Spectrally-efficient FDMA-CPM systems

This paper concerns with the design of spectrally-efficient Frequency-Division-Multiple-Access (FDMA) multiuser systems based on Continuous-Phase-Modulation (CPM). A class of FDMA-CPM is proposed to accommodate multiple users in a subchannel and therefore admits significantly improved spectral-efficiency. Phase spacing is incorporated into the system to improve the Euclidean distance property, especially for FDMA-CPM systems with small frequency spacing. The impacts of the phase spacing and frequency spacing are then evaluated in terms of the distance property, which shows that the proposed FDMA-CPM systems have a comparable error performance to the single user systems. The proposed strategy is exemplified by systems having spectral-efficiency varying from 1.67 bits/s/Hz to 12 bits/s/Hz, which shows significantly improved spectral efficiency is obtained comparing with existing systems given the same signal to noise ratio.