Determination of Optimal Channel Spacing Based on Spectrums for Spreading Codes in Split Channel BFSK

Abstract

This paper proposes optimal channel spacing for Split Channel BFSK (Binary Frequency Shift Keying) with direct sequence spread spectrum. To this end, first, the inter-channel interference is observed for various spreading gains and codes through computer simulation. The data rate is 1 MHz and two tone spacing of SC-BFSK is 4 MHz. The receiver filter bandwidth for each tone is 700 kHz. The spreading code is selected between random PN (Pseudo Noise) code or all 1. According to the results, it is confirmed that optimum inter-channel spacing depends on the spreading gains and codes. Specifically, for small spreading gains, all 1 code shows better out-of-band interference characteristics than the PN code while PN code is preferable for large spreading gains. Therefore, neighboring channel spacing should be decided as a function of spreading gain, and a preferable spreading code exists in terms of inter-channel interference mitigation.