A wireless communication system and method for wireless communication are disclosed. One embodiment of the system includes a wireless communication device. The device includes a receiver configured to receive a data packet via a channel. The device further includes a transmitter configured to send an acknowledgment (ACK) signal via a low-rate channel upon receiving the data packet. The low-rate channel has a directional mode and an omni-directional mode. The acknowledgment signal includes a low-rate physical layer (LRP) preamble and an acknowledgment (ACK) header including a mode index field. The mode index field includes a plurality of bits indicative of whether the ACK signal is transmitted using the directional mode or the omni-directional mode.