time slots dedicated to multiplexed control information, and 4 time slots dedicated to audio data broadcast by the base device.

[0025] In a second aspect, the present invention provides a wireless RF device comprising at least one RF transmitter circuit and an RF receiver circuit connected to at least one RF antenna, the wireless RF device being configured to operate as a slave device according to the method of the first aspect.

[0026] The wireless RF device may be configured to receive audio data represented in at least one time slot in each DECT frame, and in particular the wireless RF device may comprise an audio transducer, such as a speaker, configured to generate an audio signal based on the received audio data.

[0027] In one embodiment, the wireless RF device comprises a microphone configured to capture sound and generate audio data in response, e.g., to function as a high-quality stage microphone, a teleconferencing microphone, or the like. Alternatively, or in addition, the FP comprises an analog or digital audio interface for receiving audio signals, e.g., a wireless RF transmitter for transmitting sounds from a musical instrument or the like. In particular, the wireless RF device is a headset or other device including a combination of a microphone and an acoustic transducer configured to generate an acoustic signal in response to a received audio signal. In particular, the speaker may be in the form of an earphone, a headphone, or an in-ear device.

[0028] In a third aspect, the present invention provides a FP configured to operate as a master device according to the method of the first aspect.

[0029] The FP, or base unit, may be a stand-alone device with a multi-channel audio output interface with multiple analog and / or digital audio outputs configured to output audio signals corresponding to audio data received from multiple wireless RF devices. Alternatively, the FP may form part of another device, e.g., a live performance or studio audio system such as an audio mixing console. In particular, the base unit may be further configured to broadcast an audio signal represented as audio data represented in at least one time slot within each DECT frame.

[0030] In a fourth aspect, the present invention provides a system comprising a plurality of PPs according to the second aspect, and a FP according to the third aspect.

[0031] In particular, the system may include an audio reproduction system having at least one speaker configured to generate an acoustic output in response to audio data transmitted from at least one of the plurality of PPs and reproduced by the plurality of FPs.

[0032] To enable multiple audio channels, the system may include multiple FPs according to a third aspect, each of the multiple FPs configured to receive audio data from multiple PPs according to the second aspect, and the multiple FPs configured to perform synchronized coordination.

[0033] In particular, the system may be one of a teleconferencing system, a live performance wireless audio system, a boardroom conferencing system, a classroom audio system, or a parliamentary or conference audio system.

[0034] In particular, the system may include at least eight, for example between eight and sixteen, mobile devices configured to establish a wireless RF connection to the base unit using audio data transmission in each of the time slots of each DECT frame.

[0035] In a fifth aspect, the present invention provides use of a system according to the fourth aspect in one or more of a teleconferencing system, a wireless audio system for live performances, a boardroom conferencing system, a classroom audio system, or a parliamentary or conference audio system.

[0036] It will be appreciated that the necessary RF transmit and receive circuitry, antennas and programming required to carry out the method of the first aspect will be known to those skilled in the art based on the description of the method of the present invention herein.

[0037] In a sixth aspect, the present invention provides program code comprising a first code portion and a second code portion, the program code being configured to perform a method according to the first aspect when the first code portion is executed on a processor in a plurality of child devices (e.g., according to the second aspect) and when the second code portion is executed on a processor in a parent device (e.g., according to the third aspect).

[0038] In particular, the first and second code portions may be stored in memory within respective chips of the first and second devices, or on one or more tangible storage media, or may be available over the Internet in a downloadable version. The first and second code portions may be in a general code format or in a processor-specific format.

[0039] It is understood that the same advantages and embodiments described for the first aspect apply to the further described aspects as well, and further, it is understood that the described embodiments can be mixed in any way between all the described aspects. [Brief explanation of the drawings]

[0040] The present invention will now be described in more detail with reference to the accompanying figures. [Figure 1] 1 shows a simplified block diagram of a system consisting of three handset devices transmitting one-way audio to a base device that broadcasts control information to wireless RF devices according to the DECT protocol. [Figure 2] 1 illustrates steps of a method embodiment. [Figure 3] An example of a DECT frame is shown, with each half frame having control information from the parent unit and audio data from the child unit. [Figure 4] 1 illustrates a possible example of using a full slot to broadcast multiplexed control information to multiple wireless RF devices. [Figure 5] 1 illustrates example components of a wireless RF microphone device and a corresponding wireless RF receiver device. [Figure 6A] 10 illustrates an example DECT frame structure for an embodiment with audio multicast to multiple wireless RF devices. [Figure 6B] 10 illustrates an example DECT frame structure for an embodiment with audio multicast to multiple wireless RF devices.

