Transcoder-Free Operation/ Out-of-Band Transcoder Control 

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Transcoder-Free Operation/ Out-of-Band Transcoder Control

Acronym: OoBTC

UID: 1541

Main responsibility: N4


References for WI " Transcoder-Free Operation "

Document Title/Contents
NP-000529 WID for Out of band Transcoder Control
Impacted Specifications  
TS 24.008[5]   TS 26.108 Mobile radio interface Layer 3 specification; Core network protocols; Stage 3  
New Dedicated Specifications  
TS 23.153 Out of band Transcoder Control; Stage 2


Initially, this WI was started for Release 99. However, a significant amount of open issues were not closed on time so the WI was postponed to Release 4 and all remaining issues identified in Release 99 were resolved.


Out-of-Band Transcoder is the mechanism to establish the Transcoder Free Operation. Transcoder Free Operation (TrFO) is defined as the configuration of a speech or multimedia call for which no transcoder device is physically present in the communication path between the source codecs and hence no control or conversion or other functions can be associated with it.

In case of mobile to fixed network calls, the term "Transcoder free operation" is applicable for the TrFLs carrying compressed speech. TrFLs (Transcoding free link) refers to a bearer link where compressed voice is being carried between bearer endpoints. The TrFO usually ends at the Gateway to the PSTN where the speech is transcoded e.g. to G.711.


Although the main reason for avoiding transcoding in mobile-to-mobile calls has been speech quality, the transmission of compressed information in the CN and CN-CN interface of the cellular network also offers the possibility of bandwidth savings. Therefore Out-of-Band Transcoder Control is not limited to mobile-to-mobile calls but can be applied for calls to or from an external network as well.

In order to allocate transcoders for a call inside the network, and to select the appropriate codec type inside the UEs, signalling procedures are defined to convey the codec type selected for a call to all the affected nodes (UEs and potential transcoding points inside the network). Also, codec negotiation capabilities have been defined to enable the selection of a codec type supported in all the affected nodes, i.e. to resolve codec mismatch situations. This codec negotiation maximises the chances of operating in compressed mode end-to-end for mobile-to-mobile calls.

To allow transport of information in a compressed way in transmission networks, these networks make use of the transport -independent call control protocol as specified in TS 23.205 that provides means for signalling codec information, negotiation and selection of codecs end-to-end.

Transparent End-to-End PS mobile streaming application


Acronym: PSTREAM

UID: 1539

Main responsibility: S4


References for WI " Transparent End-to-End PS mobile streaming application "

Document Title/Contents
SP-000345 WI Description
Impacted Specifications  
TS 26.233     TS 26.234 Transparent end-to-end packet switched streaming service (PSS); General description   Transparent end-to-end packet switched streaming service (PSS); Protocols and codecs  
New Dedicated Specifications  


Streaming refers to the ability of an application to play synchronised media streams, like audio and video, in a continuous way while those streams are being transmitted to the client over a data network.

The applications which can be built on top of streaming services can be classified into “on-demand” and “live” information delivery. Examples of the first category are music and news-on-demand applications. Live delivery of radio and television programs are examples of the second category.

PSS-only mobiles are envisaged as their complexity would be lower than for conversational services: there is no need for media input devices, media encoders and some protocols can be avoided.


Streaming over fixed-IP networks is already a major application. While the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C) have developed a set of protocols used in fixed-IP streaming services, for 3G systems, the 3G packet-switched streaming service (PSS) fills the gap between 3G MMS, e.g. downloading, and conversational services.


This feature enables a multitude of streaming applications to be deployed by independent content providers. The advantage from a user’s perspective is to have access to a much broader set of content as in a closed configuration.


The 3GPP streaming is to be used both on top of GPRS/EDGE and UMTS. As an issue specific to mobile streaming, applicable to both types of access networks (GPRS and UMTS), the coupling between the browser and the streaming client have been addressed. Indeed, some mobile terminals have limited possibility of software plug-ins. Also specific to mobile, a default set of streaming protocols and codecs has been specified.


By contrast to the fixed Internet access, connection time is much more costly and the quality can be much worse, in particular in Release 4, as no specific content protection has been developed in this Release.


The mobile streaming service standardized by this feature covers the different components: streaming protocols, media transport protocols and multimedia codecs. Note that the wideband codec ITU-T G.722.2 has been made allowable for this release 4 work item, while the "AMR-WB service" is a feature which is part of the 3GPP Release 5.

TS 26.233 defines the usage scenarios, overall high level end-to-end service concept, and lists terminal-related functional components. It also lists any identified service interworking requirements. PSS protocols for control signalling, scene description, media transport and media encapsulations are specified in TS 26.234. TS 26.234 also specifies the codecs for speech, audio, video, still images, bitmap graphics, and text. Vector graphics belongs to the extended PSS features and is not specified in 3GPP Release 4.

