Stochastic multipulse-PAM: a subspace modulation technique with diversity

• Authors: Arnt-Børre Salberg;Alfred Hanssen
• Venue: Signal Processing
• Year: 2003

In this paper, we introduce a non-conventional communication technique appropriately named Stochastic Multipulse-PAM (SM-PAM). SM-PAM systems operate by transmission of stochastic processes residing in low-dimensional subspaces. The transmitted signal is thus inherently stochastic, which is beneficial from a low-probability of intercept transmission point of view. The underlying structure of the transmission is such that the information is actually coded by the subspaces themselves, rather than by fixed coordinates in a preassigned basis, as is the case for conventional communication. We introduce a Fourier-based version of SM-PAM, and show that intersymbol interference (ISI) may readily be mitigated by employing a zero-forcing strategy and the insertion of a cyclic prefix in the transmitted vector. A substantial part of this paper is devoted to the derivation of matched subspace detectors for the transmitted SM-PAM waveform, for various classes of interference. We carry out a performance evaluation of SM-PAM, which shows that a proper energy scaling of the transmitted stochastic symbol vector has positive effects on the performance of the system. Various interesting scenarios are demonstrated by numerical simulations. The proposed multidimensional, stochastic, broadband, non-coherent communication technique buys security and diversity at the expense of spectral efficiency. We believe that SM-PAM may be important for non-standard applications where high data rates are not mandatory, but where security and interference rejection is imperative.