Application of Quasi Orthogonal Short Sequence Families in Pattern Division Multiple Access - A Non Orthogonal Multiple Access Technique

Abstract

Non-orthogonal multiple access (NOMA) techniques are an effective tool for increasing the user capacity in 5G networks. In NOMA users occupy a same resource element in any given time, and user separation is achieved through different interference cancellation strategies. For instance, in NOMA techniques that use short spreading codes (MUSA), interference cancellation (IC), is necessary since the codes do not have full orthogonality due to their short length compared to the number of users. In the other version of NOMA, Pattern Division Multiple Access (PDMA), sequences represent patterns that are assigned to users in a same Resource Element (RE). And need again to be separated by IC or some other advanced receiver technique. In the paper we give a method of an algebraic construction of short quasi orthogonal PDMA patterns that are ideally suited for use in NOMA PDMA. Not only there is a large number of patterns in the family (where we define a family as a set of patterns with the same length and weight), but they have excellent separation properties. The construction is based on properties of Polynomials over Finite fields. We show that within each family it is also possible to construct patterns with different weights (level of diversity). Using link level simulations we establish the performance of our sequences, and compare them with PN sequences as well as with sequences in the other PDMA literature.