bination with spatial multiplexing schemes (in the presence of multiple transmit antennas). Compared to long spreading codes, short spreading codes need smaller spreading factor and higher spectral efficiency. The short spreading codes can be optimized to achieve the Welch bound1 on cross-correlation, which can be leveraged for multi-user detection and inter-UE In mathematics, Welch bounds are a family of inequalities corresponding to the problem of evenly spreading set of unit vectors in a vector space. If {X1 Xm} are unit vectors in Cn. We define (Xi,Xj) where the inner product is defined in Cn. Then, the following inequalities are given Ak = If m VI n, then the vectors {Xn} can orthonormal set in Cn. In this case, Cmax 0 and the bounds are void. Consequently, interpretation of the bounds is only meaningful if m > n. New Radio Access Physical Layer Aspects (Part 1) 357 interference cancellation for synchronized reception. Moreover, it can be easily combined with spatial precoding to further mitigate the cross-correlation and enhance the non- orthogonal multiple access capacity. A large number of the existing non-orthogonal multiple access schemes are based on linear spreading. For this type of spreading-based NOMA schemes, the same type of NOMA receivers can be utilized. The NOMA receiver consists of three parts. The first part is multi- user detector where the superposed received signal is processed jointly across the UEs to derive the LLR for each UE. The second part is the channel decoder which receives the LLR from multi-user detector and decodes the transmitted codeword. The output from the channel decoder can be either a decoded codeword when the decoding is successful or an intermediate LLR for each bit refined through the message passing decoding process. The third part is the iteration between the multi-user detector and the channel decoder, where they can exchange both soft-LLR information and hard decision information. We will focus on multi-user detector here and in particular, we will focus on elem