ware and hardware components can be readily the cognitive algorithms. In general, it is possible to reused from implementation to implementation. SDR provide significant flexibility with a series of tunable also provides the management structure for the de- hardware components that are under the direct control scription, creation, and tear-down of waveforms. In of the cognitive software. In the case of a cognitive several respects, SDR offers the same capabilities system that can support a large number of protocols and supported by OSs; SDR is actually a superset of the ca- air interfaces, it is desirable to have a generic underlying pabilities provided by an OS. SDR must support a variety hardware structure. of cores, some of which may be deployed simultaneously The addition of a series of generalized computing in the same system. This capability is like a distributed structures underlying the cognitive engine implies that os designed to run over a heterogenous hardware envi- the cognitive engine must contain hardware-specific ronment, where heterogenous in this context means not Communications Engineering Desk Reference; ISBN: 9780123746481 Copyright © 2006 Elsevier Inc. All rights reserved CHAPTER 2.4a The software defined radio as a platform for cognitive radio only general purpose processors (GPPs), but also digital section is to explore hardware for SDR from a radio signal processors (DSPs), field-programmable gate arrays standpoint. Figure 2.4a-1 (a) shows a basic radio receiver. (FPGAs), and custom computing machines (CCMs). As one example based on the basic radio receiver archi- Furthermore, SDR must support the RF and intermediate tecture, Figure 2.4a-1(b) shows a design choice made frequency (IF) hardware that is necessary to interface the possible by digital signal processing techniques, in which computing hardware with radio signals. This support is the sampling process for digital signal processing can be largely a tuning structure coupled with a standardized placed in any of several locations and s