Patent Publication Number: US-2021176680-A1

Title: Apparatus for the configuration of a wireless radio connection and method of configuring a wireless radio connection

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of the foreign priority of German Patent Application No. 10 2019 133 684.8, filed on Dec. 10, 2019, the entirety of which is incorporated herein by reference. 
     FIELD OF DISCLOSURE 
     The invention concerns an apparatus for the configuration of a wireless radio connection and a method of configuring a wireless radio connection. 
     BACKGROUND 
     In radio networks having a plurality of access points, for example WiFi or 5G a wireless audio end device like for example a microphone or a headphone is connected to an access point (AP), to which it sends its audio data or from which it receives same. The audio transmission should be effected as far as possible interruption-free and with low latency (that is to say in real time) in order for example at the microphone to avoid strongly perceptible echo effects or at the headphone to avoid a loss in synchronization in relation to a video signal. If the audio end device is moved it can happen that the connection quality to the previous access point decreases and a better connection can be achieved by a change in the access point (so-called roaming or handover). Depending on the respective technology involved that transition causes short interruptions in the connection, for example due to a change in the radio channel or due to scanning operations to establish the most appropriate access point. Depending on the respective radio technology those interruptions can be pronounced to differing degrees and can adversely affect the audio signal. For example in the case of WiFi radio networks that procedure causes a number of interruptions in the audio signal of in part over 50 ms duration, which can be acoustically perceptible to the user. A similar problem occurs in radio systems with only one access point in which however different radio channels are used if a change in the radio channel in operation is necessary. 
     In known radio systems brief interruptions due to scanning, roaming and handover processes are typically compensated by buffering of the data packets for 100 ms or more. For data packets which have been lost renewed transmission can also be required. At any event however that increases the latency of the audio signal because all packets are put into intermediate storage. In addition a data transmission with an at least briefly increased data rate is necessary, but that is not always available. For wireless audio systems however both interruptions are to be avoided and also latency is to be reduced or minimized. In that respect the aim is latencies of below 10 ms (from the recording transducer to the radio signal). 
     Known WLAN networks already support various methods of reducing the time duration of the interruption in data streams. For example the current AP can provide a list of adjacent APs and the channels used by them. Therefore not all possible channels have to be scanned, but it is sufficient to scan only the channels used by adjacent APs. In that way the number of required scanning processes is reduced. In addition authentication of the AP or the WLAN station can be transmitted in advance to the future AP in order to reduce the length of the interruption in the actual roaming process from several 100 ms to about 50 ms. That eliminates fresh negotiation of the encryption. 
     Due to scanning or roaming or configuration processes related thereto in the network however interruptions which are acoustically perceptible to the user in the audio signal of for example about 50 ms duration or more can nonetheless occur. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to reduce perceptible interruptions caused by scanning, roaming/handover or by a channel change in the wirelessly transmitted audio signal without in that case increasing latency. 
     The object is attained by an apparatus as set forth in claim  1 . Claims  12  and  13  concern methods according to the invention. 
     The invention is based on the realization that speech or singing normally always includes periods of time like for example pauses in which an interruption in transmission does not cause disruption or can be very well concealed and which are often long enough to carry out scanning, roaming/handover or other configuration processes in the radio connection. For example pauses are mostly longer than 50 ms and often even markedly longer than 100 ms. According to the invention, based on an analysis of the transmitted audio signal, a configuration process in the radio connection like for example the change in the access point or the channel change can be timed in such a way that the interruptions occur in such periods of time and are therefore not or scarcely perceptible in the audio signal. For that purpose in analysis of the audio signal time periods are detected or predicted, in which a transmission error or an interruption in transmission can be particularly well concealed. Many different methods of error concealment are known. 
