Software defined cognitive radios

The wide proliferation of wireless services and applications with increasing bandwidth needs is rapidly creating a spectrum shortage. However, the problem is caused primarily by inefficient legacy spectrum allocation policies, so that even when some applications suffer from lack of bandwidth, there is idle capacity in other bands. To deal with this challenge, the FCC, ITU and other regulatory organizations have begun to explore an open spectrum policy implemented by programmable wireless networks. Such wireless networks use cognitive, software reconfigurable radios to increase the efficiency of spectrum access. In particular such programmable wireless networks maximize the availability and enhance the quality of service of diverse applications using the most appropriate access network, or an aggregation of such networks, for any given local conditions. A software defined radio (SDR) terminal is essentially a reconflgurable system that can be dynamically programmed in software to reconfigure the characteristics of the hardware through the use of clearly defined APIs residing on top of a flexible hardware layer. The SDRs use different types of hardware to accomplish various communication tasks. In addition to the grammability and flexibility provided by the DSPs and software-driven communication parameters such as modulation, medium access, cryptography, etc, software defined radios also provide field service capability. So, when requirements change, code downloads, upgrades and modifications are relatively easy to execute. Ultimately, the success of the programmable wireless network vision will hinge on its ability to meet the high level needs of users, service providers, network operators and hardware and software developers. Ubiquitous access to applications with proper quality levels, low cost services, user friendliness, fast and open service creation, lifetime and flexibility of equipment, common execution environment, fast product design and manufacturing, to mention a few, translate into well defined technology requirements. In this tutorial we will discuss system, circuit and implementation issues necessary to design a programmable wireless network that meets these requirements.