# Constant Envelope Modulation Techniques for Limited Power Millimeter Wave Links
## 5 Results for Different CCI Scenarios  
The simulation results for the different CCI scenarios are presented in the following. First, it is assumed that the interferer transmits at the very same frequency as the required transmission. Then, a frequency shift, \(\Delta f\), is introduced to the interferer carrier.  
The analytical Equation (18) for the SER in the presence of interference and AWGN depends on the signal to interference (SIR) power ratio at the receiver, on the modulation index (\(2\pi h\)), and the constellation order (M). The case when the carrier frequencies of the transmitter and the interferer are identical is studied. Note that for Figure 6, the \"Analytical AWGN only\" curve refers to the situation where the PAM constellation order is M = 4 and the modulation index is \(2\pi h=0.6\). In Figure 6a, we show the dependence on the SIR parameter. As expected, a higher SIR results in a lower SER. Figure 6b shows the SER dependence on the modulation index, \(2\pi h\). As the value of \(2\pi h\) is increased, the SER decreases. Finally, Figure 6c demonstrates the dependence on the constellation M. Smaller constellations show a better performance.  
Interferer shift in frequency results in phase \(\theta(t)=2\pi\Delta ft\), where \(\Delta f\) is the difference in carrier frequencies. Figure 7 presents the spectrum of the CE-OFDM, CE-MTO, and the CW interference. Note that for the CE-MTO, \(T_{chip}\) is the time duration of a series \"chip\", while for the CE-OFDM, \(T_{chip}=T_{symbol}/N\), where N is the number of subcarriers. The inspection of Figure 7 reveals that the CE-MTO spectrum is null for the \(\Delta f\cdot T_{chip}\)= integer. The interference is located at \(\Delta f\cdot T_{chip}=2\). Comparing the two modulation techniques reveals a slight difference between the spectrum of the CE-OFDM and that of the CE-MTO.  
Figure 5: Comparison of the SER as a function of \(E_{b}/N_{0}\) for interfered link in the present of additive white Gaussian noise (AWGN). \(N_{chip}=16\), \(N=14\), M = 4, \(2\pi h=0.6\) and SIR = 15 dB.  
Figure 6: Comparison of the SER as a function of \(E_{b}/N_{0}\) for the interfered link, \(N_{chip}=16\), and \(N=14\). (a) M = 4; \(2 nh=0.6\); and SIR = 10, 15, and 20 dB. (b) M = 4; SIR = 20 dB; and \(2 nh=0.4\), 0.5, and 0.6. (c) \(2 nh=0.6\); SIR = 20 dB; and M = 4, 8, and 16.  
Figure 8a-c shows the graphs of the SER as a function of \(E_{b}/N_{0}\). The results in Figure 8a-c have been obtained for \(N=14\) orthogonal waveforms of \(N_{chip}=16\) chips. The order constellation is M = 4 and the modulation index is \(2\pi h=0.6\). It is assumed that the signal to interference power ratio is SIR = 15 dB for different frequency shift values, \(\Delta f\cdot T_{chip}\). In Figure 8a, where \(\Delta f\cdot T_{chip}=0.3\), the performance of CE-MTO is revealed to be better than that of CE-OFDM. However, in Figure 8b, where \(\Delta f\cdot T_{chip}=0.6\), the CE-OFDM demonstrates a better performance than that of CE-MTO. The curves in Figure 8c refer to \(\Delta f\cdot T_{chip}=1\). In this scenario, the performance of CE-MTO and that of CE-OFDM are identical. The results obtained in Figure 8a-c are as expected when examining the spectrum as given in Figure 7.  
Figure 8: _Cont._  
Figure 7: Comparison of the spectrum as a function of the normalized frequency.