Optimum wireless communication through unknown obscuring environments using the time-reversal principle: theory and experiments

Wireless communication in unknown and cluttered environments is an important problem which has several practical applications such as communication in urban areas and disaster areas. This paper presents a method to optimize communication efficiency in such environments. The method applies to communication between a transmitting array and receiving array where the transmitting array sends out a 'probe' signal and, at the receiving array, the transfer matrix can be constructed. From this measurement, we perform time-reversal and eigen analysis. The highest eigen value is the best possible transmission efficiency and its corresponding eigen vector represents the transmitting excitation at the transmitting elements to achieve maximum efficiency. The nature of this method makes it possible to operate and optimize in unknown, random, and cluttered environments. Here, we present the theory of time-reversal communication, show relevant numerical examples, and illustrate the experimental verification.