A method for accessing a channel in a wireless local area network system, the method performed by a station comprising: receiving, from an access point, channel access information for restricting a channel access to a group of stations during a channel access period within a beacon interval; determining whether the station is allowed to access a channel during the channel access period based on the channel access information; and accessing the channel during the channel access period if it is determined that the station is allowed to access the channel, wherein the channel access information includes a group ID field indicating the group of stations that is allowed to access the channel during the channel access period, a channel access period start field indicating a start time of the channel access period, a channel access period duration field indicating a duration of the channel access period wherein the step of accessing the channel comprises: contending with other stations to transmit a power save poll frame; sending the power save poll frame to the access point; receiving a data frame from the access point; and transmitting an acknowledgement, ACK, message in response to the data frame to the access point. receiving, from an access point, channel access information for restricting a channel access to a group of stations during a channel access period within a beacon interval; determining whether the station is allowed to access a channel during the channel access period based on the channel access information; and accessing the channel during the channel access period if it is determined that the station is allowed to access the channel, wherein the channel access information includes a group ID field indicating the group of stations that is allowed to access the channel during the channel access period, a channel access period start field indicating a start time of the channel access period, a channel access period duration field indicating a duration of the channel access period wherein the step of accessing the channel comprises: contending with other stations to transmit a power save poll frame; sending the power save poll frame to the access point; receiving a data frame from the access point; and transmitting an acknowledgement, ACK, message in response to the data frame to the access point. a group ID field indicating the group of stations that is allowed to access the channel during the channel access period, a channel access period start field indicating a start time of the channel access period, a channel access period duration field indicating a duration of the channel access period wherein the step of accessing the channel comprises: contending with other stations to transmit a power save poll frame; sending the power save poll frame to the access point; receiving a data frame from the access point; and transmitting an acknowledgement, ACK, message in response to the data frame to the access point. contending with other stations to transmit a power save poll frame; sending the power save poll frame to the access point; receiving a data frame from the access point; and transmitting an acknowledgement, ACK, message in response to the data frame to the access point.