Diversity scheme

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Terrestrial microwave radio system with two antenna arrays configured for space-diversity

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 common technique for combatting fading and co-channel interference and avoiding error bursts. It is based on the fact that individual channels experience different levels of fading and interference. Multiple versions of the same signal may be transmitted and/or received and combined in the receiver. Alternatively, a redundant forward error correction code may be added and different parts of the message transmitted over different channels. Diversity techniques may exploit the multipath propagation, resulting in a diversity gain, often measured in decibels.

The following classes of diversity schemes can be identified:

  • Polarization 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: at any given time, the transmitter selects the best user among candidate receivers according to the qualities of each channel between the transmitter and each receiver. A receiver must feed back the channel quality information to the transmitter using limited levels of resolution, in order for the transmitter to implement Multiuser diversity.
  • Cooperative diversity: Achieves antenna diversity gain by using the cooperation of distributed antennas belonging to each node.

See also[edit]

External links[edit]

  • K. T. Wong [1] & A. K.-Y. Lai, “Inexpensive Upgrade of Base-Station Dumb-Antennas by Two Magnetic Loops for ‘Blind’ Adaptive Downlink Beamforming,” IEEE Antennas & Propagation Magazine, vol. 47, no. 1, pp. 189-193, February 2005.[2]
  • for an example of field measured benefits of reception diversity 2 in mobile handsets technologies , see Christian Le Floc’h, Regis Duval,Gerard Pousset,Gaël Scott,"S-UMTS band radio propagation performances evaluation: reception diversity 2 field measurements methodology and results", June 18, 2008, [3]