Dae-Soon Cho

Implementation of an efficient UE decoder for 3G LTE system

In order to migrate toward 4G, studies on 3G LTE (Long Term Evolution) have been announced recently in the 3GPP(3rd Generation Partnership Project) and standardization is under way. Therefore, 3G LTE (Long Term Evolution) systems have been designed and developed over many countries. We also have been developing a 3G LTE testbed system at ETRI. 3G LTE system is adopting OFDM (Orthogonal Frequency Division Multiplexing) method, especially 2times2 MIMO (Multiple Input Multiple Output) OFDM and convolutional and turbo encoder for control channels and data channels respectively. In this paper, we describe the structure and implementation method of control channels and data channels of the UE decoder which is being developed at ETRI and propose an efficient implementation method to minimize clock cycle to complete the derate matching algorithm of shared channel data.

Design of Downlink Control Channels for Millimeter Wave Mobile Hotspot Network System

Recently, according to the survey, one of the most frequent place to use mobile internet is the moving vehicle, such as bus, subway and train. Therefore, the high speed data rate services for mobile group vehicles moving at high speed are severely required. We design and develop a new system, which can support upto 2.5Gbps data rate services for mobile group vehicles moving at high speed over 400km/h, e.g., KTX (Korea Train Express), TGV (Train a Grande Vitesse) and ICE (InterCity Express), etc. in ETRI (Electronics and Telecommunications Research Institute). In this paper, we propose and design a new structure of the physical layer downlink control channels, and furthermore, we verified the performance of the downlink control channels by computer simulation. Especially, we compared the performance between floating point simulation and fixed point simulation. We verified the performance gap is under 0.5dB. Currently, we develop the test-bed of MHN system and have a target to demonstrate the real time performance of the MHN system on the outdoor environment in 2014. Outdoor demonstration will be done in subway in 1st step. In this paper, we are focusing on the performance of MHN DL control channels, especially on the fixed performance to develop RTL design in test-bed system. We also show the performance of these channels meet the required SNR.

Optimal time allocation for two-way relay channel using physical-layer network coding

This study proposes an optimal time allocation scheme for two-way relay channel (TWRC) using the physical-layer network coding (PNC). In other words, this study analytically determines the optimal transmit time durations for the first and the second time slot, which maximise the achievable sum rate under a sum time constraint for a given squared magnitude of the channel coefficients and transmit power values. Numerical results show that the achievable sum rate for the proposed optimal time allocation is greater than or equal to that for equal time allocation.

Performance of downlink control channels for Mobile Hotspot Network system

Currently, the high speed data rate services for mobile group vehicles moving at high speed are acutely required. In ETRI (Electronics and Telecommunications Research Institute), we have been developing the Mobile Hotspot Network (MHN) system that can support over 1.2Gbps data rate services for mobile group vehicles moving at high speed over 400km/h, e.g., KTX, TGV, etc. In this paper, new frame structures and pilot patterns for FDD (Frequency Division Duplex) and TDD (Time Division Duplex) of MHN system are proposed. Furthermore, the physical downlink control channels are defined, and we show the structure of designed downlink control channels. We verified the performance of the downlink control channels by computer simulation. Currently, we are developing the test-bed of MHN system and having a target to demonstrate the real time performance of the MHN system on the outdoor environment in 2014. In this paper, we are focusing at the performance of MHN DL control channels. We also show the performance of these channels meet the required SNR.

Implementation of MHN enhanced mobile backhaul system

Recently, data usage of end users are deeply increasing in the moving vehicles, such as subway, train and bus. In order to meet this requirement, we are designing and developing the 5th generation mobile backhaul system in ETRI (Electronics and Telecommunications Research Institute). This system is MHN-E (Mobile Hotspot Network — Enhanced) system, which support maximum 10Gbps with up to 500km/h. In this paper, we show the feasibility if we can apply SFMF (Single Frequency Multi Flow) in real time running mobile communication system, which is the key feature of MHN-E system. We measured the real-time performance of MHN-E test-bed system and verified the performance attained 2.5Gbps data throughput using SFMF.

Implementation of downlink control channels for millimeter wave mobile hotspot network system

Currently, the need of high speed data rate services at mobile group vehicles moving at high speed has been increased. In ETRI (Electronics and Telecommunications Research Institute), we have been designing and developing a new wireless mobile backhaul system, Mobile Hotspot Network (MHN) system, which can support over 1Gbps data rate services for mobile group vehicles moving at high speed over 400km/h at KTX (Korea Train Express) train. In this paper, resource allocations and procedures of downlink control channels of MHN system are introduced. Performances of the downlink control channels are verified by computer simulation. Furthermore, implementtations of the downlink control channels are described. We have developed the MHN test-bed system and had a target to demonstrate the real time performance of the MHN system in the outdoor environment at the end of 2015. Outdoor demonstration will be done in subway at line 8 subway in Seoul, Korea.

Downlink control channel for mobile backhaul

A downlink control channel is proposed for mobile backhaul in hierarchical telecommunications network. The mobile backhaul will suffer from degradation of performance caused by fast variation of channel. To cope with this deterioration, we propose to use FDM-type control channel and precoding 4 antennas for beamforming. The first OFDM symbol is common control field which having resource index of the following control channel. Simulation result shows that the proposed control channel has better performance than that of LTE if the precoding matrix is appropriately selected.

Performance of implemented 4×4 MIMO receiver for 3G LTE advanced system

3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) Advanced standards are currently under way, where 4×4 MIMO (Multiple Input Multiple Output) scheme is the minimum structure. One of the best solutions to support the maximum data rate transmission is to adopt a MIMO scheme, especially spatial multiplexing mode, which means that each antenna port can transmit separate data. To realize this algorithm, the main issue is to cancel interferences added to each antenna port, and therefore, the algorithm at the receiver should have good performances. In the aspect of implementation, MMSE (Minimum Mean Square Error) detection algorithm is a reasonable method considering both complexity and performance. Furthermore, an iterative receiver (IR) algorithm can also be applied to this system. An IR algorithm has a tradeoff between complexity and performance. In this paper, we designed a reasonable and implementable MIMO receiver structure and showed performance for 3GPP LTE Advanced system, and verified that hard decoded bits, PIC-MMSE (Parallel Interference Cancellation - MMSE) and 1-iteration PIC are enough to meet the required SNR using the implemented test-bed system.