A method for digital communication in a system including a gateway apparatus, a first radio communication apparatus, and a second radio communication apparatus, the method including: at the first radio communication apparatus, sending first data to the gateway apparatus during a first time slot of a radio frame, the radio frame including a common slot, the first time slot allocated to the first radio communication apparatus for data transmission, and a second time slot allocated to the second radio communication apparatus for data transmission; determining whether the first data has been received by the gateway apparatus; upon determining that the first data has not been received by the gateway apparatus, sending a relay request signal to the second radio communication apparatus during the common slot of the radio frame; in response to the relay request signal, receiving a response signal from the second radio communication apparatus.