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|Other Titles: ||Ultra-wide band communication systems for indoor environments by applying optimization methods|
|Authors: ||賀敏慧;Ho, Min-Hui|
|Keywords: ||基因演算法;粒子群聚演算法;非同步粒子群聚最佳化法;動態差異型演化法;超寬頻;接收能量;多目標函數;位元錯誤率;多輸入多輸出;通道容量;Genetic Algorithm;particle swarm optimization;asynchronous particle swarm optimization;Dynamic Differential Evolution;Ultra-wide band;Received Power;Multiple Objective Functions;Bit error rate;Multiple-Input Multiple-Output;channel capacity|
|Issue Date: ||2013-04-13 12:01:32 (UTC+8)|
|Abstract: ||本研究計劃擬以基因演算法（Genetic Algorithms, GA）、粒子群聚演算法（Particle Swarm Optimization, PSO）、非同步粒子群聚最佳化法（Asynchronous Particle Swarm Optimization, APSO）與動態差異型演化法（Dynamic Differential Evolution, DDE）最佳化法則於室內超寬頻（Ultra Wideband, UWB）通訊系統之研究。第一部份研究的目標是探討在一般大型室內環境UWB無線通訊系統上對接收能量的影響。考慮的通訊系統為脈衝無線電UWB通訊系統，接收天線均勻分佈在環境內。利用演算法來最佳化發射天線位置，計算發射天線與接收天線間之通道接收能量，須使接收能量相對於傳送能量相差–40dB內。若接收能量未及–40dB內，此稱為失效點。本研究以『最少發射天線個數』及『最佳發射天線位置』達到『接收能量滿足系統要求』。在正確的選擇與擺設下，可以有效降低相同頻道的干擾，藉由模擬去計算UWB系統在真實環境下之覆蓋率。此外，亦研究藉由演算法找到『最少發射天線個數』及『最佳發射天線位置』，使系統的『位元錯誤率降低』及『接收能量提升』之『多目標』最佳化。利用射線彈跳追蹤法，計算出發射天線與接收天線間之通道頻率響應與脈衝響應，並求出通訊過程中的『位元錯誤率』與『接收能量』，其中接收點的位元錯誤率大於10–6或接收能量未及–40dB內，只要一項不符合系統要求稱為失效，並將不合格接收點個數交給演算法做適應值分析。本研究將演算法和射線彈跳追蹤法結合模擬複雜環境，選用適當發射天線的位置預測無線電波傳輸時的特性，可以提升通訊品質。|
第二部份研究以演算法調整智慧型天線發射端的激發電壓與信號饋入線長度，使得傳輸『位元錯誤率降低』。發射端是環型UWB天線陣列，接收端則是單一一個UWB偶極天線。首先利用射線追蹤法計算出任意給定室內環境之脈衝響應，根據已知的天線陣列以及考慮具同步電路的脈衝無線電UWB通訊系統，利用演算法做最佳化的運算，期望能合成出具有指向性的輻射場型並對系統效能做分析，進而將此結果應用在室內無線區域的通訊上。此外，亦研究多輸入多輸出（Multiple Input Multiple Output, MIMO）UWB智慧型陣列天線，以演算法做最佳化天線場型的調整，使得MIMO-UWB系統『通道容量提高』。為了因應未來更高傳輸率以及傳輸品質，其UWB系統本身即具有高通道容量的特性，另一方面，MIMO可以有效的用來增加通道容量，為了滿足未來高傳輸率的需求，合併此二者是可以增加傳輸容量以及增強傳輸距離。MIMO-UWB智慧型天線系統可在電波傳送與接收方面利用波束合成的技術，提供同一頻道多個使用者同時使用的功能，以增加系統的容量與改善通訊品質。本研究中，發射和接收天線皆由八根UWB偶極天線所構成之環型陣列，和一般以天線場型為目標函數所不同的地方是，本研究擬以室內通信『通道容量提高』做最佳化，利用演算法調整發射天線的激發電壓和信號饋入線長度，尋找出滿足『最高通道容量』時的天線場型，此種場型最能滿足室內無線通訊的需求。
The genetic algorithm （GA）, particle swarm optimization （PSO）, asynchronous particle swarm optimization （APSO） and dynamic differential evolution （DDE） are used to optimizing the objective functions (criterion for measuring the effectiveness of the obtained optimized algorithm solution) and solved in indoor ultra-wide band （UWB） communication system. First, the optimal locations of the transmitter antenna for maximum received power in large area (>10m) UWB wireless communication systems with a mobile transmitter and uniformly distributed receivers are evaluated in the whole indoor environment, algorithm optimizers are used to search the best location of the transmitter antenna to maximize the received powers. The number of the receiver points is chosen as the objective function where the received power from any transmitter is less than –40dB. An optimization procedure for the location of the transmitter is employed to minimize the number of the transmitting antennas and maximize the received power in the coverage area. Based on the shooting and bouncing ray/image （SBR/Image） performance, the channel received power for any given location of the transmitter can be computed. The optimal transmitting antenna location for maximizing the received power is searched by algorithms. Obtained simulation results illustrate the feasibility of using the integrated ray-tracing, and optimization methods to find the optimal transmitter locations in determining the optimized coverage of a wireless network. The investigated results can help communication engineers improve their planning and design of indoor wireless