Transcoder Free Operation

Transcription

1 GPP S.R00-0 Version.0 Version Date: March 00 0 Transcoder Free Operation 0 Stage Requirements COPYRIGHT NOTICE GPP and its Organizational Partners claim copyright in this document and individual Organizational Partners may copyright and issue documents or standards publications in individual Organizational Partner's name based on this document. Requests for reproduction of this document should be directed to the GPP Secretariat at secretariat@gpp.org. Requests to reproduce individual Organizational Partner's documents should be directed to that Organizational Partner. See for more information.

2 S.R00-0 v.0 EDITOR R. L. Bunting; REVISION HISTORY REVISION HISTORY Rev. # Descriptions Date.0 Initial publication March 00

3 S.R00-0 v.0 0 Table of Contents Table of Contents... List of Tables List of Figures INTRODUCTION.... Typical TrFO / RTO Transcoder Configurations... REFERENCES... DEFINITIONS AND ABBREVIATIONS... GENERAL FEATURE DESCRIPTION.... Normal Procedures with Successful Outcome.... Exception Procedures or Unsuccessful Outcome.... Alternative Procedures.... Interactions with Other Wireless Services... Requirements.... Network Requirements.... TrFO / RTO Interaction with Services... 0

4 S.R00-0 v.0 None Included List of Tables

5 S.R00-0 v.0 List of Figures Figure : Typical Vocoder Arrangement Prior to TrFO/RTO... Figure : TrFO Bearer Arrangement... Figure : RTO Transcoder Arrangement (Mobile-to-Mobile)... Figure : RTO Transcoder Arrangement (MS-to-PSTN / PSTN-to-MS)...

6 S.R00-0 v INTRODUCTION Transcoder Free Operation [] (TrFO) is the transport of compressed speech, from legacy mobiles, in a packet transport network through the elimination of unnecessary coding and decoding of the signal by intermediate elements in the bearer path. Transcoders may be associated either with the RAN or Media Gateway (MGW). By transporting only the compressed speech, TrFO achieves bandwidth efficiencies in the bearer stream and reduces round trip delays introduced by unnecessary transcoding. Also, TrFO may increase voice quality. TrFO is not applicable to VoIP. TrFO is a capability of the Legacy MS domain. 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 a mechanism for configuring a call such that no transcoders are needed in the core network. The vocoders that are needed for this call are located in the Mobile Station (MS). Remote Transcoder Operation (RTO) is a mechanism for configuring a call such that a transcoder resource is needed in the core network. RTO does not imply a tandem operation, instead only a single resource may be needed. E.g. To support a MS to PSTN call, a transcoder is inserted at the MGW or BSC. For a MS to MS call, where the codecs in the two MS differ, a transcoder is needed in the network. This eliminates the typical tandem use where two transcoders are used to transcode the two endpoints to a common but unique protocol for transport. RTO is just a special case of TrFO.. Typical TrFO / RTO Transcoder Configurations Figures - illustrate some of the many possible TrFO / RTO network configurations. Because of the flexibility for transcoder location (e.g. MGW or RAN), the figure does not show precise transcoder placement. For figures -, the network architecture could be either Intra-LMSD or Inter-LMSD (e.g. the call may be contained completely in a single LMSD or the compressed bearer may be between two separate LMSDs). In the figures, the solid lines and objects represent bearer paths and transcoders or vocoders that are in the bearer path. The drawing elements that are shown in gray represent the corresponding elements that were included in previous figures that are no longer required in the situation illustrated.

7 S.R00-0 v.0.. Figure-: Typical Vocoder Arrangement Prior to TrFO/RTO A typical vocoder arrangement for LMSD Step- is shown in Figure-. This arrangement requires the placement of two vocoders in the bearer path even though the two endpoints are utilizing compatible codecs. This tandem arrangement of transcoders is typical for LMSD Step- and is the configuration that the TrFO enhancement avoids. MS/ codec transcoder transcoder codec/ MS E G G E G. G. 0 Figure-: Typical Vocoder Arrangement Prior to TrFO/RTO.. Figure-: TrFO Bearer Arrangement Using TrFO, the two tandem transcoders shown in Figure- are eliminated as part of the codec negotiation on call setup. The native (compressed) speech provided by the two compatible vocoders is transported through the network without the additional delays and bandwidth or quality losses added by using two unnecessary transcoders. This arrangement is illustrated in Figure-. Note that the unneeded transcoders are shown in dotted blue in the diagram with an end-to-end bearer transport of compressed () speech illustrated. This figure illustrates a mobile-to-mobile call, where the mobiles have compatible codecs. The network configuration could be either Intra-LMSD or Inter-LMSD. MS/ codec transcoder transcoder codec/ MS 0 0 Figure-: TrFO Bearer Arrangement.. Figure-: RTO Transcoder Arrangement (Mobile-to-Mobile) The next configuration worth noting is the RTO. For RTO a single transcoder may be necessary in a bearer path when the two end point codecs are incompatible. There are still noteworthy efficiencies, since the tandem configuration as illustrated in Figure- is reduced to one, not a pair of transcoders. This is illustrated in Figure-. The network configuration could be either Intra- LMSD or Inter-LMSD. Depending on network configuration and vocoder placement, the transcoder placement shown could be either in the RAN or the MGW.

