While presenting this XFEST course in one location a rather astute (and frustrated) engineer raised his hand and asked " ... this is all great and I understand what you've presented, but how do I recover the data at the receiver?" What he's really asking about is system synchronization.
fred harris once wrote an introductary paper on modem design entitled "Let's Assume the System is Synchronized", poking fun at most treatments of the wireless radio. His point being that most descriptions gloss over the most critical part of a wireless communications link. In fact, this is where most companies in this business make their money. Designing the system, and in particular the receiver timing and symbol recovery can be tricky. Many factors such as transmit power, channel noise, multi-path, fading, signal bandwidth, and many other non-ideal conditions make reciever design a closely held secret within many companies.
The purpose of this XFEST course was to present Xilinx solutions for the Digital Front End only - meaning just the dgitial up conversion (DUC) of a baseband signal onto a carrier tone; and the digital down conversion (DDC) of that signal to baseband at the receiver. These functions have traditionally existed in the analog domain as costly, sensitive components. This course makes a strong case for the current trend of moving the DUC/DDC functions into the digital domain within and FPGA. While those are critical building blocks, going beyond that scope would require an intensive semester course on modem design. If you are interested, fred harris (lower case intended; his choice), teaches a graduate level course at San Diego State University on Digital Modem Design.
