When analysing the rate differences of wireless communication systems in Rayleigh fading environments, we need to consider the capacity and diversity gains provided by these configurations.
MISO Rate: 4x4 (4 transmit antennas, 4 receive antennas)
- The system can leverage transmit diversity, where the base station sends the same signal across multiple antennas, and receive diversity, where the user combines signals received from multiple antennas.
- Beamforming can be used to improve the SNR at the user end, enhancing reliability and effective data rate.
MIMO Rate: 8x4 (8 transmit antennas, 4 receive antennas)
- Both the base station and the user have multiple antennas, allowing for spatial multiplexing, which enables the transmission of multiple independent data streams.
- The system can exploit both diversity and multiplexing gains, improving both reliability and capacity.
- The additional antennas at the base station provide more spatial degrees of freedom, enhancing the system's ability to combat fading and interference.
Comparison
- Capacity: The MIMO system (8x4) generally offers a higher capacity compared to the MISO system (4x4) due to the ability to send more independent data streams and better exploit spatial diversity.
- Diversity Gain: Both systems benefit from diversity gain. However, MIMO can achieve it at both the transmitter and receiver ends, providing better performance in fading environments.
- Spatial Multiplexing: The MIMO configuration can achieve a higher spatial multiplexing gain than the MISO configuration, allowing for a greater increase in data rate.
- Beamforming and SNR: Both configurations can use beamforming to improve SNR, but MIMO benefits more from the additional antennas at the base station, which can enhance both beamforming and spatial multiplexing capabilities.
In summary, the MIMO configuration with 8 antennas at the base station and 4 antennas at each user typically provides a higher data rate and better performance in Rayleigh fading environments compared to the MISO configuration with 4 antennas at both the base station and each user. This is due to the additional spatial multiplexing and diversity gains available in MIMO systems.
You may go through the following MathWorks documentation links to learn more about ‘RF Blockset’ models in MATLAB:
