Abstract: In a method for transmitting a radio access control channel (RACH) preamble, steps may include supplying power to a device, checking a base time offset for the device, generating a random time offset used to transmit the RACH preamble, and transmitting the RACH preamble based on the checked base time offset or the generated random time offset. Devices having the same base time offset may be grouped together, and devices in a same group may transmit the RACH preamble according to their respective generated random time offsets. A device to transmit an RACH preamble includes a power supply unit, a control unit, an offset generating unit, and a communication unit.