I am taking a undergrad network course that uses Data Communications and Networking 5th edition containing diagrams and legends which I cannot decipher. Specifically the diagram on the right, has y-axis P for power, then z-axis f/N. Does this mean the fraction f/N (frequency/bit rate) or does it mean f or N. Also the start of chapter 4 explains that ratio r is data rate/signal rate or r = N/S. In the legend it gives r=1 so re-arranging the equation, shouldn't S_ave = N/1?
Also, it explains that Manchester and Differential Manchester take up twice as much bandwidth because of the voltage change during the bit but comparing the right hand side diagram below with the respective right hand side diagram above, how do you determine that it is double? Is it area under the curve?