On the Diversity-Multiplexing Tradeoff of Unconstrained Multiple-Access Channels

Yair Yona, Meir Feder

Research output: Contribution to journalArticlepeer-review


In this paper, the optimal diversity-multiplexing tradeoff (DMT) is investigated for the multiple-input multiple-output fading multiple-access channel with no power constraints (infinite constellations). For K users (K>1), M transmit antennas for each user, and N receive antennas, infinite constellations in general and lattices in particular are shown to attain the optimal DMT of finite constellations for N\ge (K+1) M-1, i.e., user limited regime. On the other hand, for N< ({K+1)M-1, it is shown that infinite constellations cannot attain the optimal DMT. This is in contrast to the point-to-point case in which the infinite constellations are DMT optimal for any M and N. In general, this paper shows that when the network is heavily loaded, i.e., K> [{1,(N-M+1)M], considering the shaping region in the decoding process plays a crucial role in pursuing the optimal DMT. By investigating the cases in which the infinite constellations are optimal and suboptimal, this paper also gives a geometrical interpretation to the DMT of infinite constellations in multiple-access channels.

Original languageEnglish
Article number7152899
Pages (from-to)4630-4662
Number of pages33
JournalIEEE Transactions on Information Theory
Issue number9
StatePublished - 1 Sep 2015


  • Infinite constellations
  • diversity-multiplexing tradeoff
  • lattices
  • multiple access channel


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