Transcoder with prevention of tandem coding of speech
First Claim
1. A transcoder, for a mobile communication system which uses a speech coding method which reduces a transmission rate of speech on a radio path, said transcoder comprising:
- a speech coder which encodes a speech signal to be transmitted to at least one mobile station into speech parameters, and decodes speech parameters received from at least one mobile station into a speech signal according to said speech coding method; and
a PCM coder which transmits an uplink speech signal to and receives a downlink speech signal from a PCM interface in the form of PCM speech samples,wherein said transcoder transmits and receives said speech parameters in a subchannel formed by at least one least significant bit of said PCM speech samples simultaneously with said PCM speech samples, in order to prevent tandem coding of speech in a mobile-to-mobile call.
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Accused Products
Abstract
A transcoder which prevents tandem coding of speech in a mobile-to-mobile call within a mobile communication system uses a speech coding method for reducing transmission rate on the radio path. The transcoder includes a speech coder, which encodes the speech signal into speech parameters for transmission to a mobile station, and decodes the speech parameters received from the mobile station into a speech signal according to the speech coding method, as well as a PCM coder for transmitting an uplink speech signal to and for receiving a downlink speech signal from a PCM interface in the form of PCM speech samples. In addition to the normal operation, the transcoder transmits and receives speech parameters through a PCM interface in a subchannel formed by least significant bits of the PCM speech samples. Thus, it is possible to prevent tandem coding while maintaining the standard PCM interface, and the signaling and services associated thereto.
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Citations
35 Claims
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1. A transcoder, for a mobile communication system which uses a speech coding method which reduces a transmission rate of speech on a radio path, said transcoder comprising:
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a speech coder which encodes a speech signal to be transmitted to at least one mobile station into speech parameters, and decodes speech parameters received from at least one mobile station into a speech signal according to said speech coding method; and a PCM coder which transmits an uplink speech signal to and receives a downlink speech signal from a PCM interface in the form of PCM speech samples, wherein said transcoder transmits and receives said speech parameters in a subchannel formed by at least one least significant bit of said PCM speech samples simultaneously with said PCM speech samples, in order to prevent tandem coding of speech in a mobile-to-mobile call. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method for preventing tandem coding of speech in a mobile-to-mobile call, said method comprising:
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encoding a speech signal by a speech coding method which reduces transmission rate and provides speech parameters; transmitting said speech parameters over a radio interface to a first transcoder in the mobile communication network; decoding said speech parameters by said speech coding method to restore said speech signal; transmitting said speech signal from said first transcoder to a second transcoder as PCM speech samples; and transmitting said speech parameters, received over said radio interface, from said first transcoder to said second transcoder simultaneously with said PCM speech samples in a subchannel formed by at least one least significant bit of said PCM speech samples.
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34. An arrangement for preventing tandem coding of speech in a mobile communication system in which mobile stations and the mobile communication network include speech coders which transmit a speech signal over a radio path in the form of speech coding parameters at a speech coding rate, and in which a mobile-to-mobile call includes, in the mobile communication network, a tandem connection of two speech coders having a normal PCM interface between speech coders in said tandem connection, wherein at least one of said speech coders being arranged to provide a subchannel in at least one least significant bit of PCM speech samples in said PCM interface for forwarding said speech coding parameters provided by said at least one speech coder in at least one mobile station through the mobile communication network without decoding or encoding being carried out in said speech coders of the mobile communication network.
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35. A transcoder for a mobile communication system which uses a speech coding method which reduces a transmission rate of speech on a radio path, said transcoder comprising:
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a speech coder which encodes a speech signal to be transmitted to at least one mobile station into speech parameters, and decodes speech parameters received from at least one mobile station into a speech signal according to said speech coding method; and a PCM coder which transmits an uplink speech signal to and receives a downlink speech signal from a PCM interface in the form of PCM speech samples, wherein said transcoder transmits and receives said speech parameters in a subchannel formed by at least one least significant bit of said PCM speech samples simultaneously with said PCM speech samples, in order to prevent tandem coding of speech in a mobile-to-mobile call, wherein said transcoder forwards said speech parameters received in a speech frame from said subchannel to said at least one mobile station without encoding, but possibly modified according to control information of said uplink frame, said speech coder continuously encode PCM speech samples into speech parameters, and said transcoder transmits said speech parameters encoded from the PCM speech samples to said at least one mobile station, if said transcoder does not receive speech parameters from said subchannel properly.
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Specification