Han-Kyu Park

New Rayleigh fading channel estimator based on PSAM channel sounding technique

A new channel estimator, termed as the sinc interpolator, based on the pilot symbol assisted modulation channel sounding is proposed for Rayleigh fading channels. This method uses sinc function to estimate channel state information. A Wiener filtering estimator known to have optimum performance needs a priori information of autocorrelation function of the channel gain, Doppler frequency and signal-to-noise ratio to optimize filter coefficients. But the proposed method does not need a priori information while its performance is similar to that of the Wiener filtering estimator.

Numerical analysis of the propagation characteristics of multiangle multislot coaxial cable using moment method

In this paper, multiangle multislot coaxial cable is analyzed qualitatively and quantitatively. This is the extended result of the previous studies of the single-slot coaxial cable. The properties of this cable have been studied by many authors, especially for the surface-wave type. However, the slotted coaxial cable utilizing leaky waves has not been treated rigorously despite its wide use. In this paper, a numerical analysis of a leaky coaxial cable with a multiangle multislot configuration is performed to obtain many useful results, which are impossible to derive employing the approximate model frequently used in this area. Using the moment method, the propagation constant has been obtained for the leaky coaxial cable as a function of various parameters. Several slot configurations are considered to give insight into the properties of coupling loss and transmission loss complicated by simultaneous existence of leaky and surface waves.

Bow-tie-shaped meander slot antenna for 5 GHz application

A bow-tie-shaped meander slot antenna fed by a microstrip line is proposed for 5 GHz applications. A conventional bow-tie slot antenna has a broad bandwidth; however, it is relatively large, and is thus inappropriate for miniaturized communication systems. Meanwhile, the meander slot antenna has small size, but its bandwidth is quite narrow. To realize miniaturized antennas having large bandwidth, we combine the bow-tie slot and meander slot geometries heuristically. Simulation results, confirmed by measured data, show that, for antennas designed to operate at 5.25 GHz, the proposed antenna is 65.5% smaller in size than the bow-tie antenna and the bandwidth is 3 times larger than that of the meander slot antenna.

The coexistence of OFDM-based systems beyond 3G with fixed service microwave systems

In this paper, we study the coexistence of orthogonal frequency division multiplexing (OFDM)-based systems beyond 3G (B3G) and point-to-point (P-P) fixed service (FS) microwave systems. The advanced general analytical model derived via a power spectral density (PSD) analysis proposed in this paper has two advantages in comparison with the conventional minimum coupling loss (MCL) method. First, the interfering signal power that appears in the band of a victim system can be easily assessed without a spectrum emission mask. Second, when transmit power is not allocated to some subcarriers overlapping the band of the victim system in order to mitigate B3G OFDM-based systems interference with other systems, the general analytical model can successfully assess the interference from the B3G systems into FS systems, whereas the MCL method incorporating the spectrum emission mask cannot be applied in the presence of the same interference condition. The proposed model can be derived in a closed form and is simply implemented with the help of simulation, and thus the solution can be obtained in significantly reduced time. Through application of the proposed model, coexistence results are analyzed in a co-channel and adjacent channel with respect to guard band and minimum separation distance.

The Koch island fractal microstrip patch antenna

The Koch island fractal patch antenna is introduced in order to reduce the antenna size. By the space-filling property of fractal geometry, this antenna reveals lower resonant frequency than that of a normal square patch antenna. Based on experimental results, it is found that as iteration and iteration factor increases, the resonant frequency of this patch antenna decreases, while maintaining a radiation pattern similar to that of normal square patch.

Principal ratio combining for pre/post-RAKE diversity

We propose a pre/post-RAKE combining technique using the RAKE structures at both the transmitter and the receiver. An optimal solution for the pre-RAKE and post-RAKE combining weights is presented using principal ratio combing (PRC). We have shown that the performance of the proposed pre/post-RAKE improves as the number of pre-RAKE fingers increases.

Compact meander-type slot antennas

A meander-type slot antenna fed by a strip line is proposed for miniaturized personal communication systems. By varying the slot geometry of the antenna, we have studied the changes of the resonant frequency of this antenna. The size of this meander-type slot antenna is about 56% smaller than the conventional meander slot antenna. Simulated and measured results are presented.

A deterministic channel simulation model for spatially correlated Rayleigh fading

We propose a deterministic vector channel simulation model for generating the fading waveforms that satisfy not only rigorous temporal correlation but also arbitrary spatial correlation by means of Doppler phase difference sampling. The proposed method is more efficient than the conventional pseudonoise (PN) filtered Gaussian model with coloring process in evaluating the laboratory level performance of the mobile communication systems employing adaptive arrays or space diversity.

A spatially and temporally correlated fading model for array antenna applications

In this paper, a new channel model is proposed. Since it is spatially and temporally correlated simultaneously, this new model is well consistent with the real environment of array antenna applications. The widely used sum of scattered waves and the measurement-based model have a common drawback of imperfect statistical properties, reducing the reliability of simulation results. The new model (spatially and temporally correlated fading model [STCFM]) is derived rigorously in the spatiotemporal domain so that it can provide high accuracy for the evaluation of the array antenna system. Simulation results show that direction of arrival (DOA) and angle of spread (AOS) are well defined in STCFM, BPSK with two-branch maximal ratio combining and DBPSK with differential detection are considered to verify the spatial and temporal correlation robustness of the new model, respectively. As is shown, the simulation results agree well with the theory.

Performance of 2-D RAKE receiver in a correlated frequency-selective Nakagami-fading

The bit error rate (BER) performance and the characteristics of a two-dimensional (2-D) RAKE receiver operating in a correlated frequency-selective Nakagami-fading environment are analyzed. Correlated fading between array elements whose fading statistics are identical across the same RAKE branch, as well as an arbitrary number of RAKE-branches with arbitrary finding statistics, are assumed. We derived an approximated signal-to-noise ratio (SNR) statistics for one RAKE branch with correlated multiple antennas, which is extended to that for multiple RAKE branches with arbitrary fading statistics, i.e., a 2-D RAKE receiver. The receivers performance and characteristics are analyzed using the cumulative distribution function of the SNR at the 2-D RAKE receiver output and the BER under various conditions, Numerical results show that the improvement In performance of the 2-D RAKE receiver is brought about by the average SNR and diversity gains, which are identified by two parameters specifying the gamma distribution of SNR.