Table 2 Qualitative comparison of the complexity of different strategies
Multiple access | NOMA | SDMA | RSMA | ||
|---|---|---|---|---|---|
Strategy | SC–SIC | SC–SIC per group | MU–LP | RS | 1-layer RS |
Encoder complexity | Encode K streams | Encode K streams | Encode K streams | Encode K private streams plus additional common streams | Encode K+1 streams |
Scheduler complexity | Very complex as it requires to find aligned users and decide upon suitable user ordering | Very complex as it requires to divide users into orthogonal groups, with aligned users in each group and decide upon suitable user ordering in each group | Complex as MU–LP requires to pair together semi-orthogonal users with similar channel gains | Complex as it requires to decide upon suitable decoding order of the streams with the same stream order | Simpler user scheduling as RS copes with any user deployment scenario, does not rely on user grouping and user ordering |
Receiver complexity | Requires multiple layers of SIC. Subject to error propagation | Requires multiple layers of SIC in each group and a single layer of SIC if groups are made of 2 users. Subject to error propagation | Does not require any SIC | Requires multiple layers of SIC. Subject to error propagatio | Requires a single layer of SIC for all users. Less subject to error propagation |