Abstract
This study is a literature survey of multimodal biometric systems (MBS) that present the most important publications in this research area. We first provide an overview of important concepts in multimodal biometric recogntion. Then we provide a snapshot of the current state of research in multimodal biometrics with regards to modalities, fusion functions and remaining challenges. Lastly, we cover and analyze the existing biometric system according to modality. Some challenges are the creation of multimodal databases, the lack of reusability biometrics module and a unified framework and the improvement of usability and the authentication systems.