[0041] The figures illustrate particular ways of practicing the invention, and these figures should not be construed as limiting other possible embodiments that may fall within the scope of the appended set of claims. DETAILED DESCRIPTION OF THE INVENTION

[0042] FIG. 1 shows a simplified diagram of three wireless RF devices, slaves PP1, PP2, and PP3, each configured to convey a respective audio signal AD1, AD2, or AD3 represented in a digital data packet transmitted in an RF representation to a wireless RF receiving device, master, or base station, using a DECT-based protocol. The master (FP) regenerates the received audio data into respective audio signals A1, A2, and A3. According to a preferred embodiment of the present invention, the slave devices PP1, PP2, and PP3 are synchronized using control information transmitted from the master (FP) as broadcast common information BC transmitted to all of the slave devices PP1, PP2, and PP3 in one or more time slots within each DECT frame. Thus, because all control information is transmitted in the broadcast time slots BC, only a limited portion of the frame is occupied with control information, e.g., for synchronization purposes, thereby leaving room for transmission of audio data from the slave devices PP1, PP2, and PP3 in both the uplink and downlink portions of each frame. In this way, multiple child devices PP1, PP2, PP3 transmitting high quality, i.e., high rate, audio data can be connected to a single parent device FP. The transmitted audio is still low latency and highly reliable due to synchronization, and preferably, the child devices PP1, PP2, PP3 are controlled and synchronized to continuously transmit one audio data packet in each of the predetermined time slots within each frame.

[0043] 2 illustrates steps of an embodiment of a wireless RF communication method for RF communicating multiple digital audio data according to the DECT protocol. First, a plurality of slave devices (P_PPx) are provided, each configured to transmit audio data according to a DECT-compatible protocol, the audio data being represented in a frame of a wireless RF signal including multiple time slots. A master device (P_FP) is also provided, configured to receive the wireless RF signal from the slave devices and regenerate the respective audio data represented therein. The method includes the master device broadcasting multiplexed control information (B_CI) to the multiple slave devices in each DECT frame, including, for example, synchronization information, so that the multiple slave devices can transmit their own audio data in different predetermined time slots within each frame. Next, the multiplexed control information is received by each of the multiple slave devices (R_CI), and the control information targeted for each slave device is extracted from the multiplexed control information (E_CI), thereby enabling each slave device to determine in which time slot to transmit its own audio data and avoid collisions. Finally, the multiple slave devices transmit audio data in each time slot within each frame (T_A). Preferably, the master device receives the successive frames and performs the step of regenerating an audio signal based on the audio data transmitted from each of the plurality of slave devices.

[0044] Figure 3 shows an implementation of the present invention, where time slots TS in both the TX and RX parts of each DECT frame are used to transmit audio data from multiple PPs, here eight PPs designated PP0 to PP7, to the FP. Using the DECT full slot and π / 4-DQPSK modulation in the B field, 1280 bits are available for payload data. To protect the audio decoder, a 16-bit CRC (one per transmission) is used, resulting in 1248 bits of encoded audio per frame (124.8 kbps).

[0045] In Figure 3, each 10 ms DECT frame is divided into 24 time slots TS, and the first two slots in each half-frame, i.e., slots 0, 1, 12, and 13, for a total of four time slots, are dedicated to the broadcast of control information by the parent FP for reception by all PPs. As can be seen, each PP has two time slots dedicated to transmitting audio data, one in each half-frame. For example, PP0 transmits data in time slots TS 2 and 14.

