9,616 research outputs found
Content Based Status Updates
Consider a stream of status updates generated by a source, where each update
is of one of two types: high priority or ordinary (low priority). These updates
are to be transmitted through a network to a monitor. However, the transmission
policy of each packet depends on the type of stream it belongs to. For the low
priority stream, we analyze and compare the performances of two transmission
schemes: (i) Ordinary updates are served in a First-Come-First-Served (FCFS)
fashion, whereas, in (ii), the ordinary updates are transmitted according to an
M/G/1/1 with preemption policy. In both schemes, high priority updates are
transmitted according to an M/G/1/1 with preemption policy and receive
preferential treatment. An arriving priority update discards and replaces any
currently-in-service high priority update, and preempts (with eventual resume
for scheme (i)) any ordinary update. We model the arrival processes of the two
kinds of updates, in both schemes, as independent Poisson processes. For scheme
(i), we find the arrival and service rates under which the system is stable and
give closed-form expressions for average peak age and a lower bound on the
average age of the ordinary stream. For scheme (ii), we derive closed-form
expressions for the average age and average peak age of the high priority and
low priority streams. We finally show that, if the service time is
exponentially distributed, the M/M/1/1 with preemption policy leads to an
average age of the low priority stream higher than the one achieved using the
FCFS scheme. Therefore, the M/M//1/1 with preemption policy, when applied on
the low priority stream of updates and in the presence of a higher priority
scheme, is not anymore the optimal transmission policy from an age point of
view
Reliable Transmission of Short Packets through Queues and Noisy Channels under Latency and Peak-Age Violation Guarantees
This work investigates the probability that the delay and the peak-age of
information exceed a desired threshold in a point-to-point communication system
with short information packets. The packets are generated according to a
stationary memoryless Bernoulli process, placed in a single-server queue and
then transmitted over a wireless channel. A variable-length stop-feedback
coding scheme---a general strategy that encompasses simple automatic repetition
request (ARQ) and more sophisticated hybrid ARQ techniques as special
cases---is used by the transmitter to convey the information packets to the
receiver. By leveraging finite-blocklength results, the delay violation and the
peak-age violation probabilities are characterized without resorting to
approximations based on large-deviation theory as in previous literature.
Numerical results illuminate the dependence of delay and peak-age violation
probability on system parameters such as the frame size and the undetected
error probability, and on the chosen packet-management policy. The guidelines
provided by our analysis are particularly useful for the design of low-latency
ultra-reliable communication systems.Comment: To appear in IEEE journal on selected areas of communication (IEEE
JSAC
Multicast With Prioritized Delivery: How Fresh is Your Data?
We consider a multicast network in which real-time status updates generated
by a source are replicated and sent to multiple interested receiving nodes
through independent links. The receiving nodes are divided into two groups: one
priority group consists of nodes that require the reception of every update
packet, the other non-priority group consists of all other nodes without the
delivery requirement. Using age of information as a freshness metric, we
analyze the time-averaged age at both priority and non-priority nodes. For
shifted-exponential link delay distributions, the average age at a priority
node is lower than that at a non-priority node due to the delivery guarantee.
However, this advantage for priority nodes disappears if the link delay is
exponential distributed. Both groups of nodes have the same time-averaged age,
which implies that the guaranteed delivery of updates has no effect the
time-averaged freshness.Comment: IEEE SPAWC 201
Optimizing Age of Information in Wireless Networks with Perfect Channel State Information
Age of information (AoI), defined as the time elapsed since the last received
update was generated, is a newly proposed metric to measure the timeliness of
information updates in a network. We consider AoI minimization problem for a
network with general interference constraints, and time varying channels. We
propose two policies, namely, virtual-queue based policy and age-based policy
when the channel state is available to the network scheduler at each time step.
We prove that the virtual-queue based policy is nearly optimal, up to a
constant additive factor, and the age-based policy is at-most factor 4 away
from optimality. Comparing with our previous work, which derived age optimal
policies when channel state information is not available to the scheduler, we
demonstrate a 4 fold improvement in age due to the availability of channel
state information
Uplink Age of Information of Unilaterally Powered Two-way Data Exchanging Systems
We consider a two-way data exchanging system where a master node transfers
energy and data packets to a slave node alternatively. The slave node harvests
the transferred energy and performs information transmission as long as it has
sufficient energy for current block, i.e., according to the best-effort policy.
We examine the freshness of the received packets at the master node in terms of
age of information (AoI), which is defined as the time elapsed after the
generation of the latest received packet. We derive average uplink AoI and
uplink data rate as functions of downlink data rate in closed form. The
obtained results illustrate the performance limit of the unilaterally powered
two-way data exchanging system in terms of timeliness and efficiency. The
results also specify the achievable tradeoff between the data rates of the
two-way data exchanging system.Comment: INFOCOM 2018 AOI Wkshp, 6 page
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