Tactical Wireless Communications and Networks: Design Concepts and Challenges

2.7 Concluding Remarks

2.7.1 What Happens Before Modulation and After Demodulation?

In the next chapter, we will discuss what happens before modulation and after demodulation over the tactical network node protocol stack layers. We will discuss some concepts of information theory where a set of information symbols are encoded before being modulated over the communications channel. We will discuss error control coding, source coding, the relationship between error control coding and modulation, and will review the channel capacity concepts and see how channel coding can help us use a simple modulation and demodulation technique. Channel coding techniques are usually implemented at the data link layer (DLL). An objective of this book is to help you understand how the protocol stack layers in tactical communications and networking relate to each other and how some techniques (such as error control coding) can be implemented at different layers of the protocol stack. Even if you specialize in a particular protocol stack layer, this book should help you choose design concepts that complement the other layers.

2.7.2 Historical Perspective

Today, with the advances in microprocessor technology and the low cost of memory, the ability of communications and networking to transmit information is bounded only by the physical layer's ability to transmit bits at a higher rate. There are physical limits on how many bits per second a medium can transmit. We have come a long way since Samuel Morse ...