A space–time code (STC) is a method employed to improve the reliability of data transmission in wireless communication systems using multiple transmit antennas. STCs rely on transmitting multiple, redundant copies of a data stream to the receiver in the hope that at least some of them may survive the physical path between transmission and reception in a good enough state to allow reliable decoding. In telecommunications, transmission is the act of transmitting electrical messages (and the associated phenomena of radiant energy that passes through media). ... Wireless is an old-fashioned term for a radio transceiver (a mixed receiver and transmitter device), referring to its use in wireless telegraphy early on, or for a radio receiver. ... A Yagi-Uda antenna An antenna or aerial is an electrical device designed to transmit or receive radio waves or, more generally, any electromagnetic waves. ... Redundancy in information theory is the number of bits used to transmit a message minus the number of bits of actual information in the message. ... In radio terminology, a receiver is an electronic circuit that receives a radio signal from an antenna and decodes the signal for use as sound, pictures, navigational-position information, etc. ... A transmission medium is any material substance, such as fiber-optic cable, twisted-wire pair, coaxial cable, dielectric-slab waveguide, water, or air, that can be used for the propagation of signals, usually in the form of modulated radio, light, or acoustic waves, from one point to another. ...

Space time codes may be split into two main types:

• Space–time trellis codes (STTCs)^[1] distribute a trellis code over multiple antennas and multiple time-slots and provide both coding gain and diversity gain.
• Space–time block codes (STBCs)^[2][3] act on a block of data at once (similarly to block codes) and provide only diversity gain, but are much less complex in implementation terms than STTCs.

STC may be further subdivided according to whether the receiver knows the channel impairments. In coherent STC, the receiver knows the channel impairments through training or some other form of estimation. These codes have been studied more widely because they are less complex than their non-coherent counterparts. In noncoherent STC the receiver does not know the channel impairments but knows the statistics of the channel.^[4] In differential space–time codes neither the channel nor the statistics of the channel are available.^[5] Space–time trellis codes (STTCs) are a type of space–time code used in multiple-antenna wireless communications. ... In telecommunication, a convolutional code is a type of error-correcting code in which (a) each m-bit information symbol (each m-bit string) to be encoded is transformed into an n-bit symbol, where m/n is the code rate (n >= m) and (b) the transformation is a function... In telecommunications, diversity reception refers to a method for improving reception of a transmitted signal, by receiving and processing multiple versions of the same transmitted signal. ... Space–time block coding is a technique used in wireless communications to transmit multiple copies of a data stream across a number of antennas and to exploit the various received versions of the data to improve the reliability of data-transfer. ... The Railway Block Code is a system of bells used to send simple messages about train operations from one signalbox to another. ... Channel, in communications (sometimes called communications channel), refers to the medium through which information is transmitted from a sender (or transmitter) to a receiver. ... Differential space–time codes[1][2] are a way of transmitting data in wireless communications. ...

See also

• Diversity reception — the concept from which STC arose.
• MIMO Communications — the term for a wireless communication system employing multiple antennas at both transmit and receive.

In telecommunications, diversity reception refers to a method for improving reception of a transmitted signal, by receiving and processing multiple versions of the same transmitted signal. ...

References

1. ^ Vahid Tarokh, Nambi Seshadri, and A. R. Calderbank (March 1998). "Space–time codes for high data rate wireless communication: Performance analysis and code construction". IEEE Transactions on Information Theory 44 (2): 744–765. DOI:10.1109/18.661517.
2. ^ S.M. Alamouti (October 1998). "A simple transmit diversity technique for wireless communications". IEEE Journal on Selected Areas in Communications 16 (8): 1451–1458.
3. ^ Vahid Tarokh, Hamid Jafarkhani, and A. R. Calderbank (July 1999). "Space–time block codes from orthogonal designs". IEEE Transactions on Information Theory 45 (5): 744–765. DOI:10.1109/18.771146.
4. ^ Marzetta, T.L. and Hochwald, B.M. (January 1999). "Capacity of a mobile multiple-antenna communication link in Rayleigh flat fading". IEEE Transactions of Information Theory 45 (1): 139–157. DOI:10.1109/18.746779.
5. ^ V. Tarokh and H. Jafarkhani (July 2000). "A Differential Detection Scheme for Transmit Diversity". IEEE Journal on Selected Areas in Communications 18 (7). DOI:10.1109/49.857917.