System and method for OFDMA tone allocation in next generation Wi-Fi networks
An orthogonal frequency division multiple access (OFDMA) frame tone allocation includes a 256 tone payload consisting of 228 data and pilot tones and 28 null tones. The 28 null tones consist of guard tones and at least one direct current (DC) tone. In one example, the 256 tone payload consists of 224 data tones, 4 common pilot tones, and 28 null tones. In another example, the 256 tone payload consists of 222 data tones, 6 common pilot tones, and 28 null tones. In yet another example, the 256 tone payload may consist of 220 data tones, 8 common pilot tones, and 28 null tones. The OFDMA frame may be a downlink OFDMA frame or an uplink OFDMA frame.
1. A method for receiving an uplink frame in a wireless communication system, the method comprising:
receiving, by an access point (AP), an uplink orthogonal frequency division multiple access (OFDMA) frame over a channel spanning at least 20 megahertz (MHz) in the frequency domain, wherein the uplink OFDMA frame comprises resource units (RUs) communicated by different mobile devices, wherein each of the RUs in the uplink OFDMA frame carries at least two pilot tones; and
performing residual carrier frequency offset estimation on the uplink OFDMA frame by tracking phase components of the pilot tones carried by each of the RUs.
2. The method of claim 1 , wherein the pilot tones of a first RU in the uplink OFDMA frame are separate from the pilot tones of a second RU in the OFDMA frame.
3. The method of claim 1 , wherein the RUs include a first RU having a first number of pilot tones, and a second RU having a second number of pilot tones different from the first number of pilot tones.
4. The method of claim 1 , wherein the uplink OFDMA frame further includes data tones, and wherein at least some of the data tones and pilot tones are partitioned into a first RU having a first number of tones or a second RU having a second number of tones, the second number being double the first number.
5. The method of claim 1 , wherein the uplink OFDMA frame has a 256-tone payload over a 20 MHz channel, including data tones, null tones, and the pilot tones.
6. The method of claim 1 , wherein performing residual carrier frequency offset estimation comprises performing residual carrier frequency offset estimation according to the formula:
ɛ
^
=
θ
^
n
2
π
,
where
θ
^
n
=
∠
[
∑
k
=
pilots
Y
n
,
k
(
H
k
P
n
,
k
)
*
]
=
∠
[
e
j
2
π
n
ɛ
∑
k
=
pilots
H
k
2
]
where Y is the received signal, n is the symbol index, k is the subcarrier index where pilots are located, H is the channel, P is the pilot, and ε is the residual carrier frequency offset.
7. An apparatus comprising:
a processor; and
a computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
receive an uplink orthogonal frequency division multiple access (OFDMA) frame over a channel spanning at least 20 megahertz (MHz) in the frequency domain, wherein the uplink OFDMA frame comprises resource units (RUs) communicated by different mobile devices, wherein each of the RUs in the uplink OFDMA frame carries at least two pilot tones; and
perform residual carrier frequency offset estimation on the uplink OFDMA frame by tracking phase components of the pilot tones carried by the RUs.
8. The apparatus of claim 7 , wherein the RUs include a first RU having a first number of pilot tones, and a second RU having a second number of pilot tones different from the first number of pilot tones.
9. The apparatus of claim 7 , wherein the uplink OFDMA frame further includes data tones, and wherein at least some of the data tones and pilot tones are partitioned into a first RU having a first number of tones or a second RU having a second number of tones, the second number being double the first number.
10. The apparatus of claim 7 , wherein the uplink OFDMA frame has a 256-tone payload over a 20 MHz channel, including data tones, null tones, and the pilot tones.
11. The apparatus of claim 5 , wherein performing residual carrier frequency offset estimation comprises performing residual carrier frequency offset estimation according to the formula:
ɛ
^
=
θ
^
n
2
π
,
where
θ
^
n
=
∠
[
∑
k
=
pilots
Y
n
,
k
(
H
k
P
n
,
k
)
*
]
=
∠
[
e
j
2
π
n
ɛ
∑
k
=
pilots
H
k
2
]
where Y is the received signal, n is the symbol index, k is the subcarrier index where pilots are located, H is the channel, P is the pilot, and ε is the residual carrier frequency offset.
