5 Physical Layer for E-UTRA

36.3003GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Overall descriptionRelease 17Stage 2TS

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

5.0 Frame structures and channels

Downlink and uplink transmissions are organized into radio frames with 10 ms duration. Three radio frame structures are supported:

– Type 1, applicable to FDD;

– Type 2, applicable to TDD;

– Type 3, applicable to LAA secondary cell operation only.

Frame structure Type 1 is illustrated in Figure 5.1-1. Each 10 ms radio frame is divided into ten equally sized sub-frames. Each sub-frame consists of two equally sized slots. Each slot can further be divided into three subslots that may have different sizes. For FDD, 10 subframes, 20 slots, or up to 60 subslots are available for downlink and uplink transmission in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency domain.

Figure 5.1-1: Frame structure type 1

Frame structure Type 2 is illustrated in Figure 5.1-2. Each 10 ms radio frame consists of two half-frames of 5 ms each. Each half-frame consists of eight slots of length 0.5 ms and three special fields: DwPTS, GP and UpPTS. The length of DwPTS and UpPTS is configurable subject to the total length of DwPTS, GP and UpPTS being equal to 1ms. Both 5ms and 10ms switch-point periodicity are supported. Subframe 1 in all configurations and subframe 6 in configuration with 5ms switch-point periodicity consist of DwPTS, GP and UpPTS. Subframe 6 in configuration with 10ms switch-point periodicity consists of DwPTS only. All other subframes consist of two equally sized slots.

For TDD, GP is reserved for downlink to uplink transition, and UpPTS is reserved in NB-IoT. Other Subframes/Fields are assigned for either downlink or uplink transmission. Uplink and downlink transmissions are separated in the time domain.

Figure 5.1-2: Frame structure type 2 (for 5ms switch-point periodicity)

Table 5.1-1: Uplink-downlink allocations.

Configuration	Switch-point periodicity	Subframe number
Configuration	Switch-point periodicity	0	1	2	3	4	5	6	7	8	9
0	5 ms	D	S	U	U	U	D	S	U	U	U
1	5 ms	D	S	U	U	D	D	S	U	U	D
2	5 ms	D	S	U	D	D	D	S	U	D	D
3	10 ms	D	S	U	U	U	D	D	D	D	D
4	10 ms	D	S	U	U	D	D	D	D	D	D
5	10 ms	D	S	U	D	D	D	D	D	D	D
6	5 ms	D	S	U	U	U	D	S	U	U	D

Frame structure Type 3 is applicable to LAA secondary cell operation with normal cyclic prefix only. Each 10 ms radio frame is divided into ten equally sized sub-frames. Each sub-frame consists of two equally sized slots. The 10 subframes within a radio frame are available for downlink or uplink transmissions.

Sidelink transmissions are defined for sidelink discovery, sidelink communication and V2X sidelink communication between UEs. The sidelink transmissions use the same frame structure as the frame structure that is defined for uplink and downlink when UEs are in network coverage; however, the sidelink transmission are restricted to a sub-set of the uplink resources in time and frequency domain.

For NB-IoT, the frame structure is described in clauses 5.1.1a and 5.2.1a.

The physical channels of E-UTRA are:

Physical broadcast channel (PBCH)

– The coded BCH transport block is mapped to four subframes within a 40 ms interval;

– 40 ms timing is blindly detected, i.e. there is no explicit signalling indicating 40 ms timing;

– Each subframe is assumed to be self-decodable, i.e. the BCH can be decoded from a single reception, assuming sufficiently good channel conditions.

Physical control format indicator channel (PCFICH)

– Informs the UE and the RN about the number of OFDM symbols used for the PDCCHs;

– Transmitted in every downlink or special subframe.

Physical downlink control channel (PDCCH)

– Informs the UE and the RN about the resource allocation of PCH and DL-SCH, and Hybrid ARQ information related to DL-SCH;

– Carries the uplink scheduling grant;

– Carries the sidelink scheduling grant.

Enhanced physical downlink control channel (EPDCCH)

– Informs the UE about the resource allocation of DL-SCH, and Hybrid ARQ information related to DL-SCH;

– Carries the uplink scheduling grant;

– Carries the sidelink scheduling grant.

MTC physical downlink control channel (MPDCCH)

– Informs the UE about the resource allocation of DL-SCH, and Hybrid ARQ information related to DL-SCH;

– Carries Hybrid ARQ ACK in response to uplink transmissions.

– Carries the uplink scheduling grant;

– Carries the direct indication information.

Short physical downlink control channel (SPDCCH)

– Informs the UE about the resource allocation of DL-SCH, and Hybrid ARQ information related to DL-SCH;

– Carries the uplink scheduling grant.

Physical Hybrid ARQ Indicator Channel (PHICH)

– Carries Hybrid ARQ ACK/NAKs in response to uplink transmissions.

Physical downlink shared channel (PDSCH)

– Carries the DL-SCH and PCH.

Physical multicast channel (PMCH)

– Carries the MCH.

Physical uplink control channel (PUCCH)

– Carries Hybrid ARQ ACK/NAKs in response to downlink transmission;

– Carries Scheduling Request (SR);

– Carries CSI reports.

Short physical uplink control channel (SPUCCH)

– Carries Hybrid ARQ ACK/NAKs in response to downlink transmission;

– Carries Scheduling Request (SR).

Physical uplink shared channel (PUSCH)

– Carries the UL-SCH.

Physical random access channel (PRACH)

– Carries the random access preamble.

Relay physical downlink control channel (R-PDCCH)

– Informs the RN about the resource allocation of DL-SCH, and Hybrid ARQ information related to DL-SCH;

– Carries the uplink scheduling grant.

Physical sidelink broadcast channel (PSBCH)

– Carries system and synchronization related information, transmitted from the UE.

Physical sidelink discovery channel (PSDCH)

– Carries sidelink discovery message from the UE.

Physical sidelink control channel (PSCCH)

– Carries control from a UE for sidelink communication and V2X sidelink communication.

Physical sidelink shared channel (PSSCH)

– Carries data from a UE for sidelink communication and V2X sidelink communication.

Narrowband Physical broadcast channel (NPBCH)

– The coded BCH transport block is mapped to sixty four subframes within a 640 ms interval;

– 640 ms timing is blindly detected, i.e. there is no explicit signalling indicating 640 ms timing.

Narrowband Physical downlink shared channel (NPDSCH)

– Carries the DL-SCH and PCH for NB-IoT UEs.

