6 User and Control Plane Protocols

3GPP43.051GSM/EDGE Overall descriptionRelease 17Stage 2TS

This clause provides an overview on the user and control plane protocols of GERAN. For detailed description of each of the layer, please refer to the corresponding specification (see below).

6.1 Identifiers in GERAN

The identities listed below shall be used for an MS connected, via GERAN through an Iu interface, to the CN. The identities for an MS connected, via GERAN through a Gb interface, to the CN are defined in Release 99 and can be found in 3GPP TS 23.060.

6.1.1 IMSI, TMSI and P-TMSI

The International Mobile Subscriber Identity (IMSI), Temporary Mobile Subscriber Identity (TMSI) and Packet Temporary Mobile Subscriber Identity (P-TMSI) are defined in 3GPP TS 23.003.

6.1.2 G-RNTI

A GERAN Radio Network Temporary Identity (G-RNTI) shall be allocated to a mobile station by the BSS when an RRC connection is established between this mobile station and the GERAN. It identifies the MS within GERAN and may be used the same way TLLI is currently used over the radio interface in (E)GPRS (A/Gb mode). The G-RNTI is defined in 3GPP TS 44.118. It is 32 bits in length and contains the serving BSC identity (SBSC-id) and the MS identity (S-RNTI) which is unique within the area of its serving BSC.

6.1.3 NSAPI, RAB ID and RB ID

The UMTS definitions and mapping amongst NSAPI, RAB ID and RB ID shall be used for GERAN 3GPP TS 23.060.

The Network layer Service Access Point Identifier (NSAPI) and IMSI are used for network layer routing. In the MS, NSAPI identifies the PDP-SAP. In the SGSN and GGSN, NSAPI identifies the PDP context associated with an MM context.

In communication with BSS across the Iu-ps and Um interfaces, the RAB ID is used to identify the radio access bearer and shall be identical to the NSAPI value. In the BSS, the RAB ID identifies the BSS RAB context. The RAB ID shall uniquely identify the RAB for a specific CN domain and a particular MS.

GERAN establishes exactly one radio bearer to realize each RAB. Within the MS and the GERAN, the RB ID shall uniquely identify the radio bearer for a particular MS.

6.1.4 RB Id, RRB Id, and TFI

An RB Id (Radio Bearer Identity) identifies an RB (Radio Bearer). An RB Id has one of 32 possible values. Signalling radio bearers use RB Ids 0 to 4; user radio bearers use the rest. RB Ids are assigned at RB establishment and remain assigned until the radio bearer or the RRC connection is released.

An RRB Id (Reduced Radio Bearer Identity) identifies a TBF on FACCH, SACCH, or SDCCH. An RRB Id has one of 8 possible values. For such TBFs carrying SRBs, RRB Ids are implicitly assigned when the DBPSCH is assigned. For such TBFs carrying URBs, the mapping between RB Id and RRB Id is given at RB setup.

A TFI (Temporary Flow Identity) identifies a TBF (Temporary Block Flow) on PDTCHs. A TFI has one of 32 possible values. For SBPSCHs, when a TBF is established, one unique TFI is assigned accross all SBPSCHs that carry the TBF. Uplink and downlink TFIs are independent, i.e., assignment of a TFI in one direction does not constrain the TFI used in the other direction. The GERAN establishes the association between RB Id and TFI when the TBF is established. For DBPSCHs, TFIs are implicitly assigned to TBFs when the corresponding RB is allocated on the DBPSCH, and remain assigned until the RB is deallocated from the DBPSCH. For each RB on a DBPSCH, the TFI equals the RB Id.

A TBF on one or more TCHs is the only user of the TCHs; hence, no specific MAC-layer identifier is needed.

6.1.5 USF

For a TBF on one or more PDTCHs, USF (Uplink State Flag) is sent in the downlink and identifies which TBF may use the next block (or blocks) on the uplink SBPSCH or DBPSCH. A USF has one of 8 values.

A unique USF is assigned per timeslot for the duration of the TBF. The GERAN establishes the association between TFI and USFs when the TBF is established.

6.1.6 SAI

The SAI (Service Area Identifier) identifies a Service Area that consists of one or more GERAN and UTRAN cells. It is defined in [25]. The SAI is unique within the PLMN. The SAI is used over the Iu interface for mechanism such as inter-system handover, location services, charging etc.

The SAI is constructed as follows:

SAI = MCC + MNC + LAC + SAC

6.1.7 BSC-id

Each BSC that supports the Iu interface will be allocated a BSC-id (Base Station Control Identifier). The BSC-id is constructed the same way as the RNC-id, which is defined in [25]. The BSC-id and the RNC-id are allocated from the same addressing space and are unique within the PLMN. The BSC-id together with the PLMN-id is used for addressing BSCs over the Iur-g and the Iu interface.

6.1.8 LAI for 3G core network

For the case the network does not support common Location Areas for the 2G and 3G CNs, a GERAN cell that supports Iu mode of operation needs to support an additional Location Area Identity (LAI) for the 3G CN [25] [26]. For the case the network supports common Location Areas for the 2G and 3G CN, a GERAN cell supporting both A/Gb and Iu modes of operation may not need an additional LAC for the 3G CN. The LAI is unique within the PLMN.

The LAI is constructed as follows:

LAI = MCC + MNC + LAC

NOTE: It is FFS whether the full LAC for the 3G CN needs to be broadcast in the cell. It might be possible to share part of it with the LAC for the 2G CN.

6.1.9 RAI for the 3G core network

For the case the network does not support common Routing Areas for the 2G and 3G CN, a GERAN cell that supports Iu mode of operation needs to support an additional Routing Area Identity for the 3G [25] [26]. For the case the network supports common Routing Areas for the 2G and 3G CN, a GERAN cell supporting both A/Gb and Iu modes of operation may not need an additional RAC for the 3G CN. The RAI is unique within the LAI.

The RAI is constructed as follows:

RAI = LAI + RAC

NOTE: It is FFS whether the full RAC for the 3G CN needs to be broadcast in the cell. It might be possible to share part of it with the RAC for the 2G CN.

6.1.10 GRA Identity

A GERAN Registration Area (GRA) is identified by the GRA Identity. GRAs consist of one or more cells and are allowed to overlap as well as to overlap BSCs/RNCs and LAs/RAs. One or more GRA Identities are broadcast in the cell.

6.1.11 GERAN internal Cell Identity

A GERAN cell identity (GC-id) will be used to address cells in GERAN. The GC-id consists of the BSC-id identifying the BSC controlling the cell and a cell identity CI unique within that BSC. The same CI is used to address the cell for both A/Gb mode and Iu mode.

NOTE: In GERAN A/Gb mode, the CI is unique within the Location Area and in GERAN Iu mode, the CI needs to be unique within the BSC Area.

6.2 Relay

The relay function of GERAN functionality and whether some functions need to be standardized are FFS.

6.3 Radio Resource Control (RRC)

RRC is a layer 3 control plane protocol for radio resource management.

6.3.1 RRC Functions

The Radio Resource Control (RRC) layer handles the control plane signalling of Layer 3 between the MSs and the GERAN. The RRC performs the following functions:

– Broadcast of information provided by the non-access stratum (Core Network): The RRC layer performs system information broadcasting from the network to all MSs. The system information is normally repeated on a regular basis. The RRC layer performs the scheduling, segmentation and repetition when such broadcasting is carried on BCCH. This function supports broadcast of higher layer (above RRC) information. This information may be cell specific or not. As an example RRC may broadcast Core Network location service area information related to some specific cells.

