A method in a communication device (14, 25) for processing a received data unit (190, 354), the method comprising: determining, using an identifier of at least one intended receiver specified in a first field (114, 124, 126, 136), whether the communication device is one of the at least one intended receiver, wherein the first field is included in a physical layer, PHY, header of the received data unit; determining a time period based on a duration specified in a second field (176, 196), wherein the second field is included in the received data unit; determining a value of an indicator in a third field in the PHY header, wherein the indicator is an exclusive use indication indicating whether a transmit opportunity, TxOP, is reserved for exclusive use by the at least one intended receiver; and based on (i) a result of determining the value of the indicator and (ii) a result of determining whether the communication device is an intended receiver of the data unit: if it is determined that i) the communication device is not an intended receiver of the data unit, and ii) the indicator in the third field in the PHY header is set to true, determining a time interval during which the communication device need not listen for incoming data units and causing at least a portion of the communication device to sleep during the determined time interval; and if it is determined that the indicator in the third field in the PHY header is set to false, causing the communication device to listen for potentially relevant incoming data units during the determined time interval. determining, using an identifier of at least one intended receiver specified in a first field (114, 124, 126, 136), whether the communication device is one of the at least one intended receiver, wherein the first field is included in a physical layer, PHY, header of the received data unit; determining a time period based on a duration specified in a second field (176, 196), wherein the second field is included in the received data unit; determining a value of an indicator in a third field in the PHY header, wherein the indicator is an exclusive use indication indicating whether a transmit opportunity, TxOP, is reserved for exclusive use by the at least one intended receiver; and based on (i) a result of determining the value of the indicator and (ii) a result of determining whether the communication device is an intended receiver of the data unit: if it is determined that i) the communication device is not an intended receiver of the data unit, and ii) the indicator in the third field in the PHY header is set to true, determining a time interval during which the communication device need not listen for incoming data units and causing at least a portion of the communication device to sleep during the determined time interval; and if it is determined that the indicator in the third field in the PHY header is set to false, causing the communication device to listen for potentially relevant incoming data units during the determined time interval. if it is determined that i) the communication device is not an intended receiver of the data unit, and ii) the indicator in the third field in the PHY header is set to true, determining a time interval during which the communication device need not listen for incoming data units and causing at least a portion of the communication device to sleep during the determined time interval; and if it is determined that the indicator in the third field in the PHY header is set to false, causing the communication device to listen for potentially relevant incoming data units during the determined time interval.