A Model for Coherent Communication Gain in Distributed Wireless Networks

In this paper, generalized expressions for system gain in a coherent communication system are developed. In an ad hoc or distributed network, the transmit and receive operations can be coordinated at the RF level to produce an array gain, similar to a fixed antenna array; such formations are known as coherent distributed arrays. The system examined in this paper consists of two open-loop coherent distributed arrays: one transmitter array and one receiver array. The gain of the entire system containing both arrays is described by the coherent communication gain. The concept of group array factor, which is the multi-receiver extension of array factor, is also introduced. Group array factor allows for a characterization of gain independent from propagation model and properties of the individual transmitters and receivers. The univariate optimization problem of maximizing group array factor as a function of transmitter array beam angle in the azimuth plane is described, and a practical bounding on the search space is introduced. The physical dimensions of the communication system are analyzed in terms of their influence on the objective function, and a condition for guaranteeing convexity of the bounded objective function is given. An example transmitter array-receiver array system is introduced and used to showcase the concepts herein.