A Closed-loop Cross-Layer Scheme for Wireless Multiuser Transmissions

Abstract To improve transmission efficiency of wireless communication systems, cross-layer design is investigated, which can adapt to the dynamically variable wireless channel characters. In this paper, a novel cross-layer design for multi-user system is proposed to improve system performance. The Beamforming-MIMO cross-layer system is scheduled through combining multilevel adaptive modulation (AM) at physical layer with truncated automatic repeat request (ARQ) protocol at data link layer, and feed backing modulation mode, ARQ request and transmit weight vector from receiver, in order to improve multi-antennas system performance. This paper derives close-form expressions of the system spectral efficiency and the outage probability for wireless multiuser MIMO transmissions. It shows by simulation that, compared to Alamouti's cross-layer system and SISO cross-layer system, this cross-layer system can achieve better performance. And we analyze the impact of the transmit antenna number and mobile user number on the performance.