Method and device for transmitting ACK PPDU

1. A method of communicating in a wireless local area network, the method comprising:

receiving a plurality of uplink (UL) physical layer protocol data units (PPDUs) from a plurality of stations;

transmitting, when a first type of acknowledgment is selected, a broadcast acknowledgement (ACK) frame to the plurality of stations, the broadcast ACK frame comprising a first block acknowledgement; and

transmitting, when a second type of acknowledgment is selected, an acknowledgment physical layer protocol data unit (ACK PPDU), the ACK PPDU comprising a first signal field, a second signal field and a data portion,

wherein the first signal field comprises bandwidth information, the bandwidth information indicating a bandwidth over which the ACK PPDU is transmitted,

wherein the data portion comprises a second block acknowledgement,

wherein the first signal field having a first rotated phase over at least one first subcarrier group, each first subcarrier group having bandwidth of 20 MHz,

the second signal field having a second rotated phase over a plurality of second subcarrier groups, each second subcarrier group having bandwidth that is less than 20 MHz;

wherein the first rotated phase is realized by multiplying a first multiplication value to the at least one first subcarrier group, the first multiplication value selected from +1, −1 and +j wherein +1, −1, and +j are rotational multipliers, and

wherein the second rotated phase is realized by multiplying a second multiplication value to the at least one subcarrier group of the plurality of second subcarrier groups, the second multiplication value selected from +1 and −1.

2. The method of claim 1 wherein each of the plurality of UL PPDUs includes at least one duration field, and all duration fields in all of the plurality of UL PPDUs have a same value.

3. The method of claim 1 wherein the first signal field is associated with a first fast Fourier transform (FFT) size and the data portion is associated with a second FFT size; and wherein the second FFT size is four times the first FFT size.

4. The method of claim 3

wherein the first FFT size is 64 and the second FFT size is 256 when the operating bandwidth is 20 MHz;

wherein the first FFT size is 128 and the second FFT size is 512 when the operating bandwidth is 40 MHz;

wherein the first FFT size is 256 and the second FFT size is 1024 when the operating bandwidth is 80 MHz; and

wherein the first FFT size is 512 and the second FFT size is 2048 when the operating bandwidth is 160 MHz.

5. A device for communicating in a wireless local area network, the device comprising:

a radio frequency module configured to transmit and receive radio signals;

a processor operatively coupled with the radio frequency module; and

memory disposed to said processor, said memory including instructions, when executed by said processor, causes the processor to:

process a plurality of uplink (UL) physical layer protocol data units (PPDUs) received from a plurality of stations;

cause the radio frequency module to transmit, when a first type of acknowledgment is selected, a broadcast acknowledgement (ACK) frame to the plurality of stations, the broadcast ACK frame comprising a first block acknowledgement; and

cause the radio frequency module to transmit, when a second type of acknowledgment is selected, an acknowledgment physical layer protocol data unit (ACK PPDU), the ACK PPDU comprising a first signal field, a second signal field and a data portion,

wherein the first signal field comprises bandwidth information, the bandwidth information indicating a bandwidth over which the ACK PPDU is transmitted,

wherein the data portion comprises a second block acknowledgement,

wherein the first signal field has a first rotated phase over at least one first subcarrier group, each first subcarrier group having bandwidth of 20 MHz,

the second signal field has a second rotated phase over a plurality of second subcarrier groups, each second subcarrier group having bandwidth that is less than 20 MHz;

wherein the first rotated phase is realized by multiplying a first multiplication value to the at least one first subcarrier group, the first multiplication value selected from +1, −1 and +j wherein +1, −1, and +j are rotational multipliers, and

wherein the second rotated phase is realized by multiplying a second multiplication value to the at least one subcarrier group of the plurality of second subcarrier groups, the second multiplication value selected from +1 and −1.

6. The device of claim 5 wherein each of the plurality of UL PPDUs includes at least one duration field, and all duration fields in all of the plurality of UL PPDUs have a same value.

7. The device of claim 5 wherein the first signal field is associated with a first fast Fourier transform (FFT) size and the data portion is associated with a second FFT size; and wherein the second FFT size is four times the first FFT size.

8. The device of claim 7 wherein the first FFT size is 64 and the second FFT size is 256 when the operating bandwidth is 20 MHz;

wherein the first FFT size is 128 and the second FFT size is 512 when the operating bandwidth is 40 MHz;

wherein the first FFT size is 256 and the second FFT size is 1024 when the operating bandwidth is 80 MHz; and

wherein the first FFT size is 512 and the second FFT size is 2048 when the operating bandwidth is 160 MHz.

9. A method of communicating in a wireless local area network, the method comprising:

receiving a plurality of uplink (UL) physical layer protocol data units (PPDUs) from a plurality of stations; and

transmitting, in response to the received US PPDU's, an acknowledgement physical layer protocol data unit (ACK PPDU), the ACK PPDU comprising a first signal field, a second signal field and a data portion,

wherein the first signal field comprises bandwidth information, the bandwidth information indicating a bandwidth over which the ACK PPDU is transmitted,

wherein the data portion comprises the block acknowledgement for the plurality of UL PPDUs,

wherein the first signal field having a first rotated phase over at least one first subcarrier group, each first subcarrier group having bandwidth of 20 MHz,

the second signal field having a second rotated phase over a plurality of second subcarrier groups, each second subcarrier group having bandwidth that is less than 20 MHz;

wherein the first rotated phase is realized by multiplying a first multiplication value to the at least one first subcarrier group, the first multiplication value selected from +1, −1 and +j wherein +1, −1, and +j are rotational multipliers, and

wherein the second rotated phase is realized by multiplying a second multiplication value to the at least one subcarrier group of the plurality of second subcarrier groups, the second multiplication value selected from +1 and −1.

10. The method of claim 9 wherein each of the plurality of UL PPDUs includes at least one duration field, and all duration fields in all of the plurality of UL PPDUs have a same value.

11. The method of claim 9 wherein the first signal field is associated with a first fast Fourier transform (FFT) size and the data portion is associated with a second FFT size; and wherein the second FFT size is four times the first FFT size.

12. The method of claim 11

wherein the first FFT size is 64 and the second FFT size is 256 when the operating bandwidth is 20 MHz;

wherein the first FFT size is 128 and the second FFT size is 512 when the operating bandwidth is 40 MHz;

wherein the first FFT size is 256 and the second FFT size is 1024 when the operating bandwidth is 80 MHz; and

wherein the first FFT size is 512 and the second FFT size is 2048 when the operating bandwidth is 160 MHz.