System-on-a-chip VLSI has long been discussed and has many meanings, with the most compelling being a design which has components at a level above what is presently being used. In the past this sometimes simply been a heterogeneous design which simultaneously includes either analog with digital or non-transistor structures or even simply just different kinds of digital circuitry (e.g. dedicated logic with a programmable core). While all of these have design challenges beyond that necessary for a single circuit type, it is the possible inclusion of all the above (analog, non-transistor, various types of digital) which rises to the level of a true System-on-a-chip. This represents the integration of all the functions which were previously interconnected on a PC board or boards, which is one level higher than what has been previously possible.above Such high levels of integration are required in those applications which are cost, power and size sensitive and the most clear example of such products are systems which support wireless communications in portable devices. This can range from cell phones to portable multimedia terminals and demonstrations of these systems are now beginning to appear which have integration of both the analog and digital functions as well as passive elements that are compatible with CMOS. These prototypical System-on-a-chip implementations are further complicated by the various types of digital computation which are required, ranging from control processing for protocols and user interface, up to the highest speed dedicated digital circuitry for the early stages of the link demodulation. The demand for the most efficient integrated solution requires a simultaneous optimization of the passive devices, analog circuits as well as the computational structures used to implement the digital processing. The choice of the latter is particularly important as the various approaches can range over many orders of magnitude in size and energy efficiency.The design of portable wireless systems is particularly rich in that it not only involves the circuit design, but a number of other fields including communication theory, radio architecture, RF analog design and software. It is the possibility of integration of circuit structures that support these highly diverse areas that results in the conclusion that System-on-chip VLSI has finally arrived.