Degradation of the MIMO channel capacity due to additional noises of amplifiers

It is theoretically well known that a multiple input multiple output (MIMO) system can offer higher channel capacity than a conventional wireless system. The MIMO capacity is increased as a function of signal‐to‐noise ratio (SNR) and a number of antenna elements at both the transmitter and receiver. To realize MIMO capability in practical use, the implementation of all electronic devices is necessary to be considered. Amplifiers become the most common devices assembled at the transmitter and receiver with the purpose of overcoming the power loss in the wireless channel. High power amplifier (HPA) and low noise amplifier (LNA) are the special types of amplifiers that are compulsory for the transmitter and receiver, respectively. Both devices have the same function to provide the reliable power gains while adding as little noise as possible. For a MIMO system, the channel capacity sensitively grows as a function of SNR. Therefore, the changes in SNR due to HPA and LNA definitely degrade the system capacity. In this paper, the degradation due to both devices is investigated by taking the gain and noise figure of these amplifiers into account. The new formula of MIMO channel capacity including amplifier characteristics is originally proposed. The results indicate the remarkable consideration on using amplifiers as they may degrade the capacity up to 26%. This can be the guideline for MIMO researchers to spare the capacity margin caused by the additional noises of amplifiers. Copyright © 2008 John Wiley & Sons, Ltd.