The Telecom Protocols

Codec Management Objectives Codec Management has following goals: 1.) Optimize the voice quality. 2.) Optimize the bandwidth efficiency 3.) Optimize the transcoder resource in MGW. 4.) Optimize the delay Voice Quality: Voice quality is measured in terms of the level, attenuation, delay, echo, and so on and may be used as a basis for the iQoS assessments for conventional VoIP. Voice Quality is measured in terms of R-value and below 50 are not recommended. Standards                                     Intrinsic quality (R) ------------------------------------------------------ ITU G.711 (64kbps)                                  94.3 ITU G.728 (12.kbps)                                 74.3 ETSI GSM-FR (13kbps)                           74.3 ETSI GSM-HR (5.6kbps)                          71.3 ETSI GSM-EFR (12.2kbps)                      89.3 ----------------------------------------------------- Transcoding can be harmful for voice quality of a

In Early legacy telephone network, A call between the two mobiles involved with two transcoding function at both the end which decrease the voice quality. The Transcoding Function done by the TRAU (Transcoding and Rate Adaptation Unit) to compress and decompress the speech.  TFO (Tandem Free Operation) enables to avoid the traditional double speech encoding / decoding in MS to MS call configurations. TFO uses in-band signalling and procedures for transcoders to enable compressed speech to be maintained between a pair of transcoders.   So the main objective of TFO is the improvement of the voice quality for calls between 2 mobile subscribers, but no resource optimisation is introduced  as transcoder functions are always present in the path. If TFO is activated between two end nodes, TFO Frames with compressed speech (e.g. AMR in LSB) as payload are carried over 8 or 16 kbit/s channels mapped onto the least or two least significant bits of the 64 kbit/s PCM speech sa

In Early legacy telephone network, A call between the two mobiles involved with two transcoding function at both the end which decrease the voice quality. The Transcoding Function done by the TRAU (Transcoding and Rate Adaptation Unit) to compress and decompress the speech.  Transcoder Free Operation (TrFO) is transport of compressed speech, which eliminates unnecessary coding and decoding of the signals when both end uses the same codecs. TrFO utilizes out of band signaling capabilities that include the ability to determine the negotiated codec type to be used at the two end nodes.  If the two end nodes are capable of the same codec operations, it may be possible to traverse the entire packet network using only the compressed speech (of the preferred codec). TrFO is basic function of codec Management.  Following are the benefits of achieving the TrFO:  1.) Improve the voice quality because of elimination of coding and decoding of suppressed codecs. 2.) We can optimize

HEX VALUE                                                       CAUSE ---------------------------------------------------------------- 03                                                               No route to destination 06                                                               Channel unacceptable 08                                                               Preemption 0E                                                              Query on Release QoR 10                                                               Normal clearing 11                                                               User busy 12                                                               No user responding 13                                                               No answer from user (user alerted) 14                                                              Subscriber absent 15                                                              Call rejected 1

Service Name                              HEX                                    BINARY ================================================== CLIP                                           11                                      00010001 CLIR                                           12                                      00010010  COLP                                          13                                      00010011  COLR                                          14                                      00010100  All Call Forward                           20                                      00100000  CFU                                             21                                      00100001 All Conditional call forward           28                                      00101000  CFB                                             29                                      00101001 CFNRY                                       2A                            

Here is UMTS subscriber call flow with the core network. MS-A                                               MSC                                                      MS-B **************************************************************************************************** -------Initial_UE(CM_SERVICE_REQ) -->| ------------Dir_Trnx(AUTH_REQ)         <--| -------------Dir_Trnx(AUTH_RSP)         -->| ---------------SecurityModeCmd            <--| --------------SecurityModeComp           -->| -----Dir_Trnx(TMSI_RELOC_CMD)   <--| ----Dir_Trnx(TMSI_RELOC_COMP)  -->|   -------------Dir_Trnx(SETUP)            -->| ---------Dir_Trnx(CALL_PROC)        <--| ----------------RabAssignReq               <--| ----------------RabAssignRsp               -->|                                                                      |-->  PAGING  ---------------------------                                        

Location Update Flow : ***********************************************************************  Mobile Station                                                                 MSC ************************************************************* ----------------------Initial_UE(CM_SERVICE_REQ)  -->| ---------------------------Dir_Trnx(AUTH_REQ)         <--| ---------------------------Dir_Trnx(AUTH_RSP)          -->| -----------------------------Cipher Mode Command     <--| -----------------------------Cipher Mode Complete      -->| ---------------------Dir_Trnx(TMSI_RELOC_CMD)   <--| ----------------------Dir_Trnx(LOCUPD_ACCEPT)    <--| ------------------------TMSI_RELOC_COMP            <--| --------------------------------Clear Cmd                     <--| --------------------------------Clear Comp                   -->| *********************************************************************** CM Service Request/Location Upd