A data transmission method comprises receiving a channel access request to a radio receiving unit from a mobile station of the telecommunication system, and performing an operation on the channel access request using a predefined configuration of devices and algorithms of the radio receiving unit. After filtering the background noise from the channel access request; a characteristic of the channel access request against at least one predefined detection rule, and the channel access request is considered valid if the characteristic of the channel access request fulfils the detection rule. Essentially, the detection rule is not dependent on the configuration of the radio receiving unit.