Narrowband Physical downlink control channel (NPDCCH)

– Informs the NB-IoT UE about the resource allocation of PCH and DL-SCH;

– Carries the uplink scheduling grant for the NB-IoT UE;

– Carries the direct indication information.

Narrowband Physical uplink shared channel (NPUSCH)

– Carries the UL-SCH and Hybrid ARQ ACK/NAKs in response to downlink transmission for the NB-IoT UE;

– Carries SR for the NB-IoT UE.

Narrowband Physical random access channel (NPRACH)

– Carries the random access preamble for the NB-IoT UE;

– Carries SR for the NB-IoT UE.

5.1 Downlink Transmission Scheme

5.1.1 Basic transmission scheme based on OFDM

The downlink transmission scheme is based on conventional OFDM using a cyclic prefix. The OFDM sub-carrier spacing is Δf = 15 kHz. 12 consecutive sub-carriers during one slot correspond to one downlink resource block. In the frequency domain, the number of resource blocks, N_RB, can range from N_RB-min = 6 to N_RB-max = 110 per CC or per Cell in case of CA or DC.

In addition, there are also four reduced sub-carrier spacings, Δf_low = 7.5 kHz, Δf_low1 = 2.5 kHz, Δf_low2 = 1.25 kHz and Δf_low3 ≈ 0.37 kHz for both MBMS-dedicated cell and MBMS/Unicast-mixed cell.

In case of 15 kHz sub-carrier spacing there are two cyclic-prefix lengths, corresponding to seven and six OFDM symbols per slot respectively.

– Normal cyclic prefix: T_CP = 160×Ts (OFDM symbol #0), T_CP = 144×Ts (OFDM symbol #1 to #6)

– Extended cyclic prefix: T_CP-e = 512×Ts (OFDM symbol #0 to OFDM symbol #5)

where T_s = 1/ (2048 × Δf)

In case of 7.5 kHz sub-carrier spacing, there is only a single cyclic prefix length T_CP-low = 1024×Ts, corresponding to 3 OFDM symbols per slot.

In case of 2.5 kHz sub-carrier spacing, there is only a single cyclic prefix length T_CP-low1 = 3072×Ts, corresponding to 1 OFDM symbol per slot.

In case of 1.25 kHz sub-carrier spacing, there is only a single cyclic prefix length T_CP-low2 = 6144×Ts, corresponding to 1 OFDM symbol per subframe.

In case of 0.37 kHz sub-carrier spacing, there is only a single cyclic prefix length T_CP-low3 = 9216×Ts, corresponding to 1 OFDM symbol per 3 ms slot as defined in TS 36.211 [4], clause 4.1.

For MBMS-dedicated cells, the PMCH bandwidth can be indicated to be larger than the carrier bandwidth. In particular, a PMCH bandwidth of 30, 35 or 40 PRBs (corresponding to 6/ 7/ 8MHz) can be indicated when the carrier bandwidth is 15 or 25 PRBs (corresponding to 3/ 5 MHz).

In case of FDD, operation with half duplex from UE point of view is supported.

5.1.1a Basic transmission scheme based on OFDM for NB-IoT

The downlink transmission scheme for NB-IoT is as described in clause 5.1.1, with the differences that in the frequency domain, there is one resource block for an NB-IoT carrier, the OFDM sub-carrier spacing Δf = 15 kHz always, and in case of FDD, only operation with half duplex from NB-IoT UE point of view is supported. There can be more than one NB-IoT carrier configured as described in clause 5.5a.

5.1.2 Physical-layer processing

The downlink physical-layer processing of transport channels consists of the following steps:

– CRC insertion: 24 bit CRC for PDSCH and NPDSCH;

– Channel coding: Turbo coding based on QPP inner interleaving with trellis termination, or Tail Biting Convolutional Coding for NPDSCH;

– Physical-layer hybrid-ARQ processing;

– Channel interleaving;

– Scrambling: transport-channel specific scrambling on DL-SCH, BCH, and PCH. Common MCH scrambling for all cells involved in a specific MBSFN transmission;

– Modulation: QPSK, 16QAM, 64QAM, 256QAM and 1024QAM;

– Layer mapping and pre-coding;

– Mapping to assigned resources and antenna ports.

5.1.3 Physical downlink control channels

The downlink control signalling (PDCCH) is located in the first n OFDM symbols where n ≤ 4 and consists of:

– Transport format and resource allocation related to DL-SCH and PCH, and hybrid ARQ information related to DL-SCH;

– Transport format, resource allocation, and hybrid-ARQ information related to UL-SCH;

– Resource allocation information related to SL-SCH and PSCCH.

Transmission of control signalling from these groups is mutually independent.

Multiple physical downlink control channels are supported and a UE monitors a set of control channels.

Control channels are formed by aggregation of control channel elements, each control channel element consisting of a set of resource elements. Different code rates for the control channels are realized by aggregating different numbers of control channel elements.

QPSK modulation is used for all control channels.

Each separate control channel has its own set of x-RNTI.

There is an implicit relation between the uplink resources used for dynamically scheduled data transmission, or the DL control channel used for assignment, and the downlink ACK/NAK resource used for feedback.

The physical layer supports R-PDCCH for the relay.

The enhanced physical downlink control channel (EPDCCH) carries UE-specific signalling. It is located in UE-specifically configured physical resource blocks and consists of:

– Transport format, resource allocation, and hybrid ARQ information related to DL-SCH;

– Transport format, resource allocation, and hybrid-ARQ information related to UL-SCH;

– Resource allocation information related to SL-SCH and PSCCH.

Multiple EPDCCHs are supported and a UE monitors a set of EPDCCHs.

EPDCCHs are formed by aggregation of enhanced control channel elements, each enhanced control channel element consisting of a set of resource elements. Different code rates for EPDCCHs are realized by aggregating different numbers of enhanced control channel elements. An EPDCCH can use either localized or distributed transmission, differing in the mapping of enhanced control channel elements to the resource elements in the PRBs.

EPDCCH supports C-RNTI and SPS C-RNTI and UL Semi-Persistent Scheduling V-RNTI and SL-RNTI and SL-V-RNTI and SL Semi-Persistent Scheduling V-RNTI, and AUL C-RNTI, and SRS-TPC-RNTI. If configured, EPDCCH is applicable in the same way as PDCCH unless otherwise specified.

The MTC physical downlink control channel (MPDCCH) is used for bandwidth-reduced operation and carries common and UE-specific signalling.

Multiple MPDCCHs are supported and a UE monitors a set of MPDCCHs.

