e or operating environment. In the messaging example, this class can include all the There are two open SDR architectures, GNURadio and messaging information needed for updating the state of the system. Given this encapsulation, a class such as the headphone in the ongoing example can be used not 2.4a.4.1 GNURadio only in the computer example, but also in other sys- items, such as a personal music player, an interface to an GNURadio [7] is a Python-based architecture (see section airplane sound system, or any other appropriate type of Python) that is designed to run on general-purpose com- system. The relationship class encompasses an aspect of puters running the Linux OS. GNURadio is a collection the class; thus, context can be provided through the of signal processing components and supports primarily use of aspects. Unlike CBP, AOP requires the creation one RF interface, the universal software radio peripheral of new language constructs that can associate an aspect (USRP), a four channel up- and down-converter board to a particular class; to this end, there are several lan- coupled with ADC and DAC capabilities. This board also guages (AspectJ, AspectC++, and Aspect#, among allows the use of daughter RF boards. GNURadio in others). general is a good starting point for entry-level SDR and CHAPTER 2.4a The software defined radio as a platform for cognitive radio should prove successful in the market, especially in the In recent years, implementations of CORBA have amateur radio and hobbyist market. GNURadio does appeared on DSP and FPGA, but traditionally CORBA suffer from some limitations-namely, (1) that it is reliant has been written for GPP. Furthermore, system calls are on GPP for baseband processing, thus limiting its signal performed through an OS, requiring an os on the processing capabilities on any one processor, and (2) it implementation. In the case of the SCA, the os of lacks distributed computing support, limiting solutions to choice is a portable operating system interface (POSIX) single-processor