Analysis of a Pseudo-Noise Addressing System for Multiple Access Communication with Applications of Error-Correcting Codes

摘要

The thesis describes several modulation schemes to be used in a random access discrete address (RADA) system. This RADA system uses only one common frequency as carrier, and no synchronization of the net is supposed. Recognition of the transmissions between pairs of talkers involves the use of pseudo-random sequences as individual addresses of each subscriber. Detection of a particular pseudo-random sequence, contaminated by the noise formed by the simultaneous transmissions of other sequences, is accomplished by correlation methods. A comparative study is presented for the transmission of the information by the RADA system. The following methods are described and analyzed: an M-ary system, where the information is represented by cyclic shifts of the pseudo-random sequence used as the recipient's address, and pulse code modulation (PCM) where the information is represented by a '1' or '0'. Finally, the effect of encoding the information digits via error-correcting codes is investigated. Here, use of cyclic block codes and convolutional codes are presented. It is concluded that the use of convolutional codes would improve the performance of RADA systems. (Author)