Chien-Ching Chiu

Channel capacity of multiple-input multiple-output ultra-wideband systems with single co-channel interference

In this paper, the channel capacity of multiple-input multiple-output ultra-wideband (MIMO-UWB) systems with single co-channel interference (CCI) is calculated. A ray-tracing approach is used to calculate the wanted channel frequency response, and the channel frequency response is further used to calculate the corresponding channel capacity. By the ray-tracing approach, two different antenna arrays are applied to our simulation to observe whether MIMO can reduce CCI. Also the effects caused by the two antenna arrays for the desired system and CCI are quantified. Copyright

Optimal Relay Antenna Location in Indoor Environment Using Particle Swarm Optimizer and Genetic Algorithm

An optimization procedure for the location of the relay transceiver in ultra-wideband wireless communication system is presented. The impulse responses of different transceiver locations are computed by shooting and bouncing ray/image (SBR/Image) techniques and inverse fast Fourier transform (IFFT). By using the impulse responses of these multi-path channels, the bit error rate (BER) performance for binary pulse amplitude modulation (BPAM) impulse radio UWB communication system are calculated. Based on the BER performance, the outage probability for any given relay location of the transceiver can be computed. The optimal relay antenna location for minimizing the outage probability is searched by genetic algorithm (GA) and particle swarm optimizer (PSO). The transmitter is in the center of the whole indoor environment and the receivers are uniform distributed with 1.5 meter intervals in the whole indoor environment. Two cases are considered as following: (I) Two relay transceivers with two different cases are employed. First, the whole space is divided into two areas and one relay transceiver is used in each area. The optimal relay antenna locations are searched in each area respectively. Second, the two optimal relay locations are searched in the whole space directly without any prior division. (II) Four relay transceivers with two different cases are employed. First, the whole space is divided into four areas and one relay transceiver is used in each area. The optimal relay antenna locations are searched in each area respectively. Second, the four optimal relay locations are searched in the whole space directly without any prior division. Numerical results have shown that our proposed method is effective for finding the optimal location for relay antenna to reduce BER and outage probability.

Optimisation of channel capacity for multiple-input multiple-output smart antenna using a particle swarm optimiser

In this study, the channel capacity of indoor multiple-input multiple-output ultra-wide band (MIMO-UWB) transmission for a smart antenna is described. A particle swarm optimiser (PSO) is used to synthesise the radiation pattern of the directional circular arc array to maximise the capacity performance in an indoor MIMO-UWB communication system. The UWB impulse responses of the indoor channel for any transmitter-receiver location are computed by applying shooting and bouncing ray/image techniques, inverse fast Fourier transform and Hermitian processing. By using the calculated frequency response, the capacity performance of the synthesised antenna pattern on an MIMO-UWB system can be computed. Based on the topography of the circular antenna array and the capacity formula, the array pattern synthesis problem can be reformulated into an optimisation problem and solved by the PSO algorithm. PSO optimisation is applied to a high-order non-linear optimisation problem. The novelties of our approach are not only choosing capacity as the cost function instead of the sidelobe level of the antenna pattern, but also considering the antenna feed length effect of each array element. The cost function for the problem is non-smooth and discontinuous with respect to the antenna pattern. It is difficult to solve by gradient methods, since the derivative is hard to derive. The strong point of the PSO algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. The simulation results show that the synthesised antenna array pattern is effective to focus maximum gain on the line-of-sight path which scales as the number of array elements.

Ultra-wideband outdoor communication characteristics with and without traffic

The BER performance for ultra-wideband (UWB) outdoor communication in LOS and NLOS environments with and without traffic is investigated. We obtain the impulse responses of the UWB outdoor environment by both 2.5D SBR-Image method and inverse Fourier transform techniques. The 2.5D SBR-Image method is first considered for two-dimensional environment simulated without heights of obstacles by ray tubes. Then, heights of the obstacles are taken into consideration between the transmitters and receivers. If the height of ray is lower than that of obstacles, the ray is neglected for the receivers. This effectively reduces the simulating time. By using the impulse response of multipath channels, the BER performance for binary pulse amplitude modulation communications over the radio UWB system is evaluated. We have performed computer simulations in LOS and NLOS environments with and without traffic in dense building areas. Numerical results have shown that the multipath effect caused by moving vehicles in the outdoor LOS and NLOS environments has a great impact on BER performance. Rake receivers are used to improve the outage probability. The relationship between traffic and BER performance is investigated; meanwhile, the characteristics of LOS and NLOS outdoor UWB environments are analyzed. Our investigation results can help improve planning and design of the UWB system.

A novel search method to reduce PAPR of an OFDM signal using partial transmit sequences

One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. As ordinary PTS technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub-blocks. In this paper, we propose a novel PTS technique with reduced complexity that each level inverts twice of phase factor bits from previous level. Then we also use initial random phase sequence to find the better search way of PAPR reduction. Numerical results show that the proposed method can achieve significant reduction in search complexity with little performance degradation. Copyright

Channel Capacity of Multiple-Input Multiple-Output Systems for Optimal Antenna Spacing by Particle Swarm Optimizer

The geometrical shape of antenna arrays for maximizing the average channel capacity of the system in a multiple-input multiple-output link is investigated. The optimum element spacing of the transmitting antenna is also included. The frequency responses of transceiver antenna with different element spacing are computed by ray-tracing techniques, and the channel frequency response is further used to calculate corresponding channel capacity. The transmitter is set in the center of the indoor environment and the receivers are with uniform intervals distribution in the whole wooden table. Linear shaped array, L shaped array, T shaped array and rectangular shaped array with non-uniform inter-element spacing are investigated for both line-of-sight and non-LOS scenarios. The optimal element spacing of antenna for maximizing the channel capacity is searched by particle swarm optimizer. Numerical results have shown that our proposed method is effective for increasing average channel capacity. It is also found that L shaped array has the highest channel capacity and the improvement ratio for rectangular shaped array is the largest.

Comparison of Dynamic Differential Evolution and Genetic Algorithm for MIMO-WLAN Transmitter Antenna Location in Indoor Environment

A novel optimization procedure for the location of the transmitter in

Novel Directional Radiation Pattern by Genetic Algorithms in Indoor Wireless Local Loop

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