A decoder decodes a set of data streams received at a receiver based on a tree search that employs a subset of decoding constellation points. The decoder can form a tree wherein each level of the tree corresponds to one of the set of data streams. Each level of the tree includes a plurality of nodes corresponding to a set of candidate constellation points, wherein the set of candidate constellation points indicating possible values of data received via the set of data streams. For tree levels beyond an initial tree level, the decoder expands each node (that is, calculates the metrics for nodes of the next tree level) for only a subset of candidate constellation points, wherein the subset of candidate constellation points is based on a sign value of the node.