6 Mapping of transport channels to physical channels for the 3.84 Mcps option

25.2213GPPPhysical channels and mapping of transport channels onto physical channels (TDD)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

This clause describes the way in which transport channels are mapped onto physical resources, see figure 19. Sub-clauses 6.1 and 6.2 do not apply to 3.84 Mcps MBSFN IMB. Mappings between transport channels and physical resources for 3.84 Mcps MBSFN IMB are described in sub-clause 6.3.

Transport Channels	Physical Channels
DCH	Dedicated Physical Channel (DPCH)


BCH	Primary Common Control Physical Channel (P-CCPCH)

FACH	Secondary Common Control Physical Channel (S-CCPCH)
PCH

RACH	Physical Random Access Channel (PRACH)


USCH	Physical Uplink Shared Channel (PUSCH)

DSCH	Physical Downlink Shared Channel (PDSCH)

	Paging Indicator Channel (PICH)

	MBMS Indication Channel (MICH)

	Synchronisation Channel (SCH)

	Physical Node B Synchronisation Channel (PNBSCH)

HS-DSCH	High Speed Physical Downlink Shared Channel (HS-PDSCH)

	Shared Control Channel for HS-DSCH (HS-SCCH)

	Shared Information Channel for HS-DSCH (HS-SICH)

E-DCH	E-DCH Physical Uplink Channel (E-PUCH)

	E-DCH Random Access Uplink Control Channel (E-RUCCH)

	E-DCH Absolute Grant Channel (E-AGCH)

	E-DCH Hybrid ARQ Indicator Channel (E-HICH)

Figure 19: Transport channel to physical channel mapping

6.1 Dedicated Transport Channels

6.1.1 The Dedicated Channel (DCH)

A dedicated transport channel is mapped onto one or more physical channels. An interleaving period is associated with each allocation. The frame is subdivided into slots that are available for uplink and downlink information transfer. The mapping of transport blocks on physical channels is described in TS 25.222 ("multiplexing and channel coding").

Figure 20: Mapping of Transport Blocks onto the physical bearer

For NRT packet data services, shared channels (USCH and DSCH) can be used to allow efficient allocations for a short period of time.

6.1.2 The Enhanced Uplink Dedicated Channel (E-DCH)

The enhanced uplink dedicated channel is mapped on one or several E-PUCH, see subclause 5.3.13.

6.1.2.1 E-DCH/E-AGCH Association and Timing

The E-DCH is always associated with a number of E-DCH Absolute Grant Channels (E-AGCH) and one hybrid ARQ indicator channel (E-HICH). A grant of E-DCH transmission resources may be transmitted to the UE on any one of the associated E-AGCH. All relevant Layer 1 control information related to an E-DCH TTI is transmitted in the associated E-AGCH and E-HICH.

The E-DCH related time slot information that is carried on the E-AGCH refers to the next valid E-PUCH allocation, which is given by the following limitation: There shall be an offset of n_E-AGCH  6 time slots between the E-AGCH carrying the E-DCH related information and the first indicated E-PUCH (in time) for a given UE. The E-DCH related time slot information shall not refer to two subsequent radio frames but shall always refer to either the same or the following radio frame, as illustrated in figure 20a. Note that the figure only shows the E-AGCH that carries the E-DCH related information for the given UE.

Figure 20a: Timing for E-AGCH and E-DCH for different radio frame configurations for a given UE

6.1.2.2 E-DCH/E-HICH Association and Timing

All E-DCH operations within the cell are associated with the same E-HICH channelisation code. A single E-HICH channelisation code exists in the cell per E-DCH TTI (10ms). For a given UE, a HARQ acknowledgement indicator is synchronously linked with the E-DCH TTI transmission to which it relates. There is thus a one-to-one association between an E-DCH TTI transmission and its respective HARQ acknowledgment indicator on the associated E-HICH.

The associated E-HICH shall reside on the first instance of the E-HICH channelisation code to occur after n_E-HICH timeslots have elapsed since the start of the last E-PUCH of the corresponding E-DCH TTI (see examples of figure 20b). The value of n_E-HICH is configurable by higher layers within the range 4 to 44 timeslots.

Figure 20b: Timing for E-DCH and E-HICH for a given UE

The HARQ acknowledgement indicator associated with an E-DCH transmission is transmitted using one of 240 signature sequences carried by the associated E-HICH channelisation code. Which signature sequence r = 0, 1, 2,…239 is used is calculated for each E-DCH resource allocation using the information signalled on the associated E-AGCH as follows:

where:

– t₀ is the bit position (1…n_TRRI) of the first active timeslot in the timeslot resource related information bitmap (see [7]) on E-AGCH and where bit position 1 corresponds to the lowest-numbered timeslot

– q₀ is the allocated channelisation code index (1,2,3,…Q₀)

– Q₀ is the spreading factor of the allocated uplink channelisation code

6.2 Common Transport Channels

6.2.1 The Broadcast Channel (BCH)

The BCH is mapped onto the P-CCPCH. The secondary SCH codes indicate in which timeslot a mobile can find the P-CCPCH containing BCH.