12. A method for transmitting an uplink signal in a wireless network, the method comprising:
transmitting, by a first mobile device, a first resource unit (RU) in an uplink orthogonal frequency division multiple access (OFDMA) frame, the OFDMA frame carrying the first RU and at least a second RU transmitted by a second mobile device, wherein the first RU carries at least two pilot tones and the second RU carries at least two pilot tones that are separate from the at least two pilot tones carried by the first RU, wherein the at least two pilot tones carried by the first RU and the at least two pilot tones carried by the second RU are used by an access point to perform carrier frequency offset estimation on the uplink OFDMA frame.
13. The method of claim 12 , wherein the access point performs carrier frequency offset estimation on the uplink OFDMA frame by tracking phase components of the at least two pilot tones carried by the first RU and the at least two pilot tones carried by the second RU.
14. The method of claim 12 , wherein the RUs include a first RU having a first number of pilot tones, and a second RU having a second number of pilot tones different from the first number of pilot tones.
15. The method of claim 12 , wherein the uplink OFDMA frame further includes data tones, and wherein at least some of the data tones and pilot tones are partitioned into a first RU having a first number of tones or a second RU having a second number of tones, the second number being double the first number.
16. The method of claim 12 , wherein the uplink OFDMA frame has a 256-tone payload over a 20 MHz channel, including data tones, null tones, and the pilot tones.
17. The method of claim 12 , wherein performing residual carrier frequency offset estimation comprises performing residual carrier frequency offset estimation according to the formula:
ɛ
^
=
θ
^
n
2
π
,
where
θ
^
n
=
∠
[
∑
k
=
pilots
Y
n
,
k
(
H
k
P
n
,
k
)
*
]
=
∠
[
e
j
2
π
n
ɛ
∑
k
=
pilots
H
k
2
]
where Y is the received signal, n is the symbol index, k is the subcarrier index where pilots are located, H is the channel, P is the pilot, and ε is the residual carrier frequency offset.
18. A first mobile device comprising:
a processor; and
a computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
transmit a first resource unit (RU) in an uplink orthogonal frequency division multiple access (OFDMA) frame, the OFDMA frame carrying the first RU and at least a second RU transmitted by a second mobile device, wherein the first RU carries at least two pilot tones and the second RU carries at least two pilot tones that are separate from the at least two pilot tones carried by the first RU, wherein the at least two pilot tones carried by the first RU and the at least two pilot tones carried by the second RU are used by an access point to perform carrier frequency offset estimation on the uplink OFDMA frame.
19. The first mobile device of claim 18 , wherein the access point performs carrier frequency offset estimation on the uplink OFDMA frame by tracking phase components of the at least two pilot tones carried by the first RU and the at least two pilot tones carried by the second RU.
20. The first mobile device of claim 18 , wherein the RUs include a first RU having a first number of pilot tones, and a second RU having a second number of pilot tones different from the first number of pilot tones.
21. The first mobile device of claim 18 , wherein the uplink OFDMA frame further includes data tones, and wherein at least some of the data tones and pilot tones are partitioned into a first RU having a first number of tones or a second RU having a second number of tones, the second number being double the first number.
22. The first mobile device of claim 18 , wherein the uplink OFDMA frame has a 256-tone payload over a 20 MHz channel, including data tones, null tones, and the pilot tones.
23. The first mobile device of claim 18 , wherein performing residual carrier frequency offset estimation comprises performing residual carrier frequency offset estimation according to the formula:
ɛ
^
=
θ
^
n
2
π
,
where
θ
^
n
=
∠
[
∑
k
=
pilots
Y
n
,
k
(
H
k
P
n
,
k
)
*
]
=
∠
[
e
j
2
π
n
ɛ
∑
k
=
pilots
H
k
2
]
where Y is the received signal, n is the symbol index, k is the subcarrier index where pilots are located, H is the channel, P is the pilot, and ε is the residual carrier frequency offset.