     Further advantageous embodiments are described in claims  2 - 11  and  14 - 15 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantageous configurations are shown in the drawings in which: 
         FIG. 1  shows a block diagram of an apparatus for the configuration of a wireless radio connection for audio transmission in a first embodiment, 
         FIG. 2  shows a diagram illustrating a time sequence of configuration of a wireless radio connection according to the state of the art, 
         FIG. 3  shows a diagram illustrating a time sequence according to the invention of configuration of a wireless radio connection for audio transmission, 
         FIG. 4  shows a time sequence of switching over of a wireless radio connection for audio transmission, 
         FIG. 5  shows a block diagram of an apparatus for the configuration of a wireless radio connection for audio transmission in a second embodiment, 
         FIG. 6  shows a block diagram of an apparatus for the configuration of a wireless radio connection for audio transmission in a third embodiment, and 
         FIG. 7  shows a flow chart of a method according to the invention of configuring a wireless radio connection for audio transmission. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows in a first embodiment of the invention a block diagram of an apparatus for the configuration of a unidirectional wireless radio connection for audio transmission. In this case the apparatus  100  can be part of a mobile audio device, like for example a wireless microphone. Configuration of the wireless radio connection can include switching over a radio channel or radio frequency in use to another radio channel or radio frequency. In this case the base station to which the mobile audio device is connected remains the same. In another example configuration of the wireless radio connection can include roaming, that is to say a change in the base station to which the mobile audio device has a radio connection. In this case however the radio frequency or the radio channel is often also changed. Configuration of the wireless radio connection can also include other processes which can lead to interruptions in the transmitted audio signal, for example calibration in high-frequency processing. 
     In this embodiment the apparatus  100  includes an audio input or sound transducer  110 , an audio processing unit  120 , an audio analyzer  130  and a transmitting unit  140 . The audio processing unit  120  can include various amplifiers, optionally an analog-digital converter (ADC) and other usual functions. It generates a first audio signal  122  which is output to the transmitting unit  140  so that the latter generates a high-frequency signal modulated with the first audio signal. That is radiated by way of an antenna  150  which is connected to the transmitting unit  140  and sends the wireless audio signal  155  to a base station  300 . In this case the wireless transmission can be effected for example in accordance with the WiFi (or IEEE 802.11) standard. It is however also possible for the wireless transmission to be effected using another method. Irrespective of the actual transmission it can often happen that the apparatus  100  can briefly not transmit during operation, for example while another transmitting frequency or another transmitting channel is being sought or selected or if the mobile device including the apparatus  100  is moved and in so doing is too far away from its base station. 
     According to the invention the audio signal  121  is analyzed by the audio analyzer  130  to detect or predict a time period at which configuration of the wireless network (possibly after error concealment) causes as few disturbances as possible in the audio signal at the receiver. In that case analysis over a period of some seconds may be adequate, for example 5-120 seconds. By way of example a signal pause detector  135  can detect pauses in the audio signal. Such a detected time period is identified by a control or trigger signal  131  which the audio analyzer  130  outputs to the transmitting unit  140 . The control or trigger signal  131  indicates that an interruption in the audio signal at that time will cause only a slight or no audible disruption for the user. The transmitting unit thereupon controls configuration processes of the wireless network like scanning or roaming in such a way that they take place during the time period indicated by the control or trigger signal  131 . 
     A particularity in this respect is that the apparatus operates in real time and the audio signal is therefore to pass the apparatus with minimum latency. For that reason there is as little buffering as possible between the audio input or sound transducer  110  and transmission by the transmitting unit  140 . Therefore the apparatus produces a very low latency of for example at most 10 ms, preferably at most 2 ms, for the audio signal. 
     Speech signals and singing signals usually consist of segments, with loud and soft or silent segments alternating. In that respect the loud segments can correspond to syllables or parts of syllables while silent segments are pauses therebetween, including pauses between words. The silent segments can be used for example for breathing but there can also be pauses which are caused by occlusion of the vocal apparatus at given sounds. For example the word “happy” includes a pause during the sound “p” which can be about 100 ms long because the lips are closed. Pauses between words are often 200 ms in length or longer. Human speakers differ from each other however, inter alia due to individually different pause lengths. 
