20 research outputs found
Frameless ALOHA with Reliability-Latency Guarantees
One of the novelties brought by 5G is that wireless system design has
increasingly turned its focus on guaranteeing reliability and latency. This
shifts the design objective of random access protocols from throughput
optimization towards constraints based on reliability and latency. For this
purpose, we use frameless ALOHA, which relies on successive interference
cancellation (SIC), and derive its exact finite-length analysis of the
statistics of the unresolved users (reliability) as a function of the
contention period length (latency). The presented analysis can be used to
derive the reliability-latency guarantees. We also optimize the scheme
parameters in order to maximize the reliability within a given latency. Our
approach represents an important step towards the general area of design and
analysis of access protocols with reliability-latency guarantees.Comment: Accepted for presentation at IEEE Globecom 201
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
Reliability-Latency Performance of Frameless ALOHA with and without Feedback
This paper presents a finite length analysis of multislot type frameless ALOHA based on a dynamic programming approach. The analysis is exact, but its evaluation is only feasible for moderate number of users due to the computational complexity. The analysis is then extended to derive continuous
approximations of its key parameters, which, apart from providing an insight into the decoding process, make it possible to estimate the packet error rate with very low computational complexity. Finally, a feedback scheme is presented in which the slot access scheme is dynamically adapted according to the approximate analysis in order to minimize the packet error rate. The results indicate that the introduction of feedback can substantially improve the performance of frameless ALOH
Reliability-Latency Performance of Frameless ALOHA with and without Feedback
This paper presents a finite length analysis of multislot type frameless ALOHA based on a dynamic programming approach. The analysis is exact, but its evaluation is only feasible for moderate number of users due to the computational complexity. The analysis is then extended to derive continuous
approximations of its key parameters, which, apart from providing an insight into the decoding process, make it possible to estimate the packet error rate with very low computational complexity. Finally, a feedback scheme is presented in which the slot access scheme is dynamically adapted according to the approximate analysis in order to minimize the packet error rate. The results indicate that the introduction of feedback can substantially improve the performance of frameless ALOH
Ultra-Reliable Communication in 5G Wireless Systems
Wireless 5G systems will not only be "4G, but faster". One of the novel
features discussed in relation to 5G is Ultra-Reliable Communication (URC), an
operation mode not present in today's wireless systems. URC refers to provision
of certain level of communication service almost 100 % of the time. Example URC
applications include reliable cloud connectivity, critical connections for
industrial automation and reliable wireless coordination among vehicles. This
paper puts forward a systematic view on URC in 5G wireless systems. It starts
by analyzing the fundamental mechanisms that constitute a wireless connection
and concludes that one of the key steps towards enabling URC is revision of the
methods for encoding control information (metadata) and data. It introduces the
key concept of Reliable Service Composition, where a service is designed to
adapt its requirements to the level of reliability that can be attained. The
problem of URC is analyzed across two different dimensions. The first dimension
is the type of URC problem that is defined based on the time frame used to
measure the reliability of the packet transmission. Two types of URC problems
are identified: long-term URC (URC-L) and short-term URC (URC-S). The second
dimension is represented by the type of reliability impairment that can affect
the communication reliability in a given scenario. The main objective of this
paper is to create the context for defining and solving the new engineering
problems posed by URC in 5G.Comment: To be presented at the 1st International Conference on 5G for
Ubiquitous Connectivit
On the Performance of Irregular Repetition Slotted ALOHA with an Age of Information Threshold
The present paper focuses on an IoT setting in which a large number of
devices generate time-stamped updates addressed to a common gateway. Medium
access is regulated following a grant-free approach, and the system aims at
maintaining an up-to-date knowledge at the receiver, measured through the
average network age of information (AoI). In this context, we propose a
variation of the irregular repetition slotted ALOHA (IRSA) protocol. The
scheme, referred to as age-threshold IRSA (AT-IRSA), leverages feedback
provided by the receiver to admit to the channel only devices whose AoI exceeds
a dynamically adapted target value. By means of detailed networks simulations,
as well as of a simple yet tight analytical approximation, we demonstrate that
the approach can more than halve the average network AoI compared to plain
IRSA, and offers notable improvements over feedback-based state-of-the-art
slotted ALOHA solutions recently proposed in the literature