communication. Besides, the algorithm are used to search the multiple objective functions which maximize the received power and minimize the bit error rate （BER） in indoor UWB communication system. The impulse responses of different transceiver antenna locations are computed by SBR/Image techniques, and the channel impulse response is further used to calculate corresponding BER. The BER performance of the binary pulse amplitude modulation （B-PAM） impulse radio UWB system is calculated. The objective function is chosen as the number of the receiver points where the received power from any transmitter is less than –40dB or at 100M bps transmission rate and for a BER > 10-6. Numerical results show that the performance for increasing of received power and decreasing of BER by optimization algorithm is quite good.
The second part, a circular array of eight UWB printed dipole transmitting antennas, which the excitation voltage and feed length was regulated by algorithm, is used to minimize the BER. The receiving antenna is one UWB dipole antenna. The UWB impulse responses of the indoor channel for any transmitter-receiver location are computed by SBR/Image techniques, inverse fast Fourier transform and Hermitian processing. By using the impulse response of multipath channel, the performance of the B-PAM impulse radio UWB system with circular antenna array can be calculated. Based on the topography of the circular antenna array and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the algorithm. The algorithm is used to regulate the antenna excitation voltage and feed length of each array element to minimize the BER performance of the communication system. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the LOS path which scales as the number of array elements. In other words, the receiver can increase the received signal energy to noise ratio. The synthesized array pattern also can mitigate severe multipath fading in complex propagation environment. As a result, the BER can be reduced substantially in indoor UWB communication system. Moreover, communication characteristic of indoor multiple-input multiple-output （MIMO）UWB circular antenna array is presented. The transmitting and receiving antennas are both circular array of eight UWB printed dipole antennas. By using the frequency responses of multipath channel, the channel capacity of the MIMO-UWB system with circular antenna array can be calculated. Based on the topography of the antenna and the channel capacity formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the algorithm. The algorithm is used to regulate the antenna excitation voltage and feed length of each array element to maximize the channel capacity performance of the communication system. The algorithm optimization is applied to a high order nonlinear optimization problem. The novelties of our approach is not only choosing channel capacity as the objective function instead of side-lobe level of the antenna pattern, but also consider the antenna excitation voltage and feed length effect of each array element. The strong point of the algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. Obtained simulation results illustrate MIMO-UWB smart antenna transmission dramatically increases channel capacity not only due to the beamforming gain and diversity gain but also MIMO spatial multiplexing technique makes full use of multipath fading.
|Appears in Collections:||[電機工程學系暨研究所] 學位論文|
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