# What does it mean to plot a PAM signal over a number of symbols?

Our course has been using the book Introduction to Communication Systems by Upamanyu Madhow for our communications course. There is a question in the book on page 87 Software lab 2.1 which is

Consider a pair of independently modulated signals, $$u_c(t) = \sum_{n=1}^{n=N} b_c[n]p(t − n)$$ and $$u_s(t) = \sum_{n=1}^{n=N} b_s[n]p(t−n)$$, where the symbols $$b_c[n], b_s[n]$$ are chosen with equal probability to be $$+1$$ and $$-1$$, and $$p(t) = I_{[0,1]}(t)$$ is a rectangular pulse. Let N = 100.

Use Matlab to plot a typical realization of $$u_c(t)$$ and $$u_s(t)$$ over 10 symbols. Make sure you sample fast enough for the plot to look reasonably “nice.”

I want to ask what is the meaning of plotting $$u_c(t)$$ and $$u_s(t)$$ over 10 symbols.

$$10$$ symbols means that you choose $$N=10$$, i.e., you plot realizations of
$$u_c(t)=\sum_{n=0}^{9}b_c[n]p(t-n)$$
$$u_s(t)=\sum_{n=0}^{9}b_s[n]p(t-n)$$
in the range $$t\in[0,10]$$.