Carrier cooperation can reduce the transmit power in parallel MIMO broadcast channels with zero-forcing

Christoph Hellings, Stephan Herrmann, Wolfgang Utschick

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Even though parallel multiple-input multiple-output (MIMO) broadcast channels are known to be separable from an information theoretic point of view, performing separate encoding and decoding on each of the parallel channels has been shown to be potentially suboptimal in broadcast channels with linear transceivers. In this paper, we show that suboptimality of such a carrier-noncooperative transmission also occurs in broadcast channels with zero-forcing and quality of service constraints if time-sharing is not allowed. The proof is given by constructing a minimal example and identifying a rate tuple that is achievable using carrier-cooperative zero-forcing with a certain sum power but requires a higher sum power with carrier-noncooperative zero-forcing. This observation is of practical relevance since zero-forcing without time-sharing is a popular assumption in the design of low-complexity optimization algorithms.

Original languageEnglish
Article number6484991
Pages (from-to)3021-3027
Number of pages7
JournalIEEE Transactions on Signal Processing
Issue number12
StatePublished - 2013


  • Dirty paper coding
  • linear transceivers
  • multiple-input multiple-output (MIMO)
  • multiuser multicarrier systems
  • parallel broadcast channels
  • power minimization
  • quality of service
  • separable and inseparable channels
  • zero-forcing


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