An algebraic family of complex lattices for fading channels with application to space-time codes

A new approach is presented for the design of full modulation diversity (FMD) complex lattices for the Rayleigh-fading channel. The FMD lattice design problem essentially consists of maximizing a parameter called the normalized minimum product distance d_p² of the finite signal set carved out of the lattice. We approach the problem of maximizing d_p² by minimizing the average energy of the signal constellation obtained from a new family of FMD lattices. The unnormalized minimum product distance for every lattice in the proposed family is lower-bounded by a nonzero constant. Minimizing the average energy of the signal set translates to minimizing the Frobenius norm of the generator matrices within the proposed family. The two strategies proposed for the Frobenius norm reduction are based on the concepts of successive minima (SM) and basis reduction of an equivalent real lattice. The lattice constructions in this paper provide significantly larger normalized minimum product distances compared to the existing lattices in certain dimensions. The proposed construction is general and works for any dimension as long as a list of number fields of the same degree is available.