Systems, methods, and devices for communicating in a wireless network are described herein. In an aspect, a method of transmitting a data unit includes generating a data unit. The data unit includes one or more short training field (STF) sequences. The method further includes encoding each of the STF sequences with a pseudo-random spreading code. The code is based on an addressee of the data unit. The method further includes transmitting, at a transmitter, the data unit over a wireless channel. In another aspect, a method of processing a data unit includes receiving, at a receiver, a data unit. The data unit includes one or more STF sequences. The method further includes determining whether the data unit comprises one or more differentially encoded symbols. The method further includes receiving one or more long training field (LTF) sequences when the data unit does not comprise one or more differentially encoded symbols.