Degraded broadcast and superposition coding
Research context
postgraduate concept · established · As of 2026-10-10
For a physically degraded memoryless broadcast channel X→Y1→Y2, independent private-message rates are achieved by superposition with R2≤I(U;Y2) and R1≤I(X;Y1|U), unioned over p(u,x).
Key knowledge
For a physically degraded memoryless broadcast channel X→Y1→Y2, independent private-message rates are achieved by superposition with R2≤I(U;Y2) and R1≤I(X;Y1|U), unioned over p(u,x). Under the degraded assumption this region is capacity, with U carrying the weaker receiver's layer. A general broadcast law does not inherit the degraded converse simply because one receiver has a better measured signal-to-noise ratio.
Values and equations
R2≤I(U;Y2); R1≤I(X;Y1|U), U→X→Y1→Y2
- U
- Superposition auxiliary random variable
- R1,R2
- Private-message rates, bits per channel use
- Y1,Y2
- Strong and degraded receiver outputs
Conditions and scope
- The conditional law factors p(y1,y2|x)=p(y1|x)p(y2|y1); messages and input constraints are specified.
- Time-sharing is included through the auxiliary distribution, and no feedback is assumed.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Author checked this English statement, displayed equation where present and stated hypotheses against these source locations: Physically degraded broadcast channel superposition region; DM-MAC pp. 28–35, broadcast pp. 38–47, distortion pp. 48–52, Wyner–Ziv/Slepian–Wolf pp. 53–59, relay pp. 78–94, multicast pp. 100–116. The check is bounded to the recorded claims; no complete proof reconstruction, software proof replay or universal literature completeness is claimed.
2026-10-10 · Author source-body/statement/equation/domain check, with graph associations scoped individually. Separate independent content/source/inventory review is required before branch closure.
Entry details
Permanent link to this entry ↗- Record identity
- research-info-degraded-broadcast
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference