**5.2. The most appropriate biometric traits of a person that can easily be identified by robot**

Interaction depends on the extent of communication between robots and humans. Human and a robot can construct a communication between each other using several forms. Proximity to each other is the main factor that impacts the communication forms between human and robot. Thus, communication and interaction can be classified into two general categories [27]:


Choosing biometric traits that robot should use to identify the user should be compatible with the aforementioned interaction categories. For the remote interaction, the biometric traits whose raw features are images such as face, ear, and iris are not convenient choices, since the majority of remote interaction is conducted by voice communication. Therefore, speech recognition may be the best choice, since it is suitable for direct (different room) and mobile calling. For proximate interaction (face-to-face interaction) and in order to create more real interaction, identification process should use a biometric trait that does not require direct contact with the user in order to capture the biometric traits such as face, ear, and voice, which are captured from a far distance.

Consolidating multiple features that are acquired from different biometric sources in order to construct a person recognition system is defined as multibiometric systems. For example, fingerprint and palmprint traits, or right and left iris of an individual, or two different samples of the same ear trait may be fused together to recognize the person more accurate and reliable than unimodal biometric systems. Due to the use of more than one biometric source, many of the limitations of unimodal systems can be overcome by the multimodal biometric

Person Identification Using Multimodal Biometrics under Different Challenges

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Multibiometric systems are able to compensate a shortage of any source using the other source of information. In addition, the difficulty of circumvention of multiple biometric sources simultaneously creates more reliable systems than unimodal systems. On the other hand, the unimodal biometric systems are low cost and require less enrollment and recognition time compared to multimodal systems. Hence, it is essential to carefully analyze the tradeoff between the added cost and the benefits earned when making a business case for

systems [28].

**Figure 9.** Various scenarios in a multimodal biometric system.
