EP2311295A1 - Procédé et entité de transcodeur pour une exploitation sans transcodage (tfo) dans un réseau de télécommunication - Google Patents

Procédé et entité de transcodeur pour une exploitation sans transcodage (tfo) dans un réseau de télécommunication

Info

Publication number
EP2311295A1
EP2311295A1 EP08785963A EP08785963A EP2311295A1 EP 2311295 A1 EP2311295 A1 EP 2311295A1 EP 08785963 A EP08785963 A EP 08785963A EP 08785963 A EP08785963 A EP 08785963A EP 2311295 A1 EP2311295 A1 EP 2311295A1
Authority
EP
European Patent Office
Prior art keywords
transcoder
transcoder entity
entity
free operation
tfo
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP08785963A
Other languages
German (de)
English (en)
Inventor
Francesco Agnoni
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of EP2311295A1 publication Critical patent/EP2311295A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/18—Service support devices; Network management devices
    • H04W88/181—Transcoding devices; Rate adaptation devices

Definitions

  • the present invention relates to a method according to the preamble of claim 1.
  • a transcoder entity and a program embodying the invention is also described.
  • GSM Global System for Mobile communications
  • the speech signal is first encoded in the originating mobile device.
  • the encoding results in a compressed speech signal.
  • GSM Global System for Mobile communications
  • a transcoder converts the voice channel coding between the GSM coding format and the standard Pulse Code Modulation (PCM) format in communication systems, e.g. converts a 16kbps signal to a 64kbps signal, for transmission in other parts of communication networks.
  • PCM Pulse Code Modulation
  • the speech signal is transcoded again to a bit rate of 16kbps in another transcoder, if it is sent through the air interface to the destination mobile device where it is finally decoded.
  • This configuration of the two speech transcoders, which are responsible for the coding and the decoding is called "Tandem Operation".
  • the double transcoding described causes degradation in the speech quality and is therefore problematic.
  • the speech quality may be improved if the transcoding of the compressed speech signal is avoided. This approach is feasible if the originating and destination devices are adjusted to use the same speech coding algorithms.
  • Tandem Free Operation which intends to avoid the transcoding and raise the quality of the speech transmission has been standardized in GSM. TFO is suitable for transmission of wideband speech e.g.
  • AMR Adaptive Multi-Rate
  • 3GPP 3 rd Generation Partnership Project
  • Tandem Free Operation as defined by the standard 3GPP TS 28.062 version 7.0.0 (2007-06) is intended to avoid the double speech encoding/decoding during a voice call.
  • the originating and destination devices are using the TFO protocol and the same speech codec, it is possible to transmit the speech frames received from the originating device to the destination device without transcoding the speech signal.
  • TFO messages are used in order to achieve the synchronization in a TFO connection and also throughout the TFO as a means for controlling the operation.
  • TFO frames are exchanged and TFO is established.
  • the objective of TFO synchronization is to check among others if the transcoder entities participating in the call are capable of TFO and if the codec and the coding standards match e.g. if a device using the GSM coding standard communicates with another device using the GSM coding standard.
  • the TFO frames can contain information on synchronization, codec type, system identification e.g. GSM, absence or presence of embedded TFO messages, and other information.
  • the TFO protocol as implemented into the transcoder entities is ruled by a state machine which contains, among others, two states, one where the protocol is in regular operation and one where the synchronization of the transcoders participating in a TFO session has been lost. Transition to the state of regular operation occurs when the transcoder entity acting as TFO endpoint starts to receive TFO frames sent to it by its remote TFO partner. Transition to the state where synchronization has been lost occurs when the TFO endpoint stops to receive consecutive TFO frames from the remote side.
  • a new transcoder entity can be introduced into the call.
  • the new transcoder entity which is handling the call after the handover is not synchronized with the distant transcoder entity.
  • Loss of synchronization causes a restart of the speech encoding by the transcoder entity acting as a starting point but in this case the encoded speech is generated starting from narrowband speech and not from wideband speech. This results in transmission of lower speech quality, and the quality may be further affected by other resulting effects like a speech path delay jump, speech distortion, or a fallback from wideband speech to narrowband speech for a period of time.
  • the method described in claim 1 is performed. Furthermore, the invention is embodied in a transcoder entity and a program as described in the further independent claims. Embodiments of the invention are described in the dependent claims.
  • a method in a telecommunication network is proposed for engaging a first transcoder entity in a tandem free operation session comprising a second transcoder entity.
  • the transcoder entities control the tandem free operation session and the insertion of transcoders into the session and perform a synchronization procedure of the first transcoder entity and the second transcoder entity.
  • the first transcoder entity sends tandem free operation frames to the second transcoder entity during execution of the synchronization procedure.
  • the invention can be embodied in a transcoder entity for engagement in a tandem free operation with a second transcoder entity in a telecommunication network.
  • the transcoder entity comprises a controller which controls the tandem free operation session.
  • the controller also controls the insertion of transcoders in the tandem free operation session.
  • the controller performs a synchronization procedure of the transcoder entity and the second transcoder entity and controls the sending of tandem free operation frames between the transcoder entities during the tandem free operation session.
  • the controller sends the tandem free operation frames from the transcoder entity to the second transoder entity during execution of the synchronization procedure.
  • the method can also be embodied in a program which is, for example, stored on a data carrier or loadable into a transcoder entity, e.g. as a sequence of signals.