– Broadcast of information related to the access stratum (GERAN): The RRC layer performs system information broadcasting from the network to all MSs. The system information is normally repeated on a regular basis. The RRC layer performs the scheduling, segmentation and repetition when such broadcasting is carried on BCCH. This function supports broadcast of typically cell-specific information.

– Establishment, re-establishment, maintenance and release of an RRC connection between the MS and the GERAN: The establishment of an RRC connection is initiated by a request from higher layers at the MS side to establish the first Signalling Connection for the MS. The establishment of an RRC connection includes an optional cell re-selection, an admission control, and a layer 2 signalling link establishment. The release of an RRC connection can be initiated by a request from higher layers to release the last Signalling Connection for the MS or by the RRC layer itself in case of RRC connection failure. In case of connection loss, the MS requests re-establishment of the RRC connection. In case of RRC connection failure, RRC releases resources associated with the RRC connection.

– Establishment, reconfiguration and release of Radio Bearers: The RRC layer can, on request from higher layers, perform the establishment, reconfiguration and release of Radio Bearers in the user plane. A number of Radio Bearers can be established to an MS at the same time. At establishment and reconfiguration, the RRC layer performs admission control and selects parameters describing the Radio Bearer processing in layer 2 and layer 1, based on information from higher layers.

– Assignment, reconfiguration and release of radio resources for the RRC connection: Depending on the RRC and MAC states, the RRC layer may handle the assignment of radio resources needed for the RRC connection including needs from both the control and user planes. The RRC layer may reconfigure radio resources during an established RRC connection. RRC indicates to the MS resource allocations for purposes of inter system handovers.

– RRC connection mobility functions: The RRC layer performs evaluation, decision and execution related to RRC connection mobility during an established RRC connection, such as handover, preparation of handover to UTRAN or other systems, cell re-selection and cell/GRA update procedures, based on e.g. measurements done by the MS.

– Release of signalling connections: The RRC layer provides the necessary functions for the GERAN or the MS to request the release of a signalling connection.

– Paging/notification: The RRC layer can broadcast paging information from the network to selected MSs on PCCCH making use of the MAC layer services. Higher layers on the network side can request paging and notification. The RRC layer can also initiate paging during an established RRC connection.

– Listening to BCCH: The RRC layer may need to listen to the BCCH of the serving cell for working out whether Iu mode is supported in this cell. The RRC layer listens to the BCCH of neighbouring cells for neighbour cell measurements; the RRC layer also receives paging information on the PCCCH.

– Routing of higher layer PDUs: This function performs at the MS side routing of higher layer PDUs to the correct higher layer entity, at the GERAN side to the correct RANAP entity.

– Control of requested QoS: This function shall ensure that the QoS requested for the Radio Bearers can be met. This includes the allocation of a sufficient number of radio resources.

– MS measurement reporting and control of the reporting: The measurements performed by the MS are controlled by the RRC layer including both GSM/EDGE air interface and other systems. The RRC layer is responsible for sending information that control the MS measurement reporting when using the SACCH channel. The RRC layer also performs the reporting of the measurements from the MS to the network using SACCH.

– Power control: The RRC layer controls parameters for normal power control, enhanced power control and fast power control.

– Control of ciphering: The RRC layer provides procedures for setting of ciphering (on/off) between the MS and GERAN.

– Integrity protection: This function controls integrity protection and performs integrity protection those RRC messages that are considered sensitive and/or contain sensitive information.

– Support for Location Services. Signaling between MS and GERAN to support positioning of an MS.

– Timing advance control. The RRC controls the operation of timing advance on dedicated basic physical subchannels.

– Set-up, reconfiguration and release of the transport channels. The RRC is responsible for the set-up, reconfiguration and release of the transport channels when FLO is used.

6.3.2 RRC Connection Levels

The different levels of RRC connection between MS and GERAN are listed below:

– No signalling connection exists
The MS has no relation to GERAN, only to CN. For data transfer, a signalling connection has to be established.

– A signalling connection exists
There is an RRC connection between the MS and GERAN. The MS position can be known on different levels:

– GERAN Registration Area (GRA) level
The MS’s position is known on GERAN registration area level. GRA is a specified set of cells, which can be identified in the PBCCH.

– Cell level
The MS’s position is known on cell level.

6.3.3 RRC Connection Modes

Two modes of operation are currently defined for the MS, RRC-Idle mode and RRC-Connected mode.

After power on, the MS in RRC-Idle mode may transmit a request to establish an RRC connection with the GERAN. In RRC-Idle mode the MS is identified by non-access stratum identities such as IMSI, TMSI and P-TMSI. In addition, the GERAN has no own information about the individual MSs in RRC-Idle mode, and can only address e.g. all MSs in a cell or all MSs monitoring a specific paging occasion.

The RRC-Connected mode is entered when the RRC connection is established between the MS and the GERAN. The MS is assigned a radio network temporary identity (G-RNTI) to be used as MS identity. MS is identified within a GERAN with the G-RNTI.

Three states are defined in RRC-Connected mode: RRC-Cell_Shared state, RRC-Cell_Dedicated state and RRC-GRA_PCH state.

In RRC-Cell_Shared state, no dedicated basic physical subchannel is allocated to the MS and the position of the MS is known by GERAN on cell level;

In RRC-Cell_Dedicated state, the MS is assigned one or more dedicated basic physical subchannels in the uplink and downlink, which it can use anytime. Furthermore, the MS may be assigned one or more shared basic physical subchannels. The position of the MS is known by GERAN on cell level.

In RRC-GRA_PCH state, no basic physical subchannel is allocated to the MS. No uplink activity is possible. The location of the MS is known on GERAN Registration area level.

The behaviour of the MS in each of these states is defined in 3GPP TS 44.118.

The MS leaves the RRC-connected mode and returns to RRC-idle mode when the RRC connection is released or at RRC connection failure.

6.3.4 RRC Connection Mobility

6.3.4.1 RRC Connection mobility in RRC-Idle mode

When the mobile station is in RRC-Idle mode, the CN knows the location of the mobile station at RA or LA level depending on the CN domain. There is no knowledge of the MS location within the BSS and paging is required to trigger an RRC connection establishment prior to any transfer with the MS. Such establishment moves the MS to RRC-Connected mode.

6.3.4.2 RRC Connection mobility in RRC-Connected mode

Handover procedures are used by the GERAN to control the mobility of the mobile station in RRC-Cell_Dedicated state. Such procedures are used to completely modify the channels allocated to the mobile station, e.g. when the cell is changed.

The GERAN is in charge of tracking the location of the mobile station, at cell or GRA level, when in RRC-Cell_Shared state or RRC-GRA_PCH state respectively. In such case, the CN to which a signalling connection is established knows the location of the mobile station at the BSS level. Cell Update and GRA update procedures are defined to let the serving BSS know about any cell or GRA change.

Cell reselection to a new cell or new GRA may involve signalling exchanges between the mobile station and the source BSS through the Iur-g interface, depending on the mobile station’s RRC state. A Serving BSS relocation may then be triggered by the source BSS.

Upon cell update, serving BSS relocation is triggered. Upon GRA update, it is an implementation issue whether to trigger a serving BSS relocation or not.

A cell can belong to several GRAs.

It is FFS whether RRAs may also be defined. An RRA could cover both GERAN and UTRAN cells. Cell/RRA updates may then not be triggered though the MS is moving from a GERAN/UTRAN cell to a UTRAN/GERAN cell.

6.3.5 RRC protocol and messages

The RRC protocol and the related RRC messages are defined in [24].

