316 research outputs found
Effect of slot type identification on frame length optimization
In dense radio frequency identification (RFID) systems, reducing reading times is crucial. For tag anti-collision management, most RFID systems rely on frame slotted ALOHA (FSA). The most common method to reduce the reading time for large tag populations is optimization of the number of slots per frame. The slot duration in real RFID systems is determined by the slot type (idle, successful, or colliding). Furthermore, by detecting the strongest transponder, colliding slots can be transformed to successful slots, a phenomenon known as the capture effect. Additionally, RFID readers might be capable of identifying slot types using the physical layer which reduces the colliding slot time because at this moment the reader can immediately terminate the connection as there is no need to reply with invalid acknowledge and wait for the time-out. In this paper, we provide a novel approach for analytical estimation of the optimal frame length. Our approach yields a novel closed form equation for the frame length that takes into account durations of different slot types, the capture effect, and the probability of slot type identification. Experimental results for FM0 encoding show that our technique achieves a total reading time reduction between 5.5% and 11.3% over methods that do not take into account slot type identification. However, the reduction in reading time is maximally 9%, 6%, and 1% for Miller encoding scheme with M = 2, 4, and 8, respectively
Stable Throughput and Delay Analysis of a Random Access Network With Queue-Aware Transmission
In this work we consider a two-user and a three-user slotted ALOHA network
with multi-packet reception (MPR) capabilities. The nodes can adapt their
transmission probabilities and their transmission parameters based on the
status of the other nodes. Each user has external bursty arrivals that are
stored in their infinite capacity queues. For the two- and the three-user cases
we obtain the stability region of the system. For the two-user case we provide
the conditions where the stability region is a convex set. We perform a
detailed mathematical analysis in order to study the queueing delay by
formulating two boundary value problems (a Dirichlet and a Riemann-Hilbert
boundary value problem), the solution of which provides the generating function
of the joint stationary probability distribution of the queue size at user
nodes. Furthermore, for the two-user symmetric case with MPR we obtain a lower
and an upper bound for the average delay without explicitly computing the
generating function for the stationary joint queue length distribution. The
bounds as it is seen in the numerical results appear to be tight. Explicit
expressions for the average delay are obtained for the symmetrical model with
capture effect which is a subclass of MPR models. We also provide the optimal
transmission probability in closed form expression that minimizes the average
delay in the symmetric capture case. Finally, we evaluate numerically the
presented theoretical results.Comment: Submitted for journal publicatio
Combining distributed queuing with energy harvesting to enable perpetual distributed data collection applications
This is the peer reviewed version of the following article: Vazquez-Gallego F, Tuset-Peiró P, Alonso L, Alonso-Zarate J. Combining distributed queuing with energy harvesting to enable perpetual distributed data collection applications. Trans Emerging Tel Tech. 2017;e3195 , which has been published in final form at https://doi.org/10.1002/ett.3195. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.This paper presents, models, and evaluates energy harvesting–aware distributed queuing (EH-DQ), a novel medium access control protocol that combines distributed queuing with energy harvesting (EH) to address data collection applications in industrial scenarios using long-range and low-power wireless communication technologies. We model the medium access control protocol operation using a Markov chain and evaluate its ability to successfully transmit data without depleting the energy stored at the end devices. In particular, we compare the performance and energy consumption of EH-DQ with that of time-division multiple access (TDMA), which provides an upper limit in data delivery, and EH-aware reservation dynamic frame slotted ALOHA, which is an improved variation of frame slotted ALOHA. To evaluate the performance of these protocols, we use 2 performance metrics: delivery ratio and time efficiency. Delivery ratio measures the ability to successfully transmit data without depleting the energy reserves, whereas time efficiency measures the amount of data that can be transmitted in a certain amount of time. Results show that EH-DQ and TDMA perform close to the optimum in data delivery and outperform EH-aware reservation dynamic frame slotted ALOHA in data delivery and time efficiency. Compared to TDMA, the time efficiency of EH-DQ is insensitive to the amount of harvested energy, making it more suitable for energy-constrained applications. Moreover, compared to TDMA, EH-DQ does not require updated network information to maintain a collision-free schedule, making it suitable for very dynamic networks.Peer ReviewedPostprint (author's final draft
Modern Random Access for Satellite Communications
The present PhD dissertation focuses on modern random access (RA) techniques.
In the first part an slot- and frame-asynchronous RA scheme adopting replicas,
successive interference cancellation and combining techniques is presented and
its performance analysed. The comparison of both slot-synchronous and
asynchronous RA at higher layer, follows. Next, the optimization procedure, for
slot-synchronous RA with irregular repetitions, is extended to the Rayleigh
block fading channel. Finally, random access with multiple receivers is
considered.Comment: PhD Thesis, 196 page
Spectrum slicing for multiple access channels with heterogeneous services
Wireless mobile networks from the fifth generation (5G) and beyond serve as platforms for flexible support of heterogeneous traffic types with diverse performance requirements. In particular, the broadband services aim for the traditional rate optimization, while the time-sensitive services aim for the optimization of latency and reliability, and some novel metrics such as Age of Information (AoI). In such settings, the key question is the one of spectrum slicing: how these services share the same chunk of available spectrum while meeting the heterogeneous requirements. In this work we investigated the two canonical frameworks for spectrum sharing, Orthogonal Multiple Access (OMA) and Non-Orthogonal Multiple Access (NOMA), in a simple, but insightful setup with a single time-slotted shared frequency channel, involving one broadband user, aiming to maximize throughput and using packet-level coding to protect its transmissions from noise and interference, and several intermittent users, aiming to either to improve their latency-reliability performance or to minimize their AoI. We analytically assessed the performances of Time Division Multiple Access (TDMA) and ALOHA-based schemes in both OMA and NOMA frameworks by deriving their Pareto regions and the corresponding optimal values of their parameters. Our results show that NOMA can outperform traditional OMA in latency-reliability oriented systems in most conditions, but OMA performs slightly better in age-oriented systems
Fresh Multiple Access: A Unified Framework Based on Large Models and Mean-Field Approximations
Information freshness has attracted increasingly attention in the past decade
as it plays a critical role in the emerging real-time applications. Age of
information (AoI) holds the promise of effectively characterizing the
information freshness, hence widely considered as a fundamental performance
metric. However, in multiple-device scenarios, most existing works focus on the
analysis and optimization of AoI based on queueing systems. The study for a
unified approach for general multiple access control scheme in
freshness-oriented scenarios remains open. In this paper, we take into
consideration the combination of the fundamental freshness metric AoI and
multiple access control schemes to achieve efficient cross-layer analysis and
optimization in freshness-oriented scenarios, which is referred to as fresh
multiple access. To this end, we build a unified framework with a discrete-time
tandem queue model for fresh multiple access. The unified framework enables the
analysis and optimization for general multiple access protocols in fresh
multiple access. To handle the high dimension framework embedded in fresh
multiple access, we introduce large model approaches for the Markov chain
formulation in AoI oriented scenarios. Two typical AoI-based metric are studied
including age of incorrect information (AoII) and peak AoII. Moreover, to
address the computational complexity of the large model, we present mean-field
approximations which significantly reduces the dimension of the Markov chain
model by approximating the integral affect of massive devices in fresh multiple
access.Comment: accepted by Journal of Communications and Network
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