Almost affinely disjoint subspaces

Liu, Hedongliang; Polyanskii, Nikita; Vorobyev, Ilya; Wachter-Zeh, Antonia

doi:10.1016/j.ffa.2021.101879

Cited by 5 publications

(2 citation statements)

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“…Coding sequences have been devised for massive access, including Walsh sequences and decorrelated sequences [40], or almost affinely disjoint subspaces [41], where it is possible to characterize the Hamming weight distribution of pseudorandom sequences [42], and Khachatrian-Martirossian construction to enable K > n users signal in n dimensions simultaneously, where K ≈ 1 2 n log 2 n is the optimal scaling [2, Slides 57-59]. Furthermore, it has been shown that when the inputs are constrained to ±1, it is possible to have K n. Zadoff-Chu sequences provide low complexity and constant-amplitude output signals, and have been widely used in 3GPP LTE air interface, including the control and traffic channels [43].…”

Section: A Related Workmentioning

confidence: 99%

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The Interplay of Spectral Efficiency, User Density, and Energy in Random Access Protocols with Retransmissions

Malak¹

2022

Preprint

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The fifth-generation of wireless communication networks is required to support a range of use cases such as enhanced mobile broadband (eMBB), ultra-reliable, low-latency communications (URLLC), massive machine-type communications (mMTCs), with heterogeneous data rate, delay, and power requirements. The 4G LTE air interface uses extra overhead to enable scheduled access, which is not justified for small payload sizes. We employ a random access communication model with retransmissions for multiple users with small payloads at the low spectral efficiency regime. The radio resources are split non-orthogonally in the time and frequency dimensions. Retransmissions are combined via Hybrid Automatic Repeat reQuest (HARQ) methods, namely Chase Combining and Incremental Redundancy with a finite buffer size constraint C buf . We determine the best scaling for the spectral efficiency (SE) versus signal-to-noise ratio (SNR) per bit and for the user density versus SNR per bit, for the sum-optimal regime and when the interference is treated as noise, using a Shannon capacity approximation. Numerical results show that the scaling results are applicable over a range of η, T , C buf , J, at low received SNR values. The proposed analytical framework provides insights for resource allocation in general random access systems and specific 5G use cases for massive URLLC uplink access.

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Section: A Related Workmentioning

confidence: 99%

“…where (41) follows from σ t = σ, (42) from dividing both the numerator and the denominator terms by (mσ 2 ) 2 , and the last step in (43) from assuming that ρ tj = ρ, and defining j ∈S t,−j 1 a tj =0 = J t − 1.…”

Section: Appendixmentioning

confidence: 99%