|Yongce Chen||Virginia Tech, USA|
|Yan Huang||Virginia Tech, USA|
|Yi Shi||Virginia Tech, USA|
|Thomas Hou||Virginia Tech, USA|
|Wenjing Lou||Virginia Tech & National Science Foundation, USA|
|Sastry Kompella||Naval Research Laboratory, USA|
In recent years, degree-of-freedom (DoF) based models were proven to be very successful in studying MIMO-based wireless networks. However, most of these studies assume channel matrix is of full-rank. Such assumption, although attractive , quickly becomes problematic as the number of antennas increases and propagation environment is not close to ideal. In this paper, we address this problem by developing a general theory for DoF-based model under rank-deficient conditions. We start with a fundamental understanding on how MIMO's DoFs are consumed for spatial multiplexing (SM) and interference cancellation (IC) in the presence of rank deficiency. Based on this understanding, we develop a general DoF model that can be used for identifying DoF region of a multi-link MIMO network and for studying DoF scheduling in MIMO networks. Specifically, we found that shared DoF consumption at transmit and receive nodes is critical for optimal allocation of DoF for IC. The results of this paper serve as an important tool for future research of many-antenna based MIMO networks. Index Terms-MIMO, rank deficiency, degree of freedom (DoF), interference cancellation.