       FIG. 2  firstly shows a diagram illustrating a time sequence of configuration of a wireless radio connection according to the state of the art. By way of example this can be a WLAN or WiFi radio connection. In that case a given radio channel Ch 2  is used for transmission or reception. If the quality of the radio connection becomes worse or for some other reason a search or scan process begins at the time t 1 ′. For active scanning the transmitter briefly interrupts transmission, switches to another channel Ch 1  and transmits a query on the other channel Ch 1  in order to establish whether the channel Ch 1  is occupied or delivers a better signal quality. Alternatively the device can only receive even without transmitted query whether data are already being transmitted on the other channel Ch 1  (passive scanning). Here however the reception duration should be greater, depending on a respective radio system, for example for WLAN networks 100 ms while active scanning only takes about 20-30 ms. If the channel Ch 1  is not yet occupied by another radio connection the base station using that channel can send a corresponding response signal, from which then for example there entails an identification of the base station and the network as well as the signal quality. In that respect this can be the same base station to which there is the current radio connection, or another base station. 
     The scanning process can be repeated a number of times, for example at a time t 2 ′ on another channel Ch 3 . When finally a free channel which can be alternatively used has been found, for example with better signal quality than the current channel Ch 2 , the transmitter finally switches over its transmission frequency permanently to that channel at a time t 3 ′. If in that case the base station is changed then the switching-over effect is identified as “roaming”. In known devices configuration of the radio connection, that is to say for example scanning and roaming, is carried out completely independently of the audio signal or useful signal. Therefore the configuration periods can coincide with relevant audio contents S 2 , S 3 , in which case audio data are lost and popping or other interference noises can occur. That is indicated in  FIG. 2  at the times t 1 ′ and t 3 ′. The same problem can also occur in further network configuration processes, for example if the transmitting unit  140  carries out a calibration operation. 
       FIG. 3  shows a diagram illustrating the time sequence according to the invention in respect of configuration of a wireless radio connection for audio transmission. In this case the audio signal is analyzed and, in this example, silent segments are detected or predicted. A corresponding trigger or control signal  131  Trig, which is generated by the audio analyzer  130 , indicates the silent segments to the transmitting unit  140 . The transmitting unit  140  can use that signal to implement configuration of the radio connection, like for example scanning or roaming. For that purpose the transmitting unit  140  can have a suitable configuration unit like for example a scanning or roaming unit  145  which carries out configuration of the radio connection corresponding to the trigger/control signal  131 . Thus configuration of the radio connection can now take place at times t 1 , t 2 , t 3  which are in the pauses in the audio signal so that the audio signal does not suffer disruption. For analysis of the audio signal a duration of some seconds to minutes is sufficient to be able to predict silent segments. 
     In this example the trigger/control signal  131  indicates possible times at which a configuration process can take place because the audio signal has a pause or at least is of a very low amplitude. For that purpose for example the mean signal power of the audio signal can be calculated within a window of 10-20 ms. If the value is below a threshold value a pause is recognized. The audio analyzer can also determine an adaptive threshold value for that purpose. Alternatively the trigger/control signal  131  can also indicate times at which the audio signal is admittedly of a greater amplitude but—at least for a duration of at least 50 ms—particularly good error concealment can be carried out at the receiver end, for example in the case of uniform longer sounds. By way of example in singing, compared to speech, individual sounds are often relatively long and uniform so that an interruption can be easily hidden electronically (by error concealment) at the receiver. The audio analyzer  130  can detect or predict suitable appropriate times, as is described hereinafter. 
       FIG. 4  shows details of the time sequence of a process for switching over a wireless radio connection for audio transmission. As described above the audio signal includes loud segments S 1 , S 2 , S 3  separated by silent segments or pauses. The loud segments are of differing lengths, for example in the region of 50 ms-200 ms. Likewise the pauses can be of different lengths. A first pause which at time t 41  follows the first loud segment S 1  is of a duration of d 1 . A second pause which follows at the time t 42  the second loud segment S 2  is of a duration of d 2  before a third loud segment S 3  begins. To minimize latency audio analysis is effected in real time so that assumptions have to be made about the pause length to be expected, at the beginning of the pause. The audio analyzer  130  can establish for example that the first pause of the length d 1  is too short for configuration tasks. Therefore the control signal Trig  131  does not show any pause. In the second pause in contrast the audio analyzer  130  after a certain time d 21  establishes that the pause is probably sufficiently long for configuration tasks for example because most pauses which occurred in the preceding five seconds (or most of those pauses which were at least of a given length d 21 ) were at least 100 ms long. At that time therefore the control signal Trig  131  indicates a pause. The remaining useable pause here is of a length of d 22 , that is to say the total length of the pause d 2  less the time d 21  required for detection of the pause. In that case the time d 21  required for detection of the pause can also be shorter or longer than the remaining useable pause d 22  if the remaining useable pause d 22  is sufficient for the respective configuration task. It will be noted that the actual length d 22  of the remaining useable pause at that time t 42 +d 21  is normally not yet known. In an embodiment a pause is indicated only when, on the basis of statistics, a remaining pause length d 22  of at least N ms is to be expected (for example with N=50). The indicated pause can last until, at the time t 42 +d 2 , the beginning of the next loud segment S 3  is detected. If the pause is used for configuration and at that time a configuration process is still running that can be broken off so that the speech signal S 3  can be transmitted as far as possible without delay. 
