Noncoherent unitary space-time modulated DSSS systems in multipath channels

In this paper, in order to effectively apply unitary space-time modulation to the direct-sequence spread-spectrum multiple-access (DSSS-MA) networks, we propose a low-rate, noncoherent, unitary, and space-time modulated DSSS system supporting any number of transmit antennas based on Walsh matrices. The proposed scheme simultaneously performs bandwidth spreading and space-time coding and outperforms those using high-rate, conventional unitary space-time constellations. Furthermore, the proposed scheme allows for a simple detector structure based on fast Walsh transforms.