Priority Enabled Grant-Free Access With Dynamic Slot Allocation for Heterogeneous mMTC Traffic in 5G NR Networks

Abstract

Although grant-based mechanisms have been a predominant approach for wireless access for years, the additional latency required for initial handshake message exchange and the extra control overhead for packet transmissions have stimulated the emergence of grant-free (GF) transmission. GF access provides a promising mechanism for carrying low and moderate traffic with small data and fits especially well for massive machine type communications (mMTC) applications. Despite a surge of interest in GF access, how to handle heterogeneous mMTC traffic based on GF mechanisms has not been investigated in depth. In this paper, we propose a priority enabled GF access scheme which performs dynamic slot allocation in each 5G new radio subframe to devices with different priority levels on a subframeby-subframe basis. While high priority traffic has access privilege for slot occupancy, the remaining slots in the same subframe will be allocated to low priority traffic. To evaluate the performance of the proposed scheme, we develop a two-dimensional Markov chain model which integrates these two types of traffic via a pseudo-aggregated process. Furthermore, the model is validated through simulations and the performance of the scheme is evaluated both analytically and by simulations and compared with two other GF access schemes. Index Terms-Grant-free access, NR numerology, mMTC traffic, dynamic slot allocation, two-dimensional Markov chain, pseudo-aggregated process. I. INTRODUCTION S IMULTANEOUS packet transmissions over the same radio resource cause performance deterioration for wireless access due to potential collisions among transmissions from competing devices. In fourth generation (4G) cellular networks, i.e., long term evolution-advanced (LTE-A), this

A Priority-Based Semi-Grant-Free NOMA: Protocol Design and Performance Analysis

“…The main idea behind GF-NOMA is to surpass the ALOHA approach in terms of reliability while achieving the same latency performance, by utilizing successive interference cancellation (SIC) and allowing multiple devices to use the same radio resource block (RRB) in a random fashion. The performance of GF-NOMA schemes has been the focus of several research works [28]- [29]. The authors of [28] proposed a dynamic compressive sensing (CS) multi-user-detection (MUD) scheme that exploits the temporal correlation of active devices and carried out an analysis in terms of performance.…”

“…Based on the proposed model, they derived closed-form expressions for evaluating the user detection probability, channel estimation error, and total system DR. In [29], the authors proposed a priority-based GF access scheme that performs dynamic slot allocation to devices with different priority levels in a subframe-by-subframe manner. The proposed scheme can guarantee access to high-priority devices, while also offering a satisfactory performance to low-priority ones.…”

Sensor Selection and Distributed Quantization for Energy Efficiency in Massive MTC

“…The reason is that, given the presence of communication errors, a higher precision (i.e., more quantization bits) implies a weaker codeword protection (cf. (8)). This translates into a poorer decoding and, therefore, into larger BER and PER.…”

“…In mMTC, according to the type of traffic, we can distinguish two main classes: event-driven (e.g., emergency scenarios) or periodic (e.g., smart metering, industrial control networks, among others) [5], [7]. In the first case, due to the low or sporadic traffic arrival patterns, the use of random-access protocols presents clear benefits [8]. Contrarily, for applications characterized by periodic patterns (e.g., the information is retrieved by polling the sensors every certain time) or deterministic arrivals (e.g., data is communicated within a given time frame), conflict-free access mechanisms such as configured scheduling, become more suitable than random-access strategies [9], [10].…”