25,156 research outputs found
Searching with Measurement Dependent Noise
Consider a target moving with a constant velocity on a unit-circumference
circle, starting from an arbitrary location. To acquire the target, any region
of the circle can be probed for its presence, but the associated measurement
noise increases with the size of the probed region. We are interested in the
expected time required to find the target to within some given resolution and
error probability. For a known velocity, we characterize the optimal tradeoff
between time and resolution (i.e., maximal rate), and show that in contrast to
the case of constant measurement noise, measurement dependent noise incurs a
multiplicative gap between adaptive search and non-adaptive search. Moreover,
our adaptive scheme attains the optimal rate-reliability tradeoff. We further
show that for optimal non-adaptive search, accounting for an unknown velocity
incurs a factor of two in rate.Comment: Information Theory Workshop (ITW) 201
When Can a Relay Reduce End-to-End Communication Delay?
The impact of relaying on the latency of communication in a relay channel is
studied. Both decode-forward (DF) and amplify-forward (AF) are considered, and
are compared with the point-to-point (P2P) scheme which does not use the relay.
The question as to whether DF and AF can decrease the latency of communicating
a number of bits with a given reliability requirement is addressed. Latency
expressions for the three schemes are derived. Although both DF and AF use a
block-transmission structure which sends the information over multiple
transmission blocks, they can both achieve latencies lower that P2P. Conditions
under which this occurs are obtained. Interestingly, these conditions are more
strict when compared to the conditions under which DF and AF achieve higher
information-theoretic rates than P2P.Comment: 6 pages, 4 figure
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