|
| Type | Advantage | Disadvantage | Key feature |
|
| PD-NOMA | (i) Is not affected by apparent near-far
(ii) 20% uplink spectral efficiency increase
(iii) 30% downlink throughput increase [64] | (i) High receiver complexity needs improvement in chip technology
(ii) Power domain multiplexing is in the research phase
(iii) SIC increases the system signalling overhead | (i) For user multiplexing, PD-NOMA utilized the power domain multiple access
(ii) At receiver, SIC scheme is used
(iii) Take advantage of different channel conditions |
| SCMA | (i) Three times increase in spectral efficiency
(ii) 2.8 times uplink system capacity upgrade
(iii) 8% and 5% increase in coverage gain and downlink throughput, respectively [64] | (i) Optimization and design of the code are difficult
(ii) Increased interference between users
(iii) High-dimensional modulation (HDM) required | (i) SCMA utilizes sparse spreading sequence, based on LDS-OFDM
(ii) Spreading with low-density signatures and bit-to-constellation mapping are combined in SCMA
(iii) Codebooks are created by multidimensional constellation. Users’ codewords are taken from codebooks |
| MUSA | (i) Block Error Rate (BLER) is low
(ii) Huge number of users’ access is supported
(iii) Spectral efficiency increased by 1.5 times [64] | (i) Interuser interference is increased
(ii) Spread symbol design is challenging | (i) MUSA is an upgraded scheme of CDMA via code domain multiplexing
(ii) At the transmitter, MUSA achieved higher overloading through low-correlation spreading sequences
(iii) SIC is performed at the receiver side, to decode superimposed symbols |
| PDMA | (i) 2-3 times uplink system capacity increased
(ii) 1.5 times spectral efficiency increase in downlink system | (i) The pattern optimization and design are challenging
(ii) Increase interference between users | (i) Nonorthogonal patterns are used in PDMA
(ii) Multiplexing is achieved in space domain, power domain, code domain, and their composite domain
(iii) Code domain multiplexing is similar to SCMA
(iv) Low Complexity Quasi-ML SIC detection is utilized in PDMA |
|
