  Most of the calculations in standard sphere decoders are redundant, in the
sense that they either calculate quantities that are never used or calculate
some quantities more than once. A new method, which is applicable to lattices
as well as finite constellations, is proposed to avoid these redundant
calculations while still returning the same result. Pseudocode is given to
facilitate immediate implementation. Simulations show that the speed gain with
the proposed method increases linearly with the lattice dimension. At dimension
60, the new algorithms avoid about 75% of all floating-point operations.
