Degrees of Freedom of WirelessNetworks - Whata DifferenceDelay Makes

syedguci.edu Abstract-We explore theimpactofpropagation delay onthedegrees offreedom ofwireless interference networks. ForK > 2userinterference channel weshowthrough an example thatpropagation delays canincrease thedegrees offreedomby uptoa factor ofK/2.We provide an exampleofnodeplacement fora 4 userinterference networksuchthatthepropagation delaysforline-of- sight communication allowperfect interference alignment. We showthatevenifnodesarerandomly placed, one canalmost surely achieve sufficient interference alignment toapproach theupperbound onthedegrees offreedom by choosing thebasicsymbolduration smallenough. An analogy withdeterministic channel modelsispointed outasaninteresting mechanism totranslate propagation delaybasedinterference alignment schemes todelay-free Gaussian channel models. I.INTRODUCTION