On the size of binary MWBE sequence sets

CDMA (Code Division Multiple Access) allows distinct users to communicate simultaneously on the same frequency band using binary sequences uniquely allocated to each user. For a given sequence length, we are confronted with a trade off between large set size (maximizing user capacity) and low maximum absolute inner product (minimizing instantaneous interference). Significant effort has been devoted to constructing upper bounds on set size and lower bounds on maximum inner products or correlation. Here we examine a common lower bound on inner products, show its inadequacy in certain cases, and improve it using an upper bound on set size.