在本論文中，我們針對具有多重輸出入天線陣列之多載波分碼多重接取系統，提出一種結合功率分配及天線選擇的方法。此方法能在具有頻率選擇性之瑞雷衰減通道中，具體有效地提昇位元錯誤率之效能。多重輸出入天線陣列配合空間時間區塊碼之使用能增加系統之空間分集階數，而多載波分碼多重接取系統則能藉由頻域擴展及多載波調變之使用，使系統具有頻率分集之特性及多重接取之能力。我們所提出之方法結合這些系統之優點，並且經由在每一個子載波上選出具有較大通道增益之發射天線，並進而經將有限的發射功率適當地分配在每一個子載波所選出之發射天線上，而達到提昇整體系統效能之目的。

我們提出的方法首先在每個子載波上選出具有最大弗羅賓尼斯（Frobenius）範數之發射天線，同時利用注水(water-filling)演算法將發射功率適切地分配到每個子載波上，使整體效能有效地提昇。天線選擇演算法乃是以範數之大小作為選擇之依據，選出每個子載波上的最佳天線，其運算執行在空間分集維度。另一方面，功率分配則是作用在頻域分集維度，其目的在使通道容量最大化。系統效能可以經由適當地結合以上這兩種方法而得到有效的改善。將有限的發射功率分配到各個子載波上以使通道容量最大化，乃是限制最佳化問題，我們可藉由拉格朗治乘數法來求解。模擬結果顯示我們所提出的方法使系統效能得到具體有效的提昇。

In this thesis, we present a combined scheme of power allocation and antenna
selection to improve the bit error rate (BER) performance for multiple input
multiple output (MIMO) multicarrier code division multiple access (MC-CDMA)
systems over frequency selective Rayleigh fading channels. MIMO configurations
with space-time block code (STBC) technology can enhance system performance
by improving the spatial diversity order, while MC-CDMA systems provide frequency
diversity and multiple access capability by frequency domain spreading
and multicarrier modulation. The proposed scheme combines the advantages of
these technologies by appropriately selecting the transmit antennas with higher
channel gain and allocating the limited transmission power resources among them
to improve the overall system performance.
The scheme we proposed is to first select the best transmit antenna with
highest channel Frobenius norm for each subcarrier. Then, the transmission power
is allocated among these subcarriers by water-filling (WF) algorithm to improve
the overall system performance. The antennas selection is performed in spatial
diversity dimension on each subcarrier employing the norm-based criterion, with
the power being allocated in frequency diversity domain to maximize the channel
capacity across the subcarriers. The power allocation among the subcarriers is
a constrained optimization problem that can be solved by using the Lagrange
multiplier method. Simulation results show that the new scheme can provide
considerable performance gain.

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