8 S.R00-0 v.0 MS/ codec transcoder transcoder codec/ MS E K K Figure-: RTO Transcoder Arrangement (Mobile-to-Mobile) K K.. Figure-: RTO Transcoder Arrangement (MS-to-PSTN / PSTN-to-MS) Figure-, illustrates the RTO transcoder arrangement for a Mobile-to-PSTN and PSTN-to-Mobile call. The compressed speech bearer could be either Intra-LMSD or Inter-LMSD. Again, there are no restrictions on the transcoder placement. MS/ codec transcoder transcoder PSTN E P PCM PCM 0 REFERENCES PCM Figure-: RTO Transcoder Arrangement (MS-to-PSTN / PSTN-to-MS) PCM [] Work Item Name: Transcoder Free Operation; GPP-000; Submission Date: 00/0/; Work Item Status: Proposed [] A.S000-B v.0 CDMA Tandem Free Operation Specification -Release B (TIA--A), August 00 DEFINITIONS AND ABBREVIATIONS BSC CN Inter-LMSD Intra-LMSD MGW MS MSC PSTN RTO Base Station Controller Core Network Between two distinct LMSD systems (e.g. the architecture of LMSD Step-). In the context of TrFO/RTO, a compressed speech bearer path is established between media gateways located in two different systems. Within the same LMSD system (e.g. a mobile-to-mobile, mobile-to-pstn or PSTN-to-mobile call that is treated within a single LMSD system) Media GateWay Mobile Station Mobile Switching Center Public Switched Telephone Network Remote Transcoder Operation: a network capability for endpoints with

9 S.R00-0 v.0 TFO TrFO incompatible codecs. RTO attempts to enable the bearer by matching the incompatible codecs with a single transcoder. Ideally compressed speech is passed between the endpoints. For circumstances where a single transcoder is not available to enable the bearer, two tandem transcoders may be required to find a match between the endpoints. Tandem Free Operation Transcoder Free Operation: a network capability for mobile-to-mobile calls, where the mobiles have identical codecs. TrFO enables the bearer path without introducing vocoders in the bearer path. Compressed speech is passed between the mobile endpoints GENERAL FEATURE DESCRIPTION A typical use of end-to-end TrFO is a mobile-to-mobile call where the same codec is used for each Mobile Station and no additional transcoders are required in the transport network. Alternatively for a mobile to PSTN call, the only transcoder required may be at the Core Network (CN) to PSTN boundary (e.g. transcoding at the edge). The situation requiring a single transcoder is described here as RTO Where a change to the call state of a transcoder free connection occurs, such that compressed speech cannot be maintained, a transcoder or pair of transcoders may be required in the path (e.g. handoff to a system not capable of TrFO, or at the edge of a CN network). In the situation where additional handoffs occur and TrFO can be supported, the call should revert to TrFO. TrFO is an enhancement over Tandem Free Operation [] (TFO) because it increases transport bandwidth efficiency. See also Figures through in the INTRODUCTION for additional illustrations of possible transcoder arrangements using TrFO and RTO.. Normal Procedures with Successful Outcome Authorization The subscriber is authorized to use this service without prior arrangement. The network performs TrFO configuration and no subscriber authorization is required. De-Authorization The subscriber is authorized to use this service without prior arrangement. The network performs TrFO configuration and no subscriber deauthorization is needed. Registration TrFO is a network enhancement. It is not offered as a subscriber service and no registration for this service is required. De-Registration Not Required, see Registration above.