MPDCCHs are formed by aggregation of enhanced control channel elements, each enhanced control channel element consisting of a set of resource elements. Different code rates for MPDCCHs are realized by aggregating different numbers of enhanced control channel elements. An MPDCCH can use either localized or distributed transmission, differing in the mapping of enhanced control channel elements to the resource elements in the PRBs.

MPDCCH supports RA-RNTI, P-RNTI, C-RNTI, Temporary C-RNTI, SPS C-RNTI, SC-RNTI and G-RNTI. For non-BL UEs in RRC_CONNECTED, MPDCCH supports SI-RNTI.

The short physical downlink control channel (SPDCCH) carries UE-specific signalling. It is located in UE-specifically configured physical resource blocks and consists of:

– Transport format, resource allocation, and hybrid ARQ information related to DL-SCH;

– Transport format, resource allocation, and hybrid-ARQ information related to UL-SCH;

Multiple SPDCCHs are supported and a UE monitors a set of SPDCCHs.

SPDCCHs are formed by aggregation of short control channel elements (SCCEs), each short control channel element consisting of a set of resource elements. Different code rates for SPDCCHs are realized by aggregating different numbers of SCCEs. An SPDCCH can use either localized or distributed transmission, differing in the mapping of SCCEs to the resource elements in the PRBs.

SPDCCH supports C-RNTI and SPS C-RNTI. If configured, SPDCCH is applicable in the same way as PDCCH unless otherwise specified.

For NB-IoT, the narrowband physical downlink control channel (NPDCCH) is located in available symbols of configured subframes. Within a PRB pair, two control channel elements are defined, with each control channel element composed of resources within a subframe. NPDCCH supports aggregations of 1 and 2 control channel elements and repetition. NPDCCH supports C-RNTI, Temporary C-RNTI, P-RNTI, RA-RNTI, SC-RNTI, G-RNTI, and SPS C-RNTI.

5.1.4 Downlink Reference signal and synchronization signals

The downlink cell-specific reference signals consist of known reference symbols inserted in the first and third last OFDM symbol of each slot for antenna port 0 and 1. There is one cell-specific reference signal transmitted per downlink antenna port. The number of downlink antenna ports for the transmission of cell-specific reference signals equals 1, 2, or 4.

Physical layer provides 504 unique cell identities using Synchronization signals and resynchronization signals.

The downlink MBSFN reference signals consist of known reference symbols inserted every other sub-carrier in the 3rd, 7th and 11th OFDM symbol of sub-frame in case of 15 kHz sub-carrier spacing and extended cyclic prefix; every four sub-carriers in the 2nd, 4th and 6th symbol of sub-frame in case of 7.5 kHz sub-carrier spacing; every four sub-carriers in the single symbol of slot in case of 2.5 kHz sub-carrier spacing; every six sub-carriers in the single symbol of subframe in case of 1.25 kHz sub-carrier spacing; and every twelve sub-carriers for MBSFN reference signal pattern type 1 or every six sub-carriers for MBSFN reference signal pattern type 2 in the single symbol of 3 ms slot in case of 0.37 kHz sub-carrier spacing as defined in TS 36.211 [4], clauses 4.1 and 6.10.2.2.4.

In addition to cell-specific reference signals and MBSFN reference signals, the physical layer supports UE-specific reference signals, positioning reference signals, CSI reference signals, and discovery signals.

A UE may assume presence of the discovery signals consisting of cell-specific reference signals, primary and secondary synchronization signals, configurable resynchronization signals, and configurable CSI reference signals.

5.1.4a Downlink Reference signal and synchronization signals for NB-IoT

The downlink narrowband reference signal consists of known reference symbols inserted in the last two, or the third and fourth, OFDM symbols of each slot depending on the frame structure Type, for NB-IoT antenna port 0 and 1, except invalid subframes, and subframes transmitting NPSS or NSSS, and certain subframes in frame structure Type 2. There is one narrowband reference signal transmitted per downlink NB-IoT antenna port. The number of downlink NB-IoT antenna ports equals 1 or 2.

In addition to narrowband reference signals, the physical layer supports Narrowband Positioning Reference Signals (NPRS).

Physical layer provides 504 unique cell identities using the narrowband secondary synchronization signal. It is indicated whether or not the UE may assume the cell ID is identical for NB-IoT and LTE. In case the cell IDs are identical, a UE may use the downlink cell-specific reference signals for demodulation and/or measurements when the number of NB-IoT antenna ports is the same as the number of downlink cell-specific reference signal antenna ports.

5.1.5 Downlink multi-antenna transmission

Multi-antenna transmission with up to 8 transmit antennas is supported. The maximum number of codeword is two irrespective to the number of antennas with fixed mapping between code words to layers. For slot/subslot based transmission, multi-antenna transmission with up to 4 transmit antennas is supported. The maximum number of codeword is one irrespective of the number of antennas with fixed mapping between codewords and layers.

Spatial division multiplexing (SDM) of multiple modulation symbol streams to a single UE using the same time-frequency (-code) resource, also referred to as Single-User MIMO (SU-MIMO) is supported. When a MIMO channel is solely assigned to a single UE, it is known as SU-MIMO. Spatial division multiplexing of modulation symbol streams to different UEs using the same time-frequency resource, also referred to as MU-MIMO, is also supported.

In addition, the following techniques are supported:

– Code-book-based pre-coding with a single pre-coding feedback per full system bandwidth when the system bandwidth (or subset of resource blocks) is smaller or equal to12RB and per 5 adjacent resource blocks or the full system bandwidth (or subset of resource blocks) when the system bandwidth is larger than 12RB.

– Non-code-book-based pre-coding with or without pre-coding feedback.

– Rank adaptation with single rank feedback referring to full system bandwidth. Node B can override rank report.

– Non-precoded CSI-RS operation is supported by CLASS A eMIMO-Type with one CSI-RS resource. This operation comprises schemes where different CSI-RS ports have the same wide beam width and direction and hence generally cell wide coverage.

– Beamformed CSI-RS operation is supported by CLASS B eMIMO-Type with one or more CSI-RS resources. This operation comprises schemes where (at least at a given time/frequency) CSI-RS ports have narrow beam widths and hence not cell wide coverage, and (at least from the eNB perspective) at least some CSI-RS port-resource combinations have different beam directions.

5.1.5a Downlink multi-antenna transmission for NB-IoT

Transmit diversity, specifically space frequency block coding (SFBC), is supported if two NB-IoT antenna ports are used.

