12,329 research outputs found
Bits Through Bufferless Queues
This paper investigates the capacity of a channel in which information is
conveyed by the timing of consecutive packets passing through a queue with
independent and identically distributed service times. Such timing channels are
commonly studied under the assumption of a work-conserving queue. In contrast,
this paper studies the case of a bufferless queue that drops arriving packets
while a packet is in service. Under this bufferless model, the paper provides
upper bounds on the capacity of timing channels and establishes achievable
rates for the case of bufferless M/M/1 and M/G/1 queues. In particular, it is
shown that a bufferless M/M/1 queue at worst suffers less than 10% reduction in
capacity when compared to an M/M/1 work-conserving queue.Comment: 8 pages, 3 figures, accepted in 51st Annual Allerton Conference on
Communication, Control, and Computing, University of Illinois, Monticello,
Illinois, Oct 2-4, 201
Zero-Error Capacity of a Class of Timing Channels
We analyze the problem of zero-error communication through timing channels
that can be interpreted as discrete-time queues with bounded waiting times. The
channel model includes the following assumptions: 1) Time is slotted, 2) at
most "particles" are sent in each time slot, 3) every particle is delayed
in the channel for a number of slots chosen randomly from the set , and 4) the particles are identical. It is shown that the
zero-error capacity of this channel is , where is the unique
positive real root of the polynomial .
Capacity-achieving codes are explicitly constructed, and a linear-time decoding
algorithm for these codes devised. In the particular case , ,
the capacity is equal to , where is
the golden ratio, and the constructed codes give another interpretation of the
Fibonacci sequence.Comment: 5 pages (double-column), 3 figures. v3: Section IV.1 from v2 is
replaced with Remark 1, and Section IV.2 is removed. Accepted for publication
in IEEE Transactions on Information Theor
Covert Bits Through Queues
We consider covert communication using a queuing timing channel in the
presence of a warden. The covert message is encoded using the inter-arrival
times of the packets, and the legitimate receiver and the warden observe the
inter-departure times of the packets from their respective queues. The
transmitter and the legitimate receiver also share a secret key to facilitate
covert communication. We propose achievable schemes that obtain non-zero covert
rate for both exponential and general queues when a sufficiently high rate
secret key is available. This is in contrast to other channel models such as
the Gaussian channel or the discrete memoryless channel where only
covert bits can be sent over channel uses, yielding
a zero covert rate.Comment: To appear at IEEE CNS, October 201
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