LTE; 5G; Physical layer procedures for shared spectrum channel access (3GPP TS 37.213 version 15.3.0 Release 15)

RTS/TSGR-0137213vf30

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Publication Date
13-Apr-2020
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Completion Date
14-Apr-2020
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ETSI TS 137 213 V15.3.0 (2020-04)
TECHNICAL SPECIFICATION
LTE;
5G;
Physical layer procedures for shared spectrum channel access
(3GPP TS 37.213 version 15.3.0 Release 15)
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3GPP TS 37.213 version 15.3.0 Release 15 1 ETSI TS 137 213 V15.3.0 (2020-04)
Reference
RTS/TSGR-0137213vf30
Keywords
5G,LTE
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ETSI
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3GPP TS 37.213 version 15.3.0 Release 15 2 ETSI TS 137 213 V15.3.0 (2020-04)
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provisions).

"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.

ETSI
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3GPP TS 37.213 version 15.3.0 Release 15 3 ETSI TS 137 213 V15.3.0 (2020-04)
Contents

Intellectual Property Rights ................................................................................................................................ 2

Legal Notice ....................................................................................................................................................... 2

Modal verbs terminology .................................................................................................................................... 2

Foreword ............................................................................................................................................................. 4

1 Scope ........................................................................................................................................................ 5

2 References ................................................................................................................................................ 5

3 Definitions, symbols and abbreviations ................................................................................................... 5

3.1 Definitions .......................................................................................................................................................... 5

3.2 Symbols .............................................................................................................................................................. 5

3.3 Abbreviations ..................................................................................................................................................... 6

4 Channel access procedure ........................................................................................................................ 6

4.1 Downlink channel access procedures ................................................................................................................. 6

4.1.1 Channel access procedure for transmission(s) including PDSCH/PDCCH/EPDCCH ................................. 6

4.1.2 Channel access procedure for transmissions including discovery signal transmission(s) and not

including PDSCH ......................................................................................................................................... 8

4.1.3 Channel access procedure for transmissions including PDCCH and not including PDSCH ........................ 8

4.1.4 Contention window adjustment procedure ................................................................................................... 8

4.1.5 Energy detection threshold adaptation procedure ......................................................................................... 9

4.1.6 Channel access procedure for transmission(s) on multiple carriers ............................................................ 10

4.1.6.1 Type A multi-carrier access procedures ................................................................................................ 10

4.1.6.1.1 Type A1 ........................................................................................................................................... 10

4.1.6.1.2 Type A2 ........................................................................................................................................... 10

4.1.6.2 Type B multi-carrier access procedure .................................................................................................. 11

4.1.6.2.1 Type B1 ........................................................................................................................................... 11

4.1.6.2.2 Type B2 ........................................................................................................................................... 11

4.2 Uplink channel access procedures .................................................................................................................... 11

4.2.1 Channel access procedure for uplink transmission(s) ................................................................................. 12

4.2.1.1 Type 1 UL channel access procedure .................................................................................................... 15

4.2.1.2 Type 2 UL channel access procedure .................................................................................................... 16

4.2.2 Contention window adjustment procedure ................................................................................................. 16

4.2.3 Energy detection threshold adaptation procedure ....................................................................................... 18

4.2.3.1 Default maximum energy detection threshold computation procedure ................................................. 18

Annex X (informative): Change history ............................................................................................... 20

History .............................................................................................................................................................. 21

ETSI
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3GPP TS 37.213 version 15.3.0 Release 15 4 ETSI TS 137 213 V15.3.0 (2020-04)
Foreword

This Technical Specification has been produced by the 3rd Generation Partnership Project (3GPP).

The contents of the present document are subject to continuing work within the TSG and may change following formal

TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an

identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.

y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,

updates, etc.

z the third digit is incremented when editorial only changes have been incorporated in the document.

ETSI
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3GPP TS 37.213 version 15.3.0 Release 15 5 ETSI TS 137 213 V15.3.0 (2020-04)
1 Scope

The present document specifies and establishes the characteristics of the physical layer procedures for shared spectrum

channel.
2 References

The following documents contain provisions which, through reference in this text, constitute provisions of the present

document.

- References are either specific (identified by date of publication, edition number, version number, etc.) or

non-specific.
- For a specific reference, subsequent revisions do not apply.

- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including

a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same

Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".

[2] 3GPP TS 36.104: "Evolved Universal Terrestrial Radio Access (E-UTRA); Base Station (BS)

radio transmission and reception".

[3] 3GPP TS 36.101: "Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment (UE)

radio transmission and reception".

[4] 3GPP TS 36.213: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer

procedures".
3 Definitions, symbols and abbreviations
3.1 Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 [1] apply. A term defined in the

present document takes precedence over the definition of the same term, if any, in TR 21.905 [1].

3.2 Symbols
For the purposes of the present document, the following symbols apply:
CW Contention window for a given priority class
CW Maximum contention window for a given priority class
max, p
CW Minimum contention window for a given priority class
min,p
T Maximum channel occupancy time for a given priority class
mcot,p
T Maximum Uplink channel occupancy time for a given priority class
ulmcot,p
X Energy detection threshold
Thresh
X Maximum energy detection threshold
Thresh_max
ETSI
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3GPP TS 37.213 version 15.3.0 Release 15 6 ETSI TS 137 213 V15.3.0 (2020-04)
3.3 Abbreviations

For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An

abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in

TR 21.905 [1].
AUL-DFI Autonomous UL Downlink feedback indication
COT Channel Occupancy Time
LAA Licensed Assisted Access
MCOT Maximum Channel Occupancy Time
4 Channel access procedure
4.1 Downlink channel access procedures

An eNB operating LAA Scell(s) shall perform the channel access procedures described in this clause for accessing the

channel(s) on which the LAA Scell(s) transmission(s) are performed.
4.1.1 Channel access procedure for transmission(s) including
PDSCH/PDCCH/EPDCCH

The eNB may transmit a transmission including PDSCH/PDCCH/EPDCCH on a carrier on which LAA Scell(s)

transmission(s) are performed , after first sensing the channel to be idle during the slot durations of a defer duration T ;

N N

and after the counter is zero in step 4. The counter is adjusted by sensing the channel for additional slot

duration(s) according to the steps below:

1) set N = N , where N is a random number uniformly distributed between 0 and CW , and go to step 4;

init init p
2) if N > 0 and the eNB chooses to decrement the counter, set N = N −1;

3) sense the channel for an additional slot duration, and if the additional slot duration is idle, go to step 4; else, go to

step 5;
N = 0
4) if , stop; else, go to step 2.

5) sense the channel until either a busy slot is detected within an additional defer duration T or all the slots of the

additional defer duration T are detected to be idle;

6) if the channel is sensed to be idle during all the slot durations of the additional defer duration T , go to step 4;

else, go to step 5;

If an eNB has not transmitted a transmission including PDSCH/PDCCH/EPDCCH on a carrier on which LAA Scell(s)

transmission(s) are performed after step 4 in the procedure above, the eNB may transmit a transmission including

PDSCH/PDCCH/EPDCCH on the carrier, if the channel is sensed to be idle at least in a slot duration T when the eNB

is ready to transmit PDSCH/PDCCH/EPDCCH and if the channel has been sensed to be idle during all the slot

durations of a defer duration T immediately before this transmission. If the channel has not been sensed to be idle in a

slot duration T when the eNB first senses the channel after it is ready to transmit or if the channel has been sensed to

be not idle during any of the slot durations of a defer duration immediately before this intended transmission, the

eNB proceeds to step 1 after sensing the channel to be idle during the slot durations of a defer duration .

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3GPP TS 37.213 version 15.3.0 Release 15 7 ETSI TS 137 213 V15.3.0 (2020-04)

The defer duration T consists of duration T = 16us immediately followed by m consecutive slot durations where

d f p
T T

each slot duration is T = 9us , and includes an idle slot duration T at start of ;

f f
sl sl

A slot duration T is considered to be idle if the eNB senses the channel during the slot duration, and the power

4us

detected by the eNB for at least within the slot duration is less than energy detection threshold X .

Thresh
Otherwise, the slot duration T is considered to be busy.

CW ≤ CW ≤ CW is the contention window. CW adjustment is described in clause 4.1.4.

min,p p max,p p
CW and CW are chosen before step 1 of the procedure above.
min,p max,p

m , CW , and CW are based on channel access priority class associated with the eNB transmission, as

p min,p max,p
shown in Table 4.1.1-1.
X adjustment is described in clause 4.1. 5
Thresh

If the eNB transmits discovery signal transmission(s) not including PDSCH/PDCCH/EPDCCH when N > 0 in the

procedure above, the eNB shall not decrement N during the slot duration(s) overlapping with discovery signal

transmission.

