在這篇論文中，我們提出了一種不必使用循環字首(Cyclic Prefix)來克服多路徑干擾的多重 擷取之技術。此系統稱為區塊混和多工存取技術(Block Scrambling Multiple Access)。在區塊混和多工存取系統中，我們將會一串碼組送入快速複立葉轉換中，以藉此來產生一連串的正交載波。之後，我們再將資料和這些正交載波相乘。在接收端，我們會再送同一串碼組，進入快速複利葉轉換中，產生一連串的正交載波，之後再將這些載波取共軛，以藉此來進行解調的工作。這和正交分頻多工存取技術最大的不同之處在於，區塊混和多工存取系統不需要將資料送入快速複利葉轉換中，因此，區塊混和多工存取系統不需要循環字首來克服多路徑的干擾。此外，區塊混和多工存取系統，可以藉由他的第二個低通濾波器來抑制雜訊，所以，他會具有比正交分頻多工存取技術更好的系統效能。再加上， 區塊混和多工技術，可以提供比正交分頻多工存取技術更高的頻寬利用效率。不過，再具有多路徑干擾的情況下區塊混和多工無法支援很穩定的用戶數。因此， 在第五章，我們提出了區塊混和分碼多工存取技術(Block Scrambling-Code Division Multiple Access)來解決這個問題。區塊混和分碼多工技術，也具備不錯的頻寬利用效率及系統效能。在第七章，我們將區塊混和多工存取和區塊混和分碼多工存取整合在一起成為，區塊混和多工-分碼多工存取技術(Block Scrambling
Multiple Access - Code Division Multiple Access)。此系統，具備以上兩個系統的優點，擁有非常棒的頻寬利用效率及系統效能。並且她總共能支援比區塊混和多工技術多M 備的用戶數。

In this thesis, we proposed a multiple access to overcome cyclic prefix (CP) of orthogonal frequency division multiple access (OFDMA). This system was called block scrambling multiple access (BSMA). In OFDMA, it sent data into IFFT to produce orthogonal data. In BSMA, we sent a code sequence into FFT to produce orthogonal subcarriers. Then we would let the data multiply with these orthogonal subcarriers. In other words, we used FFT to achieve
multi-carrier system. We did not need so many oscillator like MC-CDMA. In the receiver, we did not send signal into FFT to recover. So, we did not need CP, just like OFDMA, to overcome multipath interference (MI). So, BSMA combined the benefit of MC-CDMA, BSMA did not CP to overcome MI and BSMA did not as many as oscillator to produce subcarriers. Besides, BSMA could use its second LPF to reduce AWGN noise. So, BSMA could enhance
BER performance by its FFT size. But, BSMA had a drawback. That was BSMA could not provide a stable number of users in the multipath fading channel. We would discuss it in the Chapter 3. In this thesis, we would prove BSMA could work in the AWGN channel and Rayleigh fading channel. And we would proof BSMA could enhance BER performance by its FFT size. Besides, we would provide another system block scrambling - code division multiple access (BS-CDMA) to overcome the problem of users number of BSMA. At the final,
we would combine BSMA with BS-CDMA as BSMA-CDMA. BSMA-CDMA had BSMA’s bandwidth efficiency and M times supportable uses number than BSMA. We would prove BSMA could work in the Rayleigh fading channel.

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