     In an embodiment, during discontinuance of the configuration operation or up to the end thereof audio data can be stored temporarily (for example 1-3 speech segments or 20 ms to 100 ms) in a buffer memory and then read out again at a slightly increased speed or data rate so that the data are not lost and thus signal jumps are avoided. In that way error concealment at the receiver becomes easier. It will be noted that this functions in the mobile device only if the radio connection has sufficient band width to transmit the additional data. In a variant, in regard to the data read out at the increased data rate, the pauses contained in the speech signal can be shortened (time stretching) in order not to alter the pitch of the speech segments. 
     In an embodiment the audio analyzer  130  measures the length of the silent segments or pauses continuously, periodically or over a given period of time and applies corresponding statistics, at least from values of the seconds or minutes which have just elapsed. Taking those statistics but in addition also general empirical values or earlier measurements or other sources it is possible to define a minimum length d 21  of a pause, for example 10 ms, in order to sufficiently reliably detect pauses. If a pause of the minimum length were detected in the audio signal the audio analyzer can indicate that by the trigger/control signal  131 . The length of the pause to be expected is user- and situation-specific and can already be predicated after a short training phase on the basis of the statistics. For example it is possible to establish that the pauses which are at least X ms long on average last for at least Y ms (for example with X=20, Y=50 or X=100, Y=500). Alternatively or in addition the analyzer  130  can also measure the length of the loud segments S 1 , S 2 , S 3  in order in that way to predict the beginning or the length of the next pause. For example it is possible to establish that the loud segments on average last no longer than X ms (for example with X=200) or that after loud segments of a certain length X ms there follows a pause of typically at least Y ms. With that information which can vary from speech to speech and individually from speaker to speaker it is possible for the pause to be more quickly recognized. 
     In another variant the audio analyzer  130  can investigate the length and uniformity of individual loud segments S 1 -S 3  and detect particularly uniform and long loud segments. For example a particularly uniform loud segment can have a particularly high autocorrelation. That can be measured within a moving window of for example 10-20 ms in length. As described above that can also be used for configuration as in this case error concealment can be particularly effectively implemented at the receiver. In that way an interruption in the audio signal, caused by the configuration operation, can be concealed at that time at the receiver better than usual. 
     An advantage of the described statistical method is that it requires no speech recognition and no syntactical or semantic analysis. It is therefore independent of the speech actually being used. A further advantage is that the method can very quickly adapt to the respective user and/or the respective situation. 
       FIG. 5  in an embodiment of the invention shows a block diagram of an apparatus for the configuration of a wireless radio connection for audio transmission. The apparatus  200  in this embodiment can include a mobile audio device like for example a body-pack receiver, an in-ear monitor or also a mobile telephone. In this embodiment the apparatus  200  includes a transmitting/receiving unit  240 , an audio processing unit  220 , an audio analyzer  230  and an audio output or sound transducer  210 . Similarly to the audio processing unit  120  the audio processing unit  220  can have various amplifiers, optionally a digital-analog converter (DAC) and other usual functions. It receives an audio signal  222  from the transmitting/receiving unit  240  which it has obtained by demodulation of a modulated HF signal received from the base station  300 . The audio analyzer  230  can include for example a pause detector  235 . 
