2012/08/14 by Lu Yang, Wei Zhang, Yang, Lu +1
Computer Science · Mathematics · #FOS: Computer and information sciences #Information Theory (cs.IT) #cs.IT #math.IT
paper · pdf · doi:10.48550/arxiv.1208.2900
18 pages 6 figures, minor revisions in Abstract and Introduction of version 1
arxiv created 2012/08/24 · arxiv updated 2012/08/27
In this paper, the achievable DoF of MIMO X channels for constant channel coefficients with Mt antennas at transmitter t and Nr antennas at receiver r (t,r=1,2) is studied. A spatial interference alignment and cancelation scheme is proposed to achieve the maximum DoF of the MIMO X channels. The scenario of M1≥ M2≥ N1≥ N2 is first considered and divided into 3 cases, 3N2<M1+M2<2N1+N2 (Case A), M1+M2≥2N1+N2 (Case B), and M1+M2≤3N2 (Case C). With the proposed scheme, it is shown that in Case A, the outer-bound (M1+M2+N2)/(2) is achievable; in Case B, the achievable DoF equals the outer-bound N1+N2 if M2>N1, otherwise it is 1/2 or 1 less than the outer-bound; in Case C, the achievable DoF is equal to the outer-bound 2/3(M1+M2) if (3N2-M1-M2)\mod 3=0, and it is 1/3 or 1/6 less than the outer-bound if (3N2-M1-M2)\mod 3=1 or 2. In the scenario of Mt≤ Nr, the exact symmetrical results of DoF can be obtained.