6.2.2 The Paging Channel (PCH)

The PCH is mapped onto one or several S-CCPCHs so that capacity can be matched to requirements. The location of the PCH is indicated on the BCH. It is always transmitted at a reference power level.

To allow an efficient DRX, the PCH is divided into PCH blocks, each of which comprising N_PCH paging sub-channels. N_PCH is configured by higher layers. Each paging sub-channel is mapped onto 2 consecutive PCH frames within one PCH block. Layer 3 information to a particular UE is transmitted only in the paging sub-channel, that is assigned to the UE by higher layers, see [15]. The assignment of UEs to paging sub-channels is independent of the assignment of UEs to page indicators.

6.2.2.1 PCH/PICH Association

As depicted in figure 21, a paging block consists of one PICH block and one PCH block. If a paging indicator in a certain PICH block is set to ‘1’ it is an indication that UEs associated with this paging indicator shall read their corresponding paging sub-channel within the same paging block. The value N_GAP>0 of frames between the end of the PICH block and the beginning of the PCH block is configured by higher layers.

Figure 21: Paging Sub-Channels and Association of PICH and PCH blocks

6.2.3 The Forward Channel (FACH)

The FACH is mapped onto one or several S-CCPCHs. The location of the FACH is indicated on the BCH and both, capacity and location can be changed, if required. FACH may or may not be power controlled.

6.2.4 The Random Access Channel (RACH)

The RACH has intraslot interleaving only and is mapped onto PRACH. The same slot may be used for PRACH by more than one cell. Multiple transmissions using different spreading codes may be received in parallel. More than one slot per frame may be administered for the PRACH. The location of slots allocated to PRACH is broadcast on the BCH. The PRACH uses open loop power control. The details of the employed open loop power control algorithm may be different from the corresponding algorithm on other channels.

6.2.5 The Uplink Shared Channel (USCH)

The uplink shared channel is mapped on one or several PUSCH, see subclause 5.3.5.

6.2.6 The Downlink Shared Channel (DSCH)

The downlink shared channel is mapped on one or several PDSCH, see subclause 5.3.6.

6.2.7 The High Speed Downlink Shared Channel (HS-DSCH)

The high speed downlink shared channel is mapped on one or several HS-PDSCH, see subclause 5.3.9.

6.2.7.1 HS-DSCH/HS-SCCH Association and Timing

The HS-DSCH is always associated with a number of High Speed Shared Control Channels (HS-SCCH). The number of HS-SCCHs that are associated with an HS-DSCH for one UE can range from a minimum of one HS-SCCH (M=1) to a maximum of four HS-SCCH (M=4). All relevant Layer 1 control information is transmitted in the associated HS-SCCH i.e. the HS-PDSCH does not carry any Layer 1 control information.

The HS-DSCH related time slot information that is carried on the HS-SCCH refers to the next valid HS-PDSCH allocation, which is given by the following limitation: There shall be an offset of n_HS-SCCH  4 time slots between the HS-SCCH carrying the HS-DSCH related information and the first indicated HS-PDSCH (in time) for a given UE. The HS-DSCH related time slot information shall not refer to two subsequent radio frames but shall always refer to either the same or the following radio frame, as illustrated in figure 21A. Note that the figure only shows the HS-SCCH that carries the HS-DSCH related information for the given UE.

Figure 21A: Timing for HS-SCCH and HS-DSCH for different radio frame configurations for a given UE

6.2.7.2 HS-SCCH/HS-DSCH/HS-SICH Association and Timing

The HS-SCCH is always associated with one HS-SICH. The association between the HS-SCCH in DL and HS-SICH in UL shall be pre-defined by higher layers and is common for all UEs.

The UE shall transmit the HS-DSCH related ACK / NACK on the next available associated HS-SICH with the following limitation: There shall be an offset of n_HS-SICH  17 time slots between the last allocated HS-PDSCH (in time) and the HS-SICH for the given UE. Hence, the HS-SICH transmission shall be made in the next or next but one radio frame, following the HS-DSCH transmission, as illustrated in figure 21B. Note that the figure only shows the HS-SICH that carries the HS-DSCH related ACK / NACK for the given UE.

Figure 21B: Timing for HS-DSCH and HS-SICH for different radio frame configurations for a given UE

6.3 Mapping of TrCHs for the 3.84 Mcps MBSFN IMB option

The following mappings are supported:

– BCH mapped to P-CCPCH.

– FACH mapped to S-CCPCH

– MICH (no transport channel is mapped to MICH)