When you are trying to arrive at a complex Embedded Systems and Communications solution, You will think of a DSP. Now that computers and embedded devices are used in most electronic devices, DSP is a way you can process, transform, analyze and generate fast analog data, in Real Time.
When a product has to be made small, the board real estate is limited or it has to be manufactured in large numbers.... SoC is the Answer. A Microprocessor evolved into a Microcontroller by packing many external chips into one chip. Now uC Card along with the other blocks like A-D, Port Drivers, Networking elements, Display Driver and other peripherals can be packed into one chip.
Very-large-scale integration (VLSI) is the process of creating integrated circuits by combining thousands of transistors into a single chip. VLSI began in the 1970s when complex semiconductor and communication technologies were being developed. The microprocessor is a VLSI device. Some VLSI System Design Topics for study at EECS Course WEB Sites