STBC, Space–time block coding, is a technique used in wireless communications to transmit multiple copies of a data stream through a series of antennas, and to exploit received versions to improve the reliability of the data.

The waves transmitted in the transmission medium suffer degradation and since the path taken by each of the versions is different, some of the copies will be more damaged than others. That is why more than one data stream is sent; Redundancy is used to more accurately receive the sent signal.

In fact, STBC combines all copies of the received signal to optimally extract as much information as possible from each of them.

STBCs are usually orthogonal. This means that the STBC is designed in such a way that the vectors representing any pair of columns taken from the encoding matrix is ​​orthogonal. The result of this is simple, linear, optimal decoding at the receiver. Its most serious disadvantage is that all but one of the codes that satisfy this criterion must sacrifice some of their data rates.

There are also "near-orthogonal STBCs" that can achieve higher data rates, and even a better hit rate under very harsh conditions.

Alamouti") invented the simplest of all STBCs in 1998, although he mentioned the term "SBTC" itself. It was designed for a dual-transmission antenna and the coding matrix is:

This is a very special STBC, as it is the only orthogonal STBC that can achieve its full gain diversity without sacrificing its data rate.

The importance of Alamouti's proposal is that it was the first demonstration of a coding method that allows all diversity with linear transformation at the receiver, in addition, it was the first open loop to transmit the technical diversity that was in this capacity.