5.1.6 MBSFN transmission

MBSFN is supported for the MCH transport channel. Multiplexing of transport channels using MBSFN and non-MBSFN transmission is done on a per-sub-frame basis. Additional reference symbols, transmitted using MBSFN are transmitted within MBSFN subframes.

5.1.7 Physical layer procedure

5.1.7.1 Link adaptation

Link adaptation (AMC: adaptive modulation and coding) with various modulation schemes and channel coding rates is applied to the shared data channel. The same coding and modulation is applied to all groups of resource blocks belonging to the same L2 PDU scheduled to one user within one TTI and within a single stream.

5.1.7.2 Power Control

Downlink power control can be used.

5.1.7.3 Cell search

Cell search is the procedure by which a UE acquires time and frequency synchronization with a cell and detects the Cell ID of that cell. E-UTRA cell search supports a scalable overall transmission bandwidth corresponding to 72 sub-carriers and upwards.

E-UTRA cell search is based on following signals transmitted in the downlink: the primary and secondary synchronization signals. If a resynchronization signal is transmitted in the downlink, it can be used to re-acquire time and frequency synchronization with the cell.

The primary and secondary synchronization signals are transmitted over the centre 72 sub-carriers in the first and sixth subframe of each frame. The resynchronization signals are transmitted over 2 consecutive PRBs. The time and frequency positions of the resynchronization signal (if transmitted) are configurable.

Neighbour-cell search is based on the same downlink signals as initial cell search.

5.1.7.3a Cell search for NB-IoT

NB-IoT is based on following signals transmitted in the downlink: the primary and secondary narrowband synchronization signals. The narrowband primary synchronization sequence is transmitted over 11 sub-carriers from the first subcarrier to the eleventh subcarrier in the sixth subframe of each frame, and the narrowband secondary synchronization sequence is transmitted over 12 sub-carriers in the NB-IoT carrier in the tenth subframe for FDD and the first subframe for TDD of every other frame.

5.1.8 Physical layer measurements definition

The physical layer measurements to support mobility are classified as:

– within E-UTRAN (intra-frequency, inter-frequency);

– between E-UTRAN and GERAN/UTRAN (inter-RAT);

– between E-UTRAN and non-3GPP RAT (Inter 3GPP access system mobility).

For measurements within E-UTRAN two basic UE measurement quantities shall be supported:

– Reference signal received power (RSRP);

– Reference signal received quality (RSRQ).

In addition, the following UE measurement quantity may be supported:

– Received signal strength indicator (RSSI);

– Reference signal signal to noise and interference ratio (RS-SINR).

RSRP measurement is based on the following signals:

– Cell-specific reference signals; or

– CSI reference signals in configured discovery signals; or

– Resynchronization Signal; or

– Narrowband secondary synchronization signal for NB-IoT UEs.

5.1.9 Coordinated Multi-Point transmission

For DL CoMP, multiple transmission points are coordinated in their downlink data transmission.

The UE may be configured to measure and report the CSI of a set of non-zero power CSI-RS resources.

The UE may also be configured with one or more interference measurements. Each interference measurement is associated with one CSI-interference measurement (CSI-IM) resource, which is a set of REs on which the UE measures interference.

The UE may also be configured with multiple CSI processes. Each CSI process defines the CSI measurement associated with one non-zero power CSI-RS resource and one CSI-IM resource.

5.1.10 Wake-up signal for NB-IoT

The narrowband wake-up signal is transmitted over 12 sub-carriers in the frequency domain in the NB-IoT carrier in available symbols of configured subframes. It conveys 504 unique cell identities, as per the narrowband secondary synchronization signal.

5.1.11 Wake-up signal for BL UE or UE in enhanced coverage

The wake-up signal is transmitted over 2 physical resource blocks in the frequency domain in available symbols of configured subframes. It conveys 504 unique cell identities, as per the secondary synchronization signal.

5.2 Uplink Transmission Scheme

5.2.1 Basic transmission scheme

For both FDD and TDD, the uplink transmission scheme is based on single-carrier FDMA, more specifically DFTS-OFDM. It also supports multi-cluster assignment of DFTS-OFDM.

Figure 5.2.1-1: Transmitter scheme of SC-FDMA

The uplink sub-carrier spacing Δf = 15 kHz. The sub-carriers are grouped into sets of 12 consecutive sub-carriers, corresponding to the uplink resource blocks. 12 consecutive sub-carriers during one slot correspond to one uplink resource block. In the frequency domain, the number of resource blocks, N_RB, can range from N_RB-min = 6 to N_RB-max = 110 per carrier or per CC in case of CA or DC.

There are two cyclic-prefix lengths defined: Normal cyclic prefix and extended cyclic prefix corresponding to seven and six SC-FDMA symbol per slot respectively.

– Normal cyclic prefix: T_CP = 160×Ts (SC-FDMA symbol #0) , T_CP = 144×Ts (SC-FDMA symbol #1 to #6)

– Extended cyclic prefix: T_CP-e = 512×Ts (SC-FDMA symbol #0 to SC-FDMA symbol #5)

5.2.1a Basic transmission scheme for NB-IoT

For NB-IoT uplink transmission, both single-tone transmission and multi-tone transmission are defined.

For single-tone transmission, there are two numerologies defined: 3.75 kHz and 15 kHz subcarrier spacing, based on single-carrier FDMA as described in clause 5.2.1, with the following differences: In the frequency domain, resource blocks are not defined. If the uplink sub-carrier spacing Δf = 15 kHz, there are 12 consecutive sub-carriers. If the uplink sub-carrier spacing Δf = 3.75 kHz, there are 48 consecutive sub-carriers.

Single-tone transmission with 3.75 kHz subcarrier spacing is organized into slots with 2ms duration, each of which consists of seven symbols located from beginning of the slot. The slot boundary is aligned with sub-frame boundaries of frame structure Type 1. One symbol of 3.75 kHz subcarrier spacing consists of 8448 Ts of symbol with CP length of 256Ts. The remaining time (2304Ts) of the slot is used as a guard period.

Multi-tone transmission is based on single-carrier FDMA as described in clause 5.2.1, with the difference that resource blocks are not defined. There are 12 consecutive uplink sub-carriers with uplink sub-carrier spacing Δf = 15 kHz. The sub-carriers can be grouped into sets of 3, 6, or 12 consecutive subcarriers.

A resource unit, schedulable for single-tone NPUSCH with UL-SCH transmission, is defined as a single 3.75 kHz sub-carrier for 32 ms or a single 15 kHz sub-carrier for 8 ms. A resource unit, schedulable for multi-tone NPUSCH with UL-SCH transmission is defined as 3 sub-carriers for 4 ms; or 6 sub-carriers for 2 ms; or 12 sub-carriers for 1ms. A resource unit, schedulable for NPUSCH with ACK/NAK transmission, is defined as a single 3.75 kHz sub-carrier for 8 ms or a single 15 kHz sub-carrier for 2 ms.

