Method and apparatus for transmitting control information in wireless local area network using multi-channel

1. A method of transmitting control information in a wireless local area network (WLAN) system, the method comprising:

transmitting, by a transmitting station, a first physical (PHY) preamble over a first sub-channel to a first receiving station;

transmitting, by the transmitting station, a second PHY preamble over a second sub-channel to a second receiving station; and

transmitting, by the transmitting station, data symbols using N spatial streams transmitted over the first sub-channel to the first receiving station and M spatial streams transmitted over the second sub-channel to the second receiving station on an overlapped time resource,

wherein the first PHY preamble comprises control information necessary to demodulate and decode the data symbols transmitted over the N spatial streams,

wherein the second PHY preamble comprises control information necessary to demodulate and decode the data symbols transmitted over the M spatial streams,

wherein the first PHY preamble comprises information on a number of spatial streams among the N spatial streams for the first receiving station transmitted over the first sub-channel,

wherein the second PHY preamble comprises information on a number of spatial streams among the M spatial streams for the second receiving station transmitted over the second sub-channel,

wherein the first PHY preamble and the second PHY preamble are simultaneously transmitted,

wherein the first PHY preamble and the second PHY preamble have an identical number of training sequences, and

wherein the N and the M are natural numbers.

2. The method of claim 1 , wherein the first sub-channel and the second sub-channel are non-contiguous frequency bands.

3. The method of claim 2 , wherein the first sub-channel and the second sub-channel have an identical bandwidth.

4. The method of claim 2 , wherein:

the first PHY preamble further comprises information about the number of training sequences transmitted over the first sub-channel, and

the second PHY preamble further comprises information about the number of training sequences transmitted over the second sub-channel.

5. The method of claim 4 , wherein:

each of the first PHY preamble and the second PHY preamble comprises four training sequences,

the first PHY preamble comprises information about the number of spatial streams transmitted over the first sub-channel, and

the second PHY preamble comprises information about the number of spatial streams transmitted over the second sub-channel.

6. The method of claim 1 , wherein a first modulation and coding scheme (MCS) value, applied to an orthogonal frequency division multiplexing (OFDM) symbol of data transmitted over the first sub-channel and a second MCS applied to an OFDM symbol of data transmitted over the second sub-channel are differently set.

7. The method of claim 6 , wherein:

the first PHY preamble comprises an index indicating the first MCS, and

the second PHY preamble comprises an index indicating the second MCS.

8. The method of claim 6 , wherein:

the first PHY preamble comprises an MCS feedback request message, requesting a reception STA which receives at least one spatial stream transmitted over the first sub-channel to send an adequate candidate MCS index in order to update the first MCS, and

the second PHY preamble comprises an MCS feedback request message, requesting a reception STA which receives at least one spatial stream transmitted over the second sub-channel to send an adequate candidate MCS in order to update the second MCS.

9. A wireless apparatus operating in a wireless local area network (WLAN) system using a multi-channel obtained by aggregating a first sub-channel and a second sub-channel, the wireless apparatus comprising:

a processor; and

a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to:

send a first physical (PHY) preamble over the first sub-channel to a first receiving station;

send a second PHY preamble over the second sub-channel to a second receiving station; and

send data packets using N spatial streams transmitted over the first sub-channel to the first receiving station and M spatial streams transmitted over the second sub-channel to the second receiving station on an overlapped time resource,

wherein the first PHY preamble comprises control information necessary to demodulate and decode the data symbols transmitted over the N spatial streams,

wherein the second PHY preamble comprises control information necessary to demodulate and decode the data symbols transmitted over the M spatial streams,

wherein the first PHY preamble comprises information on a number of spatial streams among the N spatial streams for the first receiving station transmitted over the first sub-channel,

wherein the second PHY preamble comprises information on a number of spatial streams among the M spatial streams for the second receiving station transmitted over the second sub-channel,

wherein the first PHY preamble and the second PHY preamble are transmitted on an overlapped time resource,

wherein the first PHY preamble and the second PHY preamble have an identical number of training sequences, and

wherein the N and the M are natural numbers.