Young-eil Kim

Statistical characterization of the UWB propagation channel in indoor residential environment

This paper presents a statistical characterization of an ultra wideband (UWB) indoor propagation channel based on measurements conducted in various types of high-rise apartments in several cities of Korea. Measurements were carried out in the frequency band of 3–10 GHz. Various communication links were considered including both line-of-sight (LOS) and non-LOS (NLOS) scenarios, which covered within-the-room and room-to-room propagations. The measurement procedure allows us to characterize both the large-scale and the small-scale statistics of the channel. The aim here is to study in more detail the statistical characteristics of the UWB propagation channel and to provide insight for future statistical channel modeling work. Channel characteristics examined include the distance and frequency dependency of path loss, shadowing fading statistics, and multipath temporal-domain parameter statistics such as the mean excess delay, RMS delay spread, and the number of dominant paths. Copyright

A modified S-V clustering channel model for the UWB indoor residential environment

In this paper, a new modified Saleh-Valenzuela (S-V) clustering channel model is proposed based on the measurement data collected in various types of high-rise apartments under different propagation scenarios in the ultra-wideband (UWB) frequency band of 3-10 GHz. A new distribution, namely, mixtures of two Poisson processes is proposed to model the ray arrival times. This new distribution fits the empirical data much better than the single Poisson process proposed in the conventional S-V model. The measurement procedure allows the small-scale amplitude fading statistics to be studied. Analysis results show that they can be well modeled by either lognormal, Nakagami or Weibull distributions whose parameters i.e. standard deviation, m-parameter and b-shape parameter, respectively, are lognormal distributed random variables. These parameters are found to be invariant across the excess delay. Additionally, the temporal correlation between adjacent path amplitudes is also investigated. The amplitude temporal correlation coefficients are found to be relatively small and thus, can be assumed to be negligible in reality. The proposed model can provide a more realistic simulation platform for the UWB communication systems.

Statistical characterization of the UWB propagation channel in various types of high-rise apartments

The paper presents a statistical characterization of an ultra-wideband (UWB) indoor propagation channel based on measurements conducted in various types of high-rise apartments in several cities in Korea. Measurements were carried out in the frequency band of 3-10 GHz. Various communication links were considered including both line-of-sight (LOS) and non-LOS (NLOS) scenarios which cover within-the-room and room-to-room propagation. The measurement procedure allows us to characterize both the small-scale and the large-scale statistics of the channel. The aim is to study in more detail the behavior of the UWB propagation channel and to provide more of the measurement data required for the standardization activities in the IEEE 802.15.4a channel modeling subgroup. Channel characteristics examined include the distance and frequency dependency of path loss, shadowing fading statistics and multipath temporal-domain parameter statistics, such as the mean excess delay, RMS delay spread and the number of dominant paths.

UWB indoor propagation channel measurements and data analysis in various types of high-rise apartments

This paper presents the extensive ultra wideband (UWB) indoor propagation channel measurements conducted in various types of high-rise apartments based in several cities in Korea. A vector network analyzer was used to measure the channel transfer functions in the frequency band of 3-10 GHz. The corresponding channel impulse responses were calculated by taking inverse Fourier transforms of the recorded channel transfer functions. Measurements were made in 8-10 distinct receiver (RX) local points throughout the apartment ranging from 1-20 m apart from the fixed transmitter location. At each RX local point; the RX was moved 25 times over a square grid of 5/spl times/5 spatial points spaced 15 cm apart. This measurement procedure allows us to characterize both the small-scale and the large-scale statistics of the channel. Various communication links were considered including both line-of-sight (LOS) and non-LOS (NLOS) scenarios. Both data analysis technique and measurement results are presented in the form of power delay profile and rms delay spread. The aim here is to study in more detail the behavior of the UWB propagation channel and to provide more measurement data required for the standardization activities in the IEEE 802.15.4a channel modeling subgroup.

