94 research outputs found
Joint source-channel coding with feedback
This paper quantifies the fundamental limits of variable-length transmission
of a general (possibly analog) source over a memoryless channel with noiseless
feedback, under a distortion constraint. We consider excess distortion, average
distortion and guaranteed distortion (-semifaithful codes). In contrast to
the asymptotic fundamental limit, a general conclusion is that allowing
variable-length codes and feedback leads to a sizable improvement in the
fundamental delay-distortion tradeoff. In addition, we investigate the minimum
energy required to reproduce source samples with a given fidelity after
transmission over a memoryless Gaussian channel, and we show that the required
minimum energy is reduced with feedback and an average (rather than maximal)
power constraint.Comment: To appear in IEEE Transactions on Information Theor
Joint source-channel coding with feedback
This paper quantifies the fundamental limits of variable-length transmission of a general (possibly analog) source over a memoryless channel with noiseless feedback, under a distortion constraint. We consider excess distortion, average distortion and guaranteed distortion (d-semifaithful codes). In contrast to the asymptotic fundamental limit, a general conclusion is that allowing variable-length codes and feedback leads to a sizable improvement in the fundamental delay-distortion tradeoff
Exact Moderate Deviation Asymptotics in Streaming Data Transmission
In this paper, a streaming transmission setup is considered where an encoder
observes a new message in the beginning of each block and a decoder
sequentially decodes each message after a delay of blocks. In this
streaming setup, the fundamental interplay between the coding rate, the error
probability, and the blocklength in the moderate deviations regime is studied.
For output symmetric channels, the moderate deviations constant is shown to
improve over the block coding or non-streaming setup by exactly a factor of
for a certain range of moderate deviations scalings. For the converse proof, a
more powerful decoder to which some extra information is fedforward is assumed.
The error probability is bounded first for an auxiliary channel and this result
is translated back to the original channel by using a newly developed
change-of-measure lemma, where the speed of decay of the remainder term in the
exponent is carefully characterized. For the achievability proof, a known
coding technique that involves a joint encoding and decoding of fresh and past
messages is applied with some manipulations in the error analysis.Comment: 23 pages, 1 figure, 1 table, Submitted to IEEE Transactions on
Information Theor
Minimum Energy to Send k Bits Through the Gaussian Channel With and Without Feedback
The minimum achievable energy per bit over memoryless Gaussian channels has been previously addressed in the limit when the number of information bits goes to infinity, in which case it is known that the availability of noiseless feedback does not lower the minimum energy per bit, which is -1.59 dB below the noise level. This paper analyzes the behavior of the minimum energy per bit for memoryless Gaussian channels as a function of k, the number of information bits. It is demonstrated that in this nonasymptotic regime, noiseless feedback leads to significantly better energy efficiency. In particular, without feedback achieving energy per bit of -1.57 dB requires coding over at least k=10[superscript 6] information bits, while we construct a feedback scheme that transmits a single information bit with energy -1.59 dB and zero error. We also show that unless k is very small, approaching the minimal energy per bit does not require using the feedback link except to signal that transmission should stop.National Science Foundation (U.S.) (Grant CCF-06-35154)National Science Foundation (U.S.) (grant CNS-09-05398
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