Service Areas are defined in GERAN. RRC procedures are identified by RRC Transaction Identifiers.

The procedures for inter-RAT cell change order between UTRAN and GERAN A/Gb mode are re-used when a cell change is ordered from/to a UTRAN cell to/from a GERAN cell in Iu mode.

The procedures for inter-RAT handover between UTRAN and GERAN A/Gb mode are re-used for inter-mode handover between GERAN Iu mode and GERAN A/Gb mode. Further consideration is however required to assess whether procedures for handover within GERAN A/Gb mode can be re-used.

6.3.6 Support of Radio Bearers in GERAN

The RRC layer is responsible for setting up radio bearers in the U-plane and the C-plane.

User Plane Radio Bearers are set-up when a Radio Access Bearer is required to be set-up by the Core Network.

Control Plane Radio Bearers are established when an RRC connection is set-up by a Mobile Station. Those comprise a set of five Signalling Radio Bearers:

– RB 0 is using DLC (as in Fig 10 of 43.051) and shall be used for all messages sent on the BCCH.

– RB 1 shall be used for all messages sent using RLC unacknowledged mode (RLC-UM).

– RB 2 shall be used for all messages sent using RLC acknowledged mode (RLC-AM), except for the RRC messages carrying higher layer (NAS) signalling.

– RB 3 and optionally RB 4 shall be used for all RRC messages carrying higher layer (NAS) signalling and sent using RLC acknowledged mode (RLC-AM).

Association of RBs 1 to 4 and logical channels is provided by the MAC protocol.

6.4 Packet Data Convergence Protocol (PDCP)

This clause provides an overview on services and functions provided by the Packet Data Convergence Protocol (PDCP). A detailed description of the PDCP is given in 3GPP TS 25.323.

6.4.1 Services provided to upper layers

The following services are provided by PDCP to upper layers:

– PDCP SDU delivery.

6.4.2 Services expected from RLC layer

– Data transfer in acknowledged mode.

– Data transfer in unacknowledged mode.

– Data transfer in transparent mode.

– Segmentation and reassembly.

– In-Sequence delivery.

6.4.3 PDCP Functions

For clarity reason, two PDCP modes are defined in the present document: transparent and non-transparent. The transparent and non-transparent modes relate respectively to the PDCP-no-header PDU and the PDCP-data PDU cases described in 3GPP TS 25.323.

The functions performed by the PDCP are dependent on the PDCP mode used.

6.4.3.1 Transparent Mode

The name "transparent" means that the PDCP layer does not change the incoming service data units (SDU), i.e. no header is added and possible TCP/IP or RTP/UDP/IP headers in the data are left untouched.

The functions of the transparent mode of PDCP are:

– Transfer of user data;

– Relocation of PDCP buffer;

– PDCP SDU buffering.

6.4.3.2 Non-Transparent Mode

The functions of the non-transparent mode of PDCP are:

– Header adaptation of the IP data streams;

– Transfer of user data;

– PDCP SDU buffering;

– Relocation support appropriate to applicable QoS requirements;

– If adopted for UTRAN, multiplexing of radio bearers onto RLC entities.

Different header adaptation mechanisms may be used by the PDCP:

– Header compression: Transport and network level headers (e.g. RTP/UDP/IP) are compressed in such a way that the decompressed headers are semantically identical to the original uncompressed headers. The IETF ROHC WG is responsible for standardising header compression schemes. Header compression is suited for standard internet applications that are not designed to work only with GERAN and especially for multimedia applications therefore the scheme will be used with generic realtime multimedia bearers.

– Header removal: Transport and network level headers (e.g. RTP/UDP/IP) are completely removed. Based on information submitted at call setup and based on information derived from lower layer (link & physical), the receiving entity can regenerate the headers. The primary application of header removal is the optimized speech bearer, and the regenerated header may not always be semantically identical to the original header.

– No header adaptation: Transport and network-level headers (e.g. RTP/UDP/IP) are forwarded.

6.5 Radio Link Control (RLC)

This clause provides an overview on services and functions provided by the Radio Link Control (RLC). A detailed description of the RLC is given in 3GPP TS 44.060 and 3GPP TS 44.160.

6.5.1 Services provided to upper layer

– Transparent data transfer. This service transmits higher layer PDUs without altering them nor adding any RLC protocol information.

– Acknowledged data transfer. This service transmits higher layer PDUs and guarantees delivery to the peer entity.

– Unacknowledged data transfer. This service transmits higher layer PDUs without guaranteeing delivery to the peer entity.

– Notification of unrecoverable errors. RLC notifies the upper layer of errors that cannot be resolved by RLC itself by normal exception handling procedures.

– Notification of discard. RLC notifies the upper layer of the higher layer PDUs (RLC SDUs) it discards.

– A local suspend/resume function (FFS): RLC operation may be suspended/resumed if requested by RRC. This service is used when the ciphering parameters need to be changed.

– A stop/continue function (FFS): RLC operation may be stopped/continued if requested by RRC. This service is used at Serving BSS relocation in order to synchronise the PDCP entities in the MS and BSS to realise a loss-less relocation.

– A reset function (FFS)

There is a single Radio Bearer per RLC instance.

6.5.2 RLC Functions

6.5.2.1 Transparent Mode

RLC has no functionality when operating in transparent mode. The incoming SDUs are transferred to the MAC layer without being altered. No upper layer protocol information is removed. No RLC protocol information is added. All necessary signalling is made out of band.

6.5.2.2 Non-Transparent Mode

In non-transparent mode, the RLC is responsible for ciphering user data blocks (RLC PDUs). This function prevents unauthorized acquisition of data.

6.5.2.2.1 Acknowledged Mode

RLC has support for the following functions in acknowledged mode. For a detailed description, see 3GPP TS 44.060 and 3GPP TS 44.160.

– Segmentation of upper layer PDUs into RLC data blocks.

– Concatenation of upper layer PDUs into RLC data blocks.

– Padding to fill out an RLC data block.

– Backward Error Correction (BEC) procedures enabling the selective retransmission of RLC data blocks. As for EGPRS R’99, either selective type I hybrid ARQ or selective type II hybrid ARQ (incremental redundancy) is used.

– Discard of RLC SDUs not yet segmented into RLC PDUs, according to the delay requirements of the associated Radio Bearer.

– Reassembly of RLC data blocks into upper layer PDUs.

– In-sequence delivery of upper layer PDUs.

– Link Adaptation.

– Ciphering.

6.5.2.2.2 Unacknowledged Mode

RLC has support for the following functions in unacknowledged mode. For a detailed description, see 3GPP TS 44.060 and 3GPP TS 44.160. No backward error correction procedure is supported in this mode.

– Segmentation of upper layer PDUs into RLC data blocks.

– Concatenation of upper layer PDUs into RLC data blocks.

– Padding to fill out an RLC data block.

– Reassembly of RLC data blocks into upper layer PDUs.

– Sequence number check to detect lost RLC blocks.

– In-order delivery of upper layer PDUs.

– Link Adaptation.

– Ciphering.

6.6 Medium Access Control (MAC)

This clause provides an overview on services and functions provided by the Medium Access Control (MAC). A detailed description of the MAC is given in 3GPP TS 44.060 and 3GPP TS 44.160.

6.6.1 Services provided to upper layers

The MAC layer allows the transmission over the physical layer of upper layer PDUs from one mobile station when operating on a dedicated basic physical subchannel, or one or more mobile stations when operating on a shared basic physical subchannel. The MAC layer handles the access to and multiplexing onto the basic physical subchannels. MAC does not allow for operation on shared basic physical subchannels using FLO.

