Browsing by Subject "Age of Information (AoI)"

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    Discrete-time queueing model of age of information with multiple information sources
    (IEEE, 2021-01-22) Akar, Nail; Doğan, Ozancan
    Information freshness in IoT-based status update systems has recently been studied through the Age of Information (AoI) and Peak AoI (PAoI) performance metrics. In this article, we study a discrete-time server arising in multisource IoT systems, which accepts incoming information packets from multiple information sources so as to be forwarded to a remote monitor for status update purposes. Under the assumption of Bernoulli information packet arrivals and a common general discrete phase-type service time distribution across all the sources, we numerically obtain the exact per-source distributions of AoI and PAoI in matrix-geometric form for three different queueing disciplines: 1) nonpreemptive bufferless; 2) preemptive bufferless; and 3) nonpreemptive single buffer with replacement. The proposed numerical algorithm employs the theory of discrete-time Markov chains of quasi-birth-death type and is matrix analytical. Numerical examples are provided to validate the accuracy and effectiveness of the proposed queueing model. We also present a numerical example on the optimum choice of the Bernoulli parameters in a practical IoT system with two sources with diverse AoI requirements.
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    ItemOpen Access
    Exact analytical model of age of information in multi-source status update systems with per-source queueing
    (IEEE, 2022-05-27) Gamgam, Ege Orkun; Akar, Nail
    We study a multisource status update system with Poisson information packet arrivals and exponentially distributed service times. The server is equipped with a waiting room holding the freshest packet from each source referred to as single buffer per-source queueing (SBPSQ). The sources are assumed to be equally important, i.e., (nonweighted) average Age of Information (AoI) or average age violation probability are used as the information freshness metrics to optimize for, and subsequently, two symmetric SBPSQ-based scheduling policies are studied in this article, namely, first source first serve (FSFS) and the earliest served first serve (ESFS) policies. By employing the theory of Markov fluid queues (MFQs), an analytical model is proposed to obtain the exact distribution of the AoI for each source when the FSFS and ESFS policies are employed at the server. Additionally, a benchmark scheduling-free scheme named single buffer with replacement (SBR), which uses a single buffer to hold the freshest packet across all sources, is also studied with a similar but less complex analytical model. We comparatively study the performance of the three policies through numerical examples in terms of the average AoI and the age violation probability averaged across all sources, in a scenario of sources possessing different traffic intensities but sharing a common service time.