and not learned Machine-readable policy-controlled radios are attrac- or software adaptive; thus, DECT is not normally tive for several reasons. One feature is the ability to "try considered an adaptive radio. out" a policy and assess it for impacts. The deployment 802.11 a has the ability to sense the bit error rate (BER) may be controlled to a few radios on an experimental of its link, and to adapt the modulation to a data rate and basis, SO it is possible to assess the observation and mea- a corresponding forward error correction (FEC) that set surement of the behaviors. If the result is undesirable, the the BER to an acceptably low error rate for data applica- policies may be removed quickly. This encourages rapid tions. Although this is adaptive modulation, 802.11 decisions by regulatory organizations. The policy-driven implementations generally are dedicated purpose-fixed approach is also attractive because spatially variant or even application-specific integrated circuit (ASIC) chips, not temporally variant regulations may be deployed. As an software defined, and thus 802.11 is not normally con- example, when a radio is used in one country, it is subject sidered to be an adaptive radio. to that country's regulations, and when the user carries it CHAPTER 2.4b Cognitive radio: The technologies required Table 2.4b-4 Properties of advanced radio classes. Radio property Software Software Software-defined Aware Adaptive Cognitive capable programmable radio radio radio radio radio radio Frequency hopping Automatic link establishment (i.e., channel selection) Programmable crypto Networking capabilities Multiple waveform interoperability In-the-field upgradable Full software control of all signal processing, crypto, and networking functionality QoS measuring/ channel state information gathering Modification of radio parameters as function of sensor inputs Learning about environment Experimenting with different settings The industry standards organizations are in the process of determining the details of what proper