Channel access method for very high throughput (VHT) wireless local access network system
A channel access method for a very high throughput (VHT) system using a bonding channel having a plurality of subchannels is provided. The method includes receiving training information comprising a training offset value through a subchannel, performing channel estimation on a full channel bandwidth comprising all subchannels when a time corresponding to the training offset value is elapsed after the training information is received, transmitting a request to send (RTS) frame to a destination station through some subchannels selected from the plurality of subchannels by one or a plurality of source stations according to a result of the channel estimation, and transmitting a clear to send (CTS) frame to one source station selected from the plurality of source stations by the destination station in response to the received RTS frame. Accordingly, an effective channel access mechanism is provided for the VHT system, and collision among stations can be avoided.
1. A method for channel estimation at a receiver in a wireless local area network, the method comprising:
receiving a Very High Throughput (VHT) signal field from a transmitter in a first bandwidth, the VHT signal field comprising a bandwidth field, a training offset field, and a position field, the bandwidth field indicating a second bandwidth, the position field indicating positions of a plurality of receivers;
receiving at least one VHT-long training field (VHT-LTF) from the transmitter in the second bandwidth based on a position of the receiver; and
estimating a multiple input multiple output (MIMO) channel based on the at least one VHT-LTF,
wherein the training offset field is set to a first value when the least one VHT-LTF is destined to only one receiver, and the training offset field is set to a second value when the least one VHT-LTF is destined to the plurality of receivers.
2. The method of claim 1 , wherein the first bandwidth is smaller than the second bandwidth.
3. The method of claim 2 , wherein the first bandwidth is 20 MHz.
4. The method of claim 2 , wherein the second bandwidth is 40 or 80 MHz.
5. The method of claim 1 , wherein the transmitter is an access point (AP), and wherein the receiver is a non-AP station.
6. An apparatus operating in a wireless local area network, the apparatus comprising:
a transceiver configured to transmit and receive radio signals; and
a processor operatively coupled to the transceiver and configured to:
receive a Very High Throughput (VHT) signal field from a transmitter in a first bandwidth, the VHT signal field comprising a bandwidth field, a training offset field, and a position field, the bandwidth field indicating a second bandwidth, the position field indicating positions of a plurality of receiving apparatuses;
receive at least one VHT-long training field (VHT-LTF) from the transmitter in the second bandwidth based on a position of the apparatus; and
estimate a multiple input multiple output (MIMO) channel based on the at least one VHT-LTF,
wherein the training offset field is set to a first value when the least one VHT-LTF is destined to only one receiving apparatus and the training offset field is set to a second value when the least one VHT-LTF is destined to the plurality of receiving apparatuses.
7. The apparatus of claim 6 , wherein the first bandwidth is smaller than the second bandwidth.
8. The apparatus of claim 7 , wherein the first bandwidth is 20 MHz.
9. The apparatus of claim 8 , wherein the second bandwidth is 40 or 80 MHz.
10. The apparatus of claim 6 , wherein:
the transmitter is an access point (AP); and
the apparatus is a non-AP station.