BPSK Direct Sequence Spread Spectrum

BPSK DS-SS signals

Spectrum

QPSK DS-SS

Dual Channel QPSK DS-SS

MSK DS-SS

MSK DS-SS

MSK DS-SS

Frequency Hopping Spread Spectrum

Spectrum

Slow FH-SS

Fast FH-SS

Hybrid DS FH SS

Complex envelope model

Complex-envelope of digital modulations

Spreading sequence 1. How to choose a spreading sequence? 2. How to generate a spreading sequence? 3. How to choose and generate a set of sequences when more than one sequences are needed, for example, in CDMA systems?

Some specification 1. Sequence elements should behave like iid random variables, i.e., the sequence should be pseudo-random. 2. It should be easy to distinguish a spreading signal from a time-shifted version of it. 3. It should be easy to distinguish a spreading signal from other spreading signals, including time-shifted versions of them, in the set. 4. It should be easy for the transmitter and the intended receiver to generate the spreading sequence. 5. It should be difficult for any unintended receiver to acquire and regenerate the spreading sequence.

Cross correlation with modulation

Binary Linear Feedback Shift Register

Binary shift register sequence

maximal-length sequence (m-sequence)

m-sequence

m-sequence

Maximal connected sets

Gold sequence

Choice of sequence

Initial code acquisition

Radiometer

Serial Search

Parallel Search

Multidwell Search