In future generation network technologies, such as 3GPP’s Narrow-
Band Internet of Things (NB-IoT), smart meters, 5G V2X, etc., there is
a need to address the uRLLC use case (ultra-reliable and low latency
communications). Estimates show that by the end of 2025, 50 billion
devices will be connected across the globe. These applications dwell on the
aforementioned technologies. Thus, the huge rollout of communicating
devices causes congestion and latency. Extensive studies and research
have to be conducted to cope up with reducing the latency and improving
the reliability of the supporting technologies.
For transmission, we focus on 5G’s millimeter-wave (mmWave) bands
which alleviate the problem of bandwidth scarcity. However high-frequency
bands do not cover larger distances. The coverage problem is addressed
by using a heterogeneous network that comprises numerous small and
macrocells, defined by transmission and reception points (TRxPs). For
such a network, random access (RA) is the pivotal task for any mobile
node to connect to TRxPs (AP), which experiences delay and congestion.
The state of art RA resource selection does not fulfill the envisioned latency
requirement of 5G and beyond 5G.
RA is considered a challenging function in which users attempt to select
an efficient TRxP within a given time. Ideally, an efficient TRxP is less
congested, minimizing delays in users’ random access. However, owing
to the nature of random access, it is not feasible to deploy a centralized
controller estimating the congestion level of each cell and delivering this
information back to users during random access. To solve this problem, we
establish an optimization problem and employ a machine- learning-based
scheme.
Additionally, an important aspect of such estimation is that it can be
approached based on machine learning architecture and hyperparameters
search. Such a method in a mobile environment is an open research
question for RA, in terms of increasing the key performance indicator
(KPI) and rewards. Most studies in literature engage neural architecture
search for supervised learning tasks, and there is limited work with regard
to deep reinforcement learning (DRL). Therefore, we also propose an
optimization framework to address the search problem of neural network
architecture. The goal is to optimize the DRL algorithm so that it yields
an additional performance improvement. This framework consists of a
performance extrapolation algorithm.
Through extensive simulations, we demonstrate that our proposed
machine learning-based approach and revealed architectures to solving
the problem discussed improve performance on random access. Specifically,
experiments demonstrate a reduction of the RA delay and significant
improvement of the access success probability. Furthermore, the proposed
extrapolation algorithm based on LSTM shows better learning curve prediction
as compared to notable regression techniques, such as linear interpolation.