InformationTheory.Shannon.BroadcastChannel.Marton.Setup
Marton's inner bound — five-variable ambient setup #
The random-coding ensemble behind Marton's inner bound carries a pair of auxiliary variables
(V₁, V₂), one per receiver, so the per-coordinate law is a quintuple (V₁, V₂, X, Y₁, Y₂)
rather than the quadruple (U, X, Y₁, Y₂) of superposition coding. This file builds that law
from a joint auxiliary distribution pV on V₁ × V₂, an input kernel K : Kernel (V₁ × V₂) α
and a broadcast channel W, together with its i.i.d. ambient measure, the coordinate facts
consumed downstream, and the three informations appearing in the region inequalities.
The input is produced by a general kernel K rather than a deterministic map x = f(v₁, v₂):
a deterministic kernel puts zero mass off its image, which is incompatible with the full-support
hypotheses hpV / hK / hW that every typicality bound in this development requires.
Main definitions #
martonJointDistribution pV K W— the per-coordinate law onV₁ × V₂ × α × β₁ × β₂.martonAmbientMeasure pV K W— its i.i.d. ambient measure onℕ → V₁ × V₂ × α × β₁ × β₂.martonInfo₁/martonInfo₂/martonInfoV₁V₂— the informationsI(V₁; Y₁),I(V₂; Y₂)andI(V₁; V₂)of the per-coordinate law, in entropy-difference form.
Implementation notes #
The informations are entropy differences over ℝ rather than InformationTheory.Shannon.mutualInfo
(valued in ℝ≥0∞), matching the form in which the typicality bounds of this development state
their exponents.
Per-coordinate joint distribution #
InformationTheory.Shannon.BroadcastChannel.Marton.martonJointDistribution
sourceThe per-coordinate Marton joint law on V₁ × V₂ × α × β₁ × β₂: the compProd chain
pV → K → W ((V₁, V₂) ∼ pV, X ∣ (V₁, V₂) ∼ K, (Y₁, Y₂) ∣ X ∼ W), reshaped from the
left-nested ((V₁ × V₂) × α) × (β₁ × β₂) to the right-nested quintuple. Two reassociations
are needed, one more than for the four-variable superposition law.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonJointDistribution.instIsProbabilityMeasure
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InformationTheory.Shannon.BroadcastChannel.Marton.martonJointDistribution_map_V
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InformationTheory.Shannon.BroadcastChannel.Marton.martonJointDistribution_singleton_pos
sourceUsed by
I.i.d. ambient measure on ℕ → V₁ × V₂ × α × β₁ × β₂ #
InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbientMeasure
sourceThe i.i.d. Marton ambient measure:
Measure.infinitePi (fun _ => martonJointDistribution pV K W).
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InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbientMeasure.instIsProbabilityMeasure
sourceUsed by
InformationTheory.Shannon.BroadcastChannel.Marton.martonV₁s
sourceThe first auxiliary coordinate ω ↦ (ω i).1.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonV₂s
sourceThe second auxiliary coordinate ω ↦ (ω i).2.1.
Equations
- InformationTheory.Shannon.BroadcastChannel.Marton.martonV₂s i ω = (ω i).2.1
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InformationTheory.Shannon.BroadcastChannel.Marton.martonXs
sourceThe channel input coordinate ω ↦ (ω i).2.2.1.
Equations
- InformationTheory.Shannon.BroadcastChannel.Marton.martonXs i ω = (ω i).2.2.1
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InformationTheory.Shannon.BroadcastChannel.Marton.martonY₁s
sourceThe first output coordinate ω ↦ (ω i).2.2.2.1.
Equations
- InformationTheory.Shannon.BroadcastChannel.Marton.martonY₁s i ω = (ω i).2.2.2.1
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InformationTheory.Shannon.BroadcastChannel.Marton.martonY₂s
sourceThe second output coordinate ω ↦ (ω i).2.2.2.2.
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- InformationTheory.Shannon.BroadcastChannel.Marton.martonY₂s i ω = (ω i).2.2.2.2
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Coordinate facts for the Marton ambient measure #
InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbient_map_coord
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InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbient_iIndepFun_coord
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InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbient_identDistrib_coord
sourceUsed by
InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbient_entropy_coord
sourceUsed by
InformationTheory.Shannon.BroadcastChannel.Marton.martonAmbient_coord_marginal_pos
sourceUsed by
The three informations of the region inequalities #
InformationTheory.Shannon.BroadcastChannel.Marton.martonInfo₁
sourceThe first-receiver information I(V₁; Y₁) = H(V₁) + H(Y₁) − H(V₁, Y₁) of the
per-coordinate Marton joint law.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonInfo₂
sourceThe second-receiver information I(V₂; Y₂) = H(V₂) + H(Y₂) − H(V₂, Y₂) of the
per-coordinate Marton joint law.
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InformationTheory.Shannon.BroadcastChannel.Marton.martonInfoV₁V₂
sourceThe auxiliary-variable dependence I(V₁; V₂) = H(V₁) + H(V₂) − H(V₁, V₂) of the
per-coordinate Marton joint law. This is the penalty subtracted from the sum rate: it is the
rate at which the two subcodebooks have to be over-provisioned for a jointly typical pair to
exist.
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