Content for TS 23.034 Word version: 18.0.0
1 Scope
2 References
3 Definitions
4 Main concepts
4.1 HSCSD service aspects
4.2 HSCSD service aspects in UTRAN Iu mode
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1 Scope p. 5
The present document contains the stage 2 service description for a High Speed Circuit Switched Data (HSCSD) on GSM/GERAN in A/Gb mode and Iu mode. HSCSD utilizes the multislot mechanism, i.e. using multiple traffic channels (/bearers) for the communication.
Additionally, the present document specifies some HSCSD related requirements for multi system mobile stations operating in UTRAN Iu mode. In UTRAN Iu mode one bearer can provide all needed data rates, and the multislot mechanism is therefore not needed. However, for inter-system handover to GERAN, certain information has to be provided by the mobile station during the service negotiation. The UTRAN Iu mode aspects concerning HSCSD are described exclusively in clause 4.2.
In analogy with ITU-T Recommendation I.130 [6] (refer to annex A) and with reference of ITU-T Recommendation Q.65 [7] VI.1 (Stage 2 of the method for characterization of services supported by an ISDN), the second stage of the HSCSD is defined as follows.
Stage 2 identifies the functional capabilities and information flows needed to support the service as described in TS 22.034. Furthermore, it identifies various possible physical locations for the functional capabilities. The output of Stage 2, which is signalling system independent, is used as an input to Stage 3, the design of signalling system and switching Recommendations.
The present document specifies functions, procedures and information which apply to GERAN Iu mode. However, functionality related to GERAN Iu mode is neither maintained nor enhanced.
2 References p. 5
The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
[1] Void.
[1a]
TR 21.905: "Vocabulary for 3GPP Specifications".
[2]
TS 45.002: "Multiplexing and multiple access on the radio path".
[3]
TS 24.008: "Mobile Radio Interface Layer 3 specification; Core Network Protocols - Stage 3".
[4]
TS 48.008: "Mobile services Switching Centre - Base Station System (MSC - BSS) interface; Layer 3 specification".
[5]
TS 24.022: "Radio Link Protocol (RLP) for data and telematic services on the Mobile Station - Base Station System (MS - BSS) interface and the Base Station System - Mobile-services Switching Centre (BSS - MSC)".
[6]
ITU-T Recommendation I.130: "Method for the characterization of telecommunication services supported by an ISDN and network capabilities of an ISDN".
[7]
ITU-T Recommendation Q.65: "The unified functional methodology for the characterization of services and network capabilities".
[8]
ITU-T Recommendation I.460: "Multiplexing, rate adaptation and support of existing interfaces".
[9]
TS 22.034: "High Speed Circuit Switched Data (HSCSD); Stage 1".
[10]
TS 43.020: "Security related network functions".
[11]
TS 44.021: "Rate adaption on the Mobile Station - Base Station System (MS - BSS) Interface".
[12]
TS 48.020: "Rate adaption on the Base Station System - Mobile-services Switching Centre (BSS - MSC) interface".
[13]
TS 27.002: "Terminal Adaptation Functions (TAF) for services using Asynchronous bearer capabilities".
[14]
TS 27.003: "Terminal Adaptation Functions (TAF) for services using synchronous bearer capabilities".
[15]
TS 45.008: "Radio Subsystem Link Control".
[16]
TS 23.008: "Organisation of subscriber data".
[17]
TS 44.018: "Mobile radio interface layer 3 specification; Radio Resource Control Protocol".
[18]
TS 43.051: "GSM/EDGE Radio Access Network; Overall description - Stage 2".
[19]
TS 25.413: "UTRAN Iu interface RANAP Signalling".
[20]
TS 25.415: "UTRAN Iu interface user plane protocols".
[21]
TS 44.118: Release 11 "Mobile radio interface layer 3 specification; Radio Resource Control (RRC) Protocol, Iu Mode".
[22]
TS 29.415: "Core Network Nb Interface User Plane Protocols".
[23]
TS 29.007: "General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN)".
[24]
TS 33.102: "3G Security; Security Architecture".
3 Definitions p. 6
For the purposes of the present document, the following terms and definitions apply:
A/Gb mode:
mode of operation of the MS when connected to the Core Network via GERAN and the A and/or Gb interfaces.
GERAN:
GSM/EDGE radio access network
HSCSD:
High Speed Circuit Switched Data
HSCSD configuration:
multislot configuration consisting of one or several full rate traffic channels for data transmission
HSCSD channel:
full rate traffic channel belonging to a HSCSD configuration
Iu mode:
mode of operation of the MS when connected to the Core Network via GERAN or UTRAN and the Iu interface. When preceded by the word GERAN or UTRAN, it means access over the Iu interface using the respective radio access network.
main channel:
only channel in a HSCSD configuration carrying an FACCH
symmetric configuration:
configuration consisting of bi-directional channels
asymmetric configuration:
configuration consisting of bi-directional channels and at least one uni directional channel
UTRAN:
UMTS radio access network
For further abbreviations see TR 21.905.
4 Main concepts p. 7
The air interface user rate in the original GSM data transmission is limited to 9,6 kbps with the 12 kbps air interface rate. The HSCSD described in the present document Stage 2 description allows higher air interface user rates to be used for transparent and non-transparent data services.
HSCSD is a feature enabling the co-allocation of multiple full rate traffic channels (TCH/F) into a HSCSD configuration. The aim of HSCSD is to provide a mixture of services with different air interface user rates by a single physical layer structure. Further improvements in data rates are achieved through enhancement of the radio interface (modulation and coding schemes), which allows higher bit rates per one GSM time slot. The available capacity of a HSCSD configuration is several times the capacity of a TCH/F, leading to a significant enhancement in the air interface data transfer rate.
