Space–time trellis codes (STTCs) are a type of
space–time code
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 r ...
used in
multiple-antenna wireless communications
Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
. This scheme transmits multiple,
redundant copies of a
generalised TCM signal distributed over time and a number of
antennas
In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies a ...
('space'). These multiple, 'diverse' copies of the data are used by the receiver to attempt to reconstruct the actual transmitted data. For an STC to be used, there must necessarily be multiple ''transmit'' antennas, but only a single ''receive'' antennas is required; nevertheless multiple receive antennas are often used since the performance of the system is improved by the resulting spatial diversity.
In contrast to
space–time block codes (STBCs), they are able to provide both coding gain and diversity gain and have a better
bit-error rate
In digital transmission, the number of bit errors is the number of received bits of a data stream over a communication channel that have been altered due to noise, interference, distortion or bit synchronization errors.
The bit error rate ...
performance. In essence they marry single channel continuous time coding with the signaling protocol being used, and extend that with a multi-antenna framework. However, that also means they are more complex than STBCs to encode and decode; they rely on a
Viterbi decoder at the receiver where STBCs need only
linear
Linearity is the property of a mathematical relationship ('' function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear ...
processing. Also, whereas in a single transmitter, single receiver framework the Viterbi algorithm (or one of the sequential decoding algorithms) only has to proceed over a trellis in a single time dimension, in here the optimal decoding also has to take into consideration the number of antennas, leading to an extraneous polynomial complexity term.
STTCs were discovered by
Vahid Tarokh et al. in 1998.
References
Wireless
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