i have seen many diversity gain plots given in the research papers. The value of DG never crosses 10dB. is there any reason behind it. Please explain.
The maximum diversity order is the product of the number of transmit and receive antennas, and is achieved by transmitting a space-time block code with an appropriate dimension.
Updated response
The maximum value of multiplexing gain for MIMO (Multiple Input Multiple Output) antennas is determined by the number of transmit and receive antennas used in the system. Specifically, the maximum multiplexing gain is equal to the minimum of the number of transmit antennas and the number of receive antennas.
For example, if a MIMO system uses 4 transmit antennas and 2 receive antennas, the maximum multiplexing gain is 2, which is the minimum of the two numbers. Similarly, if a MIMO system uses 3 transmit antennas and 6 receive antennas, the maximum multiplexing gain is 3.
Sai R N : What you describe holds for the multiplexing gain, not the diversity gain. The maximum diversity gain is equal to the number of independent random variables that exist in the channel matrix which is the number of transmit antennas * the number of receive antennas.
Thank you Prof. Emil Björnson .
But, i see many of the diversity gain plots with a maximum value of 10dB. i want to know why.
For example, i attach link for a paper published in IEEE AWPL letters.
https://ieeexplore.ieee.org/document/6878430
DOI: 10.1109/LAWP.2014.2347897
The average MIMO diversity gain is less than 1, which implies that MIMO systems do not always provide a diversity gain. However, this result is based on the average channel matrix H, which may not reflect the actual channel conditions. In practice, the MIMO diversity gain may vary depending on the realization of H and the SNR.
The maximum value of diversity gain for MIMO antennas is equal to the number of independent random variables that exist in the channel matrix, which is the number of transmit antennas * the number of receive antennas. For example, a MIMO system with 2 transmit antennas and 3 receive antennas has a maximum diversity gain of 2*3 = 6.
However, the actual diversity gain that can be achieved in practice is often lower than the theoretical maximum. This is because the channel matrix is not always perfectly independent, and there may be some correlation between the random variables. Additionally, the diversity gain can also be affected by other factors, such as the signal-to-noise ratio (SNR) and the antenna spacing.
In general, the diversity gain of a MIMO system increases with the number of transmit and receive antennas. However, there is a point of diminishing returns, and the additional diversity gain that can be achieved by increasing the number of antennas becomes smaller and smaller.
Here are some additional factors that can affect the diversity gain of a MIMO system:
- The type of fading environment. In a slow fading environment, the channel coefficients remain constant for a relatively long period of time, which allows the receiver to take advantage of the diversity offered by multiple antennas. In a fast fading environment, the channel coefficients change very rapidly, making it difficult for the receiver to exploit the diversity gain.
- The antenna spacing. The closer the antennas are to each other, the more correlated the channel coefficients will be, which will reduce the diversity gain.
- The signal-to-noise ratio (SNR). The higher the SNR, the more likely it is that the receiver will be able to decode the signal even if one or more antennas are experiencing poor reception.
Overall, the diversity gain of a MIMO system is a complex function of many factors. However, in general, the more transmit and receive antennas there are, the higher the diversity gain will be.
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