A method for performing channel access in at least one station, STA, of a wireless communication system, comprising: receiving, from an access point, AP, a first frame containing a traffic indication map, TIM, element and a restricted access window, RAW, parameter set element; determining a RAW allowing channel access of the STA based on the RAW parameter set, RPS, element; and transmitting a second frame to the AP within the determined RAW, wherein: the RAW comprises at least one slot; and the method is further characterized in that: the RPS element comprises at least one RAW assignment field, each of the at least one RAW assignment field comprising a first field indicating a slot duration and a second field indicating whether or not the channel access is restricted to paged stations, STAs, only, and wherein an index of a slot in which the STA is allowed to start accessing a channel is determined based on an association identifier, AID, of the STA and the number of slots in the RAW, wherein the index of a slot is determined based on a position index of an AID bit in the TIM element when the second field indicates that the channel access is restricted to the paged STAs only. receiving, from an access point, AP, a first frame containing a traffic indication map, TIM, element and a restricted access window, RAW, parameter set element; determining a RAW allowing channel access of the STA based on the RAW parameter set, RPS, element; and transmitting a second frame to the AP within the determined RAW, wherein: the RAW comprises at least one slot; and the method is further characterized in that: the RPS element comprises at least one RAW assignment field, each of the at least one RAW assignment field comprising a first field indicating a slot duration and a second field indicating whether or not the channel access is restricted to paged stations, STAs, only, and wherein an index of a slot in which the STA is allowed to start accessing a channel is determined based on an association identifier, AID, of the STA and the number of slots in the RAW, wherein the index of a slot is determined based on a position index of an AID bit in the TIM element when the second field indicates that the channel access is restricted to the paged STAs only. the RAW comprises at least one slot; and the method is further characterized in that: the RPS element comprises at least one RAW assignment field, each of the at least one RAW assignment field comprising a first field indicating a slot duration and a second field indicating whether or not the channel access is restricted to paged stations, STAs, only, and wherein an index of a slot in which the STA is allowed to start accessing a channel is determined based on an association identifier, AID, of the STA and the number of slots in the RAW, the RPS element comprises at least one RAW assignment field, each of the at least one RAW assignment field comprising a first field indicating a slot duration and a second field indicating whether or not the channel access is restricted to paged stations, STAs, only, and wherein an index of a slot in which the STA is allowed to start accessing a channel is determined based on an association identifier, AID, of the STA and the number of slots in the RAW, wherein the index of a slot is determined based on a position index of an AID bit in the TIM element when the second field indicates that the channel access is restricted to the paged STAs only.