Transmit diversity is the use of multiple transmit antennas to achieve reliability in
radio
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connec ...
communication.
It involves using signals that originate from two or more independent sources that have been
modulated
Signal modulation is the process of varying one or more properties of a periodic waveform in electronics and telecommunication for the purpose of transmitting information.
The process encodes information in form of the modulation or message ...
with identical
information
Information is an Abstraction, abstract concept that refers to something which has the power Communication, to inform. At the most fundamental level, it pertains to the Interpretation (philosophy), interpretation (perhaps Interpretation (log ...
-bearing signals and that may vary in their
transmission characteristics at any given instant.
It can help overcome the effects of
fading
In wireless communications, fading is the variation of signal attenuation over variables like time, geographical position, and radio frequency. Fading is often modeled as a random process. In wireless systems, fading may either be due to mul ...
, outages, and
circuit failures. When using diversity transmission and reception, the amount of received signal improvement depends on the independence of the fading characteristics of the signal as well as circuit outages and failures.
Considering antenna diversity, in many systems additional antennas may be expensive or impractical at the remote or even at the base station. In these cases, transmit diversity can be used to provide diversity benefit at a receiver with multiple transmit antennas only. With transmit diversity, multiple antennas transmit delayed versions of a signal, creating frequency-selective fading, which is equalized at the receiver to provide diversity gain.
Since transmit diversity with N antennas results in N sources of interference to other users, the interference environment will be different from conventional systems with one transmit antenna. Thus even if transmit diversity has almost the same performance as receive diversity in noise-limited environments, the performance in interference-limited environments will differ.
See also
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Antenna diversity
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Diversity gain Diversity gain is the increase in signal-to-interference ratio due to some diversity scheme, or how much the transmission power can be reduced when a diversity scheme is introduced, without a performance loss. Diversity gain is usually expressed in ...
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Diversity scheme
In telecommunications, a diversity scheme refers to a method for improving the reliability of a message signal by using two or more communication channels with different characteristics. Diversity is mainly used in radio communication and is a c ...
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Dynamic single-frequency networks
Dynamic single-frequency networks (DSFN) is a technique of using several transmitter antennas to transfer the same signal (macrodiversity) in orthogonal frequency-division multiplexing cellular networks.
DSFN is based on the idea of single frequ ...
(DSFN)
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Macrodiversity In the field of wireless communication, ''macrodiversity''D. Gesbert, S. Hanly, H. Huang, S. Shamai, O. Simeone, W. YuMulti-cell MIMO cooperative networks: A new look at interferenceIEEE Journal on Selected Areas in Communications, vol. 28, no. 9, p ...
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Multiple-input and multiple-output
In radio, multiple-input and multiple-output (MIMO) () is a method for multiplying the capacity of a radio link using multiple transmission and receiving antenna (radio), antennas to exploit multipath propagation. MIMO has become an essential e ...
(MIMO)
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Single-frequency network
A single-frequency network or SFN is a broadcast network where several transmitters simultaneously send the same signal over the same frequency channel.
Analog AM and FM radio broadcast networks as well as digital broadcast networks can operat ...
(SFN)
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Space–time block coding based transmit diversity Space–time block coding based transmit diversity (STTD) is a method of transmit diversity used in UMTS third-generation cellular systems. STTD is optional in the UTRAN air interface but mandatory for user equipment ( UE). STTD utilizes spaceâ ...
(STTD)
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Soft handover Soft handover or soft handoff refers to a feature used by the CDMA and W-CDMA standards, where a cell phone is simultaneously connected to two or more cells (or cell sectors) during a call. If the sectors are from the same physical cell site (a sect ...
References
Radio resource management
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