Multiuser signal set design for the energy-constrained linear real-additive symbol-synchronous additive white Gaussian noise channel is investigated in this correspondence. An argument is presented showing the suboptimality of binary alphabets which, in turn, uncovers a rule for the formation of multiuser signal sets. This simple rule leads to a theorem stating the dimensionality at which additional users can be added to a multiuser system without decreasing the minimum Euclidean distance. Specific vector sets with the desired property are then constructed as examples and some generalizations are discussed. The theorem may also be used as a platform for the design of more efficient multiuser codes incorporating redundant signal sets. Two such codes are presented. In particular, a code combining four-dimensional unit-energy signals with a rate-2/3 convolutional code obtains a summed rate of 1.75 bits/dimension in the two-user adder channel with received minimum Euclidean distance of 2.>

Blind equalization performance can be improved by controlling the equalizer adaption step-size according to the region in which the received signal lies in the constellation plane. A simple technique based on this principle is proposed as a modification to blind equalization algorithms, and its effectiveness is demonstrated by simulation. As an example, the algorithm of Picchi and Prati (1987) is considered since it is simpler and converges faster. The proposed modification is applied to the zero-forcing (ZF) algorithm.>