Embodiments of the present disclosure provide, among other implementations, sequence determining methods. One example method provides a sequence group, and one sequence group number is corresponding to at least two sequences, where one sequence is used for mapping to consecutive subcarriers, and at least one other sequence is used for mapping to equally-spaced subcarriers. In some embodiments of the present disclosure, as high as possible cross-correlation between a sending signal obtained after equally-spaced mapping is performed on a sequence in a sequence group can be determined, and a sending signal obtained after continuous mapping is performed on another sequence in the group.

A method for communication includes simultaneously transmitting over a wireless network from a first station to a second station at least first and second request-to-send (RTS) frames in different, respective first and second frequency channels. The first station receives first and second clear-to-send (CTS) frames transmitted in the first and second frequency channels, respectively, by the second station over the wireless network in response to the first and second RTS frames. At least one property associated with the first station is estimated by processing information extracted from both the first and second received CTS frames.