The invention relates to devices and methods for adjusting an acoustic sequence, and in particular, in a speech channel of an air interface of a mobile radio network provided for a subscriber of a mobile radio network.
A subscriber's call is transmitted compressed (by means of an AMR codec with UMTS for example) over a speech channel of an air interface. An AMR codec includes an algorithm which for example compresses 20-msec speech samples in 8 modes to bit rates AMR-Mode 7=12.2 kbps, AMR-Mode 6=10.2 kbps, AMR-Mode 5=7.95 kbps, AMR-Mode 4=7.40 kbps, AMR-Mode 3=6.70 kbps, AMR-Mode 2=5.90 kbps, AMR-Mode 1=5.15 kbps or AMR-Mode 0=4.75 kbps.
Before a (UMTS for example) speech connection is set up, an RNC (Radio Network Controller or base station/base station controller) of a mobile radio network negotiates a set of AMR modes with a switching center via which the speech connection is to pass. During connection setup or the existing connection the RNC can request a change to the current AMR mode by deleting negotiated AMR modes. Such a change of AMR mode can thus be undertaken in the switching center during the adjustment of acoustic sequences such as tones and recorded announcements.
The present invention enables an efficient adjustment of acoustic sequences in a call of a mobile radio subscriber over an air interface in which an switch between different transmission modes, each identified by a different compression of the call, can take place.
In accordance with one embodiment of the invention, tones and recorded announcements can be adjusted quickly, easily and efficiently during a call if the allowed transmission modes change. This means that transcoding before adjustment is not required.
An adjustable acoustic sequence is usefully stored in all selectable transmission modes so that adjustment of acoustic sequences is made easier in accordance with invention for all possible transmission modes.
The compression data records are preferably stored in a switching center of the mobile radio network over which the voice sequences of the subscriber are transmitted, from where they are easily accessible.
Further features and advantages of the invention are described below in the description with respect to exemplary embodiments illustrated in the drawings. The Figures show:
Sequence 1 is shown in a first compression (used in a first transmission mode) as data record A1 (=reference number 11 in
C1 is shorter than sequence 1 and shorter than A1 and shorter than B1, since C1 is a stronger compression of the content of sequence 1 than A1 and B2. A stronger compression can for example be used for a higher-quality of a transmission channel and/or lower quality requirements.
In a switching center (circuit or packet switching center; MSC or media gateway etc) 20-msec speech samples 1 (time sections of the call) are converted from a for example linearized signal scanned at 8 kHz or a 11-18 A-law coded signal of a subscriber into the currently valid transmission mode (AMR mode etc) A or B or C (=transcoded).
When a speech channel is set up the (one or more) transmission modes A, B, C to be used between the RNC and a switching center for transmission of speech signals 1, 8 of the subscriber are pre-selected (negotiated), from which during the communication of the subscriber a current transmission mode A or B or C to be used (=e.g. now or at a definable point in time) is selectable.
For example 8 transmission modes (AMR mode etc) are possible, from which 3 transmission modes A, B, C (corresponding to “AMR modes 7, 5, 0” in accordance with
Tones and announcements are present as for example 8 compression data records (Samples 11-18) transcoded in all 8 AMR modes in memory 10 in
Mode A=7.95 kbps with 159 bits or 95 bytes (including bit stuffing) per 20-msec speech sample. Mode A=4.75 kbps with 75 bits or 95 bytes (including bit stuffing) per 12-msec speech sample.
When a tone or announcement is to be adjusted, the currently valid AMR mode is first determined and the associated sample with the number 11 is selected and transmitted e.g. in Mode A. Then the next sample with the number 2 and so on is sent in the same mode A in each case. After the sample N−1 in Mode A has been sent out, the RNC deletes this currently valid Mode A and Mode B from the existing mode set to initiate a change of mode. The result of this is that for transmission of the next sample N there must be a change to the next possible mode C. Therefore the sample with the number n−1 is sent from the appropriate sequence of samples (transcoded in the new Mode C to be used) for this tone or this announcement.
Since this method only requires administration of the samples to be transmitted and no ongoing transcoding from the original signal, reacting to a change of AMR mode in the switching center requires minimal effort. This method is also applicable to other codec types, especially if speech samples of the same length are only ever to be transcoded with this codec.
This application claims priority to International Application No. PCT/DE01/03715, which was published in the German language on Apr. 3, 2003, which was filed in the German language on Sep. 26, 2001, the contents of which are hereby incorporated by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/DE01/03715 | 9/26/2001 | WO |