A Space-Time Transmission Scheme for Large MIMO Systems

In this letter, we propose a space-time transmission scheme (STTS) for large multiple-input multiple-output (MIMO) communication systems. These systems are primarily used to transmit a huge amount of data. The existing spacetime block codes (STBCs) are not suitable for these systems due to the fact that these STBCs require very large channel coherence time (more than the number of transmit antennas), render poor data rate (less than one), and aim at full spatial diversity. In a practical large MIMO system with one thousand transmit and one thousand receive antennas, the diversity order of 10
⁶
can be achieved; however, such a high value of diversity order is not required in practical systems. Therefore, an STTS with good data rate, parsimoniously utilized temporal dimensions, and symbol-wise decoding is essentially required for practical large MIMO systems. In this letter, we emphasize design of a new STTS by relaxing the constraint of achieving full spatial diversity. In the proposed STTS, the data rate of the large MIMO system is increased at the expense of the reduction in spatial diversity order. An approximate expression of symbol error rate of the proposed system is obtained-based on the moment generating function of the instantaneous received signal-to-noise ratio. Further, it is shown that the diversity order of the proposed STTS-based system is one less than the number of receive antennas.