Implementation of cooperative communications using ultrasonic wireless terminals

In this paper, an experimental framework that enables observing the performance improvements provided by cooperative diversity schemes is introduced. Unlike the RF based test-beds proposed in the literature, a wireless network consisting of ultrasonic terminals has been implemented. It has been shown that terrestrial applications of the ultrasonic communications provide an effective computer-aided experiment environment on which various cooperative physical layer protocols can be tested. Using this empirical setup, a digital relaying based bi-directional communication scenario has been examined where two users exchange information by employing differential binary modulation and network coding via a relay. The direct and relayed bit-wise XOR-ed and differential encoded signals are combined based on maximum likelihood (ML) detection at the receivers to prevent performance loss due to error propagation. Bit Error Rate (BER) measurement results have verified the theoretical studies in the literature by demonstrating that full diversity order is obtained.