[0046] In this way, instead of having a return channel in the second half of the DECT frame, 5 ms of audio is transmitted in each half-frame, and the proposed DECT frame design provides a duplex connection. Using a DECT full-slot duplex bearer connection, an audio bandwidth of 124.8 kbps from PP to FP can be obtained, which corresponds to a maximum of 8 PPs connected to one FP. The theoretical maximum microphone density is 104 (using 13 synchronized FPs), but a maximum of 80 (10 synchronized FPs) is more preferable (this example also applies to products operating within the European Union).

[0047] Figure 4 shows an example implementation of one full slot that the FP broadcasts to all PPs. In this particular implementation, the full slot contains a 640-bit B field, which includes a header and multiplexed A field data channels assigned to each PP. In the case of an intracell handover, the PP uses two A field data channels that are broadcast during the handover.

[0048] 5 shows the components of a particular embodiment of a handset device (PP) in the form of a wireless microphone and a corresponding base device (FP): the PP comprises a microphone and an analog-to-digital converter A / D connected to the microphone, operating at a sampling frequency of, for example, 48 kHz, which receives the analog audio signal from the microphone and converts it to digital form, the PP applies the digital signal to a digital encoder, followed by a CRC calculation and finally encrypting (AES256) the resulting data, which is finally transmitted over RF in a predetermined time slot within a DECT frame.

[0049] The parent device FP receives audio data packets from the multiple PPs and performs inverse processing including decoding the audio data from each of the PPs, and the resulting audio signals are subjected to further processing which may include Acoustic Echo Cancellation (AEC), mixing and further audio processing before a final audio output is generated, for example downgrading the combination of multiple audio signals regenerated from the multiple PPs into one or two separate audio channels.

[0050] In the device embodiment shown in Figure 5, using the DECT frame structure shown in Figure 3, the total latency obtained is approximately 24ms, and this latency is constant for all PPs.

[0051] 6A and 6B show two different DECT frame configurations for an embodiment with an audio multicast channel that broadcasts audio signals to all of a plurality of child devices. In both of these configurations, a DECT frame has 24 time slots, and is divided into two equal parts with 12 time slots each: - 16 time slots are dedicated to voice data from multiple child devices; - Four time slots are dedicated to multiplexing control information to multiple mobile devices, -Four time slots are dedicated to audio data broadcast or multicast from a parent device to multiple child devices. In Figure 6A, two consecutive time slots are dedicated to audio data broadcast or multicast in each half-frame. In Figure 6B, the two time slots dedicated to audio data broadcast or multicast in each half-frame are separated by eight time slots dedicated to audio data from multiple child devices.

[0052] In summary, the present invention provides a wireless communication method and protocol for transmitting audio data over RF from multiple wireless RF devices (PPs) to a wireless RF receiving device (FP) using the full-slot DECT protocol. The FP broadcasts multiplexed control information to multiple PPs in each frame. The multiple PPs receive the multiplexed control information and extract the control information targeted for their respective PPs from the multiplexed control information. The multiple PPs are synchronized to transmit audio data spanning both the first and second time slots of the frame in each of the time slots. This allows both the normal uplink and downlink portions of the DECT frame to be used for audio data transmission, thereby enabling multiple PPs to be connected to a single FP with high audio quality and low latency. This allows this method to be used in a teleconferencing system consisting of multiple wireless microphone devices, a wireless microphone and / or musical instrument audio system for live performances, or the like.

[0053] Although the present invention has been described with reference to specific embodiments, it should not be construed as being limited to the examples provided. The scope of the present invention should be interpreted in light of the appended set of claims. In connection with the claims, the terms "comprising" or "includes" do not exclude other possible elements or steps. Furthermore, references such as "a," "an," etc. should not be construed as excluding a plurality. Furthermore, the use of reference signs in the claims to elements shown in the figures should not be construed as limiting the scope of the present invention. Furthermore, individual features recited in different claims can potentially be advantageously combined, and references to these features in different claims do not exclude that a combination of features is not possible or advantageous.

