Myeonghun Chu

Adaptive Channel Estimation Scheme Based on LTE Uplink in V2V Environments

Vehicle communication can facilitate efficient coordination among vehicles on the road and enable future vehicular applications such as vehicle safety enhancement, infotainment, or even autonomous driving. In the 3rd Generation Partnership Project (3GPP), many studies focus on long term evolution (LTE)-based vehicle communication. Because vehicle communication is closely related to safety, it requires low latency and improved reliability. However, vehicle speed is high enough to cause severe channel distortion in vehicle-to-vehicle (V2V) environments. We can utilize channel estimation methods to approach a reliable vehicle communication systems. Conventional channel estimation schemes can be categorized as least-squares (LS), decision-directed channel estimation (DDCE), spectral temporal averaging (STA), and smoothing methods. In this study, we propose a smart channel estimation scheme in LTE-based V2V environments. The channel estimation scheme, based on an LTE uplink system, uses a demodulation reference signal (DMRS) as the pilot symbol. Unlike conventional channel estimation schemes, we propose an adaptive smoothing channel estimation scheme (ASCE) using quadratic smoothing (QS) of the pilot symbols, which estimates a channel with greater accuracy and adaptively estimates channels in data symbols. In simulation results, the proposed ASCE scheme shows improved overall performance in terms of the normalized mean square error (NMSE) and bit error rate (BER) relative to conventional schemes.

Novel Interference Cancellation of Channel Estimation Scheme Based on LTE in V2V Communications

Transportation infrastructures integrate advanced Information Technology to enable the operations and management of transportation systems. Advanced vehicle and road systems of a comprehensive concept that improve the efficiency and safety of road traffic are being built and will be commercially available through Intelligent Transport Systems (ITS) technology and services. To support ITS technology, Vehicle-To-Everything (V2X) is needed, and in the 3rd Generation Partnership Project, many studies have focused on Long Term Evolution (LTE)-based vehicle communications. In order to realize reliable and optimized communications performance in vehicle communications, which move in propagation environments at high speed, in this study, we propose a novel channel estimation scheme suited for LTE sidelink-based Vehicle-To-Vehicle systems. Conventional channel estimation schemes can be categorized as Decision-Directed Channel Estimation, spectral temporal averaging, and smoothing methods. In this study, unlike conventional channel estimation schemes, we propose a Novel Interference Cancellation of Channel Estimation (NICCE) using Quadratic Smoothing of the pilot symbols, which estimates a channel with greater accuracy, and a novel interference cancellation of channel estimation in data symbols. In simulation results, the proposed NICCE scheme shows improved overall performance in terms of the Normalized Mean Square Error and uncoded Bit Error Rate relative to conventional schemes.

3D Localization for Launch Vehicle Using Virtual TOA and AOA of Ground Stations

Generally, a ground telemetry station for a launch vehicle (LV) includes a tracking function only; therefore, position measurements for LV depend on received navigation data from on-board systems of LV or depend on estimated position from ground radar system in real time. Time of arrival (TOA) and angle of arrival (AOA) are typical location techniques for emitting targets. In this study, we propose a virtual on-board timer to estimate TOA for LV and verify its localization performance using Combined TOA and AOA localization method. For real time processing, the proposed virtual on-board timer should be created at space center and distributed to remote stations before lift-off of LV. By comparing the time stamp of the virtual on-board timer and received time, TOA and its corresponding slant range can be estimated. In order to combine the estimated TOA and AOA, we create sphere equations with the estimated range radius and vertical plane equations, to include unit vectors for the AOA direction. By solving these equations, a three-dimensional (3D) target point can be obtained. We confirm localization performance of the estimated TOA by comparing with an on-board GPS of 3rd KSLV-1 mission in January 2013.

