Diversity Scheme

The following classes of diversity schemes can be identified:

''' is added and the message is spread in time by means of Bit-interleaving before it is transmitted. Thus, Error Burst s are avoided, which simplifies the error correction.

Frequency diversity: The signal is transferred using several frequency channels or spread over a wide spectrum that is affected by frequency-selective Fading . Examples are:

--- OFDM modulation in combination with subcarrier Interleaving and Forward Error Correction

Space diversity: The signal is transferred over several different propagation paths. In the case of wired transmission, this can be achieved by transmitting via multiple wires. In the case of wireless transmission, it can be achieved by Antenna Diversity using multiple transmitter antennas ( Transmit Diversity ) and/or multiple receiving antennas ('''diversity reception'''). In the latter case, a Diversity Combining technique is applied before further signal processing takes place. If the antennas are at far distance, for example at different cellular base station sites or WLAN access points, this is called Macrodiversity ). If the antennas are at a distance in the order of one Wavelength , this is called '''microdiversity'''. A special case is phased Antenna Array s, which also can be utilized for Beamforming , MIMO channels and Space–time Coding (STC).

Polarisation diversity: Multiple versions of a signal are transmitted and received via antennas with different polarization. A Diversity Combining technique is applied on the receiver side.

Multiuser diversity: Multiuser diversity is obtained by opportunistic user scheduling at either the transmitter or the receiver. Opportunistic user scheduling is as follows that the transmit selects the best user among candidate receivers according to qualities of each channel between the transmit and each receiver. In FDD systems, a receiver must feed back the channel quality information to the transmitter with the limited level of resolution.

Cooperative Diversity : enables to achieve the Antenna diversity gain by the use of the cooperation of distributed antennas belonging to each node.

	CATEGORIES ABOUT DIVERSITY SCHEME

	antennas

	wireless communications

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