– Data transfer. This service provides unacknowledged transfer of MAC SDUs between peer MAC entities. This service does not provide any data segmentation. Therefore, segmentation/reassembly function should be achieved by upper layer.

6.6.2 MAC Functions

The functions of MAC include:

– Configuring the mapping between logical channels and basic physical subchannels. The MAC is responsible for configuring the mapping of logical channel(s) onto the appropriate basic physical subchannel(s).

– Defining logical channels to be used for each radio bearer service. This function includes mapping of signalling radio bearers onto logical channels.

– Assignment, reconfiguration and release of shared radio resources for a TBF. The MAC layer may handle the assignment of radio resources on SBPSCH(s) needed for a TBF including needs from both the control and user plane. The MAC layer may reconfigure radio resources of a TBF on SBPSCH(s).

– MS measurement reporting and control of the reporting. The MAC layer is responsible for sending information that control the MS measurement reporting when using PBCCH or PACCH channels. The MAC layer also performs the reporting of the measurements from the MS to the network using PACCH.

– Broadcasting/listening of/to PBCCH and PCCCH. The MAC layer broadcasts/listens (to) the PBCCH of the serving cell for the sending/decoding of packet system information messages. The MAC layer also sends paging information on the PCCCH and monitors the paging occasions according to the DRX cycle. Within the Mobile Station, the MAC layer notifies the RRC layer when receiving a paging message; within the network, it is responsible for aggregating and sending paging messages addressed to one or more Mobile Stations when received from the RRC layer.

– Timing advance control. The MAC layer controls the operation of timing advance on shared basic physical subchannels.

The specific functions provided by the MAC protocol when FLO is used are listed below:

– Mapping between TBFs and transport channels. The MAC is responsible for mapping of TBF(s) onto the appropriate transport channel(s).

– Selection of the appropriate transport format per transport channel. The MAC is responsible for selecting the appropriate transport format for each transport channel within the transport format set configured by RRC so that the resulting transport format combination on the coded composite transport channel belongs to the transport format combination set configured by RRC.

– Priority handling between data flows of one MS.

6.6.2.1 Additional functions for RLC transparent mode

When MAC offers services to an RLC entity in transparent mode, the following function is also supported.

– Ciphering. The MAC is responsible for ciphering user data blocks (MAC SDUs).

6.6.2.2 Additional functions for RLC non-transparent mode

When MAC offers services to an RLC entity in non-transparent mode, the following functions are supported in addition to those listed in section 6.6.2.

– Ciphering. The MAC layer is responsible for ciphering layer 2 control blocks (RLC/MAC PDUs).

– Identification of different traffic flows of one or more MSs on the basic physical subchannels. Inband identification is needed to address a flow to an MS in the downlink or identify a flow from an MS in the uplink.

– Multiplexing/demultiplexing of higher layer PDUs. This function includes priority handling between data flows of one or more mobile stations, e.g. by attributes of Radio Bearer services.

– Multiplexing/demultiplexing user and control plane data to/from the physical layer. The MAC layer is responsible for multiplexing/demultiplexing RLC data blocks and RLC/MAC control blocks.

– Scheduling of RLC/MAC data and control PDUs delivered to the physical layer on shared basic physical subchannels. This includes USF and RRBP field monitoring for uplink transfer and sharing radio resources on the downlink.

– Splitting/recombining. This includes splitting/recombining of the RLC/MAC PDU flow belonging to one or more TBF(s) onto/from several shared logical channels. This function does not apply for RLC/MAC control blocks.

6.6.3 Model of MAC

The model presented in this section does not mandate how to implement the MAC layer.

In this model, the functions of MAC are controlled by a MAC control entity and a MAC common control entity.

The MAC control entity is specific to an MS. It is controlled by RRC; at RB establishment, the MAC control entity sets-up the functions needed to support the Radio Bearer. The MAC control entity can be in one of four states MAC-Idle state, MAC-Shared state, MAC-Dedicated state or MAC-DTM state, as defined in Annex C.2. The MAC functions listed in the above sub-sections do not apply in every MAC state.

There is one and only one MAC control entity on the MS side. On the network side, there is one MAC control entity per MS. Additionally, there is one MAC common control entity per cell, which is responsible for the control of common channels and procedures.

Figure 13 below shows an example of MAC model to realise a set of Radio Bearers on the MS side (user plane only), when FLO is not used. It shows the MAC Control Entity for that MS, together with some MAC functions that are used in this case.

Figure 13. Example of MAC functions for one user (MS side – user plane)

6.6.4 MAC operation

6.6.4.1 General

The MAC layer uses TBFs (Temporary Block Flows) to offer data transport between peer RLC instances. The MAC layer supports transport of data between multiple peer RLC instances established in a single MS and the GERAN.

When FLO is used [38], the MAC layer offers TBFs to the RLC layer. Three different DCHs are introduced, namely CDCH (Control-plane DCH), UDCH (User-plane DCH) and ADCH (Associated DCH). While CDCH and UDCH are used exclusively for transmission of RLC/MAC blocks for data transfer (from control-plane and user-plane, respectively), ADCH is used exclusively for transmission of RLC/MAC control blocks. CDCH and ADCH use the signalling TFC(s) as follows:

– On a DBPSCH/F, one signalling TFC is used for all RLC/MAC blocks.

– On a DBPSCH/H, two signalling TFCs are used. The MAC layer transmits every RLC/MAC block twice in a row. The first and second transport blocks used by the RLC/MAC block use the first and second signalling TFCs, respectively.

Figure 14: Logical Channels and Transport Channels

A TBF provides unidirectional data transport on one or more basic physical subchannels of the same type (either SBPSCH or DBPSCH). RRC may reconfigure a TBF from using one or more SBPSCHs to using one or more DBPSCHs (and vice versa). More than one TBF may be allocated to a single MS in any direction. A TBF may transport data for the following combination of RLC instances:

– A single RLC instance carrying data for a URB.

– A single RLC instance carrying data for an SRB.

– A single RLC instance carrying data for a URB or an SRB, and using TBF stealing, one or more RLC instances each carrying data for an SRB for which no specific TBF is currently established. This combination is only supported by TBFs on SBPSCH.

Multiple TBFs are supported on all logical channels except TCH and common control channels.

Any MS operating in Iu mode supports multiple TBFs in uplink and downlink. MSs supports 8 uplink TBFs and 8 downlink TBFs.

6.6.4.2 TBF establishment

6.6.4.2.0 General

Uplink TBFs on SBPSCHs are established as follows:

– An MS issues a MAC-layer request followed by the GERAN returning a MAC-layer assignment. This is used when the MS is in MAC-Idle state, MAC-Shared state, or MAC-DTM state.

– An MS issues an RRC-layer request followed by GERAN returning an RRC-layer message that assigns TBFs to existing RBs on an SBPSCH. This is used when the MS is in MAC-Dedicated state.

– The GERAN sends an RRC-layer message that sets up or reconfigures RBs on an SBPSCH. This is used when the MS is in MAC-Shared state, MAC-Dedicated state, or MAC-DTM state.

Uplink TBFs on DBPSCHs are established as follows:

– An MS issues a MAC-layer request followed by the GERAN returning a MAC-layer dedicated assignment. This implicitly establishes 4 TBFs for SRBs 1 through 4. This is used when the MS is in MAC-Idle state.

– The GERAN sends an RRC-layer message that sets up or reconfigures radio bearers on a DBPSCH. This implicitly establishes 4 TBFs for SRBs 1 through 4. It may also explicitly establish TBFs and USFs for URBs. This is used when the MS is in MAC-Shared state, MAC-Dedicated state, or MAC-DTM state.

