level of software sophistication ever embedded into a radio [24]. SUO-SAS (Small Unit Operations-Situational Awareness System) Developed by DARPA to establish the operational benefits of an integrated suite of advanced communication, navigation, and situation awareness technologies. It served as a mobile communications system for small squads of soldiers operating in restrictive terrain. SUO-SAS provides a navigation function utilizing RF ranging techniques and other sensors to provide very high accuracy [22]. changes instantaneous bandwidth and/or system timing 2.4b.3.3 Cognitive radios parameters in response to offered network load may be considered adaptive. If a radio modifies intermediate A CR has the following characteristics: sensors creating frequency (IF) filter characteristics in response to channel awareness of the environment, actuators to interact with characteristics, it may be considered adaptive. In other the environment, a model of the environment that in- words, if a radio makes changes to its operating parame- cludes state or memory of observed events, a learning ters, such as power level, modulation, frequency, and SO capability that helps to select specific actions or adapta- on, it may be considered an adaptive radio. tions to reach a performance goal, and some degree of At this time, two wireless products exhibit some autonomy in action. degree of adaptation: the digital European cordless Since this level of sophisticated behavior may be telephone (DECT) and 802.11a. a little unpredictable in early deployments, and the DECT can sense the local noise floor and interference consequences of "misbehavior" are high, regulators will of all the channels from which it may choose. Based on want to constrain a CR. The most popular suggestion to this sensing capability, it chooses to use the carrier date for this constraint is a regulatory policy engine that frequencies that minimize its total interference. This has machine-readable and interpretable policies. feature is built into hardware, however, 