Adaptive compute-and-forward with lattice codes over algebraic integers

Abstract

We consider the compute-and-forward relay network with limited feedback. A novel scheme called adaptive compute-and-forward is proposed to exploit the channel knowledge by working with the best ring of imaginary quadratic integers. This is enabled by generalizing Construction A lattices to other rings of imaginary quadratic integers which may not form principal ideal domains and by showing such construction can produce good lattices for coding in the sense of Poltyrev and for MSE quantization. Since there are channel coefficients (complex numbers) which are closer to elements of rings of imaginary quadratic integers other than Gaussian and Eisenstein integers, by always working with the best ring among them, we can obtain better performance than that provided by working over Gaussian or Eisenstein integers.