The mobile streaming application allows various charging models.

Transport security aspects were covered as well (see TS 33.102 "Security architecture").

Harmonization with existing and emerging 3GPP multimedia applications has been considered whenever possible.


UMTS-only new Features

Low Chip Rate TDD option

This section was elaborated in co-operation between MCC and the following Datang Mobile experts: Liyan Yin, Ke Wang, Darun Wang, Na Wu, Guiliang Yang, Qingguo Feng, Yusong He. Many thanks to all of them.


Acronym: LCRTDD

UID: 1222

Main responsibility: RAN WG1


Structure of the feature:

UID Task name WG Acronym
  Physical layer R1 LCRTDD-Phys
  Layer 2 and layer 3 protocol aspects R2 LCRTDD-L23
  "RF radio transmission/reception, system performance requirements and conformance testing" R4 LCRTDD-RF
  UE radio access capability R2 LCRTDD-UErac
  Iub/Iur protocol aspects R3 LCRTDD-IubIur
  Low chiprate TDD interworking with GERAN GERAN  


The Work Item Description Sheets can be found in the file RAN_Work_Items_History in:

References for WI "Low Chip Rate TDD option"


Impacted Specifications / Reports
25.102 UE Radio Transmossion and Reception (TDD)
25.104 BTS Radio Transmission and Reception (FDD)
25.105 BTS Radio Transmission and Reception (TDD)
25.123 Requirements for support of Radio Resource Management (TDD)
25.142 Base station conformance testing(TDD)
25.113 Base station EMC
25.133 Requirements for support of Radio Resource Management (FDD)
25.201 Physical layer – General description
25.221 Physical channels and mapping of transport channels onto physical channels (TDD)
25.222 Multiplexing and channel coding (TDD)
25.223 Spreading and modulation (TDD)
25.224 TDD; physical layer procedures
25.225 Physical layer; measurements
25.302 Services Provided by the physical layer
25.303 UE functions and Inter-layer procedures in connected mode
25.304 UE procedures in idle mode and procedures for cell reselection in connected mode
25.305 User Equipment (UE) positioning in Universal Terrestrial Radio Access Network (UTRAN); Stage 2
25.306 UE Radio Access capabilities definition
25.321 Medium access control (MAC) protocol specification
25.331 Radio resource control (RRC) protocol specification
25.401 UTRAN Overall Description
25.402 Synchronisation in UTRAN Stage 2
25.423 UTRAN Iur Interface RNSAP Signalling
25.425 UTRAN Iur Interface User Plane Protocols for Common Transport Channel data streams
25.427 UTRAN Iub/Iur Interface User Plane Protocols for DCH data streams
25.430 UTRAN Iub Interface: General Aspects and Principles
25.433 UTRAN Iub Interface NBAP Signalling
25.435 UTRAN Iub Interface User Plane Protocols for Common Transport Channel data streams
25.922 Radio Resource Management Strategies
25.944 Channel coding and multiplexing examples
44.018 Radio Resource Control Protocol
44.060 Radio Link Control / Medium Access Control Protocol
45.002 Multiplexing and multiple access on the radio path
45.008 Radio subsystem link control
48.008 MSC-BSS interface Layer 3 specification
48.058 BSC-BTS interface Layer 3 specification
24.008 Mobile radio interface Layer 3 specification; Core network protocols; Stage 3
34.108 Common test environments for User Equipment (UE) conformance testing
34.122 Terminal conformance specification, Radio transmission and reception (TDD)
34.123-1 User Equipment (UE) conformance specification; Part 1: Protocol conformance specification
34.123-2 User Equipment (UE) conformance specification; Part 2: Implementation conformance statement (ICS) specification
34.124 Electromagnetic compatibility (EMC) requirements for Mobile terminals and ancillary equipment


New Dedicated Technical Reports
25.834 UTRA TDD low chip rate option; Radio protocol aspects
25.843 1.28 Mcps TDD UE Radio Access Capabilities
25.928 Low Chip Rate TDD Physical Layer
25.937 Low chip rate TDD Iub/Iur protocol aspects
25.945 RF requirements for 1.28 Mcps UTRA TDD option



3GPP Release 99 UTRA (Universal Terrestrial Radio Access) included two basic modes of operation: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). TDD can be introduced without needs for paired spectrum and is well-suited to asymmetric traffic.

In addition to Release 99 TDD, using a chip rate of 3.84 Mcps, Release 4 introduces an option that uses a chip rate of 1.28 Mcps. This mode is known as “1.28 Mcps TDD” through 3GPP specifications, and usually referred to as "Low Chip Rate TDD" (LCR TDD). In line with this formulation, R99 TDD is often called High Chip Rate TDD.