  • the proposed method and transcoder entity allow an advantageous engagement of a transcoder entity in a tandem free operation session with a second transcoder entity while avoiding transmission of low speech quality.
  • Fig. 1 shows basic elements of a mobile wireless network
  • Fig. 2 shows a state machine of a tandem free operation
  • Fig. 3a shows an establishment of a tandem free operation session in the prior art
  • Fig. 3b shows an establishment of a tandem free operation session according to the proposed method
  • Fig. 4 shows a flow diagram of the proposed method
  • Fig. 5 shows a transcoder entity which is adapted to perform the proposed method Detailed description
  • FIG. 1 shows some parts of a mobile telecommunications network.
  • Base Transceiver Stations (BTS) (12), (14) and (24) transmit wireless signals e.g. speech, to mobile devices (10) and (26) and receive signals from them.
  • the BTS are controlled by Base Station Controllers (BSC) (30), (32).
  • One or more intermediate networks which, for purpose of simplification, are represented by a Mobile Switching Center (MSC) (20) may also transport speech between the mobile devices (10) and (26).
  • MSC Mobile Switching Center
  • transcoder entity (16), (18) are depicted as parts of the same BSC (32), it is also possible that the transcoder entities are disposed in different BSCs.
  • Transcoder entity (16) quits the above mentioned established tandem free operation session and this causes a loss of synchronization with transcoder entity (22).
  • Transcoder entity (22) may not immediately detect the loss of synchronization with transcoder entity (16) and continue to send TFO frames while also expecting to receive TFO frames. If transcoder entity (22) does not receive three consecutive TFO frames it goes, according to GSM standards, into the state which signifies loss of synchronization.
  • transcoder entity (18) sends TFO messages to transcoder entity (22) indicating its system identification e.g. GSM and the speech codec type used.
  • Transcoder entity (22) indicates that it supports TFO by sending a TFO message back to transcoder entity (18). If both transcoder entities use compatible speech codecs they can continue the TFO session.
  • FIG. 2 shows a state machine of the tandem free operation protocol.
  • the state Not_Active (200) is the initial state of the protocol. In this state the TFO protocol is not active and no speech coding is performed.
  • the state Not_Active (200) is left and a transition to the state Wakeup (WAK) (202) occurs when a new speech call is set up or/and the local transcoder entity is activated and TFO needs to be established.
  • WAK wakeup
  • the TFO protocol waits until speech samples are received. Then a transition to the state First_Try (FIT) (204) is performed.
  • FIT First_Try
  • state Contact (206) request messages are received from the distant transcoder entity. If the codecs used by the TFO partners match, an acknowledgment message is sent to check the digital transparency of the link from the local to the distant transcoder entity. As soon as a TFO_ACK message from the distant transcoder entity has been received, both transcoder entities know that the links in both directions are digitally transparent. TFO Frames start being sent and there is a transition from state CON (206) into the state Konnect (KON) (208). In this state the local transcoder entity sends TFO frames to the distant as long as it receives TFO messages from it. The first received TFO frame causes the transition into the state Operation (OPE) (210).
  • OPE state Operation
  • the TFO protocol defines different states depending on whether a handover is a local or a distant one.
  • the handover is regarded as a local handover at the side of the transcoder entities (16) and (18) and as a distant handover at the side of the transcoder entity (22).
  • the state machine of the TFO protocol transits to state Fast_Try (FAT) (216) and then to state Fast_Contact (FAC) (218) before transiting to state OPE.
  • FAT Fast_Try
  • FAC Fast_Contact
  • the state machine transits from state OPE (210) to state Sync_Lost (SOS) (212) and can enter state Re_Kon (214) if the distant handover has been confirmed.
  • FIG. 3a shows the session established as a function of time t simultaneously at the BTS, TRA, TFO and BSC planes.
  • BTS plane (306) the frames (308a) and (308b) which are sent from the BTS to the transcoder entity are shown.
  • the Global Configuration Frames (308a) contain information on configuration parameters for the communication between the BTS plane and TRA plane.
  • the Speech Frames (308b) contain the speech which is transmitted from the BTS plane to the TRA plane.
  • the speech activity (310a, 310b) is shown.
  • TFO plane (302) the messages (312a), (312b), (312c) and (312d) that are exchanged between the transcoders and associated states (314a), (314b), (314c), (314d), (314e) of the TFO state machine, for a new TFO session to be established are shown.
  • BSC plane the flow of incoming TFO frames (306) from the BTS is shown.
  • An order for a TFO session establishment is made by sending of a TFO enable frame TFO_E (306) from the BTS plane to the TRA plane.
  • state WAK 314a
  • state FIT 314b
  • FILL messages 312a
  • the new trancoder realizes reception of three consecutive TFO frames (316) coming from the distant transcoder entity it becomes aware that a TFO session is already ongoing and that a local handover has occured.
  • the new transcoder entity transits to state FAT (314c).
  • a control of the transparency of the the link to the distant TFO partner is performed by sending of TFO DUP messages (312b).
  • the new transcoder entity transits to the state FAC (314d) if it receives TFO frames followed by TFO messages signifying loss of synchronization from the distant transcoder entity.
  • the new transcoder entity transits to state OPE (314e), sends time alignment bits T_bits (312c) and then starts to send TFO frames (312d).
  • the distant transcoder entity may transit into the state SOS since it is waiting to receive TFO frames but due to the initiation of the new TFO session it may not received these frames in time.
  • this transition to state SOS is problematic for the transmission of wideband speech. Transition to state SOS can also introduce a speech path delay and distortion of the speech signal.