The eNB shall not continuously transmit on a carrier on which the LAA Scell(s) transmission(s) are performed, for a

period exceedingT as given in Table 4.1.1-1.
mcot,p

For p = 3 and p = 4 , if the absence of any other technology sharing the carrier can be guaranteed on a long term

basis (e.g. by level of regulation), T =10ms , otherwise, T = 8ms .
mcot,p mcot,p
Table 4.1.1-1: Channel Access Priority Class
Channel
Access
m CW CW T allowed CW sizes
p min,p max,p mcot,p p
Priority Class (
1 1 3 7 2 ms {3,7}
2 1 7 15 3 ms {7,15}
3 3 15 63 8 or 10 ms {15,31,63}
4 7 15 1023 8 or 10 ms {15,31,63,127,255,511,1023}

For LAA operation in Japan, if the eNB has transmitted a transmission after N = 0 in step 4 of the procedure above,

the eNB may transmit the next continuous transmission, for duration of maximum T =4 ms, immediately after sensing

the channel to be idle for at least a sensing interval of T =34us and if the total sensing and transmission time is not

more than 1000 ⋅ T + T / T −1 ⋅ T µsec. T consists of duration T = 16us immediately followed by

 
mcot mcot j js js f
T T

two slot durations T = 9us each and includes an idle slot duration T at start of . The channel is considered

sl f sl f

to be idle for T if it is sensed to be idle during the during the slot durations of T .

js js
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3GPP TS 37.213 version 15.3.0 Release 15 8 ETSI TS 137 213 V15.3.0 (2020-04)
4.1.2 Channel access procedure for transmissions including discovery
signal transmission(s) and not including PDSCH

An eNB may transmit a transmission including discovery signal but not including PDSCH on a carrier on which LAA

Scell(s) transmission(s) are performed immediately after sensing the channel to be idle for at least a sensing interval

T = 25us and if the duration of the transmission is less than 1 ms. T consists of a duration T = 16us

drs drs f

immediately followed by one slot duration T = 9us and T includes an idle slot duration T at start of T . The

sl f sl f

channel is considered to be idle for T if it is sensed to be idle during the slot durations of T .

drs drs
4.1.3 Channel access procedure for transmissions including PDCCH and
not including PDSCH

If 'COT sharing indication' in AUL-UCI in subframe n indicates '1', an eNB may transmit a transmission in subframe

n+X, where X is subframeOffsetCOT-Sharing, including PDCCH but not including PDSCH on the same carrier

immediately after sensing the channel to be idle for at least a sensing interval T = 25us , if the duration of the

pdcch

PDCCH is less than or equal to two OFDM symbols length and it shall contain at least AUL-DFI or UL grant to the UE

from which the PUSCH transmission indicating COT sharing was received. T consists of a duration T =16us

pdcch f

immediately followed by one slot duration T = 9us and includes an idle slot duration T at start of . The

T T
sl f sl f

channel is considered to be idle for T if it is sensed to be idle during the slot durations of T .

pdcch pdcch
4.1.4 Contention window adjustment procedure

If the eNB transmits transmissions including PDSCH that are associated with channel access priority class p on a

carrier, the eNB maintains the contention window value CW and adjusts CW before step 1 of the procedure

p p
described in clause 4.1.1 for those transmissions using the following steps:
1) for every priority class p ∈{1, 2, 3, 4} set CW = CW
p min,p

2) if at least Z = 80% of HARQ-ACK values corresponding to PDSCH transmission(s) in reference subframe k

are determined as NACK, increase for every priority class p ∈{1, 2, 3, 4} to the next higher allowed

value and remain in step 2; otherwise, go to step 1.

Reference subframe is the starting subframe of the most recent transmission on the carrier made by the eNB, for

which at least some HARQ-ACK feedback is expected to be available.

