Uplink Nonorthogonal Multiple Access Technologies Toward 5G: A Survey

Table 3

Distinction between long and short sequences.

	Long sequence	Short sequence
Level of operation	Bit level/symbol level	Usually symbol level
Generation of sequence	Randomly	Carefully designed
Usage	Disperses the encoded bit sequences so that the adjacent bits are approximately uncorrelated	To facilitate MUD
Receiving technique	Requires iterative detection between symbol-level and bit-level, e.g., ESE-SIC	Symbol level detection, e.g., MPA/EPA
Synchronization requirement	Supports asynchronous transmission when combined with single carrier waveform, e.g., RSMA	Synchronization is usually required, e.g. SCMA
Blind detection	Does not support	Support