Downlink TBFs on SBPSCHs are established as follows:

– The GERAN sends a MAC-layer assignment. This is used when the MS is in MAC-Idle state, MAC-Shared state, or MAC-DTM state.

– The GERAN sends an RRC-layer message that sets up or reconfigures RBs on an SBPSCH. This is used when the MS is in MAC-Shared state, MAC-Dedicated state, or MAC-DTM state.

Downlink TBFs on DBPSCHs are established as follows:

– The GERAN sends a MAC-layer dedicated assignment. This implicitly establishes 4 TBFs for SRBs 1 through 4. The GERAN may send the MAC-layer dedicated assignment in response to an MS issuing a MAC-layer request. This is used when the MS is in MAC-Idle state.

– The GERAN sends an RRC-layer message that sets up or reconfigures RBs on a DBPSCH. This implicitly establishes 4 TBFs for SRBs 1 throguh 4. It may also explicitly establish TBFs for URBs. This is used when the MS is in MAC-Shared state, MAC-Dedicated state, or MAC-DTM state.

6.6.4.2.1 Uplink resource request from MAC-Idle state
6.6.4.2.1.1 Mobile Originated Transmission

When the mobile station is in MAC-Idle state and requests the establishment of a TBF or dedicated resource, an RLC/MAC control message (PACKET CHANNEL REQUEST or EGPRS PACKET CHANNEL REQUEST message) is sent on the PRACH. In this message, the mobile station indicates one establishment cause from the following list:-

– "Single Block Without TBF Establishment", "One Phase Access Request", "One Phase Access Request in RLC unack mode", "Short Access Request", "Two Phase Access Request", "MM Procedure", "Dedicated channel request", "Emergency call"

To establish a TBF for a user radio bearer, one of the following is used:-

– "One Phase Access Request", "One Phase Access Request in RLC unack mode", "Short Access Request", "Two Phase Access Request"

To establish a TBF or dedicated resource for a signalling radio bearer, one of the following is used:-

– "Single Block Without TBF Establishment", "MM Procedure", "Dedicated channel request", "Emergency call"

Note that "Page Response" and "Cell Update" establishment causes are only to be used in A/Gb mode.

6.6.4.2.1.2 Mobile Terminated Transmission

For mobile terminated transmission, when a paging request message containing a paging cause is sent to the mobile station, the mobile station requests resources on the PRACH using one of two establishment causes as follows:-

To respond to paging causes "Terminating Conversational Call" or "Terminating Streaming Call" the mobile station indicates:-

– "Dedicated channel request"

To respond to paging causes "Terminating Interactive Call", "Terminating Background Call", "Terminating High Priority Signalling", "Terminating Low Priority Signalling", or "Terminating – cause unknown" the mobile station indicates:-

– "MM Procedure"

6.6.4.3 TBF multiplexing and scheduling

6.6.4.3.1 Multiplexing of RLC instances on TBFs

When one TBF carries data for one RLC instance, multiplexing is trivial. This case is analogous to REL-4 and previous releases.

When one TBF, in addition to a first RLC instance, carries data for one or more RLC instances, each carrying data of an SRB for which no specific TBF is currently established, the MAC layer uses TBF stealing to multiplex data from these RLC instances onto the TBF. This stealing mechanism allows the MAC layer to send SRB data without signalling to set up a separate TBF. To send data using this mechanism, the GERAN or MS MAC layer performs the following:

– It selects one of the TBFs currently established on an SBPSCH for the MS in question.

– It adds the SRBid to the RLC/MAC header to allow the receiving MAC entity to detect that TBF stealing is used and to forward the received data to the correct RLC instance.

– It sends the SRB-related data in the next scheduling opportunity for the selected TBF.

6.6.4.3.2 Scheduling of TBFs on physical-layer resources

TBFs are scheduled on a radio-block basis according to their QoS attributes.

An established uplink TBF is scheduled as follows:

– On an SBPSCH, the MS sends data for the TBF that corresponds to the received USF. If no TBF corresponds to the received USF, the MS does not send.

– On a DBPSCH with a PDTCH-type channel combination, if the MS has more than one TBF with data to send, the MS sends data for the TBF that corresponds to the received USF. If the MS has nothing to send for the scheduled TBF, and if the MS has data to send for one or more other TBFs mapped onto the same BPSCH, the MS sends data from one of these other TBFs.

– On a DBPSCH with a PDTCH-type channel combination, if the MS has only one TBF with data to send, the MS ignores the USF and sends data for that TBF. This allows the GERAN to reduce downlink interference by not transmitting if there is no downlink data to send.

– On a DBPSCH with a PDTCH-type channel combination, when a previously inactive TBF again has data to send, the MS shall send one data block for this TBF the next time the GERAN schedules any of the MS’s TBFs. This notifies GERAN that this TBF has again become active. The GERAN decodes the TFI and then schedules this TBF according to its QoS attributes. To handle the case where the GERAN fails to decode the TFI in the data block from this TBF, a repetition scheme is standardized for the MS.

– On a DBPSCH with a TCH-type channel combination, the multiframe structure and MS stealing rules determine which TBFs are scheduled, analogous to CS operation for REL-4.

An established downlink TBF is scheduled by the GERAN.

6.6.4.4 TBF release

An uplink TBF is released as follows:

– On an SBPSCH, the GERAN releases the TBF by sending a Packet Uplink Ack/Nack with the final ack indicator set to 1.

– On a DBPSCH, the GERAN releases the TBF by releasing the DBPSCH, by releasing the corresponding radio bearer, or by reconfiguring the corresponding radio bearer to another BPSCH.

A downlink TBF is released as follows:

– On an SBPSCH, the GERAN initiates release by sending a data block with final block indicator set to 1. The MS acknowledges the release.

– On a DBPSCH, the GERAN releases the TBF by releasing the DBPSCH, by releasing the corresponding radio bearer, or by reconfiguring the corresponding radio bearer to another BPSCH.

6.6.4.5 TBF reallocation

Considering the mobile station’s multislot capabilities, GERAN may reallocate one or more of a mobile station’s TBFs:

– To a different radio frequency or a different hopping sequence. All of a mobile station’s TBFs operate on one radio frequency or one hopping sequence.

– To different timeslots (the same number, more, or fewer).

– To use a different TFI for a given TBF.

– To use different USFs for a given uplink TBF.

– To use different coding schemes or modulation-and-coding schemes.

This reallocation may be in response to a mobile-station request.

When only SBPSCHs are allocated, GERAN MAC or GERAN RRC signals the reallocation.

When at least one DBPSCH is allocated, GERAN RRC signals the reallocation.

6.7 RLC/MAC PDU Formats for different protocol modes

6.7.1 Acknowledged RLC mode

The GPRS/EGPRS channel codes RLC/MAC header and coding schemes (CS-1, … ,CS-4 and MCS-1, … , MCS-9) are used. Other coding schemes are CSD/ECSD.

6.7.2 Unacknowledged RLC mode

The GPRS/EGPRS channel codes RLC/MAC header and coding schemes (CS-1, … ,CS-4 and MCS-1, … , MCS-9) are used. Other coding schemes are CSD/ECSD when operating on a dedicated basic physical subchannel.

6.7.3 Transparent RLC mode

The transparent mode is used for example to transmit voice in GERAN. The different channel coding schemes used for voice in GSM are used. New coding schemes for 8-PSK half rate and possibly full rate speech are also required. Other coding schemes like e.g. CSD/ECSD is FFS.