A UL-SCH transport block can be scheduled over one or more than one resource unit in time.

5.2.2 Physical-layer processing

The uplink physical layer processing of transport channels consists of the following steps:

– CRC insertion: 24 bit CRC for PUSCH and NPUSCH;

– Channel coding: turbo coding based on QPP inner interleaving with trellis termination;

– Physical-layer hybrid-ARQ processing;

– Scrambling: UE-specific scrambling;

– Modulation: QPSK, 16QAM, 64QAM and 256 QAM (64 QAM and 256 QAM optional in UE) for full-PRB transmission of PUSCH, and π/2-BPSK and QPSK for sub-PRB transmission of PUSCH (optional in UE); π/2-BPSK and π/4-QPSK in single-tone transmission of NPUSCH, QPSK and optionally 16QAM for multi-tone transmission of NPUSCH;

– Mapping to assigned resources and antennas ports.

5.2.3 Physical uplink control channel

The PUCCH/SPUCCH shall be mapped to a control channel resource in the uplink.

Depending on presence or absence of uplink timing synchronization, the uplink physical control signalling for scheduling request can differ.

In the case of time synchronization being present for the pTAG, the outband control signalling consists of:

– CSI;

– ACK/NAK;

– Scheduling Request (SR).

The CSI informs the scheduler about the current channel conditions as seen by the UE. If MIMO transmission is used, the CSI includes necessary MIMO-related feedback.

The HARQ feedback in response to downlink data transmission consists of a single ACK/NAK bit per transport block in case of non-bundling configuration.

PUCCH/SPUCCH resources for SR, CSI reporting and possibly HARQ feedback are assigned and can be revoked through RRC signalling. An SR is not necessarily assigned to UEs acquiring synchronization through the RACH (i.e. synchronised UEs may or may not have a dedicated SR channel). PUCCH/SPUCCH resources for SR, CSI and HARQ feedback are lost when the UE is no longer synchronized.

PUCCH/SPUCCH is transmitted on PCell, PUCCH SCell (if such is configured in CA) and on PSCell (in DC).

The physical layer supports simultaneous transmission of PUCCH and subframe PUSCH, or of SPUCCH and (sub)slot-PUSCH. In case of SPUCCH and (sub)slot-PUSCH transmission, both the shared channel and the associated control channel shall be of the same transmission duration (slot or subslot).

5.2.3a Uplink control information for NB-IoT

The uplink control information consists of:

– ACK/NAK corresponding to NPDSCH;

– Scheduling Request (SR).

ACK/NAK corresponding to NPDSCH is transmitted with single-tone transmission on NPUSCH, with frequency resource and time resource indicated by downlink grant.

SR may be transmitted with or without Hybrid ARQ ACK/NAKs corresponding to NPDSCH. Resources for SR are assigned and can be revoked through RRC signaling. An SR is not necessarily assigned to NB-IoT UEs acquiring synchronisation through the RACH (i.e. synchronised NB-IoT UEs may or may not have SR resources configured). Resources for SR are lost when the NB-IoT UE is no longer synchronised.

5.2.4 Uplink Reference signal

For PUSCH demodulation, uplink demodulation reference signals are transmitted in the 4-th block of the slot in normal CP. In case of subslot-PUSCH, the presence and position of demodulation reference signals are indicated to the UE. Uplink demodulation reference signals are also transmitted for PUCCH demodulation. The uplink demodulation reference signals sequence length equals the size (number of sub-carriers) of the assigned resource.

The uplink reference signals are based on sequences having constant amplitude and zero autocorrelation.

For full-PRB transmission, multiple reference signals can be created:

– Based on different base sequences;

– Different shifts of the same sequence;

– Different orthogonal sequences (OCC) on DM RS.

For sub-PRB transmission of PUSCH, multiple reference signals can be created:

– Based on different base sequences;

– Different cyclic shifts of the same sequence;

– A common Gold sequence.

In addition to demodulation reference signals, the physical layer supports sounding reference signals (SRS).

5.2.4a Uplink Reference signal for NB-IoT

For single-tone NPUSCH with UL-SCH demodulation, uplink demodulation reference signals are transmitted in the 4-th block of the slot for 15 kHz subcarrier spacing, and in the 5-th block of the slot for 3.75 kHz subcarrier spacing. For multi-tone NPUSCH with UL-SCH demodulation, uplink demodulation reference signals are transmitted in the 4-th block of the slot. The uplink demodulation reference signals sequence length is 16 for single-tone NPUSCH with UL-SCH transmission, and equals the size (number of sub-carriers) of the assigned resource for multi-tone transmission.

For single-tone NPUSCH with UL-SCH transmission, multiple narrow band reference signals can be created:

– Based on different base sequences;

– A common Gold sequence.

For multi-tone NPUSCH with UL-SCH transmission, multiple narrow band reference signals are created:

– Based on different base sequences;

– Different cyclic shifts of the same sequence.

For NPUSCH with ACK/NAK demodulation, uplink demodulation reference signals are transmitted in the 3-rd, 4-th and 5-th block of the slot for 15 kHz subcarrier spacing, and in the 1-st, 2-nd and 3-rd block of the slot for 3.75 kHz subcarrier spacing. Multiple narrow band reference signals can be created:

– Based on different base sequences;

– A common Gold sequence;

– Different orthogonal sequences (OCC).

5.2.5 Random access preamble

The physical layer random access burst consists of a cyclic prefix, a preamble, and a guard time during which nothing is transmitted.

The random access preambles are generated from Zadoff-Chu sequences with zero correlation zone, ZC-ZCZ, generated from one or several root Zadoff-Chu sequences.

5.2.5a Random access preamble for NB-IoT

The physical layer random access transmission uses a 3.75 kHz or 1.25 kHz sub-carrier spacing and consists of symbol groups with frequency hopping between symbol groups. Each symbol group has a cyclic prefix and a preamble. Symbol groups with 3.75 kHz sub-scarrier spacing hop by one or six sub-carriers in frequency, and symbol groups with 1.25 kHz subcarrier spacing hop by one, three, or eighteen sub-carriers in frequency. Repetitions of groups of symbol groups hop by a pseudo-random number of sub-carriers in frequency. There are two in FDD, and four in TDD, possible cyclic prefix lengths for the random access transmission symbol groups, suitable for different maximum cell sizes.

