  A multi-access multiple-input multiple-output (MIMO) relay differential chaos
shift keying cooperative diversity (DCSK-CD) system is proposed in this paper
as a comprehensive cooperation scheme, in which the relay and destination both
employ multiple antennas to strengthen the robustness against signal fading in
a wireless network. It is shown that, with spatial diversity gains, the bit
error rate (BER) performance of the proposed system is remarkably better than
the conventional DCSK non-cooperation (DCSK-NC) and DCSK cooperative
communication (DCSK-CC) systems. Moreover, the exact BER and close-form
expressions of the proposed system are derived over Nakagami fading channels
through the moment generating function (MGF), which is shown to be highly
consistent with the simulation results. Meanwhile, this paper illustrates a
trade-off between the performance and the complexity, and provides a threshold
for the number of relay antennas keeping the user consumed energy constant. Due
to the above-mentioned advantages, the proposed system stands out as a good
candidate or alternative for energy-constrained wireless communications based
on chaotic modulation, especially for low-power and low-cost wireless personal
area networks (WPANs).
