Читать книгу Spatial Multidimensional Cooperative Transmission Theories And Key Technologies - Lin Bai - Страница 53

The MIMO system model is shown in Fig. 2.11. Consider the system with two transmitting antennas and two receiving antennas as an example. Since each receiving antenna can receive signals from different transmitting antennas, the received signals from the two receiving antennas can be expressed as

where h_ij, s_j, and n_i represent the channel gain from the jth transmitting antenna to the ith receiving antenna, the transmitted signal of the jth transmitting antenna, and the additive noise of the ith receiving antenna, respectively. Defining y = [y₁ y₂]^T, the received signal vector can be expressed by the matrix multiplication.

where channel matrix , transmitted signal vector , and noise vector . The corresponding system model can be extended to any MIMO system with M transmitting antennas and N receiving antennas. The system model expression can still be expressed by Eq. (2.145), and the channel can be assumed to be an additive white Gaussian noise channel. In the AWGN channel, the received noise vector n is assumed to be a zero-average CSCG random vector,^{8, 9} whose mean value is E(nn^H) = N₀I, covariance matrix is R, namely .

Fig. 2.11. The MIMO system model.