The eNB shall adjust the value of CW for every priority class p ∈ 1, 2, 3, 4 based on a given reference subframe

{ }
k only once.
If CW = CW , the next higher allowed value for adjusting CW is CW .
p max,p p max,p
For determining Z ,

- if the eNB transmission(s) for which HARQ-ACK feedback is available start in the second slot of subframe k ,

HARQ-ACK values corresponding to PDSCH transmission(s) in subframe k +1are also used in addition to the

HARQ-ACK values corresponding to PDSCH transmission(s) in subframe k .

- if the HARQ-ACK values correspond to PDSCH transmission(s) on an LAA SCell that are assigned by

(E)PDCCH transmitted on the same LAA SCell,

- if no HARQ-ACK feedback is detected for a PDSCH transmission by the eNB, or if the eNB detects 'DTX',

'NACK/DTX' or 'any' state, it is counted as NACK.
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3GPP TS 37.213 version 15.3.0 Release 15 9 ETSI TS 137 213 V15.3.0 (2020-04)

- if the HARQ-ACK values correspond to PDSCH transmission(s) on an LAA SCell that are assigned by

(E)PDCCH transmitted on another serving cell,

- if the HARQ-ACK feedback for a PDSCH transmission is detected by the eNB, 'NACK/DTX' or 'any' state is

counted as NACK, and 'DTX' state is ignored.
- if no HARQ-ACK feedback is detected for a PDSCH transmission by the eNB

- if PUCCH format 1b with channel selection is expected to be used by the UE, 'NACK/DTX' state

corresponding to 'no transmission' as described in clauses 10.1.2.2.1, 10.1.3.1 and 10.1.3.2.1 is counted as

NACK, and 'DTX' state corresponding to 'no transmission' is ignored in [4].
- Otherwise, the HARQ-ACK for the PDSCH transmission is ignored.

- if a PDSCH transmission has two codewords, the HARQ-ACK value of each codeword is considered separately

- bundled HARQ-ACK across M subframes is considered as M HARQ-ACK responses.

If the eNB transmits transmissions including PDCCH/EPDCCH with DCI format 0A/0B/4A/4B and not including

PDSCH that are associated with channel access priority class p on a channel starting from time t , the eNB maintains

the contention window value CW and adjusts CW before step 1 of the procedure described in clause 4.1.1 for those

p p
transmissions using the following steps:
1) for every priority class p ∈ 1, 2, 3, 4 set CW = CW
{ }
p min,p

2) if less than 10% of the UL transport blocks scheduled by the eNB using Type 2 channel access procedure

(described in clause 4.2.1.2) in the time interval between t and t + T have been received successfully,

0 0 CO

increase CW for every priority class p ∈{1, 2, 3, 4} to the next higher allowed value and remain in step 2;

otherwise, go to step 1.
where T is computed as described in clause 4.2.1.

If the CW = CW is consecutively used K times for generation of N ,CW is reset to CW only for

p max,p init p min,p
p CW = CW

that priority class for which is consecutively used K times for generation of N . K is

p max,p
init

selected by eNB from the set of values {1, 2, …,8} for each priority class p ∈ 1, 2, 3, 4 .

{ }
4.1.5 Energy detection threshold adaptation procedure

An eNB accessing a carrier on which LAA Scell(s) transmission(s) are performed, shall set the energy detection

threshold ( X ) to be less than or equal to the maximum energy detection threshold X .

Thresh Thresh_max
is determined as follows:
Thresh_max

- If the absence of any other technology sharing the carrier can be guaranteed on a long term basis (e.g. by level of

regulation) then:
T +10dB,
max
- X = min
Thresh_max
r

- X is Maximum energy detection threshold defined by regulatory requirements in dBm when such

requirements are defined, otherwise X=+Td10 B
r max
- Otherwise,
ETSI
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3GPP TS 37.213 version 15.3.0 Release 15 10 ETSI TS 137 213 V15.3.0 (2020-04)
− 72 +10 ⋅ log10(BWMHz / 20MHz) dBm,
 
 
- X = max T ,
 
 
Thres _ max max
min
 
 
T − T +()P +10 ⋅ log10(BWMHz / 20MHz)− P
 max A H TX 
 
- Where:
- T = 10dB for transmission(s) including PDSCH;

- T = 5dB for transmissions including discovery signal transmission(s) and not including PDSCH;

- P = 23 dBm;
- P is the set maximum eNB output power in dBm for the carrier;

