Nonlinear OQPSK-type (Offset Quadrature Phase
Shift Keying) modulations can be designed to have almost
constant envelope, making it suitable for systems requiring
highly-efficient and low-cost grossly nonlinear power amplifiers.
In this paper we consider the use of pseudo-random spreading
sequences for channel estimation purposes in systems employing
nonlinear OQPSK-type modulations. We consider Maximum-
Length sequences, Kasami sequences, Gold sequences and Tomlinson,
Cercas, Hughes sequences, all known to have good autocorrelation
properties, making them appropriate for channel
estimation purposes. The cross-correlation between different
OQPSK components that constitute nonlinear OQPSK-type signals
is obtained and its impact on the channel estimation
performance is evaluated. It is shown that Tomlinson, Cercas,
Hughes sequences outperform the other sequences in the channel
estimation context.