Since RLC is used in transparent mode, no RLC/MAC header has to be added.

6.8 Physical Layer (Phy)

The physical layer (layer 1) is the lowest layer in the OSI Reference Model and it supports all functions required for the transmission of bit streams on the physical medium. This clause provides an overview on services and functions provided by the Physical Layer. A detailed description of the physical layer is given in [Ref: 05 series]. The Flexible Layer One part of the physical layer is described in subclause 6.9.

6.8.1 Definitions

A physical channel uses a combination of frequency and time division multiplexing and is defined as a sequence of radio frequency channels and time slots. The complete definition of a particular physical channel consists of a description in the frequency domain, and a description in the time domain [11].

A basic physical channel is defined as a sequence of radio frequency channels and time slots. The basic physical channel uses the same timeslot in every TDMA frame. The TDMA frame number sequence is 0,1,.. FN_MAX, where FN_MAX is the maximum TDMA frame number for a hyperframe (i.e. all TDMA frames on a timeslot).

A basic physical subchannel is defined as a basic physical channel or a part of a basic physical channel and an associated multiframe structure. A basic physical subchannel can either be shared or dedicated. Example: DBPSCH/F.

A logical channel is defined by the type of data which is transferred and characterized by parameters such as channel coding and interleaving. It can be uni-directional or bi-directional [11]. Example: PDTCH/U, TCH/FS, FACCH/F.

A channel combination is defined as the combination of logical channels that is mapped on a certain basic physical subchannel. Example: TCH/FS+FACCH/F+SACCH/TF. The channel combination could also be mapped onto a basic physical channel, example: TCH/H(0,1)+FACCH/H(0,1)+SACCH/TH(0,1) [11].

6.8.2 Services provided to upper layer

The physical layer interfaces the Medium Access Control (MAC) sub-layer of Layer 2 and the Radio Resource Control (RRC) sub-layer of Layer 3. Through Service Access Points (SAP), the physical layer offers services described below:

– Access capabilities: the physical layer offers logical channels and the transmission services associated to higher layers. Logical channels are multiplexed either in a fixed predefined manner (multiframe structure) or dynamically by the MAC on basic physical subchannels. Basic physical subchannels are the units scheduled on the radio medium. Some are reserved by the network for common use (e.g. for use by a combination of PCCCH and PBCCH), others are assigned to dedicated connections with MSs (dedicated basic physical subchannels), or are assigned to a shared usage between MSs (shared basic physical subchannels).

– Error detection: the physical layer offers an error protected transmission service, it includes error detection functions and to a lower level, error correction functions. Erroneous received frames may be notified to upper layer and, depending on the need of the upper layer, offered to it. The probability of one or more errors in a physical block transferred by the physical layer is defined in 3GPP TS 45.005. Due to non specified methods of quality detection, the probability of residual errors in transferred blocks may vary between implementations.

6.8.2.1 Specific services of the physical layer in the MS

– Measurement of the signal strength of neighbouring base stations. Measurements are transferred to layer 3.

– Measurement of the signal quality of the basic physical subchannel used. Measurements are transferred to the MAC layer for reporting to the base station.

– Cell/PLMN selection in idle mode or in packet mode. In idle mode or in packet mode, the physical layer selects the best cell with its BCCH (CPBCCH only for COMPACT and for packet mode only) in close co‑operation with layer 3, meeting requirements for PLMN selection specified in 3GPP TS 42.011.

6.8.3 Logical Channels

6.8.3.1 Traffic channels

Traffic channels of type TCH are intended to carry either encoded speech or user data on dedicated basic physical subchannel. TCH can be either full rate (TCH/F) or half rate (TCH/H).

Traffic channels of type O-TCH are intended to carry encoded speech on dedicated basic physical subchannel. O-TCH can be either full rate (O-TCH/F) or half rate (O-TCH/H).

Traffic channels of type E-TCH are intended to carry user data on dedicated basic physical subchannels.

Packet data traffic channels (PDTCH) are intended to carry user data on either dedicated or shared basic physical subchannels. PDTCH’s can be either full rate (PDTCH/F) or half rate (PDTCH/H).

6.8.3.2 Control channels

Control channels carry signalling or synchronization data. Four categories of control channels are defined: broadcast, common, dedicated control channels and cell broadcast channels. Specific channels within these categories are defined in the clauses following.

6.8.3.2.1 Broadcast channels

GERAN shall reuse Release 99 broadcast channels. Any addition shall be made in a backwards compatible manner.

6.8.3.2.2 Common control type channels

GERAN common control type channels shall be based on Release 99 common control type channels. Any addition shall be made in a backwards compatible manner.

6.8.3.2.3 Dedicated control channels

On a dedicated basic physical subchannel:

i) The Fast Associated Control channel (FACCH) associated to one TCH. FACCH can either be full rate (FACCH/F, E-FACCH/F, O-FACCH/F) or half rate (FACCH/H, O-FACCH/H) depending whether it is associated to a full rate or half rate TCH.

ii) The Packet Associated Control channel (PACCH) associated to one PDTCH: The PACCH is bi-directional. PACCH/U is used for the uplink and PACCH/D for the downlink. PACCH can either be full rate (PACCH/F) or half rate (PACCH/H) depending whether it is associated to a full rate or half rate PDTCH.

iii) The Slow Associated Control channel (SACCH) associated to one TCH or PDTCH. SACCH can either be full rate (SACCH/TF) or half rate (SACCH/TH) depending whether it is associated to a full rate or half rate TCH or PDTCH. Further, the SACCH can be associated either to a TCH or PDTCH where EPC is not deployed (SACCH/T) or a TCH or PDTCH where EPC is deployed (SACCH/TP).

iv) The Enhanced Power Control channel (EPCCH) associated to one TCH or PDTCH. EPCCH can be either full rate (EPCCH/F) or half rate (EPCCH/H) depending on whether it is associated to a full rate or half rate TCH or PDTCH.

v) The Stand-alone Dedicated Control Channel (SDCCH) is a bi-directional dedicated control channel whose allocation is not linked to the allocation of a TCH [UMTS 45.003].

vi) The Enhanced Inband Associated Control Channel (E-IACCH/F) associated to one E-TCH/F.

On a shared basic physical subchannel:

i) The Packet Associated Control channel (PACCH): The PACCH is bi-directional. PACCH/U is used for the uplink and PACCH/D for the downlink. PACCH can either be full rate (PACCH) or half rate (PACCH/H) depending whether it is associated to a full rate or half rate PDTCH.

ii) The Packet Timing advance Control CHannel uplink (PTCCH/U): Used to transmit random access bursts to allow estimation of the timing advance for one MS in packet transfer mode.

iii) The Packet Timing advance Control CHannel downlink (PTCCH/D): Used to transmit timing advance updates for several MS. One PTCCH/D is paired with several PTCCH/U’s.

6.8.3.2.4 Cell Broadcast Channel (CBCH)

GERAN shall reuse Release 99 cell broadcast channel.

6.8.4 Basic Physical Subchannels

A basic physical subchannel can either be dedicated or shared.

All basic physical subchannels are bi-directional unless otherwise stated.

6.8.4.1 DBPSCH – Dedicated Basic Physical SubCHannel

A DBPSCH is for only one user and it always has an associated SACCH. A DBPSCH can either be full rate or half rate.

6.8.4.2 SBPSCH – Shared Basic Physical SubCHannel

A SBPSCH is for one or more users. A SBPSCH can either be full rate or half rate.

