Patent ID: 7965788

Claim:
A data receiving apparatus for reproducing, by using predetermined key information which is shared with a transmitting party, information data included in a modulated signal received from the transmitting party, the data receiving apparatus comprising: a demodulation section for demodulating the modulated signal and converting the demodulated signal into a multi-level signal having multi-levels; a multi-level code generation section for generating, by using the predetermined key information, a multi-level code sequence which is a pseudo random number sequence composed of a plurality of bits; a soft decision section for performing a soft decision on the multi-level signal; a converted data identification section for identifying, from the multi-level signal, a value of converted information data in accordance with some of the bits or all of the bits composing the multi-level code sequence and in accordance with a result of the soft decision performed by the soft decision section, the converted information data being generated in accordance with predetermined bits composing a multi-level code sequence at an end of the transmitting party and the information data; and a data reproduction section for reproducing the information data in accordance with the predetermined bits composing the multi-level code sequence generated by the multi-level code generation section and the converted information data, wherein the predetermined bits composing the multi-level code sequence generated by the multi-level code generation section is identical to the predetermined bits composing the multi-level code sequence at the end of the transmitting party, and the soft decision section distinguishes between a confirmed area in which the multi-level signal corresponds to the value of the converted information data uniquely, and an unconfirmed area in which the multi-level signal corresponds to a plurality of the values of the converted information data.