Claims

1. A wireless RF one-way communication method for audio data, comprising: - providing a plurality of slave devices (P_PPx), each configured to transmit, according to a DECT compatible protocol, audio data represented in frames in a wireless RF signal comprising a plurality of time slots (TS); providing a parent device configured to receive the wireless RF signals from the plurality of child devices and to reproduce each of the audio data represented therein (P_FP), - broadcasting by the parent device (B_CI) to the child devices multiplexed control information in respective DECT compatible frames, the multiplexed control information including information enabling the child devices to transmit their audio data in different predefined time slots within each frame; receiving the multiplexed control information by each of the plurality of slave devices (R_CI); Extracting control information for each of the slave devices from the multiplexed control information (E_CI); A method comprising:

2. 2. The method of claim 1, wherein the DECT compatible frame is a full slot frame.

3. 2. The method of claim 1, wherein the DECT compatible frame is selected from a long slot frame, a double slot frame, and a half slot frame.

4. A method according to any one of claims 1 to 3, wherein one or more of the time slots in each frame are dedicated to the broadcast of the multiplexed control information from the parent device.

5. 5. The method of claim 4, wherein two of the time slots in each half-frame are dedicated to broadcasting the multiplexed control information from the parent device, and the first two of the time slots in each half-frame are dedicated to broadcasting the multiplexed control information.

6. 6. A method according to claim 1, wherein the multiplexed control information is included as an A field multiplexed within a B field of one or more slots, one slot dedicated to the multiplexed control information including an A field and a B field, the B field including a header portion, a cyclic redundancy check (CRC), and a portion including the multiplexed control information.

7. A method according to any one of claims 1 to 6, wherein at least 50% of the time slots in both the first and second halves of each of the frames are dedicated to audio data transmission from the plurality of child devices.

8. The method of any one of claims 1 to 7, wherein the plurality of slave devices are synchronized to transmit audio data in each of the time slots of each of the frames, and wherein more than eight slave devices are synchronized to transmit audio data in each of the time slots of each of the frames.

9. A method according to any one of claims 1 to 8, wherein the base device is configured to receive voice data at a total rate of at least 64 kbps.

10. - broadcasting by said master device the audio data of at least one of said time slots in each of said DECT compatible frames to said plurality of slave devices; receiving the audio data of the at least one time slot by each of the plurality of slave devices; extracting, by each of said plurality of slave devices, an audio signal in response to the received audio data of said at least one time slot; The method of any one of claims 1 to 9, further comprising:

11. 11. The method of claim 10, wherein two to four of the time slots in each DECT-compatible frame are dedicated to the broadcast of the audio data from the base device, two of the time slots in each half-frame are dedicated to the broadcast of the audio data from the base device, and two consecutive of the time slots in each half-frame are dedicated to the broadcast of the audio data from the base device.

12. 12. A method according to claim 10 or 11, wherein at least four of the time slots in each of the DECT compatible frames are dedicated to the multiplexed control information, at least four of the time slots in each of the DECT compatible frames are dedicated to the audio data broadcast by the base device, and at least 16 of the time slots in each of the DECT compatible frames are dedicated to audio data transmitted from the plurality of child devices.

13. A wireless RF device (PP) comprising at least one RF transmitting circuit and an RF receiving circuit connected to at least one RF antenna, configured to operate according to the child device of the method of any one of claims 1 to 12, and comprising a microphone configured to capture sound and generate audio data accordingly, wherein the wireless RF device (PP) comprises an acoustic transducer configured to receive audio data represented in at least one time slot in each of DECT compatible frames, and configured to generate an acoustic signal based on the received audio data.

14. A wireless RF receiving device (FP) configured to operate according to the base device of the method of any one of claims 1 to 12 and further configured to broadcast an audio signal represented as audio data represented in at least one time slot in each of DECT compatible frames.

15. A plurality of wireless RF devices (PP) according to claim 13; A wireless RF receiving device (FP) according to claim 14, A system comprising: an audio reproduction system comprising at least one speaker configured to generate an acoustic output in response to audio data transmitted from at least one of said plurality of wireless RF devices (PP) and reproduced by said wireless RF receiving device (FP); a plurality of wireless RF receiving devices (FP) according to claim 14, each of said plurality of wireless RF receiving devices (FP) configured to receive audio data from a plurality of wireless RF devices (PP) according to claim 13, said plurality of wireless RF receiving devices (FP) configured to perform synchronized cooperation; a teleconferencing system, a wireless audio system for live performances, a boardroom conferencing system, a classroom audio system, or a parliamentary or conference audio system; system.

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