6.8.5 Mapping of logical channels onto basic physical subchannels

6.8.5.1 DBPSCH full rate

The following channel combinations are possible for a DBPSCH full rate:

i) TCH/F + FACCH/F + SACCH/TF;

ii) TCH/F + FACCH/F + SACCH/TPF + EPCCH/F;

iii) PDTCH/F + PACCH/F + SACCH/TF;

iv) PDTCH/F + PACCH/F + SACCH/TPF + EPCCH/F;

v) E-TCH/F + E-FACCH/F + SACCH/TF + E-IACCH/F;

vi) O-TCH/F + O-FACCH/F + SACCH/TF;

vii) O-TCH/F + O-FACCH/F + SACCH/TPF + EPCCH/F.

Figure 13 shows the multiframe mapping of the logical channels for DBPSCH/F.

frame number

0

1

2

3

4

5

6

7

8

9

10

11

12

13

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D

D

D

D

D

D

D

D

D

D

D

D

S

D

D

D

D

D

D

D

D

D

D

D

D

i

D

User Traffic

S

SACCH

i

Idle

Figure 13: DBPSCH/F – Multiframe mapping of logical channels

Note: When EPC is used, the EPCCH is mapped on the bits of the SACCH bursts.

6.8.5.2 DBPSCH half rate

The following channel combinations are possible for a DBPSCH half rate:

i) TCH/H + FACCH/H + SACCH/TH;

ii) TCH/H + FACCH/H + SACCH/TPH + EPCCH/H;

iii) O-TCH/H + O-FACCH/H + SACCH/TH;

iv) O-TCH/H + O-FACCH/H + SACCH/TPH + EPCCH/H;

v) PDTCH/H + PACCH/H + SACCH/TH;

vi) PDTCH/H + PACCH/H + SACCH/TPH + EPCCH/H.

Figure 14 shows the multiframe mapping of the logical channels for DBPSCH/H.

frame number – subchannel 0

0

1

2

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frame number – subchannel 1

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D

User Traffic

S

SACCH

i

Idle

Figure 14: DBPSCH/H – Multiframe mapping of logical channels

Note: When EPC is used, the EPCCH is mapped on the bits of the SACCH bursts.

6.8.5.3 SBPSCH full rate

Excluding CBCH, broadcast channels and common control type channels, the following channel combination is possible for a SBPSCH full rate:

– PDTCH/F + PACCH/F + PTCCH/F.

Figure 15 shows the multiframe mapping of the logical channels for SBPSCH/F. Only half of the 52-multiframe is shown, the second half being identical to the first one.

frame number

0

1

2

3

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D

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D

D

D

D

i

D

User Traffic

T

PTCCH

i

Idle

Figure 15: SBPSCH/F – Multiframe mapping of logical channels

6.8.5.4 SBPSCH half rate

The following channel combination is possible for a SBPSCH half rate:

– PDTCH/H + PACCH/H.

Figure 16 shows the multiframe mapping of the logical channels for SBPSCH/F. Only half of the 52-multiframe is shown, the second half being identical to the first one.

frame number – subchannel 0

0

1

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Figure 16: SBPSCH/H – Multiframe mapping of logical channels

6.8.6 Physical Layer Functions

An overview of the functions which create the services of the physical layer can be found in 3GPP TS 45.001.

6.8.7 Channel Coding

Table 2 gives an overview of the logical traffic channels with the corresponding type of channel and their mapping to basic physical subchannel. The list shall be considered as the possible, but not mandatory, channels.

Table 2: Channel Coding

Logical Channel

Mod.

Radio Block / Frame Size (Bits)

SB

Channel Coding

Interleaving

Basic Physical Subchannel

Type

Rate

Type

Depth (bursts)

TCH/FS [tbd] (2)

GMSK

464

8

CC

13 kbps

diag

8

DBPSCH/F

TCH/EFS [tbd] (2)

GMSK

464

8

CC

12.2 kbps

diag

8

DBPSCH/F

TCH/WFS [tbd] (3)

GMSK

464

8

CC

[tbc]

diag

8

DBPSCH/F

O-TCH/WFS[tbd] (3)

8PSK

1392

24

CC

[tbc]

diag

8

DBPSCH/F

O-TCH/WHS [tbd] (3)

8PSK

696

12

CC

[tbc]

diag

4

DBPSCH/H

TCH/HS [tbd] (2)

GMSK

232

4

CC

5.6 kbps

diag

4

DBPSCH/H

TCH/AFS

GMSK

464

8

CC

TCH/AFS4.75
TCH/AFS5.15
TCH/AFS5.90
TCH/AFS6.70
TCH/AFS7.40
TCH/AFS7.95
TCH/AFS10.2
TCH/AFS12.2

diag

8

DBPSCH/F

TCH/AHS

GMSK

232

4

CC

TCH/AHS4.75
TCH/AHS5.15
TCH/AHS5.90
TCH/AHS6.70
TCH/AHS7.40
TCH/AHS7.95

diag

4

DBPSCH/H

O-TCH/AHS

8PSK

696

12

CC

O-TCH/AHS4.75
O-TCH/AHS5.15
O-TCH/AHS5.90
O-TCH/AHS6.70
O-TCH/AHS7.40
O-TCH/AHS7.95
O-TCH/AHS10.2
O-TCH/AHS12.2

diag

4

DBPSCH/H

TCH/F

GMSK

464

8

CC

TCH/F9.6
TCH/F14.4

diag

22

DBPSCH/F

E-TCH/F

8PSK

1392

24

RS+CC

E-TCH/F28.8
E-TCH/F32.0

diag

22

DBPSCH/F

CC

E-TCH/F43.2

PDTCH/F

GMSK

464

8+4

CC

MCS1-4

rect

4

SBPSCH/F

8

CS1-4

8+4

MCS1-4

DBPSCH/F

8

CS1-4

8+4

MCS1-4

ffs

ffs

DBPSCH/F

8

CS1-4

8PSK

1392

8

MCS5-9

rect

4

SBPSCH/F

8

MCS5-9

DBPSCH/F

8

MCS5-9

ffs

ffs

DBPSCH/F

PDTCH/H

GMSK

464

8+4

CC

MCS1-4

rect

4

SBPSCH/H

8

CS1-4

8+4

MCS1-4

DBPSCH/H

8

CS1-4

8+4

MCS1-4

ffs

ffs

DBPSCH/H

8

CS1-4

8PSK

1392

8

MCS5-9

rect

4

SBPSCH/H

8

MCS5-9

DBPSCH/H

8

MCS5-9

ffs

ffs

DBPSCH/H

(2) The possibility to establish TCH/EFS, TCH/FS, TCH/HS speech channels is to be decided by 3GPP SA2

CC: Convolutional Code.

RS: Reed Solomon code.

The table above remains to be completed.

Except for the already existing logical channels, the 8PSK modulated logical channels are indicated by an "O-" prefix (as in Octal PSK).

Table 3 gives an overview of the logical control channels used for speech and circuit switched data, and their associated logical traffic channel.

Table 3: Control channel coding

Logical Channel

Mod.