5.2.6 Uplink multi-antenna transmission

The antenna configuration for uplink supports both SU-MIMO and MU-MIMO.

Closed loop and open loop types of adaptive antenna selection transmit diversity are supported for both FDD and TDD by physical layer.

The physical layer supports transmit diversity of some control formats.

5.2.7 Physical channel procedure

5.2.7.1 Link adaptation

Uplink link adaptation is used in order to guarantee the required minimum transmission performance of each UE such as the user data rate, packet error rate, and latency, while maximizing the system throughput.

Three types of link adaptation are performed according to the channel conditions, the UE capability such as the maximum transmission power and maximum transmission bandwidth etc., and the required QoS such as the data rate, latency, and packet error rate etc. Three link adaptation methods are as follows.

– Adaptive transmission bandwidth;

– Transmission power control;

– Adaptive modulation and channel coding rate.

5.2.7.2 Uplink Power control

Intra-cell power control: the power spectral density of the uplink transmissions can be influenced by the eNB. For DC, two types of power control modes are defined, mode 1 and mode 2 as specified in TS 36.213 [6]. A UE capable of DC supports at least power control mode 1 and the UE may additionally support power control mode 2. In both modes, the UE is configured with a minimum guaranteed power for each CG, as a ratio of the configured maximum UE output power Pcmax (see TS 36.101 [52] ). In power control mode 1, UE allocates up to the minimum guaranteed power to each CG and any remaining power is shared across MCG and SCG on a per transmission basis according to a priority order based on UCI type. In power control mode 2, the UE reserves the minimum guaranteed power to each CG and any remaining power is first made available to the CG where transmission starts the earliest in time.

5.2.7.3 Uplink timing control

The timing advance is derived from the UL received timing and sent by the eNB to the UE which the UE uses to advance/delay its timings of transmissions to the eNB so as to compensate for propagation delay and thus time align the transmissions from different UEs with the receiver window of the eNB.

The timing advance command for each TAG is on a per need basis with a granularity in the step size of 0.52 μs (16×T_s).

5.2.8 Coordinated Multi-Point reception

For UL CoMP, multiple reception points are coordinated in their uplink data reception.

The UE may be configured with UE-specific parameters of PUSCH DMRS sequence and cyclic shift hopping, PUCCH sequence, and PUCCH region for hybrid-ARQ feedback. These UE-specific parameters can be configured independently of the physical cell identity of the UE’s serving cell.

5.3 Transport Channels

5.3.0 Transport channel types

The physical layer offers information transfer services to MAC and higher layers. The physical layer transport services are described by how and with what characteristics data are transferred over the radio interface. An adequate term for this is "Transport Channel".

NOTE 1: This should be clearly separated from the classification of what is transported, which relates to the concept of logical channels at MAC sublayer.

Downlink transport channel types are:

1. Broadcast Channel (BCH) characterised by:

– fixed, pre-defined transport format;

– requirement to be broadcast in the entire coverage area of the cell.

2. Downlink Shared Channel (DL-SCH) characterised by:

– support for HARQ;

– support for dynamic link adaptation by varying the modulation, coding and transmit power;

– possibility to be broadcast in the entire cell;

– possibility to use beamforming;

– support for both dynamic and semi-static resource allocation;

– support for UE discontinuous reception (DRX) to enable UE power saving;

NOTE 2: the possibility to use slow power control depends on the physical layer.

3. Paging Channel (PCH) characterised by:

– support for UE discontinuous reception (DRX) to enable UE power saving (DRX cycle is indicated by the network to the UE);

– requirement to be broadcast in the entire coverage area of the cell;

– mapped to physical resources which can be used dynamically also for traffic/other control channels.

4. Multicast Channel (MCH) characterised by:

– requirement to be broadcast in the entire coverage area of the cell;

– support for MBSFN combining of MBMS transmission on multiple cells;

– support for semi-static resource allocation e.g. with a time frame of a long cyclic prefix.

Uplink transport channel types are:

1. Uplink Shared Channel (UL-SCH) characterised by:

– possibility to use beamforming; (likely no impact on specifications)

– support for dynamic link adaptation by varying the transmit power and potentially modulation and coding;

– support for HARQ;

– support for both dynamic and semi-static resource allocation.

NOTE 3: the possibility to use uplink synchronisation and timing advance depend on the physical layer.

2. Random Access Channel(s) (RACH) characterised by:

– limited control information;

– collision risk.

NOTE 4: The possibility to use open loop power control depends on the physical layer solution.

Sidelink transport channel types are:

1. Sidelink broadcast channel (SL-BCH) characterised by:

– pre-defined transport format.

2. Sidelink discovery channel (SL-DCH) characterised by:

– fixed size, pre-defined format periodic broadcast transmission;

– support for both UE autonomous resource selection and scheduled resource allocation by eNB;

– collision risk due to support of UE autonomous resource selection; no collision when UE is allocated dedicated resources by the eNB;

– support for HARQ combining, but no support for HARQ feedback.

NOTE 5: the possibility to use uplink synchronisation and timing advance depends on the physical layer.

3. Sidelink shared channel (SL-SCH) characterised by:

– support for broadcast transmission;

– support for both UE autonomous resource selection and scheduled resource allocation by eNB;

– collision risk due to support of UE autonomous resource selection; no collision when UE is allocated dedicated resources by the eNB;

– support for HARQ combining, but no support for HARQ feedback;

– support for dynamic link adaptation by varying the transmit power, modulation and coding.

NOTE 6: the possibility to use uplink synchronisation and timing advance depend on the physical layer.

5.3.1 Mapping between transport channels and physical channels

The figures below depict the mapping between transport and physical channels:

Figure 5.3.1-1: Mapping between downlink transport channels and downlink physical channels

Figure 5.3.1-2: Mapping between uplink transport channels and uplink physical channels

Figure 5.3.1-3: Mapping between sidelink transport channels and sidelink physical channels

5.3.1a Mapping between transport channels and narrowband physical channels

The figures below depict the mapping between transport and narrowband physical channels:

Figure 5.3.1a-1: Mapping between downlink transport channels and downlink narrowband physical channels

Figure 5.3.1a-2: Mapping between uplink transport channels and uplink narrowband physical channels

5.4 E-UTRA physical layer model

The E-UTRAN physical layer model is captured in TS 36.302 [9].

