High-rate code design and transmission in large MIMO systems

The problem of high-rate space-time block code (STBC) design and transmission is studied in a large multiple-input multiple-output (MIMO) system in Rayleigh fading environment. One attractive feature of large MIMO system is that a huge amount of data can be transmitted from transmitter to the receiver/multiple users. In practical systems, channel state information (CSI) is not available for decoding of the data, therefore, CSI needs to be estimated by using pilot symbols. It is shown in literature that very large number of time-slots are required for pilot transmission in large MIMO systems, it will lead to a very less number of time-slots for data transmission. In this case, a high-rate STBC is a possible way to transmit large amount of data in practical large MIMO systems. We propose a method to design a high-rate STBC by inserting the orthogonal STBCs of small dimensions and good rate. The concept of null space is used for decoding of transmitted data. The analytical performance of the proposed scheme is discussed in terms of symbol error rate.