10 S.R00-0 v Activation TrFO is a network enhancement. It is not offered as a subscriber service and no subscriber feature activation is required. De-Activation TrFO is a network enhancement. It is not offered as a subscriber service and no subscriber feature de-activation is required. Invocation Invocation of TrFO may occur in the network for mobile-to-mobile call when both ends of the call will be using the same codec. Invocation of RTO may occur for a call traversing a RTO capable network, where the only occurrence of a codec is at the network edge when the call is exiting the network for another network that is not TrFO or RTO capable (e.g. PSTN). Normal Operation with Successful Outcome 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). Call Detail Record Enhancements to call detail recording are desirable to provide the ability to determine on a per call-leg or route basis the transcoder configuration that was established for a particular call. This information is useful for customer service, trouble reporting, capacity and provisioning and is part of the general accounting information. There is not implied billing impact for these enhancements.. Exception Procedures or Unsuccessful Outcome Registration Not Applicable. De-Registration Not Applicable. Activation Not Applicable. De-Activation Not Applicable. Invocation Not Applicable.

11 S.R00-0 v Exceptions While Roaming Not Applicable. Exceptions During Intersystem Handoff Where a change to the call state of a transcoder free connection occurs, such that compressed speech cannot be maintained, a transcoder or pair of transcoders may be required in the path (e.g. handoff to a system not capable of TrFO, or at the edge of a CN network). In the situation where additional handoffs occur and TrFO can be supported, the call should revert to TrFO.. Alternative Procedures None Specified.. Interactions with Other Wireless Services The TrFO and RTO capabilities are required to support other wireless services that result in the modification or reconfiguration of the bearer path during TrFO operation (e.g. Addition and removal of conference bridge, etc) See the specific requirements below... Conferencing Introducing a Conference Bridge into a TrFO call may require the introduction of transcoders to gain a mix of the voice calls from the individual conference participants or reverting to conventional call handling at the base station in order to meet the conferencing restrictions. At the end of the conferencing restrictions, TrFO operation should be resumed... Announcements Announcements for the purpose of this description may be considered as a special case of conferencing. It may be plausible to consider at what time during the call TrFO will be invoked based on the nature of the announcement (e.g. pre-call, mid-call, or post-call). Requirements Specific requirements for the TrFO capability are listed in this section.. Network Requirements.. TrFO TrFO-00: The TrFO network capability shall enable TrFO between Mobile-to- Mobile calls when the Mobiles have compatible codecs. TrFO-00: The TrFO capability shall be provided for calls between mobile stations that are intra-lmsd (e.g. between MSs that are served by the same LMSD system).

12 S.R00-0 v RTO TrFO-00: The TrFO capability shall be provided for calls between mobile stations that are inter-lmsd (e.g. between MSs where each is served by a separate but networked LMSD). TrFO-00: The mechanism to provide TrFO shall minimize the number of vocoders in the bearer path. (For TrFO, the endpoint codecs are compatible and the minimization results in zero transcoders placed in the bearer path. If the codecs are incompatible, the resultant configuration may be RTO and a single transcoder is placed in the path. If a transcoder match cannot be found and two transcoders are required to match the circuit, then the current situation, shown in Figure- may result.) RTO-00: The RTO capability shall enable RTO between Mobile-to-Mobile calls when the Mobiles have incompatible codecs. RTO-00: The RTO capability shall be provided between mobile stations that are intra-lmsd (e.g. between MSs that are served by the same LMSD). RTO-00: The RTO capability shall be provided between mobile stations that are inter-lmsd (e.g. between MSs where each is served by a separate but networked LMSD). RTO-00: The RTO capability shall be provided between a MS and a network endpoint where incompatible codecs exist, but where a single transcoder will enable the bearer path (e.g., Mobile-to-PSTN, PSTN-to-Mobile). RTO-00: The RTO mechanism shall utilize a transcoder selected from a prioritized list of transcoders. RTO-00: The mechanism to provide RTO shall minimize the number of vocoders in the bearer path. For RTO, the endpoint codecs are not compatible and the minimization results in a single transcoder placed in the bearer path. If a transcoder match cannot be found and two transcoders are required to match the circuit, then the current situation, shown in Figure- may result.. TrFO / RTO Interaction with Services TSv-00: The TrFO and RTO mechanisms shall allow for reconfiguration of transcoders in the bearer path when needed (e.g. application of conference circuits, insertion of announcements, placing subscriber on hold, etc.) TSv-00: It may be necessary to reconfigure a TrFO or RTO bearer path due to certain telephony requirements. (e.g. transcoders may be inserted, dropped or otherwise reconfigured due to certain restrictions, like conferencing). At the end of the reconfiguration, the operation (TrFO or RTO) shall be resumed. 0