Abstract :
Link adaptation is an important approach to achieve robust, QoS-based wireless multimedia communications. Scheme switching in multiple-input multiple-output (MIMO) systems is an aspect of connection adaptation and involves selecting different MIMO transmission schemes or modes in order to adapt to the different conditions of the radio channel in order to achieve QoS delivery. Finding the most suitable switching method in MIMO links, however, remains a challenge since existing methods are either computationally complex or not always accurate. This paper presents a smart MIMO system switching method consisting of two schemes-transmit diversity (TD) and spatial multiplexing (SM)-using fuzzy logic technique. In this technique, two channel quality indicators (CQI), such as the average received signal - to - noise ratio (RSNR) and the received signal strength indicator (RSSI), are measured and passed to the fuzzy logic system as inputs, which then provides a decision – an inference. To switch between the TD and SM schemes, the switching decision of the fuzzy logic system is fed back to the transmitter. Computation results indicate that the proposed fuzzy logic-based switching technique outperforms standard static switching techniques in terms of bit error rate and spectral efficiency.
Keyword :
Fuzzy logic, link adaptation, MIMO, spatial multiplexing, transmit diversity