  In this paper, we investigate multi user chirp spread spectrum with
noncoherent detection as a continuation of our work on coherent detection in
[1]. We derive the analytical bit error ratio (BER) expression for binary chirp
spread spectrum (BCSS) in the presence of multiple access interference (MAI)
caused by correlation with other user signals because of either asynchronism or
Doppler shifts, or both, and validate with simulations. To achieve this we
analyze the signal cross correlations, and compare traditional linear chirps
with our recently-proposed nonlinear chirps introduced in [1] and with other
nonlinear chirps from the literature. In doing so we illustrate the superior
performance of our new nonlinear chirp designs in these practical conditions,
for the noncoherent counterpart of [1].
