Asynchronous interference alignment

A constant three-user interference channel wherein users are not symbol synchronous is considered. A novel practical interference alignment scheme for this channel is proposed wherein aligning interfering signals at each receiver is performed with the help of asynchronous delays which inherently exist among the received signals at each receiver node. Due to the existence of asynchronism among the users, the underlying quasi-static flat fading links are converted into frequency selective and accordingly into time varying channels with correlated coefficients across the time. This solves the lack of channel variation required for interference alignment in quasi-static scenarios. It is proved that the proposed scheme achieves the total degrees of freedom equal to 3/2 of this channel almost surely in the limit of codeword's length. Application of the proposed scheme is not limited to high signal to noise ratio (SNR) regime and it can be used in any range of SNR.

[1]  U. Grenander,et al.  Toeplitz Forms And Their Applications , 1958 .

[2]  J. H. Winters,et al.  The diversity gain of transmit diversity in wireless systems with Rayleigh fading , 1994, Proceedings of ICC/SUPERCOMM'94 - 1994 International Conference on Communications.

[3]  Amir K. Khandani,et al.  Capacity bounds for the Gaussian Interference Channel , 2008, 2008 IEEE International Symposium on Information Theory.

[4]  Venugopal V. Veeravalli,et al.  Gaussian Interference Networks: Sum Capacity in the Low-Interference Regime and New Outer Bounds on the Capacity Region , 2008, IEEE Transactions on Information Theory.

[5]  Venugopal V. Veeravalli,et al.  Gaussian interference networks: sum capacity in the low-interference regime and new outer bounds on the capacity region , 2009, IEEE Trans. Inf. Theory.

[6]  Erik Ordentlich,et al.  The Degrees-of-Freedom of the $K$-User Gaussian Interference Channel Is Discontinuous at Rational Channel Coefficients , 2009, IEEE Transactions on Information Theory.

[7]  Erik Ordentlich,et al.  On the Degrees-of-Freedom of the K-user Gaussian interference channel , 2009, 2009 IEEE International Symposium on Information Theory.

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

[9]  S.A. Jafar,et al.  Degrees of Freedom of Wireless Networks - What a Difference Delay Makes , 2007, 2007 Conference Record of the Forty-First Asilomar Conference on Signals, Systems and Computers.

[10]  Shuangqing Wei,et al.  Diversity–Multiplexing Tradeoff of Asynchronous Cooperative Diversity in Wireless Networks , 2007, IEEE Transactions on Information Theory.

[11]  Helly.  Fourier transforms in the complex domain , 1936 .

[12]  Onkar Dabeer,et al.  Capacity of MIMO systems with asynchronous PAM , 2009, IEEE Transactions on Communications.

[13]  Robert M. Gray,et al.  Toeplitz and Circulant Matrices: A Review , 2005, Found. Trends Commun. Inf. Theory.

[14]  Robert M. Gray,et al.  Toeplitz And Circulant Matrices: A Review (Foundations and Trends(R) in Communications and Information Theory) , 2006 .

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

[16]  V. Cadambe,et al.  Interference alignment with asymmetric complex signaling , 2009, 2009 47th Annual Allerton Conference on Communication, Control, and Computing (Allerton).

[17]  Gerhard Kramer,et al.  A New Outer Bound and the Noisy-Interference Sum–Rate Capacity for Gaussian Interference Channels , 2007, IEEE Transactions on Information Theory.

[18]  Hua Wang,et al.  Gaussian Interference Channel Capacity to Within One Bit , 2007, IEEE Transactions on Information Theory.

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

[20]  Fredrik Rusek,et al.  CTH04-1: On Information Rates for Faster than Nyquist Signaling , 2006, IEEE Globecom 2006.

[21]  Syed Ali Jafar,et al.  Interference Alignment and Degrees of Freedom of the $K$-User Interference Channel , 2008, IEEE Transactions on Information Theory.

[22]  Harald Haas,et al.  On Cyclic Delay Diversity in OFDM Based Transmission Schemes , 2002 .

[23]  Sergio Verdú,et al.  The capacity region of the symbol-asynchronous Gaussian multiple-access channel , 1989, IEEE Trans. Inf. Theory.

[24]  Syed A. Jafar,et al.  Can 100 speakers talk for 30-minutes each in one room within one hour and with zero interference to each other ’ s audience ? , 2007 .

[25]  Mohamed Oussama Damen,et al.  Interference alignment over asynchronous X networks , 2011, 2011 IEEE International Symposium on Information Theory Proceedings.

[26]  Syed Ali Jafar,et al.  Interference Alignment With Asymmetric Complex Signaling—Settling the Høst-Madsen–Nosratinia Conjecture , 2009, IEEE Transactions on Information Theory.

[27]  Roy D. Yates,et al.  Interference Alignment for Line-of-Sight Channels , 2008, IEEE Transactions on Information Theory.

[28]  A. M. Abdullah,et al.  Wireless lan medium access control (mac) and physical layer (phy) specifications , 1997 .

[29]  Robert M. Gray,et al.  Toeplitz And Circulant Matrices , 1977 .

[30]  Amir K. Khandani,et al.  Real Interference Alignment with Real Numbers , 2009, ArXiv.

[31]  Jean Pierre Delmas,et al.  Asymptotic eigenvalue distribution of block Toeplitz matrices and application to blind SIMO channel identification , 2001, IEEE Trans. Inf. Theory.

[32]  Aria Nosratinia,et al.  The multiplexing gain of wireless networks , 2005, Proceedings. International Symposium on Information Theory, 2005. ISIT 2005..

[33]  Sriram Vishwanath,et al.  Ergodic Interference Alignment , 2009, IEEE Transactions on Information Theory.

[34]  N. Wiener,et al.  Fourier Transforms in the Complex Domain , 1934 .

[35]  Amir K. Khandani,et al.  Signaling over MIMO Multi-Base Systems: Combination of Multi-Access and Broadcast Schemes , 2006, 2006 IEEE International Symposium on Information Theory.

[36]  Dacheng Yang,et al.  Deliberately Designed Asynchronous Transmission Scheme for MIMO Systems , 2007, IEEE Signal Processing Letters.

[37]  Syed Ali Jafar,et al.  Interference Alignment and the Degrees of Freedom of Wireless $X$ Networks , 2009, IEEE Transactions on Information Theory.

[38]  Mohamed Oussama Damen,et al.  Asynchronous Interference Channel: Degrees of Freedom and Interference Alignment , 2011, ArXiv.

[39]  Syed A. Jafar,et al.  Interference Alignment and the Degrees of Freedom for the 3 User Interference Channel , 2007 .