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Exploiting In-Slot Micro-Synchronism for S-ALOHA

Yangqian Hu, Jun-Bae Seo, Hu Jin

TL;DR

Numerical results demonstrate that the proposed backoff algorithms can achieve the throughput close to an ideal system and drastically reduce the access delay compared to S-ALOHA system.

Abstract

Proliferation of the urban Internet-of-Things (IoTs) for smart cities has fuelled massive amounts of data over wireless cellular networks. Random access (RA) system of wireless cellular networks, e.g., 5G New Radio (NR), based on S-ALOHA system should cope with ever-growing IoT traffic. This work proposes S-ALOHA system with time offsets (TOs), where one slot consists of K TOs and one packet transmission time. The length of the overall TOs is a fraction of a packet transmission time. In the system users (re)transmit to the boundary of a TO randomly selected. This enables the base station (BS) to inform the users of who transmits the first and the last packets in the slot with collision so that the two users can retransmit successfully in the following two slots respectively. Our throughput analysis compared to simulations shows that adopting even with three and four TOs surpasses the throughput limit of S-ALOHA system without TOs. Additionally, we propose two Bayesian-optimized backoff algorithms for S-ALOHA system with TOs, with which users can apply throughput-optimal (re)transmission probability or uniform backoff window even in unsaturated traffic scenarios. Numerical results demonstrate that the proposed backoff algorithms can achieve the throughput close to an ideal system and drastically reduce the access delay compared to S-ALOHA system.

Exploiting In-Slot Micro-Synchronism for S-ALOHA

TL;DR

Numerical results demonstrate that the proposed backoff algorithms can achieve the throughput close to an ideal system and drastically reduce the access delay compared to S-ALOHA system.

Abstract

Proliferation of the urban Internet-of-Things (IoTs) for smart cities has fuelled massive amounts of data over wireless cellular networks. Random access (RA) system of wireless cellular networks, e.g., 5G New Radio (NR), based on S-ALOHA system should cope with ever-growing IoT traffic. This work proposes S-ALOHA system with time offsets (TOs), where one slot consists of K TOs and one packet transmission time. The length of the overall TOs is a fraction of a packet transmission time. In the system users (re)transmit to the boundary of a TO randomly selected. This enables the base station (BS) to inform the users of who transmits the first and the last packets in the slot with collision so that the two users can retransmit successfully in the following two slots respectively. Our throughput analysis compared to simulations shows that adopting even with three and four TOs surpasses the throughput limit of S-ALOHA system without TOs. Additionally, we propose two Bayesian-optimized backoff algorithms for S-ALOHA system with TOs, with which users can apply throughput-optimal (re)transmission probability or uniform backoff window even in unsaturated traffic scenarios. Numerical results demonstrate that the proposed backoff algorithms can achieve the throughput close to an ideal system and drastically reduce the access delay compared to S-ALOHA system.
Paper Structure (17 sections, 8 theorems, 58 equations, 13 figures, 3 tables, 1 algorithm)

This paper contains 17 sections, 8 theorems, 58 equations, 13 figures, 3 tables, 1 algorithm.

Table of Contents

  1. Introduction
  2. Motivations
  3. Related Works
  4. Contributions
  5. Organization
  6. S-ALOHA System with time offsets
  7. Analysis and Algorithm Design
  8. Throughput Analysis
  9. Algorithm Design
  10. Algorithm with Uniform Backoff Window
  11. Numerical Results
  12. Conclusion
  13. Proof of Theorem \ref{['Th:Th1']}
  14. Proof of Corollary \ref{['Cr:Cr1']}
  15. Proof of Proposition \ref{['Pr:Pr1']}
  16. ...and 2 more sections

Key Result

Theorem 1

Suppose the system with $K$ TOs, where each of $n$ users always has a packet to transmit, i.e., saturated user. Throughput of this system (packets/$T$) can be obtained as where $\gamma=T/T_s$, and $T_s\triangleq (K-1)\alpha+T$.

Figures (13)

  • Figure 1: Slot structure $T_s$ with six TOs ($K=6$).
  • Figure 2: Various channel outcomes in S-ALOHA system with TO.
  • Figure 3: The last part of a slot larger than one packet transmission time.
  • Figure 4: Relationship between $\kappa$, $\tilde{\tau}^*$ and $K$.
  • Figure 5: Throughput behavior of S-ALOHA system with $\alpha=0.07$ and $0.14$.
  • ...and 8 more figures

Theorems & Definitions (10)

  • Theorem 1
  • Corollary 1
  • Corollary 2
  • Proposition 1
  • Corollary 3
  • Lemma 1
  • Remark 1
  • Lemma 2
  • Corollary 4
  • Remark 2