本文中提出使用遺傳演算法在Federal Communications Commission (FCC)規定的頻譜內產生一個超寬頻ultra-wideband(UWB)波形。吾人利用遺傳演算法找出波形的合成參數，再將每個波形相加合成出一個符合FCC 頻譜規範的波形。亦有部份文獻則是以高次微分波形做為傳送波形，但在實際電路實現上有困難且不容易達到。所以本文中提出只利用多個高斯三次微分波形合成，則可以避免上述的困擾。最後與傳統高斯微分波形比較，比較結果得出由遺傳演算法合成波形不僅比傳統的高斯微分波更符合FCC 頻譜規範，而且可以得到較佳的效能。吾人使用上述之波形配合射線彈跳追蹤法(Ray Tracing Mode)模擬真實環境，結果顯示，遺傳演算法設計出波形比傳統高斯波形大量的提升頻寬使用率(spectrum utilization rate)，減少多重路徑(multipath)干擾，降低錯誤率以及失效率(outage probability)。文章中提到的射線彈跳追蹤法，可以經由程式設定進而模擬更接近現實環境的通道。本文提出波形合成最佳化方法，不是只有侷限在超寬頻無線系統上，使用者僅需替換不同的適應函式，亦可應用與設計出其他通訊的最佳波形。模擬中利用高斯三次微分波形，只要透過遺傳演算法找到每個波形的參數後，將這些波形相加就可以得到最佳波形，吾人提出的方法是可以加以實現，而非僅於數值模擬上進行。 This paper proposes a new pulse design method to improve spectrum utilization rate and reduce the outage probability in Ultra Wide Band (UWB) system. Several third derivative Gaussian waveforms are employed to generate the pulse based on the bandwidth constraint set by the US Federal Communications Commission (FCC) mask. The genetic algorithm (GA) is used to find the optimal pulse parameter. This method is an easy way to achieve in practical circuit implementation, since COMS circuit is hard to produce one pulse with short duration and complex pulse shape. Comparisons with the traditional Gaussian pulse, the synthesis pulse by GA not only satisfies the FCC emission mask but also has high spectrum utilization rate. Simulation results show that the performances in indoor UWB system using the synthesis pulse by GA is better than that using traditional Gaussian pulse. Numerical results show that the synthesis pulse by GA is 30 percent higher in spectrum utilization rate and 65 percent lower in outage probability for the same transmission power, as well as 21 percent lower in outage probability for fixed Signal-to-noise ratio (SNR)at the receiver comparing with traditional Gaussian pulse. This proposed method not only uses in indoor UWB system but also can be extended to different communication systems by changing the system object function.