  • FIG 3b shows the TFO session establishment as a function of time t simultaneously at the BTS, TRA, TFO and BSC planes as suggested in the invention. It presents a solution to the behavior discussed above. Elements which correspond to these in Figure 3a are designated by corresponding reference signs. However in contrast to Figure 3a the TFO frames (332) are sent from the new transcoder entity to the distant transcoder entity as soon as the new transcoder entity is ordered to establish a new TFO session with the distant transcoder entity by reception from the BTS level of a TFO enable frame TFO_E (318).
  • the new transcoder entity transits from state WAK (314a) to state FIT (314b) and sends FILL messages (330a) in order to synchronize with the distant transcoder entity.
  • the FILL messages (330a) can be embedded in the TFO frames (332) which are sent from the new to the distant transcoder entity. Sending of the TFO frames (332) continues throughout the process of establishment of the new TFO session, i.e. in the states 314c and 314d, and during this period, all TFO messages (330a) and (330b) which are sent from the new transcoder entity to its distant partner for establishing the new TFO session can be embedded in the TFO frames (332). Until speech frames 308b are received, the TFO frames comprise the TFO messages and optionally a default content.
  • a timer can be started at the beginning of establishment of the new TFO session.
  • the timer can be set by default to expire after a specified period of time e.g. several seconds.
  • the purpose of the timer is to control the sending of TFO frames from the new to the distant transcoder entity.
  • the process described in Figure 3b is executed. If the timer expires and the new transcoder entity has not received any TFO frames from the distant transcoder entity, a new try for TFO establishment is initiated in the new transcoder entity.
  • the synchronization preferably proceeds the sending of TFO frames as described with respect to Figure 3a and TFO messages sent to the distant partner are sent independently from TFO frames.
  • FIG. 4 shows a flow diagram of the proposed method as executed in the new transcoder entity.
  • a new transcoder entity is ordered to establish a TFO session with the distant transcoder entity.
  • step (406) a timer is started and in step (408) the new transcoder entity initiates a TFO synchronization procedure while sending simultaneously TFO frames to the distant transcoder entity.
  • step (410) the new transcoder entity checks if the link to the distant transcoder entity is transparent by exchanging request and acknowledge messages indicating the capability of the distant transcoder entity for TFO. If it is not then in step (412) the TFO is discarded and there is no TFO establishment. In the opposite case there is a check, in step (414), if the new transcoder entity has received TFO frames from the distant transcoder entity before the timer which started at step (406) has expired. If TFO frames have been received TFO is becoming active in step (418) and the timer preferably cleared. If TFO frames have not been received before the expiration of the timer then a new TFO establishment is initialized in step (416) starting from PCM samples with narrowband speech.
  • the time until the distant transcoder entity receives TFO frames from the new transcoder entity is reduced as the frames are sent as soon as the synchronization is initiated from the new transcoder entity. Due to this, the transition of the TFO state machine in the distant transcoder entity from state OPE to state SOS is avoided and so is the restart of the encoder which uses as output PCM samples with narrowband speech.
  • the proposed method can be applied in any scenario involving TFO operation and it is e.g. not necessary that the transcoding entities are disposed in a transceiver station and a transcoder entity could for example also be located at a user device or a transit node between different networks.
  • the method is also not restricted to the case of a call from a GSM network but may also be used in a Universal Mobile Telecommunications System (UMTS) network.
  • UMTS Universal Mobile Telecommunications System
  • UMTS Universal Mobile Telecommunications System
  • UMTS Universal Mobile Telecommunications System
  • a transcoder could e.g. be located in a media gateway.
  • the proposed method can also be applied in the case of a call from a GSM network to a terminal using Voice-over- Internet protocol (VoIP).
  • VoIP Voice-over- Internet protocol
  • the invention can also be embodied in a transcoder entity (500) which can be adapted to perform any embodiments of the method as described above.
  • a transcoder entity is shown in Figure 5. It comprises a controller (508), a timer (510), one or more transcoders (502), (504) and interfaces (506) and (507) which can be adapted to exchange signals, messages or frames for communication with external entities or devices.
  • the controller (508) is adapted to control a tandem free operation session with another transcoder entity e.g. transcoder entity (514).
  • the controller (508) is also adapted to control the insertion of transcoders e.g. transcoders (502) and (504), into the tandem free operation session and their removal.
  • the controller (508) is further adapted to perform synchronization procedures of transcoder entity (500) with transcoder entity (514). For this, through interface (506), TFO messages indicating the transcoder entity's system identification e.g. GSM and the speech codec type used, are sent from transcoder entity (500) and received through interface (512) from transcoder entity (514).
  • Transcoder entity (514) indicates that it supports TFO by sending, through interface (512), a TFO message back to transcoder entity (500).
  • the controller (508) is also adapted to control the sending of TFO frames from transcoder entity (500) to transcoder entity (514) during a TFO session. Communication between transcoder entity (500) and transcoder entity (514) is shown by arrow (516).
  • Controller (508) is adapted to control the sending of TFO frames from transcoder entity (500) to transcoder entity (514) during execution of the synchronization procedure.
  • the TFO messages which are sent, for the purpose of synchronization, from transcoder entity (500) to transcoder entity (514) can be embedded in the TFO frames.
  • the controller (508) can comprise a timer (510) which is adapted to define the time period that controller (508) sends the TFO frames from transcoder entity (500) to transcoder entity (514). An expiration of the timer leads to initiation of a new synchronization procedure.
  • the elements of the transcoder entity as described above can be implemented as hardware or software or any combination of the two.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

