Hierarchical transmission of data

A communication system is disclosed that is capable of reducing data delay in transmitted hierarchized data and selecting predetermined data from the transmitted hierarchized data for communication according to conditions of the receiving end. The communication system includes a signal transmitting device 100 that hierarchizes data to be transmitted and transmits the hierarchized data, and a signal receiving device 200 that receives the data from the transmitting device. The signal transmitting device 100 includes a hierarchized data transmitting unit 1-7 that hierarchizes the data to be transmitted into a number of layers and transmits the data layers. The signal receiving device 200 includes a layer identifying unit 12 that identifies the data layers transmitted from the signal transmitting device, and a hierarchized data receiving unit 11 that selects the identified data layers according to at least one of receiving capability and a propagating environment of the signal receiving device, and receives the selected data layers.