Adaptive Transmission Scheme for Vehicle Communication System

Advances in Vehicle-to-Everything (V2X) communication attempt to enhance traffic safety by employing advanced wireless communication systems. V2X communication is a core solution to manage and advance future traffic safety and mobility. In this study, we design a system-level simulator (SLS) for Long Term Evolution (LTE)-based V2X and propose an adaptive transmission scheme for vehicle communication. The proposed scheme allocates the resource randomly in the time and frequency domains and transmits the message according to the probability of transmission. The performance analysis is based on the freeway scenario and periodic message transmission. Simulation results show that the proposed scheme can improve the cumulative distribution function (CDF) of the packet reception ratio (PRR) and the average PRR.

FSC receiver for performance improvement of D2D communication in LTE-advanced system

In this paper, we propose an advanced receiver for full suppression cancellation to reduce interference between cellular and device-to-device (D2D). The proposed receiver can suppress and cancel the interference by integrating the interference rejection combining technique with successive interference cancellation. We perform a system level simulation based on the 20-MHz bandwidth of the 3rd Generation Partnership Project (3GPP) Long Term Evolution-Advanced (LTE-Advanced) system. Simulation results show that the proposed receiver can improve signal-to-interference-plus-noise ratio, throughput, and spectral efficiency relative to conventional receivers.

Novel channel estimation scheme for backhaul system based on LTE-advanced

In this paper, we propose a channel estimation scheme in a backhaul system based on long term evolution (LTE)-Advanced. The proposed method uses the fast Fourier transform (FFT) interpolation scheme for a user moving at a high speed. This FFT interpolation scheme converts the channel frequency response obtained from a least square (LS) or minimum mean square error (MMSE) channel estimation scheme to a time domain channel impulse response by calculating the inverse FFT (IFFT). Simulation results show that the proposed channel estimation scheme can improve the normalized mean square error (NMSE), error rate, and throughput of conventional systems.

Novel detection scheme for LSAS using power allocation in Multi User scenario with LTE-A and MMB channels

In this paper, we analyze the ergodic spectral efficiency upper bound of a large-scale MIMO and the key technologies, and present new approaches for detection and power allocation. Assuming arbitrary antenna correlation and user distributions, we derive approximations of achievable rates with zero forcing(ZF), maximum ratio combining (MRC), minimum mean squared error (MMSE) and eigen-value decomposition power allocation (EVD-PA). Our simulation results show that our proposal is a better detection scheme than the conventional scheme for LSAS. Also, we used the Long Term Evolution Advanced (LTE-A) channel and the Millimeter wave Mobile Broadband (MMB) channel.

Advanced Receiver Based on Soft Decision for Interference Suppression and Cancellation in a Sidehaul System

Recently, the 3rd Generation Partnership Project (3GPP) developed a sidehaul system to cope with rapidly increasing mobile data traffic. However, numerous challenging technical problems remain to be resolved. One of the major problems is interference management between small cells. In this paper, we propose an advanced receiver based on soft decision to reduce the interference from neighboring cells in the sidehaul system. The proposed receiver can suppress and cancel interference by integrating the interference rejection combining technique with successive interference cancellation. The interference signal is updated using soft information expressed by a log-likelihood ratio. We perform a simulation based on the 20-MHz bandwidth of the 3GPP LTE-Advanced technology. Simulation results show that the proposed receiver can achieve a lower error rate and a higher throughput compared to conventional receivers.

Novel channel estimation scheme in fast fading channel applied to sidehaul system

Recently, the 3rd Generation Partnership Project (3GPP) has developed a sidehaul system to cope with the explosively increasing mobile data traffic. The sidehaul system is based on single carrier-frequency division multiple access (SC-FMDA) due to its low peak-to-average power ratio (PAPR). Also, a demodulation reference signal (DMRS) is designed to support multiple input multiple output (MIMO). In this paper, we propose the DFT-based channel estimation scheme for the sidehaul system. The proposed scheme uses the 2-dimensional minimum mean square error (2-D MMSE) interpolation scheme for the user moving at a high speed. Simulation results show that the proposed channel estimation scheme can improve the normalized mean square error (NMSE), error rate, and throughput of the conventional system.