5.4.1 Void

5.4.2 Void

5.5 Carrier Aggregation

5.5.0 General

In Carrier Aggregation (CA), two or more Component Carriers (CCs) are aggregated in order to support wider transmission bandwidths up to 640MHz. A UE may simultaneously receive or transmit on one or multiple CCs depending on its capabilities:

– A UE with single timing advance capability for CA can simultaneously receive and/or transmit on multiple CCs corresponding to multiple serving cells sharing the same timing advance (multiple serving cells grouped in one TAG);

– A UE with multiple timing advance capability for CA can simultaneously receive and/or transmit on multiple CCs corresponding to multiple serving cells with different timing advances (multiple serving cells grouped in multiple TAGs). E-UTRAN ensures that each TAG contains at least one serving cell;

– A non-CA capable UE can receive on a single CC and transmit on a single CC corresponding to one serving cell only (one serving cell in one TAG).

CA is supported for both contiguous and non-contiguous CCs with each CC limited to a maximum of 110 Resource Blocks in the frequency domain using the Rel-8/9 numerology.

CA is supported both between same and different duplex CCs.

It is possible to configure a UE to aggregate a different number of CCs originating from the same eNB and of possibly different bandwidths in the UL and the DL:

– The number of DL CCs that can be configured depends on the DL aggregation capability of the UE;

– The number of UL CCs that can be configured depends on the UL aggregation capability of the UE;

– It is not possible to configure a UE with more UL CCs than DL CCs;

– In typical TDD deployments, the number of CCs and the bandwidth of each CC in UL and DL is the same.

– The number of TAGs that can be configured depends on the TAG capability of the UE.

CCs originating from the same eNB need not to provide the same coverage.

CCs shall be LTE Rel-8/9 compatible. Nevertheless, existing mechanisms (e.g. barring) may be used to avoid Rel-8/9 UEs to camp on a CC.

The spacing between centre frequencies of contiguously aggregated CCs shall be a multiple of 300 kHz. This is in order to be compatible with the 100 kHz frequency raster of Rel-8/9 and at the same time preserve orthogonality of the subcarriers with 15 kHz spacing. Depending on the aggregation scenario, the n × 300 kHz spacing can be facilitated by insertion of a low number of unused subcarriers between contiguous CCs.

For TDD CA, the downlink/uplink configuration is identical across component carriers in the same band and may be the same or different across component carriers in different bands.

5.5.1 SRS switching between component carriers

A UE supporting CA can be capable of aggregating more downlink CCs than uplink CCs, and hence a TDD CC may operate in downlink without PUCCH/PUSCH. A UE may be configured with SRS switching between CCs so that SRS can be transmitted on a TDD CC configured without PUCCH/PUSCH. When such SRS needs to be transmitted on a TDD CC without PUCCH/PUSCH, the UE may transmit SRS on the TDD CC or skip the SRS transmission on the TDD CC depending on the priority order for the operation of SRS switching between CCs.

5.5a Multi-carrier operation for NB-IoT

For NB-IoT, multi-carrier operation is supported.

The UE in RRC_CONNECTED can be configured, via UE-specific RRC signaling, to a non-anchor carrier, for all unicast transmissions. The UE in RRC_IDLE, based on broadcast/multicast signaling, can use a non-anchor carrier for SC-PTM reception. The UE in RRC_IDLE can, based on broadcast signaling, use a non-anchor carrier for paging reception. The UE in RRC_IDLE or RRC_CONNECTED, based on broadcast signaling, can use a non-anchor carrier for random access. If the non-anchor carrier is not configured for the UE, all transmissions occur on the anchor carrier. The valid anchor and non-anchor carrier combinations are provided in Table 5.5a-1 for FDD and Table 5.5a-2 for TDD.

Table 5.5a-1: Anchor and non-anchor carrier deployment combinations in FDD

	Anchor Carrier
		In-band	Guard-band	Standalone
Non-Anchor Carrier	In-band	Valid (Note 1)	Valid (Note 1)	Valid (Note 2, Note 3)
	Guard-band	Valid (Note 1)	Valid (Note 1)	Valid (Note 2, Note 3)
	Standalone	Valid (Note 2, Note 3)	Valid (Note 2, Note 3)	Valid (Note 2)

Table 5.5a-2: Anchor and non-anchor carrier deployment combinations in TDD

	Anchor Carrier
		In-band	Guard-band	Standalone
Non-Anchor Carrier	In-band	Valid (Note 1)	Valid (Note 1)	Invalid
	Guard-band	Valid (Note 1)	Valid (Note 1)	Invalid
	Standalone	Invalid	Invalid	Valid (Note 2)

NOTE 1: Both carriers associated with the same LTE cell.

NOTE 2: Total frequency span to not exceed 20MHz and both anchor and non-anchor carriers synchronised.

NOTE 3: Not applicable to SC-PTM reception.

5.6 Sidelink

5.6.0 General

Sidelink comprises sidelink discovery, sidelink communication and V2X sidelink communication between UEs. Sidelink uses uplink resources and physical channel structure similar to uplink transmissions. However, some changes, noted below, are made to the physical channels.

5.6.1 Basic transmission scheme

Sidelink transmission uses the same basic transmission scheme as the UL transmission scheme. However, sidelink is limited to single cluster transmissions for all the sidelink physical channels. Further, sidelink uses a 1 symbol gap at the end of each sidelink sub-frame. For V2X sidelink communication, PSCCH and PSSCH are transmitted in the same subframe.

5.6.2 Physical-layer processing

The sidelink physical layer processing of transport channels differs from UL transmission in the following steps:

– Scrambling: for PSDCH and PSCCH, the scrambling is not UE-specific;

– Modulation: 256 QAM is not supported for sidelink. 64 QAM is only supported for V2X sidelink communication.

5.6.3 Physical Sidelink control channel

PSCCH is mapped to the sidelink control resources.

PSCCH indicates resource and other transmission parameters used by a UE for PSSCH.

5.6.4 Sidelink reference signals

For PSDCH, PSCCH and PSSCH demodulation, reference signals similar to uplink demodulation reference signals are transmitted in the 4-th symbol of the slot in normal CP and in the 3rd symbol of the slot in extended cyclic prefix. The sidelink demodulation reference signals sequence length equals the size (number of sub-carriers) of the assigned resource. For V2X sidelink communication, reference signals are transmitted in 3rd and 6th symbols of the first slot and 2nd and 5th symbols of the second slot in normal CP.

For PSDCH and PSCCH, reference signals are created based on a fixed base sequence, cyclic shift and orthogonal cover code. For V2X sidelink communication, cyclic shift for PSCCH is randomly selected in each transmission.

