[Paper Review] RAPID: Contention Resolution-based Random Access using Context ID for IoT

Junseok Kim, Seongwon Kim+2 more|arXiv (Cornell University)|Jan 5, 2022

IoT Networks and Protocols21 references4 citations

TL;DR

RAPID is a contention resolution-based random access protocol for IoT that uses context IDs to enable delay-sensitive devices to complete access in just two message exchanges, reducing uplink latency by 80.8% and improving reliability to 99.999% while decreasing random access load by 30.5% compared to state-of-the-art methods.

ABSTRACT

With the increasing number of Internet of Things (IoT) devices, Machine Type Communication (MTC) has become an important use case of the Fifth Generation (5G) communication systems. Since MTC devices are mostly disconnected from Base Station (BS) for power saving, random access procedure is required for devices to transmit data. If many devices try random access simultaneously, preamble collision problem occurs, thus causing latency increase. In an environment where delay-sensitive and delay-tolerant devices coexist, the contention-based random access procedure cannot satisfy latency requirements of delay-sensitive devices. Therefore, we propose RAPID, a novel random access procedure, which is completed through two message exchanges for the delay-sensitive devices. We also develop Access Pattern Analyzer (APA), which estimates traffic characteristics of MTC devices. When UEs, performing RAPID and contention-based random access, coexist, it is important to determine a value which is the number of preambles for RAPID to reduce random access load. Thus, we analyze random access load using a Markov chain model to obtain the optimal number of preambles for RAPID. Simulation results show RAPID achieves 99.999% reliability with 80.8% shorter uplink latency, and also decreases random access load by 30.5% compared with state-of-the-art techniques.

Motivation & Objective

• Address the high latency and collision issues in contention-based random access for massive IoT (mMTC) devices.
• Enable low-latency access for delay-sensitive IoT devices in coexistence with delay-tolerant devices.
• Optimize the number of preambles allocated to RAPID to minimize random access load while maintaining high reliability.
• Develop a mechanism to estimate traffic characteristics of MTC devices for dynamic access optimization.

Proposed method

• Propose RAPID, a two-message random access procedure using context IDs to resolve preamble contention without retransmission.
• Introduce Access Pattern Analyzer (APA) to estimate traffic patterns of MTC devices based on historical access behavior.
• Model random access load using a Markov chain to analyze system behavior under mixed RAPID and contention-based access.
• Determine the optimal number of preambles for RAPID by balancing load reduction and reliability requirements.
• Use context ID to uniquely identify device groups and enable fast contention resolution during random access.
• Integrate RAPID with existing 5G random access procedures to coexist with legacy contention-based access.

Experimental results

Research questions

• RQ1 How can random access latency be minimized for delay-sensitive IoT devices in a dense mMTC environment?
• RQ2 What is the optimal number of preambles to allocate to RAPID to reduce overall random access load?
• RQ3 How does RAPID perform in coexistence with traditional contention-based random access in terms of reliability and latency?
• RQ4 Can context-based grouping improve contention resolution efficiency in massive IoT access?
• RQ5 What is the impact of traffic pattern variability on RAPID’s performance and system load?

Key findings

• RAPID achieves 99.999% reliability in random access under high device density.
• RAPID reduces uplink latency by 80.8% compared to state-of-the-art contention-based schemes.
• RAPID decreases random access load by 30.5% compared to existing techniques.
• The Markov chain model accurately predicts system load and helps determine the optimal preamble allocation.
• APA effectively estimates traffic characteristics of MTC devices, enabling dynamic access optimization.
• Coexistence of RAPID and contention-based access is feasible with minimal interference when preamble allocation is properly tuned.