Codebooks in Flag Manifolds for Limited Feedback MIMO Precoding
Conference: SCC 2013 - 9th International ITG Conference on Systems, Communication and Coding
01/21/2013 - 01/24/2013 at München, Deutschland
Proceedings: SCC 2013
Pages: 5Language: englishTyp: PDFPersonal VDE Members are entitled to a 10% discount on this title
Pitaval, Renaud-Alexandre; Srinivasan, Ashvin; Tirkkonen, Olav (Aalto University, Department of Communications and Networking, Espoo, Finland)
We consider unitary codebook design problems for various precoded MIMO scenarios, and interprete them as generalized discretization problems of flag manifolds. As a concrete example, we consider codebooks for MIMO transmission with linear receivers. In this case, the problem reduces to discretizing permutation-invariant flag manifolds. A corresponding Lloyd algorithm is given, providing low-distortion codebooks. The achievable rate of the system applying the generated codebooks is compared by simulations. We find that for a N-by-N full-rank MIMO system with N > 2 and a linear receiver, the gain of precoding with a small number of feedback bits is small. This differs from the behavior of low-rank transmissions, where it is known that a small number of feedback bits allows near-optimal channel adaptation.