LCR TDD is also supported by ITU-R (where it is called “TD-SCDMA”) and Operators Harmonisation Group (OHG). LCR TDD operation mode is TDD mode. It takes advantage of varies available Multiple Access techniques: TDMA, CDMA, FDMA, SDMA. As one of IMT-2000 compliant system, LCR TDD can support all the bearer services and diversified radio propagation environments corresponding to ITU requirement.


The chip rate of LCR TDD is 1.28Mcp. The benefit of LCR TDD is that it can be supported on unpaired frequency bands of 1.6MHz hence it is more flexible than FDD and 3.84Mcps TDD that request a minimum bandwidth of 5 MHz. It can be deployed not only for high spot or high density area to provide high speed data service or to provide enhanced coverage, but also to be used alone as macro cell to provide the service coverage. LCR TDD allows deployment together with existing GSM system, with FDD system, with 3.84Mcps TDD system and should support the handover between UTRA modes (e.g., LCR TDD to 3.84Mcps TDD, LCR TDD to FDD) and between systems (e.g., LCR TDD to GSM).

Comparison between minimum bandwidth needed for FDD, HCR TDD and LCR TDD


The goal of LCR TDD is to enable the full integration of TD-SCDMA and its specific properties into the Release 4 specifications of 3GPP. In other words, the integration work of all aspects of LCR TDD is designed to maximize the commonality with the 3.84Mcps TDD. As a result of this requirement, LCR TDD shares most of the aspects of the high layer and network elements as the other modes. But LCR TDD has its unique physical layer structure and key features. Correspondingly, some elements or parameters in high layer and interface for LCR TDD are added, modified or extended to adapt physical layer features. Also the differences on RF, system performance and conformance testing requirements of LCR TDD reflect the characteristic of an LCR TDD system.


The different system impacts of LCR TDD are described hereafter.

Physical layer

The main differences between LCR TDD and UTRA R99 TDD are on physical layer, e.g. the differences on the frame structure and synchronisation scheme.


Frame structure

In LCR TDD, a radio frame has a duration of 10 ms and is subdivided into 2 sub-frames of 5 ms each, each sub-frame is then subdivided into 7 traffic time slots (“Ts”) of 675 ms duration each and 3 special time slots: DwPTS (downlink pilot timeslot), GP (guard period) and UpPTS (uplink pilot timeslot). This is different to 3.84 Mcps TDD, where there is no sub-frame. The LCR sub-frame of 5 ms allows for a faster update of power control and is well suited for smart antenna beamforming.

For high chip rate option, each 10 ms frame consists of 15 time slots, each allocated to either the uplink or the downlink. So it has both single and multiple-switching point configuration. While in the low chip rate option, the big Guard Period GP, the DwPTS and UpPTS physical channels are always between Ts0 and Ts1 whatever the level of asymmetry is, and there are always only 2 Switching Points per sub-frame.


The frame structure of LCR allows for a better control of the trade-off between quality and interference than with HCR. Indeed, given the switch of downlink to uplink, there is a risk of interference due to propagation delay. This risk of interference determines the size of cells. For the high chip rate option, there is no “DwPTS – guard – UpPTS” structure: the UL time slots are following the DL time slots immediately. This problem is avoided thanks to the guard period of LCR TDD.


Basic behaviour

In cell search procedure, unlike 3.84 Mcps TDD, the UE will search for the DwPCH at the first and then identify the scrambling code and basic midamble code.

Then, upon starting a transmission, the UE first accesses the cell through the UpPCH (uplink synchronisation burst, “power ramping”). The timing used for UpPCH is coarse and based on the DwPCH and P-CCPCH. The Node B will listen to the UpPCH burst, evaluate the timing and required power for the UE and send the information with the FPACH described below. The UE knows the correct timing and power level for the use of the PRACH, allowing for a more efficient use of resources (e.g. as the shorter initial sequence sent minimises interferences). This is similar to FDD mode “two step access”.


Physical Channels

Compared to R99 TDD, LCR TDD introduces new channels and removes others.

The following channels are introduced:

  • Two dedicated physical synchronisation channels: DwPCH and UpPCH, equal to DwPTS and UpPTS above.
  • A physical channel for random access, the Fast Physical Access CHannel (FPACH). FPACH is used by the Node B to carry, in a single burst, the acknowledgement of a detected signature with timing and power level adjustment indication to a UE.
  • A 5ms TTI (Transmission Time Interval) is also introduced

On the other hand, two physical channels of 3.84 Mcps TDD, SCH and PNBSCH, are not needed in LCR option.

The transport and logical channels do not change.


Only one burst type is used. Transmit method of TFCI, TPC, SS, different basic midamble sequences and different timeslot formats differ compared to R99 TDD.



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