Signaling over MIMO Multi-Base Systems: Combination of Multi-Access and Broadcast Schemes

Abstract

A new structure for multi-base systems is studied in which each user receives data from two nearby base stations, rather than only from the strongest one. This system can be considered as a combination of broadcast and multi-access channels. By taking advantages of both perspectives, an achievable rate region for a discrete memoryless channel modeled by Pr(y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ,y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> |x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> ,x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 </sub> ) is derived. In this model, x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> represent the transmitted signals by the transmitter one and two, respectively, and y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> denote the received signals by the receiver one and two, respectively. In this derivation, it is assumed that each transmitter is unaware of the data of the other transmitter, and therefore x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are independent. To investigate the advantage of this scheme, an efficient signaling method which works at a corner point of the achievable region for multiple-antenna scenarios is developed. In the proposed scheme, each base station only requires the state information of the channels between the other base station and each user. In this paper, the signaling scheme is elaborated for the case that each transmitter/receiver is equipped with three antennas. It is proven that in such a scenario, the multiplexing gain of four is achievable, which outperforms any other conventional schemes