Ada S. Y. Poon and Robert W. Brodersen

EE Times Communications Design Conference, October 2003

 Abstract:

In the last two decades, we have witnessed an increasing allocation of unlicensed spectra. Advanced modulation techniques such as OFDM and ultra-wideband, multi-access protocols and ad-hoc multihop networks have been proposed allowing heterogeneous wireless systems to co-exist in the same wireless channel. Multiple-antenna systems provide additional degrees of freedom to alleviate the requirements across these layers. As a modulation scheme in the physical layer, it improves the reliability against channel fluctuation by resolving the propagation paths and increases the data rate by creating parallel spatial channels. In the MAC layer, its interference suppression and avoidance capabilities alleviate the hidden terminal and exposed terminal problems. In the network layer, the wired cooperation among peer systems can be resembled by beamforming. As a result, multiple-antenna systems provide a cross-layer performance benefits and should be an indispensable component in the next generation wireless network. In this paper, we will incorporate antenna theory with physical channel modeling to understand the full scope of multiple-antenna systems in real environments. In particular, we will show the impact of physical environment, hardware cost and signal processing complexity on these cross-layer performance benefits and their trade-offs.