  This paper addresses a unified approach towards communication in
decentralized wireless networks of separate transmitter-receiver pairs. In
general, users are unaware of each other's codebooks and there is no central
controller to assign the resources in the network to the users. A randomized
signaling scheme is introduced in which each user locally spreads its Gaussian
signal along a randomly generated spreading code comprised of a sequence of
nonzero elements over a certain alphabet. Along with spreading, each
transmitter also masks its output independently from transmission to
transmission. Using a conditional version of entropy power inequality and a key
lemma on the differential entropy of mixed Gaussian random vectors, achievable
rates are developed for the users. It is seen that as the number of users
increases, the achievable Sum Multiplexing Gain of the network approaches that
of a centralized orthogonal scheme where multiuser interference is completely
avoided. An interesting observation is that in general the elements of a
spreading code are not equiprobable over the underlying alphabet. Finally,
using the recently developed extremal inequality of Liu-Viswanath, we present
an optimality result showing that transmission of Gaussian signals via
spreading and masking yields higher achievable rates than the maximum
achievable rate attained by applying masking only.
