Relay X channels without channel state information at the transmit sides: Degrees of freedom

This paper focuses on the two-user relay-assisted X channel with no channel state information (CSI) available at the transmitter side. Two relaying modes, namely half-duplex decode-and-forward (DF) and cognitive relays, are considered and the degrees of freedom (DoF) are characterized. It is shown that assisted by a half-duplex DF relay that is equipped with 2M antennas, the X channel with two M-antenna users has 4M/3 DoF, which is achievable through interference alignment (IA). Furthermore, it is shown that in this channel, an M-antenna cognitive relay (with non-causal access to information streams) provides 2M DoF using interference cancellation (IC) technique. In this setting, IC outperforms interference alignment in the cognitive relay mode, since the latter achieves 4M/3 DoF.

[1]  Amir K. Khandani,et al.  Relay-aided interference alignment for the quasi-static X channel , 2009, 2009 IEEE International Symposium on Information Theory.

[2]  Hiroshi Sato,et al.  The capacity of the Gaussian interference channel under strong interference , 1981, IEEE Trans. Inf. Theory.

[3]  Shlomo Shamai,et al.  Degrees of Freedom Region of the MIMO $X$ Channel , 2008, IEEE Transactions on Information Theory.

[4]  2015 IEEE Wireless Communications and Networking Conference Workshops, WCNC Workshops 2015, New Orleans, LA, USA, March 9-12, 2015 , 2015, WCNC Workshops.

[5]  Te Sun Han,et al.  A new achievable rate region for the interference channel , 1981, IEEE Trans. Inf. Theory.

[6]  Aylin Yener,et al.  Guiding Blind Transmitters: Degrees of Freedom Optimal Interference Alignment Using Relays , 2013, IEEE Transactions on Information Theory.

[7]  Syed Ali Jafar,et al.  Blind Interference Alignment , 2012, IEEE Journal of Selected Topics in Signal Processing.

[8]  Syed Ali Jafar,et al.  Degrees of Freedom of Wireless Networks With Relays, Feedback, Cooperation, and Full Duplex Operation , 2009, IEEE Transactions on Information Theory.

[9]  Syed A. Jafar,et al.  Aiming Perfectly in the Dark-Blind Interference Alignment Through Staggered Antenna Switching , 2011, IEEE Trans. Signal Process..

[10]  Aydin Sezgin,et al.  From non-causality to causality: degrees of freedom of the interference relay channel , 2010, 2010 44th Annual Conference on Information Sciences and Systems (CISS).

[11]  Amir K. Khandani,et al.  Communication Over MIMO X Channels: Interference Alignment, Decomposition, and Performance Analysis , 2008, IEEE Transactions on Information Theory.

[12]  Mahesh K. Varanasi,et al.  The Degrees of Freedom Regions of MIMO Broadcast, Interference, and Cognitive Radio Channels with No CSIT , 2009, ArXiv.