Karma Wangchuk

Simulation-Based Scenario-Specific Channel Modeling for WBAN Cooperative Transmission Schemes

Wireless body area networks (WBANs) are an emerging technology for realizing efficient healthcare and remote medicine for the aging society of the future. In order to improve the reliability of WBAN systems and support its various applications, channel modeling and performance evaluation are important. This paper proposes a simulation-based channel modeling for evaluating the performance of WBAN cooperative transmission schemes. The time series of path losses among seven on-body nodes are generated by the finite-difference time-domain method for seven body motions. The statistical parameters of the path loss for all the motions are also obtained. The generated path loss is then applied to the evaluation of the two-hop decode-and-forward relaying scheme, yielding an improvement in transmit power. From the evaluation of body motion, useful insights are obtained such as which relay links are more robust than others. Finally, the proposed approach is validated through comparison with a measurement-based approach.

Polarimetric Mm-wave channel measurement and characterization in a small office

This paper presents a wideband full polari-metric directional channel measurement results at 58.5 GHz in a small office room environment assuming an indoor access-point (AP) scenario in the next generation mobile systems. The delay resolution was 2.5 ns from the signal bandwidth of 400 MHz, and the double directional angular characteristics were achieved by rotating high gain horn antennas at both sides of transmitter and receiver. By identifying scattering objects from the measurement data analysis, some important observation about the channel properties were reported. The results reveal that there were a few number of dominant specular multipath components of which the relative power to that of the direct path ranged between -8 and -13 dB. It was also observed that the depolarization is not significant in most of the detected paths with cross-polarization ratio of larger than 14 dB.

Polarimetric millimeter wave propagation channel measurement and cluster properties in outdoor urban pico-cell environment

To use millimeter wave bands in future cellular and wireless networks, characterization of the radio propagation channel in outdoor urban small cell or pico cell environment is vital. In this paper we present results from analysis of wideband full polarimetric directional channel measurements in an urban pico-cell environment using the double directional millimeter wave channel sounding system we developed. Multipath clusters with excess gain ranging from −9.6 dB to −22 dB in both line of sight (LOS) and obstructed LOS cases are seen. The most significant clusters were due to first and second order reflection, and diffraction. The clusters ranged from being highly specular in nature with very small (nearly 0°) angular spread to having angular spreads of up to 5.8° in azimuth and 6.3° in elevation. Similarly the delay spread of the clusters ranged up to 2.1 ns.

Simulation based mm-wave channel model for outdoor open area access scenarios

This paper presented dominant propagation mechanisms in an outdoor open area environment through the channel measurement and ray-tracing (RT) simulation at an mm-wave band of 58.5 GHz assuming an outdoor hotspot access scenario in 5G mobile systems and WLANs. From the data analysis, multi-path clusters by first- and second-order reflection, first-order diffraction and scattering mechanisms were identified. The measurement result revealed that the multi-path clusters have relatively small power less than approximately 20 dB to the direct path other than first-order reflection from nearby buildings that can be predicted in a deterministic manner, and the channel can be well expressed by the quasi-deterministic (Q-D) channel model which supports natural description of environment-specific deterministic components separately from the other random components. Based on Q-D model, this paper presented extracted statistical channel model parameters of the random components by using RT simulation.

Cooperator selection in 2.4ghz on-body wireless body area network

The WBAN on-body multi-link radio channels at 2.4 GHz were investigated. A wearable channel sounding system using commercial off-the-shelf Zigbee radios capable of continuous, prolonged and synchronized measurement has been developed. The measured channels were statistically analyzed to identify the potential cooperator nodes for two hop relaying in a star topology WBAN. This will be useful in designing relaying and cooperative communication schemes for improving the reliability of a WBAN under various channel fading conditions. Significant performance gain for two hop link, with the selected cooperator node, over the direct link in terms of outage rate is demonstrated.