Radio Block / Frame Size (Bits)

SB

Channel Coding

Interleaving

Associated logical traffic channel

Type

Rate

Type

Depth (bursts)

FACCH/F

GMSK

464

8

CC

9.2 kbps

diag

8

TCH/F

O-FACCH/F

8PSK

1392

24

CC

9.2 kbps

diag

8

O-TCH/F

FACCH/H

GMSK

464

8

CC

4.6 kbps

diag

6

TCH/H

O-FACCH/H

8PSK

1392

24

CC

4.6 kbps

diag

6

O-TCH/H

SACCH/F

GMSK

464

8

CC

184/480 kbps

block

4

TCH/F, E-TCH/F & O-TCH/F

SACCH/H

GMSK

464

8

CC

184/480 kbps

block

4

TCH/H & O-TCH/H

SACCH/TPF

GMSK

416

8

CC

184/480 kbps

block

4

TCH/F & O-TCH/F

with EPC

SACCH/TPH

GMSK

416

8

CC

184/480 kbps

block

4

TCH/H & O-TCH/H

with EPC

E-FACCH/F

GMSK

464

8

CC

9.2kbps

block

4

E-TCH/F

E-IACCH/F

8PSK

24

–

BC

3/20 kbps

–

4

E-TCH/F

EPCCH/F

GMSK

12

–

BC

3/120 kbps

–

1

TCH/F & O-TCH/F with EPC

EPCCH/H

GMSK

12

–

BC

3/120 kbps

–

1

TCH/H & O-TCH/H with EPC

CC: Convolutional Code.

BC : Block code

Except for the already existing logical channels, the 8PSK modulated logical channels are indicated by an "O-" prefix (as in Octal PSK).

6.6.8 Enhanced Power control procedure

In addition to the normal power control, an enhanced power control scheme (EPC) shall be supported by the MS and may optionally be supported by the BSS, when operating on a DBPSCH.

EPC has a reporting period of 26 TDMA frames (120 ms). A dedicated control channel, the EPCCH, is used for the purpose of EPC. For MS power control, EPC power commands are sent on the downlink EPCCH. For BTS power control, EPC measurement reports are sent on the uplink EPCCH.

If EPC is in use, the normal SACCH (SACCH/TF or SACCH/TH) is replaced by a modified SACCH (SACCH/TPF or SACCH/TPH). The EPCCH is multiplexed with the SACCH/TP. One EPCCH frame is multiplexed with each burst of the SACCH/TP. The multiplexing is done on the physical layer.

6.8.8.1 MS implementation

Enhanced power control shall be implemented in the MS.

When on a DBPSCH, the MS shall use EPC, if so indicated by the BSS in the ASSIGNMENT COMMAND or HANDOVER COMMAND (see 3GPP 44.018).

6.8.8.1.1 MS power control

If EPC is in use, the MS shall employ the most recently commanded EPC level on each uplink DBPSCH. The power level to be employed by the MS is indicated by means of the EPC power command sent via EPCCH once every EPC reporting period. The MS shall report, in the SACCH L1 header, the RF power level used at the end of the normal power control reporting period.

NOTE: The term "normal power control" is used in this specification for clarification and is otherwise referred to as "power control".

The enhanced power control scheme is based on differential control to adjust the employed RF power level. The possible EPC power commands are the same as for fast power control used for ECSD [3GPP TS 45.008].

6.8.8.1.2 MS link quality measurement reports

When employing EPC, the MS shall use the uplink EPCCH for EPC measurement reporting.

For each DBPSCH on which EPC is in use, the received signal quality shall be measured by the MS in a manner that can be related to the average BER before channel decoding, assessed over one EPC reporting period.

The average BER shall for every EPC reporting period be mapped to the RXQUAL scale according to 45.008 [], producing the parameter RXQUAL_EPC which is reported to the network via EPCCH.

6.8.8.2 BSS implementation

Enhanced power control may optionally be implemented in the BSS.

6.9 Flexible Layer One (FLO)

6.9.1 General

The Flexible Layer One belongs to the Physical Layer. It operates on DBPSCH only.

6.9.2 Definitions

Transport Block: block exchanged on a transport channel between the physical layer and the MAC sublayer. It contains an RLC/MAC block.

Transport Channel: a transport channel is offered by the physical layer to the MAC sublayer for exchange of transport blocks. A transport channel is used to carry with a certain quality of service, a data flow over the radio interface.

Transport Format: configuration of a transport channel, including CRC size, transport block length, etc.

Transport Format Combination: allowed combination of transport format(s) of the different transport channels that are multiplexed together on a basic physical subchannel.

6.9.3 Principles

6.9.3.1 General

The radio interface protocol architecture around the Flexible Layer One (FLO) is depicted in subclause 5.1. With FLO, the physical layer offers transport channels to the MAC sublayer. A transport channel is characterized by how the information is transferred over the radio interface. The offered transport channels are Dedicated CHannels (DCH). A DCH is a channel dedicated to one MS.

Each transport channel can carry one data flow providing a certain Quality of Service (QoS). A number of transport channels can be multiplexed and sent on the same basic physical subchannel at the same time within the same TTI.

The configuration of a transport channel i.e. the number of input bits, CRC size etc. is denoted the Transport Format (TF). A number of different transport formats can be associated to one transport channel. The configuration of the transport formats is under control of the GERAN and signalled to the MS at call set-up. In both the MS and the BSS, the transport formats are used to configure the encoder and decoder units. When configuring a transport format, the GERAN can choose between a number of predefined CRC lengths and code types.

On transport channels, transport blocks (TB) are exchanged between the MAC layer and the physical layer on a transmission time interval (TTI) basis. For each TTI a transport format is chosen and indicated through the transport format indicator (TFIN). When a transport channel is inactive, a transport format with a transport block size of zero is selected.

Only a limited number of combinations of the transport formats of the different TrCH are allowed. A valid combination is called a Transport Format Combination (TFC). The set of valid TFCs on a basic physical subchannel is called the Transport Format Combination Set (TFCS). The TFCS is signalled through the Calculated Transport Format Combinations (CTFC).

In order to decode the received sequence the receiver needs to know the active TFC for a radio packet. This information is transmitted in the Transport Format Combination Indicator (TFCI) field. This field is basically a layer 1 header and has the same function as the stealing bits in GSM. Each of the TFC within a TFCS are assigned a unique TFCI value and when a radio packet is received this is the first to be decoded by the receiver. From the decoded TFCI value the transport formats for the different transport channels are known and the actual decoding can start.

In case of multislot operation, there shall be one FLO instance for each basic physical subchannel. Each FLO instance is configured independently by Layer 3 and as a result gets its own TFCS. The number of allocated basic physical subchannels depends on the multislot capabilities of the MS.

6.9.3.2 Coding / multiplexing

The coding/multiplexing unit of FLO is a combination of error detection, forward error correction, rate matching, multiplexing and interleaving of transport blocks (TB) in radio packet.

The following steps can be identified:

– CRC attachment: error detection is provided on each transport block through a cyclic redundancy check (CRC). Layer 3 configures the size of the CRC to be used. Code blocks are output from the CRC attachment.

– Channel coding: after CRC attachment, the code blocks are processed through channel coding (1/3 rate convolutional code), producing encoded blocks.

– Rate matching: in rate matching, bits of an encoded block on a transport channel are repeated or punctured. When the number of bits on a transport channel varies between different TTI, coded bits are repeated or punctured to ensure that the total bit rate after TrCH multiplexing is identical to the total channel bit rate of the allocated basic physical channel. Outputs from the rate matching are called radio frames. The rate matching produces one radio frame per encoded block, i.e. per TrCH.

– Multiplexing of transport channels: for every radio packet to be transmitted, one radio frame from each TrCH is delivered to the TrCH multiplexing. These radio frames are serially multiplexed into a Coded Composite Transport CHannel (CCTrCH).

– TFCI mapping: the coded TFCI is appended at the beginning of the CCTrCH.

– Interleaving: the coded TFCI and the CCTrCH are interleaved together on bursts. The interleaving can be either block diagonal or block rectangular and is configured by Layer 3.