     In most cases configuration of the wireless radio connection like scanning and roaming is carried out by the base station  300 . The transmitting/receiving unit  240  in the mobile device can however establish that the reception quality of the radio transmission  255  is decreasing, for example because the mobile device containing the apparatus  200  is being moved, and send a corresponding message to the base station  300 . For that purpose an audio signal  221  is passed from the audio processing unit  220  to the audio analyzer  230  which carries out an analysis operation as described above and generates a control signal Trig  231 . The message sent to the base station  300  can contain the control signal Trig  231  which indicates opportune times for reconfiguration of the radio connection  255 . 
     In another embodiment configuration of the wireless radio connection or scanning and roaming can also be carried out by the mobile device, for example by a configuration unit  245  which can be a scanning/roaming unit and which can be disposed in the transmitting/receiving unit  240 . That can be controlled directly by the control signal  231  generated by the audio analyzer  230 , as correspondingly described hereinbefore with reference to  FIG. 1 . 
     In an embodiment the base station is adapted to carry out configuration of the wireless radio connection.  FIG. 6  shows a base station  600  which can be connected to a network  650  by way of a network interface  610 . The network can be a data network like for example an LAN network or a mobile radio network. The base station also includes a radio interface  640 , for example in accordance with the WiFi/WLAN standard (IEE802.11) or a mobile radio standard, by way of which it is connected by way of the radio connection  255  to one or more mobile devices. The network interface  610  receives from the network  650  data packets which are intended for one or more of the mobile devices connected to the base station  600 , and passes other data packets received from the mobile devices into the network  650 . If configuration or reconfiguration of a given radio connection becomes necessary an audio processing unit  620  which can include a packet filter  625  extracts audio data packets of the correspond radio connection and processes the audio data contained therein, for example by partial or complete decoding. Those audio data packets can originate either from the corresponding mobile device which is connected by way of the radio connection  255  or from another subscriber connected by way of the network  650 . The audio data  621  obtained in the audio processing unit  620  are passed to an audio analyzer  630 . The audio analyzer  630  which in principle can correspond to the above-described audio analyzers  130 ,  230  and which for example can include a pause detection unit  635  analyzes the audio signal contained in the audio data  621  and sends to the radio interface  640  a trigger signal  631  which indicates a pause in that audio signal, as described above. In response to the trigger signal  631  the radio interface  640  can perform reconfiguration of the radio connection  255  or it can pass a signal to the respective mobile device so that same performs a reconfiguration of the radio connection  255 . In that case the mobile device includes a configuration unit  145 ,  245  but does not need an audio analyzer  130 ,  230 . 
     In an embodiment the invention concerns an automatically implemented method of configuring a transmitting unit for a wireless radio connection, as shown in  FIG. 7 . The method  700  includes analyzing  710  an audio input signal by an audio analyzer  130 , wherein with a statistical method in real time at least one period, for example a pause, in the audio signal is detected and possibly the length thereof to be expected is predicted, and wherein a control signal  131  is generated, which indicates the predicted period. The method  700  further includes control  720  of a transmitting unit  140  by means of the control signal  131  and transmitting  730  the audio signal by the transmitting unit  140 , wherein during the period indicated by the control signal  131  the transmitting unit effects configuration of the wireless radio connection. 
     In another embodiment the invention concerns an automatically implemented method of configuring a transmitting/receiving unit  240  for a wireless radio connection  255 . The method includes receiving an audio signal by way of a wireless radio connection, analyzing the received audio signal by an audio analyzer  230 , wherein with a statistical method in real time at least one period, for example a pause, in the audio signal is predicted and wherein a control signal  231  is generated, which indicates the predicated period. The method further includes control of the transmitting/receiving unit  240  by means of the control signal  231  and reconfiguration of the radio connection  255 , wherein reconfiguration is effected during the period indicated by the control signal  231 . Reconfiguration can be effected by the transmitting/receiving unit  240  or by the base station  300 . 
     The invention can be implemented with a processor configuratable by software. Configuration is effected by a computer-readable data carrier with instructions which are stored thereon and which are suitable for programming the processor in such a way that it executes the steps of the above-described method. 
     The invention can be used in various devices, for example for wireless microphones, body-pack transmitters, body-pack receivers, telephones, base stations or headphones.