We consider downlink transmission in a two-cell network where each base station has multiple antennas and each user has a pattern reconfigurable antenna. Without channel state information at the transmitters, existing approaches do not fully exploit the degrees of freedom (DoF) of the network due to detrimental effects of inter-cell interference and intra-cell interference. In this work, we propose a blind interference alignment scheme which can cancel both types of interference. We show that the achievable DoF is asymptotically optimal for large antenna array.

In this paper, we propose blind interference alignment (BIA) schemes using reconfigurable antenna technology to achieve high degree of freedom (DoF) or diversity gain in K-user interference channels. First, two DoF-oriented BIA schemes are proposed that fully and partially align the inter-user interference, respectively. We compare the achievable DoF of the two schemes and show that the partial BIA scheme has higher DoF than the full BIA scheme under some conditions, and vice versa. Then, three diversity-oriented BIA schemes with space-time coding are proposed to achieve both spatial diversity gain and reconfigurable antenna pattern diversity gain. With different tradeoffs among the diversity gain, the rate and the decoding complexity, the BIA with threaded algebraic space-time (TAST) codes, the BIA with orthogonal space-time block codes (OSTBCs), and the BIA with multiplexing Alamouti codes are proposed, respectively. The BIA with TAST codes can achieve the full diversity and high rate with high decoding complexity. The BIA with OSTBCs can achieve the full diversity and the linear decoding complexity but has low rate. The BIA with multiplexing Alamouti codes can achieve high rate with low decoding complexity at the expense of full diversity loss.

We consider the K-user MISO interference channel where each transmitter has multiple antennas and each receiver has a reconfigurable antenna capable of switching among several pre-set modes. The channels in different modes are assumed to be independent. We propose an interference alignment scheme without channel information at transmitters. We show that the achievable degree of freedom of the proposed scheme outperforms that in the traditional K-user MISO interference channel without the reconfigurable antenna.

Group zero-forcing (GZF) detection is an efficient and powerful detection tool that has flexible detection complexity and performance gain between the optimum detection and the ZF detection. In this paper, we give diversity and multiplexing tradeoff (DMT) analysis for a 2-layer D-BLAST transmission under GZF detection over Rayleigh MIMO channels. With M transmit antennas and N receive antennas, the DMT of such a system is shown as d_{out}(r)=(N-1)(M-\frac{r(M+1)}{2})^+ for \frac{2}{M+1}≤ r≤ \frac{2M}{M+1} and d_{out}(r)=(MN-M+1)-\frac{rN(M+1)}{2} for 0≤ r< \frac{2}{M+1}, where d_{out} denotes the diversity gain and r denotes the multiplexing gain.