Proposal of FSK modulated spread spectrum systems for enhancing frequency utilization efficiency
Noriyoshi Kuroyanagi, Lili Guo, N. Suehiro, Kohei Ohtake · 2002
In contrast with direct sequence-spread spectrum, an M-ary system characterized by frequency shift keying-spread spectrum (FSK-SS) is proposed. FSK-SS is comprised of two modulation stages; one selecting a frequency to represent the multiple levels, and the other multiplying a code sequence with the frequency. The shift frequencies are selected in a range less than the chip frequency, while satisfying an orthogonal relationship. Practical design examples show that FSK/BPSK-SS is able to achieve 1.4/spl sim/2.7 times larger capacity than that of conventional DS-SS. The interference tolerant capability is also discussed.