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.
Space time codes may be split into two main types:
*
Space–time trellis codes (STTCs)
distribute a
trellis code over multiple antennas and multiple time-slots and provide both coding gain and
diversity gain.
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Space–time block code
Space–time block coding is a technique used in wireless, wireless communications to transmit multiple copies of a data stream across a number of Antenna (radio), antennas and to exploit the various received versions of the data to improve the r ...
s (STBCs)
act on a block of data at once (similarly to
block code
In coding theory, block codes are a large and important family of Channel coding, error-correcting codes that encode data in blocks.
There is a vast number of examples for block codes, many of which have a wide range of practical applications. Th ...
s) and also provide
diversity gain but doesn't provide coding gain.
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Space–time line codes (STLCs)
and STBCs are symmetric with respect to the transmit-and-receive processes, like a
maximum-ratio combining (MRC) and maximum-ratio transmission (MRT). The STLC scheme provides full
diversity gain even when there is no full channel state information (CSI) at the receiver.
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, and
division algebra
In the field of mathematics called abstract algebra, a division algebra is, roughly speaking, an algebra over a field in which division, except by zero, is always possible.
Definitions
Formally, we start with a non-zero algebra ''D'' over a fie ...
s
over number fields have now become the standard tool for constructing such codes.
In
noncoherent STC the receiver does not know the channel impairments but knows the statistics of the channel.
In
differential space–time codes neither the channel nor the statistics of the channel are available.
See also
*
Diversity scheme – the concept from which STC arose.
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MIMO
In radio, multiple-input and multiple-output (MIMO) () is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas to exploit multipath propagation. MIMO has become an essential element of wirel ...
– the term for wireless communication systems employing multiple antennas at both a transmitter and a receiver.
References
General references
* Louay M.A. Jalloul and Sam. P. Alex, "Evaluation Methodology and Performance of an IEEE 802.16e System", Presented to the IEEE Communications and Signal Processing Society, Orange County Joint Chapter (ComSig), December 7, 2006. Available at: http://chapters.comsoc.org/comsig/meet.html
* Sam P. Alex and Louay M.A. Jalloul, "Performance Evaluation of MIMO in IEEE802.16e/WiMAX", IEEE Journal of Selected Topics in Signal Processing, VOL. 2, NO. 2, April, 2008.
{{DEFAULTSORT:Space-time code
Wireless
Radio resource management