Low-delay echo cancellation

0001The invention relates to a method and a device for Reduction in (via a telecommunications network to be transmitted, coming from a terminal) uplink data contained Echo.

0002In different telecommunication networks (especially cellular mobile radio networks such as GSM, UMTS, CDMA-based networks etc.) can in from a terminal in the direction of the mobile network sent data (uplink data) an "echo" occur which it may show that the terminal from a Speaker output acoustic signals (which on based on power transmitted to the terminal downlink data) and outputted from the more or less form weak Microphone of the terminal are received. The microphone of the ie terminal receives acoustic signals from the terminal -use, currently speaking (or the mobile radio terminal otherwise-use) terminal user and additionally a faint noise in the form of the speaker Terminal reproduced (on the downlink data from the network Terminal arrived) speech portion of an interlocutor the terminal user. The voice data received by the microphone the terminal user and the addition of the microphone recorded (false) information that a microphone in and for the Terminal has received, are common to the other party transfer of the terminal user, so that this addition to the speech signal of the terminal user's own Language as echo hears (the voice sequence of the terminal user-interlocutor, which from this to the speaker the terminal, the microphone and the microphone on the was terminal transmitted back to the caller).

0003For this purpose were in mobile networks (from, for example, www.etsi.org etc. or Jacek Biala "mobile and intelligent Networks ", Vieweg-Verlag, ISBN 3-528-15302-4, pages 109, 127 and 344 known) echo equalizer (= Echo Canceller = echo canceller) proposed. In a switching device a mobile network's data comes usually over ATM AAL-2 Compounds or other compounds to, wherein the data in a mobile radio codec format (in particular AMR format) for the compressed transmission, in particular via the air interface, are coded. For the echo equalization is the in codec format encoded speech in a language, for example, representing over time format as the TDM (Time Division Multiplex) format transcoded (ie converted in coding) and in the terminal device next uplink data contained Echo (the downlink data) is by considering the downlink data in the as far as possible reduced uplink data (Echocancellation). By avoiding this echo, the voice quality significantly improved. However, by this process transferring originating from terminal uplink data to a caller via the telecommunications network as well as transferring between calls derived data over the telecommunications network as a downlink data delay to the terminal.

0004The object of the present invention is, with a decrease the echo in coming from a terminal uplink data the delay of data through the echo reduction (Echocancellation) as efficiently as possible to optimize. The task is in each case by the subjects of the independent claims dissolved.

0005By the present invention the data to be transmitted to the terminal (Downlink data) and copies as originals or copies the terminal will be sent, while a copy or the original the downlink data transcoded to reduce Echo is used in uplink data, the downlink data arrives one hand without delay to the terminal and can on the other hand easily and efficiently in a conventional manner without modification of echo equalizers to reduce echoes in Uplink data is used.

0006Further features and advantages of the invention will be made the claims and the following description of an embodiment reference to the drawing. It shows<dl tsize="7" compact="compact"><dt>figure 1</dt><dd>schematically the formation of a known per se echoes</dd><dt>figure 2</dt><dd>an inventive echo equalization in a telecommunications network and</dd><dt>figure 3</dt><dd>an inventive reduction of the echoes under Avoidance of delay in the transmission of downlink data.</dd></dl>

0007Figure 1 shows a user a 1 of a (not shown) Microphone 2 and a speaker 3 comprehensive terminal which (2.3), for example, is in a vehicle or space. 4 The belonging to his terminal (for example, via a headset or a car handsfree etc with the terminal connected) Speaker 3 receives an at known per se, not shown mobile network and a Terminal acoustic output level downlink data x (t), which spread in the vehicle or space 4 and also as z (t) received by the microphone 2 of the terminal (or the terminal) will. The microphone of the terminal 2 receives so strong or weak by the user 1 interlocutors envoys and the speakers 3 output (downlink) data and the user of the terminal 1 (2, 3) as language etc. output data s (t), and transmits the sum of the etc (from Speakers 3 unintentionally and intentionally by the user 1 recorded) Data as a signal y (t) in a known per se manner via a mobile station, an air interface to the wireless network, etc. and on to the interlocutor of the participant 1. The caller of the subscriber 1 therefore takes a Echo was, which is to be suppressed, as it the voice quality reduced.

0008Figure 2 shows how by echo cancellers (E-cho Canceller) the interlocutors from 5 in the downlink 6 in at manner known per se via a mobile network, an air interface etc. to a terminal with a speaker 3 to be transmitted downlink data x (t) to the echo reduction be used.

0009According to the invention transmitted via the downlink 6 downlink data x (t) not only to the terminal with the speaker 3 transferred to the local acoustic output, but copied and it is a copy, regardless of the transmission in direction of the terminal (3) in an echo equalizer 7 analyzed and reduction (for example subtraction in certain time periods) of the echo in via uplink 8 to the transmitted uplink data y (t) according to the analysis in an analysis device 9 used in a processor 10th

0010Figure 3 illustrates what this means in an echo reduction 11 in one (or a) switch (MSC, media gateway, etc.) of a telecommunications network (In particular mobile network) can be carried out. Data packets 12 to 16 in the downlink 6 are of a copying machine 17 copied and transmitted to a transcoding device 18, which the decoding of the downlink data 13 from a mobile radio codec (Etc.) encoding format in an echo equalization performs appropriate format (eg, TDM). While the Copying device 17 copied downlink data in the decoder transcodes 18, a copy of (or the original) of the downlink data already on the downlink 6 be transmitted in the direction of the terminal, thereby a delay in the transfer is avoided. Also in uplink 8 data to be transmitted 19 to 22 are controlled by a decoder 23 (from a mobile radio codec format as AMR, etc.) are converted into a suitable format for echo suppression. The analyzed by an analysis device 9 (Previously transcoded) downlink stream data Kopieen be analyzed by the analyzing means 9 and the means 10 in, for example, a conventional manner to echo reduction the transcoded via the transcoder 23 Uplink data. Thereupon, the uplink data, which is now a reduced echo or, ideally, no echo have a further recoding (Transcoding) 24 again in another format (for Mobile, for example, a mobile radio codec format as AMR or any other format) and transcoded on the uplink 8 next to the interlocutor of the 5 terminal user forwarded.