The plot in Figure 7 shows that the power level for GSM does not vary too much when the size of the text increases, whereas in the 3G case, it grows linearly with the length of the SMS. Another factor which influences the power, the time, and therefore the energy, is the received signal strength. As shown in Figure 8 for both GSM and 3G, when the power of the received signal decreases, the time needed for sending the SMS increases.