The Interplay of Spectral Efficiency, User Density, and Energy in Grant-Based Access Protocols

We employ grant-based access with retransmissions for multiple users with small payloads, particularly at low spectral efficiency (SE). The radio resources are allocated via non-orthogonal multiple access (NOMA) in the time into T slots and frequency dimensions, with a measure of non-orthogonality...

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Bibliographic Details
Published in:IEEE transactions on communications 2024-06, Vol.72 (6), p.3701-3719
Main Author: Malak, Derya
Format: Article
Language:English
Subjects:
Automatic repeat request
chase combining
Density
HARQ
HARQ receiver buffer
incremental redundancy
Interference
matched filter decoding
maximum ratio combining
Multiple access
Network latency
NOMA
Nonorthogonal multiple access
Orthogonality
Payloads
Receivers
Redundancy
Resource allocation
Scaling
Signal to noise ratio
SNR per bit
Spectral efficiency
Throughput
Tin
Uplink
user density
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Summary:We employ grant-based access with retransmissions for multiple users with small payloads, particularly at low spectral efficiency (SE). The radio resources are allocated via non-orthogonal multiple access (NOMA) in the time into T slots and frequency dimensions, with a measure of non-orthogonality \eta . Retransmissions are stored in a receiver buffer with a finite size C_{\sf buf} and combined via Hybrid Automatic Repeat reQuest (HARQ), using Chase Combining (CC) and Incremental Redundancy (IR). We determine the best scaling for the SE (bits/rdof) and for the user density J/n , for a given number of users J and a blocklength n , versus signal-to-noise ratio (SNR, \rho ) per bit, i.e., the ratio E_{b}/N_{0} , for the sum-rate optimal regime and when the interference is treated as noise (TIN), using a finite blocklength analysis. Contrasting the classical scheme (no retransmissions) with CC-NOMA, CC-OMA, and IR-OMA strategies in TIN and sum-rate optimal cases, the numerical results on the SE demonstrate that CC-NOMA outperforms, almost in all regimes, the other approaches. For high C_{\sf buf} and small \eta , IR-OMA could surpass CC-NOMA. At low E_{b}/N_{0} , the SE of CC-OMA with TIN, as it exploits CC and offers lower interference, can approach the trend of CC-NOMA and outperform the other TIN-based methods. In the sum-rate optimal regime, the scalings of J/n versus E_{b}/N_{0} deteriorate with T , yet from the most degraded to the least, the ordering of the s
ISSN:0090-6778
1558-0857
DOI:10.1109/TCOMM.2024.3361550