1,721,277 research outputs found
On the impact of correlated arrivals and errors on ARQ delay terms
No full textWe analytically investigate the packet delay statistics of the selective repeat ARQ scheme with non-instantaneous feedback, with correlation both in the channel errors and the packet arrival process. We highlight interesting trends of the delay terms, which can be extremely useful for multimedia real time services over wireless
Impact of Transmission Cost on Age of Information at Nash Equilibrium in Slotted ALOHA
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On the effect of feedback errors in Markov models for SR ARQ packet delays
No full textModern communication systems require effective error control techniques for wireless links. This problem is still relevant in many applications involving recently developed IEEE standards such as 802.16, or sensors for environmental monitoring in extreme conditions. A notable example is also underwater communication with acoustic transmission, where long delays may be present. Usually, such studies assume the availability of an error-free feedback channels which is used to perform retransmission requests in an ARQ fashion. This paper discusses the performance of the selective repeat ARQ scheme in terms of packet delay when the feedback that is sent back at the transmitter's side can be erroneous. A non instantaneous noisy feedback and a Bernoulli arrival process, for different traffic intensities, are considered. The system is modeled through discrete time Markov chains, including the channel and the ARQ state. The system equations are derived and solved, and the impact of erroneous feedback is quantified. With respect to other similar contributions, the proposed approach presents the advantage of being directly implementable in any analysis using Markov chains to evaluate the system properties, instead of dedicated models. It can therefore be extended to a plethora of different scenarios, including different channel models and also including FEC features so as to obtain a hybrid ARQ scheme
Evaluation of a potential energy methodology for joint routing and scheduling in wireless mesh networks
No full textIn wireless mesh networks, joint optimization of routing and link scheduling within a time-division multiplexing approach is commonly sought to provide end users with high data rates. However, the strategies proposed to this end usually proceed by means of complex optimization models, which also often rely on oversimplified assumptions, especially for what concerns wireless interference. In the present paper, we draw a novel general framework to perform joint routing and scheduling avoiding these limitations. We evaluate sequences of link activation modes, i.e., sets of transmissions which can be performed simultaneously, and we introduce the concept of potential energy of a mesh network, thanks to which we outline efficient selection of link allocation modes in order to jointly solve routing and scheduling. A heuristic strategy derived within this framework is numerically evaluated by means of simulation and is shown to achieve very good performance, obtained with extremely low computational complexity
A Stochastic Model for Age-of-Information Efficiency in ARQ Systems with Energy Harvesting
No full textThe Role of Feedback in AoI Optimization Under Limited Transmission Opportunities
No full textScheduling updates from remote sensors is a key task for the internet of things (IoT). In this context, the mathematical concept of age of information is often used to capture the freshness of received data. This is, in turn, relevant to optimize the frequency of the exchanges, especially for resource constrained (e.g., energy-limited) sensors. Most investigations on the subject assume that the transmitter can leverage knowledge of the age of information at the receiver side to decide when to send data, even when the communication channel is unreliable. In reality, tracking the outcome of the updates would require additional consumption of resources to acquire a feedback. We investigate the optimal schedule of updates over a finite time horizon for a resource-constrained sensor that is allowed to perform a limited number of updates, as typical of IoT devices. We discuss the role of the feedback from the receiver, and whether it is convenient to ask for it whenever this causes additional energy consumption and consequently allows the transmission of a lower number of updates. We analytically identify regions for the feedback cost and the reliability of the channel where making use of feedback may or may not be beneficial
A Framework for Call Admission Control Threshold Setup and Evaluation of the Performance in WCDMA Systems
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