abled by one (ToA), and, if the hardware supports it, angle of arrival or more biometric sensors. This knowledge, coupled with (AOA). Multiple observations from multiple positions authentication goals, can prevent unauthorized users CHAPTER 2.4b Cognitive radio: The technologies required Biometrics in Order of Effectiveness Biometrics in Order of Social Acceptability 1. Palm scan 1. Iris scan 2. Hand geometry 2. Keyboard dynamics 3. Iris scan 3. Signature dynamics 4. Retina scan 4. Voiceprintb 5. Fingerprint 5. Facial scan 6. Voiceprint 6. Fingerprintc 7. Facial scan 7. Palm scanc 8. Signature dynamics 8. Hand geometryc 9. Keyboard dynamics 9. Retina scan aRequires a camera scanner butilizes a copy of the voice input (low impact) CRequires a sensor in the push-to-talk (PTT) hardware Figure 2.4b-3 Biometric sensors for CR authentication applications. Several biometric measures are low impact ones in terms of user resistance for authentication applications. from using the CR. Most radios have sensors (e.g., mi- GPS devices report time of day and provide a one- crophones) that may be used in a biometric application. pulse-per-second signal. The one-pulse-per-second signal Voice print correlation is an extension to an SDR that is is transmitted from satellites, but does not arrive at every achievable today. Requirements for quality of voice cap- GPS receiver at the same time due to differences in path ture and signal processing capacity are, of course, levied lengths. A properly designed receiver will assess the on the radio system. The source radio can authenticate propagation delay from each satellite and compensate the user and add the known identity to the data stream. each of these delays SO that the one-pulse-per-second At the destination end, decoded voice can be analyzed for output is synchronous at all receivers with only a 340 ns the purposes of authentication. jitter. This level of accuracy is adequate for many appli- Other biometric sensors can be used for CR authen- cations, such as policy gating and cha