InformationTheory.Shannon.BroadcastChannel.Marton.MarkovCore.Receiver1
Marton's inner bound — the conditional AEP for receiver 1 #
The receiver-1 error event of the Marton ensemble opens with the transmitted auxiliary word failing
to be jointly typical with the received word. The selection the encoder performs makes the law of
the transmitted auxiliary word depend on the whole pair of subcodebooks, so the transmitted word is
not distributed as an i.i.d. draw from the ambient and the ordinary AEP does not apply to it. What
does apply is a conditional statement: for whatever auxiliary and input blocks the encoder ends
up transmitting, as long as their empirical type is close to the ambient (V₁, X)-law, the channel
output makes the pair (V₁, Y₁) weakly jointly typical with probability close to one.
The type closeness has to be at a radius strictly smaller than the band radius ε, because pinning
the conditional mean of the log-likelihood costs a Lipschitz factor; martonStrongRadius is that
smaller radius and martonBandConst the factor. Weak typicality of the transmitted blocks at
radius ε is not enough: it pins an entropy alone, which leaves the conditional means free.
The type pin itself is supplied by the encoder's selection rule, which picks a strongly typical
auxiliary pair. Passing that pin from the auxiliary pair to the transmitted (V₁, X) block costs
one more radius separation, because the conditional mean of a letter statistic of the input is the
auxiliary type averaged against the input kernel; martonCoveringRadius is the radius at which the
auxiliary pair has to be pinned for the transmitted block to be pinned at martonStrongRadius.
Main definitions #
martonBandConst— the Lipschitz factor of the three band pins.martonStrongRadius— the type radius at which the transmitted blocks must be pinned.martonCoveringRadius— the radius at which the selected auxiliary pair must be pinned.
Main statements #
marton_condAEP_jointlyTypicalandmarton_condAEP_jointlyTypical_ge— the conditional AEP: the channel output of a type-pinned(V₁, X)-block is jointly typical with the auxiliary word with probability≥ 1 - tol, stated on the failure event and on its complement.marton_strongRadius_prob_tendsto_one— the ambient ensemble meets the type pin with probability tending to one, so the conditional AEP is not vacuous.marton_transmitted_stronglyTypical_le— the input drawn from a type-pinned auxiliary pair inherits the pin.marton_condAEP_selected_avg_le— the two combined: the receiver-1 error term of a selected auxiliary pair, averaged over the input tier, is below any prescribed tolerance.
Coordinate laws of the Marton ambient measure — receiver 1 #
The Markov identity V₁ — X — Y₁ #
The radius separation — receiver 1 #
InformationTheory.Shannon.BroadcastChannel.Marton.martonBandConst
sourceThe Lipschitz factor relating the type radius of the transmitted (V₁, X)-block to the width
of the three entropy bands it has to pin. The sum runs over the whole alphabet, so letters carrying
no ambient mass are budgeted for as well.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonStrongRadius
sourceThe type radius at which the transmitted (V₁, X)-block has to be pinned for the output bands
to hold at radius ε. It is a computed term of ε rather than a further parameter, so the
signatures downstream carry one radius only. It is strictly smaller than ε, and its
amplification by martonBandConst stays strictly inside ε/2, for every ensemble.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonStrongRadius_pos
sourceUsed by
The three bands — receiver 1 #
The conditional AEP — receiver 1 #
InformationTheory.Shannon.BroadcastChannel.Marton.marton_condAEP_jointlyTypical
sourceWhatever auxiliary word v₁ and input word x the encoder transmits, as long as their
empirical type is pinned to the ambient (V₁, X)-law at radius martonStrongRadius, the channel
output leaves the pair (v₁, y₁) outside the weakly jointly typical set with probability at most
tol, for every block length past a threshold depending on ε and tol alone.
The threshold is uniform in v₁, x and hence in the code, which is what lets the receiver-1
error decomposition consume it after the encoder's selection has already distorted the law of the
transmitted words. The hypotheses on pV, K, W are the Markov-kernel regularity of the
ensemble; no full-support assumption is needed. Both properties a free reference law would have to
assume are structural here: it is a probability law because the ensemble is built from a probability
measure and two Markov kernels, and its (V₁, X)- and (V₁, Y₁)-marginals are consistent because
both are marginals of the same compProd chain. A letter of zero ambient mass therefore needs no
separate treatment — it enters the type radius and the band constant like any other.
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InformationTheory.Shannon.BroadcastChannel.Marton.marton_strongRadius_prob_tendsto_one
sourceThe hypothesis of marton_condAEP_jointlyTypical is met by the ambient ensemble itself with
probability tending to one: an i.i.d. (V₁, X)-block is type-pinned at the strong radius. This
certifies that the conditional AEP is not vacuous — it is the ambient counterpart of the pinning
the encoder's selection has to preserve.
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InformationTheory.Shannon.BroadcastChannel.Marton.marton_condAEP_jointlyTypical_ge
sourceThe complement reading of marton_condAEP_jointlyTypical.
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From a type-pinned auxiliary pair to a type-pinned transmitted pair — receiver 1 #
InformationTheory.Shannon.BroadcastChannel.Marton.martonCoveringRadius
sourceThe type radius at which the selected auxiliary pair has to be pinned for the transmitted
(V₁, X) block to be pinned at martonStrongRadius. The two are separated by the alphabet size
because the conditional mean of a letter statistic of the input is an average of the auxiliary
type against the input kernel, so a type deviation of the pair is amplified by the number of
auxiliary letters before it reaches the input.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonCoveringRadius_pos
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InformationTheory.Shannon.BroadcastChannel.Marton.marton_transmitted_stronglyTypical_le
sourceThe transmitted (V₁, X) block inherits the type pin of the selected auxiliary pair: drawing
the input word letterwise from K applied to a pair whose joint type is pinned at
martonCoveringRadius leaves the pair (v₁, x) outside the strongly typical set of radius
martonStrongRadius with probability at most tol, uniformly in the selected pair.
The pin the hypothesis supplies is the full empirical type of the pair, which is finer than the
(V₁, X)-type the conclusion pins, and the ambient ensemble meets it with probability tending to
one at every positive radius, so the statement is not vacuous.
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InformationTheory.Shannon.BroadcastChannel.Marton.marton_condAEP_selected_avg_le
sourceThe receiver-1 error term of a selected auxiliary pair, averaged over the input tier: whatever
type-pinned pair the encoder selects, drawing the input word from K and passing it through the
channel leaves (v₁, y₁) outside the weakly jointly typical set with probability at most tol.
This is the form the error decomposition of Marton.ErrorAnalysis consumes, since the threshold
is uniform in the selected pair and hence in the code.
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