This paper presents an inverse scattering problem for through-wall imaging. Two separate perfect-conducting cylinders of unknown shapes are behind a homogeneous building wall and illuminated by the transverse magnetic (TM) plane wave. After an integral formulation, a discretization using the method of moment (MoM) is applied. The through-wall imaging (TWI) problem is recast as a nonlinear optimization problem with an objective function defined by the norm of a difference between the measured and calculated scattered electric field. Thus, the shape of the metallic cylinder can be obtained by minimizing the objective function. The asynchronous particle swarm optimization (APSO) is employed to find out the global extreme solution of the object function. Numerical results demonstrate that even when the initial guesses are far away from the exact shapes, and the multiple scattered fields between two conductors are serious, good reconstruction still can be obtained. In addition, the effect of Gaussian noise on the reconstruction result is investigated and the numerical simulation shows that even though the signal-noise ratio (SNR) is 20 dB, we can still get good results of reconstructions.
A multiple-input and multiple-output ultra-wideband (MIMO-UWB) system provides a higher data rate. However, the multipath effect of the intersymbol interference (ISI) increases the bit error rate (BER) and outage probability of the MIMO-UWB system. For this paper, the authors applied the real orthogonal design (ROD) to an MIMO-UWB system to improve the efficiency of that system. A ray-tracing technique and an inverse fast Fourier transform were used to get the impulse response of the indoor environment. In addition, a rake receiver was used to increase the strength of the received signal to minimize the multipath effect. For this paper, two cases of an indoor wireless MIMO-UWB system were studied: case (A) used different antenna arrays, whereas case (B) placed antenna arrays in different locations to find the best position of the transmitter. In case (A), three different shapes of antenna arrays, namely L-shape, circular-shape, and Y-shape, were used for the transmitter and receiver. The BER performance for these arrays in the UWB frequency of 3.1–10.6 GHz was examined. Numerical results showed that the outage probability of the circular array was better than that of the other two arrays. In case (B), the transmitter used was an array with two antenna elements. The optimal location for the transmitter was found by using both asynchronous particle swarm optimization (APSO) and self-adaptive dynamic differential evolution (SADDE). The numerical results indicated that the performance of APSO was better than that of SADDE.
The channel capacity of multiple-input mUltiple-output (MIMO) wireless local area network (MIMO-WLAN) systems with co-channel interference (eel) is calculated in this paper. The ability to combat eel for the MIMO-WLAN simple uniform linear array (ULA) and polarization diversity array (PDA) are investigated. The channel frequency response, which is further used to calculate the corresponding channel capacity is calculated by ray-tracing approach. Numerical results show that MIMO PDA is better than those of MIMO-ULA when interference is present.
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