Statistical analysis of amputations and trends in Korea

Epidemiological research on amputees is being continued extensively world wide, but there are different epidemiologic reports from country to country. This study undertakes an epidemiologic report of the medical records of amputees in Korea which has developed very rapidly, when compared with other countries. This study included 4258 amputees who either had an amputation and/or received prosthetic training at Yonsei University College of Medicine, Severance Hospital from January 1970 to June 1994. The most common cause of amputation was trauma (66.7%), and the second most common cause was peripheral vascular disease. While amputations due to infection or trauma were the most common in the 1950s, amputations due to peripheral vascular disease have gradually increased until they now make up 23.5% of all amputations in the 1990s. Lower limb amputation, more common than upper limb amputation, accounted for 68.7% of all amputations. Multiple amputation accounted for 9.3% of all amputations, and the occurrence rate of multiple amputation was relatively higher in cases of burn injuries, train accidents, frostbite, and Buergers disease than in cases brought about by other causes. The various amputation causes change according to the circumstances of the times, as can be seen in this study.

Rehabilitation of a triple amputee including a hip disarticulation

A multiple amputee more severe than a triple amputee is uncommon. There have been no reports on the rehabilitation outcome of a triple amputee, including hip disarticulation and transtibial amputation. The authors report the rehabilitation of a patient with left hip disarticulation, right transtibial amputation, and left trans-humeral amputation due to a train accident. He has successfully completed the rehabilitation programme and has become independent in prosthetic ambulation, activities of daily living, and driving.

Improvement of channel capacity on MIMO antenna systems with antenna pattern selection

Although MIMO (multi-input multi-output) has attracted attention as an efficient communication technology for high frequency use, the channel capacity of MIMO systems depends primarily on radio propagation. Therefore, development of a MIMO antenna system that can obtain high channel capacity in a variety of propagation environments is important. This paper focuses on antenna pattern selection (APS system) by providing multiple directional patterns that can be switched to each antenna element of the receiver according to the propagation environment.

A statistical based UWB multipath channel model for the indoor environments WPAN applications

In this paper, a statistical-based ultra-wideband (UWB) indoor channel model which incorporates the clustering of multipath components (MPCs) is proposed. The model is derived based on measurement data collected in the frequency band of 3-10 GHz in various types of high-rise apartments under different propagation scenarios. The aim here is to investigate in more detail the clustering of MPCs phenomenon. The description of clustering observed within the channel relies on two classes of parameters, namely, inter-cluster and intra-cluster parameters which characterize the cluster and MPC, respectively. All parameters are described by a set of empirical probability density functions derived from the measured data such as the distribution of clusters and MPCs, clusters and MPCs arrivals. In addition, the measurement procedure and data analysis techniques are also discussed. This model is suitable for performance analysis of WPAN systems that employ UWB technology e.g. IEEE 802.15.3a and IEEE 802.15.4a

Frequency tunable antenna for mobile TV signal reception

In this paper, the frequency tunable antenna for T-DMB application is proposed. Since the proposed antenna has the small size of 10 x 30 x 3 mm , it can be installed in the body of the mobile handsets, televisions, etc. The radiator size is reduced by patterning the helical line on both sides of the substrate and adding an open-stub beside to the ground plane. In addition to this, utilizing a varactor with a proper biasing circuit makes it possible to satisfy all the T-DMB service bands of 7 channels with 6 MHz bandwidth each. The measured result reveals the validity of the proposed antenna by showing signal reception levels shifting with every resonant frequency variation.

Compact Antenna for Prospective RFID and Wireless Sensor Transponders

This work discloses a compact planar antenna for microwave and UHF RFID and wireless sensor passive transponders. The proposed antenna takes advantage of its unique topology in order to assure conjugate matching with essentially complex impedance of the electronic chip directly embedded into radiator. Very good performance is predicted theoretically and confirmed experimentally over an operating bandwidth of actual short-range wireless system