Cross-layer Optimization and MIMO

While traditional multi-antenna-transmission research has focused on a point-to-point link, our work studies multi-antenna transmissions with scheduling in a wireless packet data network. In particular, we are interested in the coordinated design of MIMO transmission techniques at the physical layer and packet scheduling algorithms at the medium-access-control (MAC) layer. In the broader context of wireless networking, we seek methodologies for a cross-layer design and optimization in a distributed MIMO channel to achieve efficient radio resource sharing among multiple users.

Recent progress in information theory suggests that so-called dirty paper coding (DPC) achieves the sum capacity of the multi-antenna Gaussian broadcast channel. Further, when Gaussian inputs are optimal, the entire capacity region can be completely characterized by DPC. Drawing on these results and relying on the duality between broadcast and multiaccess channels, our research explores the role of multiple antennas in both types of channels. At a system performance level, we study the interaction between MIMO transmission techniques and channel-aware scheduling algorithms in an interference-limited system. From a user perspective, we also investigate the interests of users using various network utility functions. In the latter scenario, a game-theoretic approach is currently under study.

Good research is almost always associated with implementation and experimentation. One of our research thrusts is to develop a cross-layer simulation platform. Traditionally system-level simulation is performed separately at different layers. Our goal is to bridge the gap between different simulation methods for networking and transmission, and to provide a powerful tool for dynamic system performance evaluation in a cross-layer sense. Owing to the strong channel measurement and modeling capabilities at MPRG, we can actually implement our algorithms and test them in realistic channel conditions.

Our Challenges

1. Examine the role of antennas in wireless networks, particularly in a distributed-MIMO channel
    

2. Quality of service definitions for various applications using MIMO transmission
    

3. Efficient and robust information-sharing mechanisms in a distributed multiuser MIMO network to facilitate intelligent cooperation