  For many wiretap channel models asymptotically optimal coding schemes are
known, but less effort has been put into actual realizations of wiretap codes
for practical parameters. Bounds on the mutual information and error
probability when using coset coding on a Rayleigh fading channel were recently
established by Oggier and Belfiore, and the results in this paper build on
their work. However, instead of using their ultimate inverse norm sum
approximation, a more precise expression for the eavesdropper's probability of
correct decision is used in order to determine a general class of good coset
codes. The code constructions are based on well-rounded lattices arising from
simple geometric criteria. In addition to new coset codes and simulation
results, novel number-theoretic results on well-rounded ideal lattices are
presented.
