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TECHNICAL SPECIFICATION
LTE;
Physical layer procedures for
shared spectrum channel access
(3GPP TS 37.213 version 15.0.0 Release 15)
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3GPP TS 37.213 version 15.0.0 Release 15 1 ETSI TS 137 213 V15.0.0 (2018-07)
Reference
DTS/TSGR-0137213vf00
Keywords
LTE
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3GPP TS 37.213 version 15.0.0 Release 15 2 ETSI TS 137 213 V15.0.0 (2018-07)
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Foreword
This Technical Specification (TS) has been produced by ETSI 3rd Generation Partnership Project (3GPP).
The present document may refer to technical specifications or reports using their 3GPP identities, UMTS identities or
GSM identities. These should be interpreted as being references to the corresponding ETSI deliverables.
The cross reference between GSM, UMTS, 3GPP and ETSI identities can be found under
.
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
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 15.0.0 Release 15 3 ETSI TS 137 213 V15.0.0 (2018-07)
Contents
Intellectual Property Rights . 2
Foreword . 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 . 7
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 . 10
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) . 11
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
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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.
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3GPP TS 37.213 version 15.0.0 Release 15 5 ETSI TS 137 213 V15.0.0 (2018-07)
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 3GPP TR 21.905 [1] apply. A term defined
in the present document takes precedence over the definition of the same term, if any, in 3GPP 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
p
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
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3.3 Abbreviations
For the purposes of the present document, the abbreviations given in 3GPP 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
3GPP 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 sub 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 ;
d
and after the counter N is zero in step 4. The counter N 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;
4) if N = 0 , 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
d
additional defer duration T are detected to be idle;
d
6) if the channel is sensed to be idle during all the slot durations of the additional defer duration T , go to step 4;
d
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
sl
is ready to transmit PDSCH/PDCCH/EPDCCH and if the channel has been sensed to be idle during all the slot
T
durations of a defer duration immediately before this transmission. If the channel has not been sensed to be idle in a
d
slot duration T when the eNB first senses the channel after it is ready to transmit or if the channel has been sensed to
sl
be not idle during any of the slot durations of a defer duration T immediately before this intended transmission, the
d
eNB proceeds to step 1 after sensing the channel to be idle during the slot durations of a defer duration T .
d
The defer duration T consists of duration T = 16us immediately followed by m consecutive slot durations where
d f p
each slot duration is T = 9us , and T includes an idle slot duration T at start of T ;
sl f sl f
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A slot duration T is considered to be idle if the eNB senses the channel during the slot duration, and the power
sl
detected by the eNB for at least 4us within the slot duration is less than energy detection threshold X .
Thresh
Otherwise, the slot duration T is considered to be busy.
sl
CW ≤ CW ≤ CW is the contention window. CW adjustment is described in sub clause 4.1.4.
min,p p max,p p
CW CW
and 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 sub clause 4.1.4
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
T = 10ms T = 8ms
basis (e.g. by level of regulation), , otherwise, .
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 (
p )
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
j
the channel to be idle for at least a sensing interval of T =34us and if the total sensing and transmission time is not
js
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 = 9us each and T includes an idle slot duration T at start of T . The channel is considered
two slot durations
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
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 = 16us
T = 25us and if the duration of the transmission is less than 1 ms. T consists of a duration
f
drs drs
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T T
immediately followed by one slot duration T = 9us and includes an idle slot duration T at start of . 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 a PUSCH transmission indicates COT sharing, an eNB may transmit a transmission 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 is less than or equal to two OFDM symbols length and it shall contain at
pdcch
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 immediately followed by one slot duration T = 9us and T includes an idle slot
pdcch f sl f
duration T at start of . The channel is considered to be idle for T if it is sensed to be idle during the slot
T
sl f pdcch
durations of T .
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
CW CW
carrier, the eNB maintains the contention window value and adjusts before step 1 of the procedure
p p
described in sub 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
Z = 80% k
2) if at least of HARQ-ACK values corresponding to PDSCH transmission(s) in reference subframe
CW
are determined as NACK, increase for every priority class p ∈{1,2,3,4} to the next higher allowed
p
value and remain in step 2; otherwise, go to step 1.
Reference subframe k 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
{ }
p
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.
- 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
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- 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 Subclauses 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
0
the contention window value CW and adjusts CW before step 1 of the procedure described in sub clause 4.1.1 for
p p
those 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 sub clause 4.2.1.2) in the time interval between t and t + T have been received successfully,
0 0 CO
CW
increase for every priority class p ∈{1,2,3,4} to the next higher allowed value and remain in step 2;
p
otherwise, go to step 1.
where T is computed as described in Subclause 4.2.1.
CO
CW = CW CW CW
If the is consecutively used K times for generation of N , is reset to only for
p max,p init p min,p
that priority class p for which CW = CW 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
X 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
X
r
- X is Maximum energy detection threshold defined by regulatory requirements in dBm when such
r
requirements are defined, otherwise X=+Td10 B
r max
- Otherwise,
− 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;
A
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- T = 5dB for transmissions including discovery signal transmission(s) and not including PDSCH;
A
- P = 23 dBm;
H
- P is the set maximum eNB output power in dBm for the carrier;
TX
- eNB uses the set maximum transmission power over a single carrier irrespective of whether single carrier
or multi-carrier transmission is employed
−8
- 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 Subclause.
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 Subclause
i
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 Subclause 4.1.1 is determined for each carrier c and is denoted as N . N is
i c c
i i
maintained according to Subclause 4.1.5.1.1or 4.1.5.1.2.
4.1.6.1.1 Type A1
N N
Counter as described in Subclause 4.1.1 is independently determined for each carrier c and is denoted as .
i c
i
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
i
reinitialising N .
c
i
4.1.6.1.2 Type A2
Counter N is determined as described in Subclause 4.1.1 for carrier c ∈C , and is denoted as N , where c is the
j c j
j
carrier that has the largest CW 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.
4.1.6.2 Type B multi-carrier access procedure
A carrier c ∈C is selected by the eNB as follows
j
- the eNB selects c by uniformly randomly choosing c from C before each transmission on multiple carriers
j j
c ∈C , or
i
- the eNB selects c no more frequently than once every 1 second,
j
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C q
where is a set of carriers on which the eNB intends to transmit, i = 0,1,Kq −1, and is the number of carriers on
which the eNB intends to transmit.
c
To transmit on carrier
j
- the eNB shall perform channel access on carrier c according to the procedures described in Subclause 4.1.1
j
with the modifications described in 4.1.5.2.1 or 4.1.5.2.2.
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
The eNB shall not continuously transmit on a carrier c ≠ c , c ∈C , for a period exceedingT as given in Table
i j i 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 .
p
For determining CW for channel access on carrier c , step 2 of the procedure described in sub clause 4.1.3 is
p j
modified as follows
Z = 80% k
- if at least of HARQ-ACK values corresponding to PDSCH transmission(s) in reference subframe
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 Subclause 4.1.3.
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 .
p
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 sub clause for
the UE to access the channel(s) on which the LAA Scell(s) transmission(s) are performed.
4.2.1 Channel access procedure for uplink transmission(s)
The UE can access a carrier on which
...