pseudorandom sequence generator

purely random sequence can be used to spread the signal spectrum. however, in order to despread the signal, the receiver needs a replica of the transmitted sequence (in most perfect time synchronism). in practice, therefore, we generate pseudorandom or pseudonoise (PN) sequence.^[각주:1]


linear feedback shift register (LFSR)

• one canonical form of a 'binary LFSR' is a 'simple shift register generator (SSRG)'

the shift register consists of binary storage elements (boxes) which transfer their contents to the right after each clock pulse. the contents of the register are linearly combined with the binary (0, 1) coefficients

 and are fed back to the first stage.

• for spread spectrum, we are looking for a maximal length cycles (maximum length sequence, MLLFSR)^[각주:2]

if the initial state of the shift register is 0 0 0 1, then the output (from position 4) at each state would be 1 0 0 0 1 1 1 1 0 1 0 1 1 0 0.

• modular shift register generator (MSRF), which is commonly used implementation of a LFSR

1. 본 포스팅의 내용은 theory of spread-spectrum communications - a tutorial [IEEE transactions on communications May 1982], http://worthatry.tistory.com/383 의 chapter 3. pseudorandom sequence generators의 내용을 정리한 것이다. [본문으로]
2. maximum length sequence와 관련된 내용은 http://worthatry.tistory.com/382에 종합하여 정리하였다. [본문으로]