- eNB uses the set maximum transmission power over a single carrier irrespective of whether single carrier

or multi-carrier transmission is employed
- T (dBm)=⋅10 log10 3.16228⋅10 (mW / MHz)⋅ BWMHz (MHz) ;
max
- BWMHz is the single carrier bandwidth in MHz.
4.1.6 Channel access procedure for transmission(s) on multiple carriers

An eNB can access multiple carriers on which LAA Scell(s) transmission(s) are performed, according to one of the

Type A or Type B procedures described in this clause.
4.1.6.1 Type A multi-carrier access procedures

The eNB shall perform channel access on each carrier c ∈C , according to the procedures described in clause 4.1.1,

where C is a set of carriers on which the eNB intends to transmit, and i = 0,1, Kq −1 , and q is the number of carriers

on which the eNB intends to transmit.

The counter N described in clause 4.1.1 is determined for each carrier c and is denoted as N . N is maintained

i c c
i i
according to Clause 4.1.6.1.1 or 4.1.6.1.2.
4.1.6.1.1 Type A1

Counter N as described in clause 4.1.1 is independently determined for each carrier c and is denoted as N .

i c

If the absence of any other technology sharing the carrier cannot be guaranteed on a long term basis (e.g. by level of

c ∈C c ≠ c

regulation), when the eNB ceases transmission on any one carrier , for each carrier , the eNB can

j i j

resume decrementing N when idle slots are detected either after waiting for a duration of 4 ⋅T , or after

c sl
reinitialising N .
4.1.6.1.2 Type A2

Counter N is determined as described in clause 4.1.1 for carrier c ∈C , and is denoted as N , where c is the

j c j
carrier that has the largest value. For each carrier c , N = N .
p i c c
i j

When the eNB ceases transmission on any one carrier for which N is determined, the eNB shall reinitialise N for

c c
i i
all carriers.
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3GPP TS 37.213 version 15.3.0 Release 15 11 ETSI TS 137 213 V15.3.0 (2020-04)
4.1.6.2 Type B multi-carrier access procedure
c ∈C
A carrier is selected by the eNB as follows

- the eNB selects c by uniformly randomly choosing c from C before each transmission on multiple carriers

j j
c ∈C , or
- the eNB selects c no more frequently than once every 1 second,

where C is a set of carriers on which the eNB intends to transmit, i = 0,1,Kq −1, and q is the number of carriers on

which the eNB intends to transmit.
To transmit on carrier

- the eNB shall perform channel access on carrier c according to the procedures described in clause 4.1.1 with

the modifications described in clause 4.1.6.2.1 or 4.1.6.2.2.
To transmit on carrier c ≠ c , c ∈C
i j i

- for each carrier c , the eNB shall sense the carrier c for at least a sensing interval T = 25us immediately

i i mc

before the transmitting on carrier c , and the eNB may transmit on carrier c immediately after sensing the

j i

carrier c to be idle for at least the sensing interval T . The carrier c is considered to be idle for T if the

i mc i mc

channel is sensed to be idle during all the time durations in which such idle sensing is performed on the carrier

c in given interval T .
j mc
c ≠ c T

The eNB shall not continuously transmit on a carrier , c ∈C , for a period exceeding as given in Table

i j mcot,p

4.1.1-1, where the value of T is determined using the channel access parameters used for carrier c .

mcot,p j
4.1.6.2.1 Type B1
A single CW value is maintained for the set of carriers C .

For determining CW for channel access on carrier c , step 2 of the procedure described in clause 4.1.4 is modified

p j
as follows

- if at least Z = 80% of HARQ-ACK values corresponding to PDSCH transmission(s) in reference subframe k

of all carriers c ∈C are determined as NACK, increase CW for each priority class p ∈ 1, 2, 3, 4 to the

{ }
i p
next higher allowed value; otherwise, go to step 1.
4.1.6.2.2 Type B2

A CW value is maintained independently for each carrier c ∈C using the procedure described in clause 4.1.4.

p i
c CW c ∈C c

For determining N for carrier , value of carrier is used, where is the carrier with largest

init j p j1 j1
CW among all carriers in set C .
4.2 Uplink channel access procedures

A UE and a eNB scheduling UL transmission(s) for the UE shall perform the procedures described in this clause for the

UE to access the channel(s) on which the LAA Scell(s) transmission(s) are performed.

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...

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