5.6.5 Physical channel procedure

5.6.5.1 Sidelink power control

For in-coverage operation, the power spectral density of the sidelink transmissions can be influenced by the eNB.

5.6.6 Physical layer measurements definition

For measurement on the sidelink, the following basic UE measurement quantities are supported:

– Sidelink reference signal received power (S-RSRP).

– Sidelink discovery reference signal received power (SD-RSRP).

– PSSCH reference signal received power (PSSCH-RSRP).

– Sidelink reference signal strength indicator (S-RSSI).

5.7 Licensed-Assisted Access

5.7.0 General

Carrier aggregation with at least one SCell operating in the unlicensed spectrum is referred to as Licensed-Assisted Access (LAA). In LAA, the configured set of serving cells for a UE therefore always includes at least one SCell operating in the unlicensed spectrum according to Frame structure Type 3, also called LAA SCell. Unless otherwise specified, LAA SCells act as regular SCells.

LAA eNB and UE apply Listen-Before-Talk (LBT) before performing a transmission on LAA SCell. When LBT is applied, the transmitter listens to/senses the channel to determine whether the channel is free or busy. If the channel is determined to be free, the transmitter may perform the transmission; otherwise, it does not perform the transmission. If an LAA eNB uses channel access signals of other technologies for the purpose of LAA channel access, it shall continue to meet the LAA maximum energy detection threshold requirement.

The combined time of transmissions compliant with the channel access procedure described in clause 4.1.2 of TS 37.213 [90] by an eNB should not exceed 50 ms in any contiguous 1 second period on an LAA SCell.

Which LBT type (i.e. type 1 or type 2 uplink channel access) the UE applies is signalled via uplink grant for uplink PUSCH transmission on LAA SCells, except for Autonomous Uplink (AUL) transmissions.

For type 1 uplink channel access on AUL, E-UTRAN signals the Channel Access Priority Class for each logical channel and UE shall select the lowest Channel Access Priority Class (i.e, with a higher number in the Table 5.7.1-1) of the logical channel(s) with MAC SDU multiplexed into the MAC PDU. The MAC CEs except padding BSR use the highest Channel Access Priority Class (i.e, the lowest number in the Table 5.7.1-1).

For type 2 uplink channel access on AUL, the UE may select logical channels corresponding to any Channel Access Priority Class for UL transmission in the subframes signalled by E-UTRAN in common downlink control signalling.

For uplink LAA operation, the eNB shall not schedule the UE more subframes than the minimum necessary to transmit all the traffic corresponding to the selected Channel Access Priority Class or lower (i.e, with a lower number in the Table 5.7.1-1), than the:

– Channel Access Priority Class signaled in UL grant based on the latest BSR and received uplink traffic from the UE if type 1 uplink channel access procedure (see clause 4.2.1.1 of TS 37.213 [90]) is signalled to the UE;

– Channel Access Priority Class used by the eNB based on the downlink traffic, the latest BSR and received UL traffic from the UE if type 2 uplink channel access procedure (see clause 4.2.1.2 of TS 37.213 [90]) is signalled to the UE.

5.7.1 Channel Access Priority Classes

Four Channel Access Priority Classes (CAPC) are defined in TS 37.213 [90] which can be used when performing uplink and downlink transmissions in LAA carriers. Table 5.7.1-1 shows which Channel Access Priority Class should be used by traffic belonging to the different standardized QCIs. A non-standardized QCI (i.e. Operator specific QCI) should use suitable Channel Access Priority Class based on the below table, i.e. the Channel Access Priority Class used for a non-standardized QCI should be the Channel Access Priority Class of the standardized QCIs which best matches the traffic class of the non-standardized QCI.

For uplink, the eNB selects the Channel Access Priority Class by taking into account the lowest priority QCI in a Logical Channel Group.

Table 5.7.1-1: Mapping between Channel Access Priority Classes and QCI

Channel Access Priority Class ()	QCI
1	1, 3, 5, 65, 66, 67, 69, 70, 79, 80, 82, 83, 84, 85
2	2, 7, 71
3	4, 6, 8, 9, 72, 73, 74, 76
4	–

5.7.2 Multiplexing of data

Four Channel Access Priority Classes are defined in TS 37.213 [90]. If a DL transmission burst with PDSCH is transmitted, for which channel access has been obtained using Channel Access Priority Class P (1…4), E-UTRAN shall ensure the following where a DL transmission burst refers to the continuous transmission by E-UTRAN after a successful LBT:

– the transmission duration of the DL transmission burst shall not exceed the minimum duration needed to transmit all available buffered traffic corresponding to Channel Access Priority Class(es) ≤ P;

– the transmission duration of the DL transmission burst shall not exceed the Maximum Channel Occupancy Time ( as defined in Table 4.1.1-1 of TS 37.213 [90]) for Channel Access Priority Class P;

– additional traffic corresponding to Channel Access Priority Class(s) > P may only be included in the DL transmission burst once no more data corresponding to Channel Access Priority Class ≤ P is available for transmission. In such cases, E-UTRAN should maximise occupancy of the remaining transmission resources in the DL transmission burst with this additional traffic.

For uplink PUSCH transmission, there is no additional restriction at the UE (other than the multiplexing rules defined in clause 5.4.3 of TS 36.321 [13]) on the type of the traffic that can be carried in the scheduled subframes.

5.8 Short Processing Time

If Short Processing Time (SPT) for 1 ms TTI length is configured, the minimum timing from UL grant transmission to UL PUSCH transmission, and the timing from DL PDSCH transmission to HARQ feedback transmission is 3 ms.

5.9 Short Transmission Time Interval

Short TTI provides support for TTI length shorter than 1 ms DL-SCH and UL-SCH. To support the short TTI, the associated control channels, SPDCCH and SPUCCH, are also transmitted with duration shorter than 1 ms.

Over the physical layer, DL and UL transmissions use either slots or subslots when short TTI is configured. A subslot is defined to be of either 2 OFDM/SC-FDMA symbol or 3 OFDM/SC-FDMA symbol duration.

Table 5.9-1: Slot/subslot DL and UL transmission availability for different frame structure types

Frame Structure Type	Supported DL and UL transmission
1	slot, subslot
2	slot
3	–

In case of Frame structure Type 1 the DL and UL transmission duration does not have to be the same. Table 5.9-2 shows the allowed DL and UL combinations.

Table 5.9-2: DL and UL combinations for Frame Structure Type 1

DL	UL
Slot	Slot
Subslot	Slot
Subslot	Subslot

When short TTI is configured, extended cyclic prefix is not supported.