| 摘要 |
The transmission of information is getting important in the recent information-intensive society. The conventional digital modulation system for mobile communication is a phase shift keying (PSK) system or a quadrature PSK system. However, under the recent communication environment where frequency resource is limited, the modulation method described above connot satisfy the requirements of high speed transmission and mass information transmission. Moreover, it is necessary to develope a better modulation system in terms of high bandwidth efficiency and constant envelope characteristic in the non-linear communication system, such as satellite communications. Accordingly, the present invention is directed to solve the bandwidth efficiency problem resulted from the lack of frequency resource, implementing the constant envelope characteristic for the non-linear communication system, based on 16-QAM (Quadrature Amplitude Modulation) system. The present invention limits the data, which will be modulated and transmitted, to 3-bit and adds a parity bit to make them have the constant envelope in the 16-QAM system, which modulates data to be transmitted in the unit of 4-bit. And the data value of the parity bit is decided to satisfy the condition of constant envelope in accordance with the QAM signals.
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