11 research outputs found
Non-Orthogonal Contention-Based Access for URLLC Devices with Frequency Diversity
We study coded multichannel random access schemes for ultra-reliable
low-latency uplink transmissions. We concentrate on non-orthogonal access in
the frequency domain, where users transmit over multiple orthogonal subchannels
and inter-user collisions limit the available diversity. Two different models
for contention-based random access over Rayleigh fading resources are
investigated. First, a collision model is considered, in which the packet is
replicated onto available resources, of which are received
without collision, and treated as diversity branches by a maximum-ratio
combining (MRC) receiver. The resulting diversity degree depends on the
arrival process and coding strategy. In the second model, the slots subject to
collisions are also used for MRC, such that the number of diversity branches
is constant, but the resulting combined signal is affected by multiple
access interference. In both models, the performance of random and
deterministic repetition coding is compared. The results show that the
deterministic coding approach can lead to a significantly superior performance
when the arrival rate of the intermittent URLLC transmissions is low.Comment: 2019 IEEE 20th International Workshop on Signal Processing Advances
in Wireless Communications (SPAWC) - Special Session on Signal Processing for
NOMA Communication System
On Throughput Maximization of Grant-Free Access with Reliability-Latency Constraints
Enabling autonomous driving and industrial automation with wireless networks
poses many challenges, which are typically abstracted through reliability and
latency requirements. One of the main contributors to latency in cellular
networks is the reservation-based access, which involves lengthy and
resource-inefficient signaling exchanges. An alternative is to use grant-free
access, in which there is no resource reservation. A handful of recent works
investigated how to fulfill reliability and latency requirements with different
flavors of grant-free solutions. However, the resource efficiency, i.e., the
throughput, has been only the secondary focus. In this work, we formulate the
throughput of grant-free access under reliability-latency constraints, when the
actual number of arrived users or only the arrival distribution are known. We
investigate how these different levels of knowledge about the arrival process
influence throughput performance of framed slotted ALOHA with -multipacket
reception, for the Poisson and Beta arrivals. We show that the throughput under
reliability-latency requirements can be significantly improved for the higher
expected load of the access network, if the actual number of arrived users is
known. This insight motivates the use of techniques for the estimation of the
number of arrived users, as this knowledge is not readily available in
grant-free access. We also asses the impact of estimation error, showing that
for high reliability-latency requirements the gains in throughput are still
considerable.Comment: Accepted for publication in ICC'201
Opportunistic Spatial Preemptive Scheduling for URLLC and eMBB Coexistence in Multi-User 5G Networks
Sensing-Based Grant-Free Scheduling for Ultra Reliable Low Latency and Deterministic Beyond 5G Networks
5G and beyond networks should efficiently support
services with stringent and diverse QoS requirements. This includes
services for verticals that demand Ultra Reliable and Low Latency
Communications (URLLC). Scheduling strongly impacts the communication latency, and 5G NR introduces grant-free scheduling
to reduce the latency at the radio level. Grant-free scheduling can
use shared resources and the transmission of K replicas per packet
to increase the packet delivery ratio and efficiently utilize the spectrum. Previous studies have shown that existing 5G NR grant-free
scheduling has limitations to sustain URLLC requirements for aperiodic (or uncertain) and deterministic traffic that is characteristic
of verticals such as Industry 4.0 or manufacturing. In this context,
this paper proposes and evaluates a novel grant-free scheduling
scheme that can efficiently support deterministic and aperiodic uplink traffic. The scheme avoids packet collisions among UEs sharing
resources using a priority-based contention resolution process that
relies on the transmission of announcement messages in minislots
and a local channel sensing process. This study demonstrates that
the proposed sensing-based grant-free scheduling scheme outperforms current 5G NR grant-free scheduling implementations, and
can support a higher number of UEs with URLLC and deterministic requirements with a considerably lower number of radio
resources.This work has been funded by MCIN/AEI/10.13039/ 501100011033 through the project PID2020-115576RB-I00and FSE funds through the grant PRE2018-084743,the Generalitat Valenciana through the project CIGE/2021/096,by a research grant awarded by the Vicerrectorado de InvestigaciĂłn of the UMH (2022)
Internet of Things and Sensors Networks in 5G Wireless Communications
This book is a printed edition of the Special Issue Internet of Things and Sensors Networks in 5G Wireless Communications that was published in Sensors
Internet of Things and Sensors Networks in 5G Wireless Communications
This book is a printed edition of the Special Issue Internet of Things and Sensors Networks in 5G Wireless Communications that was published in Sensors