4 Frame structure

36.2113GPPEvolved Universal Terrestrial Radio Access (E-UTRA)Physical channels and modulationRelease 17TS

Throughout this specification, unless otherwise noted, the size of various fields in the time domain is expressed as a number of time units seconds.

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

– Type 1, applicable to FDD only,

– Type 2, applicable to TDD only,

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

NOTE: LAA secondary cell operation only applies to frame structure type 3.

Transmissions in multiple cells can be aggregated where up to 31 secondary cells can be used in addition to the primary cell. Unless otherwise noted, the description in this specification applies to each of the up to 32 serving cells. In case of multi-cell aggregation, different frame structures can be used in the different serving cells.

4.1 Frame structure type 1

Frame structure type 1 is applicable to both full duplex and half duplex FDD only. Each radio frame is long and consists of 10 subframes of length , numbered from 0 to 9. Subframe in frame has an absolute subframe number where is the system frame number.

For subframes using , , or , subframe is defined as two slots, and , of length each.

For subframes using , subframe is defined as one slot, , of length .

For transmissions using , a slot has a length of 92160. There are 13 slots, numbered in increasing order from 0 to 12, in a 40 ms period starting at with slot 0 starting at in the 40 ms period.

For subframes using , the subframe can further be divided into six subslots according to Table 4.1-1. Downlink subslot pattern 1 is applied if the number of symbols used for PDCCH is equal to 1 or 3 and downlink subslot pattern 2 is applied if the number of symbols used for PDCCH is equal to 2. For system bandwidths , subslot transmission is not supported in case 4 symbols used for PDCCH.

For FDD, 10 subframes, 20 slots, or up to 60 subslots are available for downlink transmission and 10 subframes, 20 slots, or up to 60 subslots are available for uplink transmissions in each 10 ms interval. Uplink and downlink transmissions are separated in the frequency domain. In half-duplex FDD operation, the UE cannot transmit and receive at the same time while there are no such restrictions in full-duplex FDD.

Figure 4.1-1: Frame structure type 1 (assuming ).

Table 4.1-1: SC-FDMA/OFDM symbols in different subslots of subframe i

Subslot number	0	1	2	3	4	5
Slot number	2i			2i+1
Uplink subslot pattern	0, 1, 2	3, 4	5, 6	0, 1	2, 3	4, 5, 6
Downlink subslot pattern 1	0, 1, 2	3, 4	5, 6	0, 1	2, 3	4, 5, 6
Downlink subslot pattern 2	0, 1	2, 3, 4	5, 6	0, 1	2, 3	4, 5, 6

4.2 Frame structure type 2

Frame structure type 2 is applicable to TDD only. Each radio frame of length consists of two half-frames of length each. Each half-frame consists of five subframes of length. Each subframe is defined as two slots, and, of length each. Subframe in frame has an absolute subframe number where is the system frame number.

The uplink-downlink configuration in a cell may vary between frames and controls in which subframes uplink or downlink transmissions may take place in the current frame. The uplink-downlink configuration in the current frame is obtained according to Clause 13 in [4].

The supported uplink-downlink configurations are listed in Table 4.2-2 where, for each subframe in a radio frame, "D" denotes a downlink subframe reserved for downlink transmissions, "U" denotes an uplink subframe reserved for uplink transmissions and "S" denotes a special subframe with the three fields DwPTS, GP and UpPTS. The length of DwPTS and UpPTS is given by Table 4.2-1 subject to the total length of DwPTS, GP and UpPTS being equal to where X is the number of additional SC-FDMA symbols in UpPTS provided by the higher layer parameter srs-UpPtsAdd if configured otherwise X is equal to 0. The UE is not expected to be configured with 2 additional UpPTS SC-FDMA symbols for special subframe configurations {3, 4, 7, 8} for normal cyclic prefix in downlink and special subframe configurations {2, 3, 5, 6} for extended cyclic prefix in downlink and 4 additional UpPTS SC-FDMA symbols for special subframe configurations {1, 2, 3, 4, 6, 7, 8} for normal cyclic prefix in downlink and special subframe configurations {1, 2, 3, 5, 6} for extended cyclic prefix in downlink.

Uplink-downlink configurations with both 5 ms and 10 ms downlink-to-uplink switch-point periodicity are supported.

– In case of 5 ms downlink-to-uplink switch-point periodicity, the special subframe exists in both half-frames.

– In case of 10 ms downlink-to-uplink switch-point periodicity, the special subframe exists in the first half-frame only.

Subframes 0 and 5 and DwPTS are always reserved for downlink transmission. For special subframe configurations 1, 2, 3, 4, 6, 7 and 8, DwPTS is split into two parts, of which the first part is a slot and the second part is of X-symbol duration within the second slot. Downlink subframes, downlink slots in the downlink subframe and DwPTS, and the X–symbol duration in the second slot of DwPTS are available for downlink transmission. The X-symbol transmission opportunity is only available for special subframe configuration 3,4 and 8.

UpPTS and the subframe immediately following the special subframe are always reserved for uplink transmission. Uplink subframes, uplink slots and UpPTS with special subframe configuration 10 are available for uplink transmission. Note that UpPTS with special subframe configuration 10 are not available for SPUCCH transmission.

In case multiple cells are aggregated, the UE may assume that the guard period of the special subframe in the cells using frame structure type 2 have an overlap of at least .

In case multiple cells with different uplink-downlink configurations in the current radio frame are aggregated and the UE is not capable of simultaneous reception and transmission in the aggregated cells, the following constraints apply:

– if the subframe in the primary cell is a downlink subframe, the UE shall not transmit any signal or channel on a secondary cell in the same subframe

– if the subframe in the primary cell is an uplink subframe, the UE is not expected to receive any downlink transmissions on a secondary cell in the same subframe

– if the subframe in the primary cell is a special subframe and the same subframe in a secondary cell is a downlink subframe, the UE is not expected to receive PDSCH/EPDCCH/PMCH/PRS transmissions in the secondary cell in the same subframe, and the UE is not expected to receive any other signals on the secondary cell in OFDM symbols that overlaps with the guard period or UpPTS in the primary cell.

For frame structure type 2, the higher-layer parameters for symbol-level resource reservation for BL/CE UEs (symbolBitmap1 and symbolBitmap2) do not apply to special subframes.

Figure 4.2-1: Frame structure type 2 (for 5 ms switch-point periodicity)

Table 4.2-1: Configuration of special subframe (lengths of DwPTS/GP/UpPTS)

Special subframe configuration	Normal cyclic prefix in downlink			Extended cyclic prefix in downlink
	DwPTS	UpPTS		DwPTS	UpPTS
		Normal cyclic prefix in uplink	Extended cyclic prefix in uplink		Normal cyclic prefix in uplink	Extended cyclic prefix in uplink
0
1
2
3
4
5
6
7
8				–	–	–
9				–	–	–
10				–	–	–

Table 4.2-2: Uplink-downlink configurations

Uplink-downlink configuration	Downlink-to-Uplink Switch-point periodicity	Subframe number
		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

4.3 Frame structure type 3

Frame structure type 3 is applicable to LAA secondary cell operation with normal cyclic prefix only. Each radio frame is long and consists of 20 slots of length, numbered from 0 to 19. A subframe is defined as two consecutive slots where subframe consists of slots and.

The 10 subframes within a radio frame are available for downlink or uplink transmissions. Downlink transmissions occupy one or more consecutive subframes, starting anywhere within a subframe and ending with the last subframe either fully occupied or following one of the DwPTS durations in Table 4.2-1. Uplink transmisisons occupy one or more consecutive subframes.