In this paper, assuming each node has delayed channel state information at the transmitter (CSIT), we investigate the achievable degrees of freedom (DOF) of MIMO two-way relay interference channel in frequency division duplex (FDD) systems, where there are K user pairs (i.e., 2K users) and each user in a user pair exchanges messages with the other user in the same user pair simultaneously via an intermediate relay. We propose a two-stage transmission scheme and derive the closed-form expressions for its achievable DOF.
Time-selectivity in fast fading channels has been one of big obstacles to attain high efficiency and diversity gain for space-times codes. Orthogonal-frequency-division-multiplexing (OFDM) combined with space-time trellis codes has been introduced to combat effect of frequency-selectivity. Subsequently, space-time block codes, space-frequency codes and concatenation with diverse error-correcting codes were investigated. However, for multiple-input multiple-out (MIMO) OFDM systems, to design high-efficiency robust space-time-frequency codes becomes one of big problems. In this paper, we presented pairwise error probability analysis of space-frequency-time block codes, and then concluded one general design criterion for space-time-frequency block codes by utilizing the frequency-correlation feature of sub-channel in mobile OFDM systems. Then, we investigated performance of space-frequency block codes for MIMO-OFDM systems with 4 transmit antennas. And comparison between space-frequency block codes and space-time block codes is performed with different number of transmit antenna. Link-level simulations on COSSAP® verified analytical results. The results show that SFBC is superior to STBC in fast fading channel. And power-delay profile of fading channel, i.e., channel order and delay spread, must be included into design consideration on space-time-frequency codes.
In this paper we present a deterministic approach of modeling wideband MIMO (multiple-input multiple-output) radio fading channel for wireless multicarrier systems. Implementation problem of downlink MIMO model for mobile station (MS) was first investigated, while space-time coding or downlink beam-forming is taken into count at base station (BS). The MIMO channel are determined by both power azimuth profile (PAP) at MS and various configuration of multiple antennas at BS. Based on tap-delay-line structure and deterministic fading channel modeling method, SIMO fading model, corresponding to any one transmitter antenna, is formed by generating doppler phase difference between two receiver antenna aided by PAP at MS. The von Mises probability density function was adopted to characterize phenomenon of nonisotropic scattering components around MS. The ultimate MIMO channel simulation model is sum of all SIMO channel with all transmitter antennas. Finally, we predicted MIMO channel capacity based on proposed simulation model with parameters of wireless multicarrier systems under specified 'Vehicular A channel' of ITU-R M.1225.
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