Secure degrees of freedom of wireless X networks using artificial noise alignment

Zhao Wang, Ming Xiao, Mikael Skoglund, H. Vincent Poor

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The problem of transmitting confidential messages in M× K wireless X networks is considered in which each transmitter intends to send one confidential message to every receiver. In particular, the secure degrees of freedom (SDOF) of the considered network are studied based on an artificial noise alignment (ANA) approach, which integrates interference alignment and artificial noise transmission. At first, an SDOF upper bound is derived for the M × K X network with confidential messages (XNCM) to be K(M-1)/K+M-2. By proposing an ANA approach, it is shown that the SDOF upper bound is tight when K=2 for the considered XNCM with time-/frequency-varying channels. For $K\ge 3$, it is shown that SDOF of K(M-1)/K+M-1 can be achieved, even when an external eavesdropper is present. The key idea of the proposed scheme is to inject artificial noise into the network, which can be aligned in the interference space at receivers for confidentiality. Moreover, for the network with no channel state information at transmitters, a blind ANA scheme is proposed to achieve SDOF of K(M-1)/K+M-1 for K,M\ge 2, with reconfigurable antennas at receivers. The proposed method provides a linear approach to secrecy coding and interference alignment.

Original languageEnglish (US)
Article number7109856
Pages (from-to)2632-2646
Number of pages15
JournalIEEE Transactions on Communications
Issue number7
StatePublished - Jul 1 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering


  • Secure degrees of freedom
  • artificial noise
  • interference alignment
  • wireless X network


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