Embodiments are provided herein for increasing low density signature space for multiplexed transmissions for a plurality of users. The embodiments include generating a virtual signature using a combination operation on a plurality of basic signatures. The generated virtual signatures are provisioned as basic resource units (BRUs) for transmissions for corresponding users. The combination operation is a row-wise or column-wise permutation for combining, in each of the virtual signatures, rows or columns of corresponding basic signatures. The rows or columns represent sequences of frequency bands at one time interval or sequences of allocated time intervals at one frequency band. Alternatively, the combination operation is intra-basic resource unit (BRU) hopping. The embodiments also include generating a plurality of BRU sets comprised of virtual signatures. Each of the BRU sets is provisioned for a corresponding user.