Figure 1 represents the network architecture to support HSCSD in A/Gb mode based on the concept of multiple independent channels in one HSCSD configuration. Figure 1a represents the network architecture to support HSCSD in GERAN Iu mode.
In case when enhanced modulation is used the number of time slots in the radio interface may not correspond to the number of data streams in the network side, for example a 28,8 kbps service may be offered through one air interface time slot, but it requires two 14,4 (16 kbps) Abis channels. Another example is bit transparent 56 kbps to 64 kbps service where two air interface time slots of 32 kbps are multiplexed onto one 64 kbps data stream on the network side.
Figure 1a: Network architecture for supporting HSCSD in GERAN Iu mode
(⇒ copy of original 3GPP image)
(⇒ copy of original 3GPP image)
A new functionality is introduced at the network and MS to provide the functions of combining and splitting the data into separate data streams which will then be transferred via n channels at the radio interface, where n = 1, 2, 3, ... 8. Once split, the data streams shall be carried by the n full rate traffic channels, called HSCSD channels, as if they were independent of each other, for the purpose of data relay and radio interface L1 error control, until to the point in the network where they are combined. However, logically the n full rate traffic channels at the radio interface belong to the same HSCSD configuration, and therefore they shall be controlled as one radio link by the network for the purpose of cellular operations, e.g. handover. This requires a new functionality in BSS.
The different user data substreams carried on the radio channels (one substream being the data flow over a single TCH) shall be mapped over the A interface or GERAN Iu interface, and vice versa, following the rules defined in TS 24.008 and TS 48.020.
In A/Gb mode, the use of resources on the A and E interfaces is restricted to one 64 kbps circuit by multiplexing the data streams into one A interface circuit (see ITU-T Recommendation I.460 [8]).
In GERAN Iu mode, the user plane at the Iu interface shall comply to the Iu UP protocol (TS 25.415). For transparent calls the Iu user plane is operated in transparent mode, version 1, for non-transparent calls it is operated in support mode for predefined SDU sizes, version 2.
After an inter-MSC SRNS relocation the user plane between the anchor MSC or MGW and the target MSC or MGW shall comply to the Nb UP protocol (TS 29.415), if the anchor MSC or MGW and the target MSC or MGW are connected via an ATM interface or IP interface. The NbUP shall be configured in support mode, the data is transported in a 64 kbit/s bit stream (for details see TS 29.007).
If both MSCs are connected via a TDM interface the use of resources on the E interface is restricted to one 64 kbps circuit (see TS 29.007).
4.1 HSCSD service aspects p. 8
At call setup a user indicates a maximum number of TCH/F, acceptable channel codings (including extensions to acceptable channel codings for ECSD channel codings), possible other modem type, and fixed network user rate values. For non-transparent HSCSD connection, in addition, wanted air interface user rate is indicated and the network resource needs, if user wishes to make use of the user initiated modification of the maximum number of TCH/F and/or wanted air interface user rate (user initiated service level up- and downgrading described in subclause 5.2.4 and subclause 5.2.4a) during the call. In case the indicated acceptable channel coding(s) implies that enhanced modulation is possible, the user may indicate a preference for channel coding asymmetry, i.e. downlink biased channel coding asymmetry, uplink biased channel coding asymmetry or channel coding symmetry. Together these parameters describe the HSCSD characteristics and network uses them to allocate an appropriate HSCSD connection.
For both transparent and non-transparent HSCSD connections the call can be established with any number of TCH/F from one up to the maximum number of TCH/F, i.e. the minimum channel requirement is always one TCH/F.
If the wanted air interface user rate requirement cannot be met using a symmetric configuration, an asymmetric configuration can be chosen. The network shall in this case give priority to fulfilling the air interface user rate requirement in downlink direction.
For non-transparent HSCSD connection the network can use dynamic allocation of resources, i.e. TCH/F, as long as the configuration is not in contradiction with the limiting values defined by the MS and the mobile equipment is capable of handling the allocated channel configuration. For transparent HSCSD connection the dynamic resource allocation is applicable, if the air interface user rate is kept constant. The change of channel configuration within the limits of minimum and maximum channel requirements is done with resource upgrading and resource downgrading procedures (described in subclause 5.2.3 and subclause 5.2.3a) during the call.
The MS may request a service level up- or downgrading during the call, if so negotiated in the beginning of the call. In the user initiated modification procedure, the user can modify the channel coding asymmetry preference when enhanced modulation is indicated. This modification of channel requirements and/or wanted air interface user rate and/or channel coding asymmetry preference is applicable to non-transparent HSCSD connections only.
4.2 HSCSD service aspects in UTRAN Iu mode p. 9
The multislot mechanism is not needed in UTRAN Iu mode, as one bearer can provide all needed data rates. In UTRAN Iu mode, consequently the parameters required for setup of a multislot call are not needed in a call setup, and the MSC shall ignore the parameters.
The parameters which are specific to multislot are (all contained in the Bearer Capability Information Element):
- Maximum number of traffic channels.
- Acceptable Channel coding(s).
- UIMI, User initiated modification indication.
- Acceptable Channel Codings extended.
4.2.1 UTRAN Iu mode to GERAN Iu mode or A/Gb mode handover p. 9
In case of handover from UTRAN Iu mode to GERAN Iu mode or A/Gb mode the multislot parameters are required in the middle of an ongoing call. A multi system mobile station supporting UTRAN Iu mode and at least one GERAN mode shall therefore always include the multislot parameters in the setup, also in UTRAN Iu mode.
