Ultra-Wide Band Communication Systems for Indoor Environments by Applying Optimization Methods
| Autor: | Min-Hui Ho, 賀敏慧 |
|---|---|
| Rok vydání: | 2013 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 101 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. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|