Uplink Multiple Access Schemes for 5G: A Survey

doi:10.3969/j.issn.1673-5188.2017.S1.004

Abstract

Abstract:

In non-orthogonal multiple access (NMA) system, signal transmitter and receiver are jointly optimized, so that multiple layers of data from more than one user can be simultaneously delivered in the same resource. To meet the 5G requirements on the number of connections and spectral efficiency, uplink NMA is becoming an important candidate technology and has been extensively studied in 3GPP. A number of uplink NMA schemes from different industrial companies have been proposed in recent 3GPP meetings. In terms of their basic technique principles, this paper classifies these NMA schemes into three categories, namely: scrambling based NMA schemes, interleaving based NMA schemes, and spreading based NMA schemes. Moreover, the key characteristics of these schemes are summarized, and the detailed introduction of each scheme is provided according to the comprehensive survey of the latest progress in 3GPP 5G standardization work.

Key words: 5G, non-orthogonal multiple access, scrambling, interleaving, spreading

YANG Shan, CHEN Peng, LIANG Lin, ZHU Jianchi, SHE Xiaoming. Uplink Multiple Access Schemes for 5G: A Survey[J]. ZTE Communications, 2017, 15(S1): 31-40.

Figures/Tables 19

References 27

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NMA scheme		Description	Standardization impact	Receiver algorithm
Category 1: Scrambling based	NOMA	•Multiple UEs with different scrambling sequences are transmitted on the same resource •NOMA can also bring in performance gain for multiple UEs with similar wideband SINR, thanks to the fast fading	•Define new scrambling sequence if needed •Power control enhancement if needed	SIC
	RSMA	Use combination of low rate channel codes and scrambling codes (and optionally different interleavers) with good correlation properties	•Define scrambling sequence and interleaver if needed •Define single carrier based new waveform for asynchronous transmission	SIC
	LSSA	Each UE’s data is bit or symbol level multiplexed with UE specific signature pattern which is unknown to others	Define signature pattern	SIC
Category 2: Interleaving based	IDMA	Use bit level interleavers to separate UEs	Define bit-level interleaver	ESE
Category 2: Interleaving based	IGMA	Use bit level interleavers and/or grid mapping pattern to separate UEs	•Define bit-level interleaver •Define sparse symbol-to-RE grid mapping pattern	ESE or chip-by-chip MAP
Category 3: Spreading based	SCMA	The coded bits of a data stream are directly mapped to a codeword from a codebook built based on a multi-dimensional constellation, and low density spreading is utilized	Define LDS code and multi-dimensional constellation	MPA, or MPA with SIC
	PDMA	A code is used to define sparse mapping from data to a group of resources, and different codes may have different diversity orders	Define LDS code matrix	BP based iterative detection and decoding
	LDS-SVE	For LDS spreading, consider UE signature vector extension, e.g., transforming and concatenating two element signature vectors into a larger signature vector	•Define LDS code•Define signature vector extension method	MPA
	MUSA	Use random complex spreading codes with short length, and the real part and imaginary part of each element in the complex spreading code are drawn from a multi-level real value set uniformly, for example, {-1, 1} or {-1, 0, 1}	Define spreading code	SIC
	NOCA	Use LTE defined low correlation sequences as spreading codes, e.g., LTE defined sequences for uplink reference signal for 1 RB case	Reuse the LTE defined sequence as spreading code	SIC
	NCMA	Spreading codes are obtained by Grassmannian line packing problem	Define spreading code	PIC
	LCRS	Apply direct spreading of modulation symbols and to transmit the spread symbols in time-frequency resources allocated for non-orthogonal transmission	Define spreading code	SIC

NMA scheme		Description	Standardization impact	Receiver algorithm
Category 1: Scrambling based	NOMA	•Multiple UEs with different scrambling sequences are transmitted on the same resource •NOMA can also bring in performance gain for multiple UEs with similar wideband SINR, thanks to the fast fading	•Define new scrambling sequence if needed •Power control enhancement if needed	SIC
	RSMA	Use combination of low rate channel codes and scrambling codes (and optionally different interleavers) with good correlation properties	•Define scrambling sequence and interleaver if needed •Define single carrier based new waveform for asynchronous transmission	SIC
	LSSA	Each UE’s data is bit or symbol level multiplexed with UE specific signature pattern which is unknown to others	Define signature pattern	SIC
Category 2: Interleaving based	IDMA	Use bit level interleavers to separate UEs	Define bit-level interleaver	ESE
Category 2: Interleaving based	IGMA	Use bit level interleavers and/or grid mapping pattern to separate UEs	•Define bit-level interleaver •Define sparse symbol-to-RE grid mapping pattern	ESE or chip-by-chip MAP
Category 3: Spreading based	SCMA	The coded bits of a data stream are directly mapped to a codeword from a codebook built based on a multi-dimensional constellation, and low density spreading is utilized	Define LDS code and multi-dimensional constellation	MPA, or MPA with SIC
	PDMA	A code is used to define sparse mapping from data to a group of resources, and different codes may have different diversity orders	Define LDS code matrix	BP based iterative detection and decoding
	LDS-SVE	For LDS spreading, consider UE signature vector extension, e.g., transforming and concatenating two element signature vectors into a larger signature vector	•Define LDS code•Define signature vector extension method	MPA
	MUSA	Use random complex spreading codes with short length, and the real part and imaginary part of each element in the complex spreading code are drawn from a multi-level real value set uniformly, for example, {-1, 1} or {-1, 0, 1}	Define spreading code	SIC
	NOCA	Use LTE defined low correlation sequences as spreading codes, e.g., LTE defined sequences for uplink reference signal for 1 RB case	Reuse the LTE defined sequence as spreading code	SIC
	NCMA	Spreading codes are obtained by Grassmannian line packing problem	Define spreading code	PIC
	LCRS	Apply direct spreading of modulation symbols and to transmit the spread symbols in time-frequency resources allocated for non-orthogonal transmission	Define spreading code	SIC