Transmtting PPDU
A method for transmitting a physical layer protocol data unit (PPDU) and a device using the same are provided. The device receives a trigger frame for requesting a transmission of a response PPDU and transmits the response PPDU. A duration of the response PPDU is calculated based on a duration of the trigger frame.
1. A method for transmitting a physical layer protocol data unit (PPDU) in a wireless local area network, the method being performed by an access point (AP), the method comprising:
transmitting a trigger frame for requesting a transmission of a response PPDU to a station, the trigger frame including a first length field and a resource allocation field, the resource allocation field indicating a resource allocated to the transmission of the response PPDU,
wherein the first length field in the trigger frame is set to a value given by:
LENGTH
=
⌈
TXTIME
-
SignalExtension
-
20
4
⌉
×
3
-
3
-
m
where TXTIME is a transmission time of the responsive PPDU,
SignalExtension is 0 microseconds (μs) or 6 μs, and m is a value satisfying LENGTH mod 3=1;
receiving the response PPDU as a response to the trigger frame from the station, the response PPDU including an L-SIG field, a repeated L-SIG field, an HE-SIG-A field, an HE-STF field and an HE-LTF field;
checking a cyclic redundancy check (CRC) of the HE-SIG-A field in the response PPDU; and
if the CRC of the HE-SIG-A field is valid and a reserved HE-SIG-A indication is not indicated, maintaining a clear channel assessment (CCA) indication as busy during a RXTIME1 defined by:
RXTIME1=20 +T HE-PREAMBLE +N SYM T SYM +T PE +SignalExtension
where:
T HE-PREAMBLE =T RL-SIG +T HE-SIG-A +T HE-STF-T +N HE-LTF T HE-LTF,SYM ,
T RL-SIG is a duration of the repeated L-SIG field,
T HE-SIG-A is a duration of the HE-SIG-A field,
T HE-STF-T is a duration of the HE-STF field,
N HE-LTF is the number of orthogonal frequency division multiplexing (OFDM) symbols in the HE-LTF field,
T HE-LTF,SYM is a duration of each OFDM symbol in the HE-LTF field,
T SYM is an OFDM symbol interval,
N
SYM
=
⌊
(
LENGTH
+
m
+
3
3
×
4
-
T
HE
-
PREAMBLE
)
/
T
SYM
⌋
-
b
PE
-
Disambiguity
,
T
PE
=
⌊
{
(
LENGTH
+
m
+
3
3
×
4
-
T
HE
-
PREAMBLE
)
-
N
SYM
T
SYM
}
/
4
⌋
×
4
,
and b PE-Disambiguity is a value obtained from the trigger frame.
2. The method of claim 1 , further comprising:
if the reserved HE-SIG-A indication is indicated, maintaining a CCA indication as busy during a RXTIME2 defined by:
RXTIME
2
=
⌈
LENGTH
+
3
3
⌉
·
4
+
20
+
SignalExtension
.
3. The method of claim 2 , further comprising:
if the CRC of the HE-SIG-A field is invalid, maintaining a CCA indication as busy during the RXTIME2.
4. The method of claim 1 , wherein m is a value further satisfying following condition:
⌈
LENGTH
+
3
3
⌉
·
4
+
20
+
SignalExtension
-
TXTIME
<
4
μs
.
5. The method of claim 1 , wherein the response PPDU further includes a second length field being set to the value of LENGTH.
6. A device for transmitting a physical layer protocol data unit (PPDU) in a wireless local area network, the device comprising:
a processor; and
a memory operatively coupled with the processor and configured to store instructions that, when executed by the processor, cause the device to perform functions comprising:
transmitting a trigger frame for requesting a transmission of a response PPDU to a station, the trigger frame including a first length field and a resource allocation field, the resource allocation field indicating a resource allocated to the transmission of the response PPDU,
wherein the first length field in the trigger frame is set to a value given by:
LENGTH
=
⌈
TXTIME
-
SignalExtenion
-
20
4
⌉
×
3
-
3
-
m
where TXTIME is a transmission time of the responsive PPDU,
SignalExtension is 0 microseconds (μs) or 6 μs, and m is a value satisfying LENGTH mod 3=1;
receiving the response PPDU as a response to the trigger frame from the station, the response PPDU including an L-SIG field, a repeated L-SIG field, an HE-SIG-A field, an HE-STF field and an HE-LTF field;
checking a cyclic redundancy check (CRC) of the HE-SIG-A field in the response PPDU; and
if the CRC of the HE-SIG-A field is valid and a reserved HE-SIG-A indication is not indicated, maintaining a clear channel assessment (CCA) indication as busy during a RXTIME1 defined by:
RXTIME1=20+ T HE-PREAMBLE +N SYM T SYM +T PE +SignalExtension
where:
T HE-PREAMBLE =T RL-SIG +T HE-SIG-A +T HE-STF-T +N HE-LTF T HE-LTF,SYM ,
T RL-SIG is a duration of the repeated L-SIG field,
T HE-SIG-A is a duration of the HE-SIG-A field,
T HE-STF-T is a duration of the HE-STF field,
N HE-LTF is the number of orthogonal frequency division multiplexing (OFDM) symbols in the HE-LTF field,
T HE-LTF,SYM is a duration of each OFDM symbol in the HE-LTF field,
T SYM is an OFDM symbol interval,
N
SYM
=
⌊
(
LENGTH
+
m
+
3
3
×
4
-
T
HE
-
PREAMBLE
)
/
T
SYM
⌋
-
b
PE
-
Disambiguity
,
T
PE
=
⌊
{
(
LEGNTH
+
m
+
3
3
×
4
-
T
HE
-
PREAMBLE
)
-
N
SYM
T
SYM
}
/
4
⌋
×
4
,
and b PE-Disambiguity is a value obtained from the trigger frame.
7. The device of claim 6 , wherein the functions further comprise:
if the reserved HE-SIG-A indication is indicated, maintaining a CCA indication as busy during a RXTIME2 defined by:
RXTIME
2
=
⌈
LENGTH
+
3
3
⌉
·
4
+
20
+
SignalExtension
.
8. The device of claim 7 , wherein the functions further comprise:
if the CRC of the HE-SIG-A field is invalid, maintaining a CCA indication as busy during the RXTIME2.
9. The device of claim 6 , wherein m is a value further satisfying following condition:
⌈
LENGTH
+
3
3
⌉
·
4
+
20
+
SignalExtension
-
TXTIME
<
4
μs
.
10. The device of claim 6 , wherein the response PPDU further includes a second length field being set to the value of LENGTH.