Cette invention se rapporte à un procédé destiné à engager une première entité de transcodeur (18) dans une session d'exploitation sans transcodage avec une deuxième entité de transcodeur (22). Les entités de transcodeurs commandent la session d'exploitation sans transcodage et l'insertion des transcodeurs dans la session. Elles exécutent également une procédure de synchronisation de la première entité de transcodeur (18) et de la deuxième entité de transcodeur (22) et envoient des trames d'exploitation sans transcodage (332). Les trames d'exploitation sans transcodage (332) sont envoyées à partir de la première entité de transcodeur (18) vers la deuxième entité de transcodeur (22) au cours de l'exécution de la procédure de synchronisation. Une entité de transcodeur et un programme qui représente l'invention sont également décrits.
EP08785963A 2008-07-07 2008-07-07 Procédé et entité de transcodeur pour une exploitation sans transcodage (tfo) dans un réseau de télécommunication Withdrawn EP2311295A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2008/058795 WO2010003451A1 (fr) 2008-07-07 2008-07-07 Procédé et entité de transcodeur pour une exploitation sans transcodage (tfo) dans un réseau de télécommunication

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EP2311295A1 true EP2311295A1 (fr) 2011-04-20

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EP08785963A Withdrawn EP2311295A1 (fr) 2008-07-07 2008-07-07 Procédé et entité de transcodeur pour une exploitation sans transcodage (tfo) dans un réseau de télécommunication

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EP (1) EP2311295A1 (fr)
CN (1) CN102090138B (fr)
WO (1) WO2010003451A1 (fr)

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Publication number Priority date Publication date Assignee Title
CN103796243B (zh) * 2012-10-30 2017-04-05 中兴通讯股份有限公司 Tfo配置参数传输方法及系统
EP3536373A1 (fr) 2013-03-15 2019-09-11 Sage Products, LLC Systèmes pour réduire l'interférence de capteur associée à des thérapies électriques
CN103650627B (zh) * 2013-06-28 2017-09-29 华为技术有限公司 语音通信方法、装置及系统

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Publication number Priority date Publication date Assignee Title
DE19544367A1 (de) * 1995-11-29 1997-06-05 Bosch Gmbh Robert Verfahren zum Übertragen von Daten, insbesondere von GSM-Daten
CN1225921C (zh) * 2001-07-27 2005-11-02 华为技术有限公司 一种在编解码器非级联方式模式下动态分配资源的方法

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Publication number Publication date
CN102090138B (zh) 2014-06-04
CN102090138A (zh) 2011-06-08
WO2010003451A1 (fr) 2010-01-14

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