Maximizing the sum rate in symmetric networks of interfering links

Sibi Raj Bhaskaran, Stephen V. Hanly, Nasreen Badruddin, Jamie S. Evans

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

2 Citations (Scopus)


We consider the power optimization problem of maximizing the sum rate of a symmetric network of interfering links in Gaussian noise. All transmitters have an average transmit power constraint, the same for all transmitters. We solve this nonconvex problem by indentifying some underlying convex structure. In particular, we characterize the maximum sum rate of the network, and show that there are essentially two possible states at the optimal solution depending on the cross-gain between the links, and/or the average power constraint: the first is a wideband (WB) state , in which all links interfere with each other, and the second is a frequency division multiplexing (FDM) state, in which all links operate in orthogonal frequency bands. The FDM state is optimal if the cross-gain between the links is above 1√2. If the cross-gain is below 1√2, then FDM is still optimal provided the average power of the links is sufficiently high. Assuming that ε < 1√2, we can say that the WB state occurs when the average power level is low (relative to the noise and the cross-gain factor between the links), but as we increase the average power level from low to high, there is a smooth transition from the WB state to the FDM state: For intermediate average power levels, the optimal configuration is a mixture, with some fraction of the bandwidth in the WB state, and the other fraction in the FDM state. This work has applications to DSL,as well as to wireless networks.

Original languageEnglish
Title of host publicationInformation Theory and Applications Workshop
Subtitle of host publicationconference proceedings: 8-13 February 2009, San Diego, CA
Place of PublicationPiscataway, NJ
PublisherInstitute of Electrical and Electronics Engineers (IEEE)
Number of pages8
ISBN (Print)9781424439904
Publication statusPublished - 2009
Externally publishedYes
EventInformation Theory and Applications Workshop, ITA 2009 - San Diego, CA, United States
Duration: 8 Feb 200913 Feb 2009


OtherInformation Theory and Applications Workshop, ITA 2009
CountryUnited States
CitySan Diego, CA

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