Dae-Soon Cho

Bio: Dae-Soon Cho is an academic researcher from Electronics and Telecommunications Research Institute. The author has contributed to research in topics: LTE Advanced & MIMO. The author has an hindex of 2, co-authored 5 publications receiving 15 citations. Previous affiliations of Dae-Soon Cho include KAIST.

Implementation of an efficient UE decoder for 3G LTE system

Abstract: 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.

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

Abstract: 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

Abstract: 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 downlink control channels for millimeter wave mobile hotspot network system

Abstract: 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.

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

Abstract: 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.

Survey on half- and full-duplex relay based cooperative communications and its potential challenges and open issues using Markov chains

Abstract: In this study, the authors address a brief survey on the half-duplex (HD) and full duplex (FD) relay based cooperative communications. Some nodes in wireless communication acting as relays can share their resource with other nodes by exploiting relaying technologies to achieve cooperative communications. Generally, the buffer-less HD relaying (HDR) limits the performance of a wireless system when the worst condition of transmitting and receiving channels of the relay occurs. The HDR is affected by pre-log factor one-half that reduces the spectral-efficiency of the wireless system. Significantly, advanced technologies in self-interference cancellation enable the FD relaying (FDR) in the cooperative wireless system to achieve high spectral efficiency. Recently, the buffer-aided FDR provides significant performance gains by exploring the concepts of Markov chain of queuing theory at relay as compared to either buffer-aided or buffer-less HDR. Finally, they outline several research challenges associated with small size, interference management, and fading channel for FDR. In addition, some research challenges remain for further investigation that is related to physical-layer security, FDR with a cross-layer approach and two-way buffer-aided FDR.

Implementation of an Encoder Based on Parallel Structure for LTE Systems

Abstract: The operation time of the encoder is one of the important implementation issues to meet the timing requirements of LTE systems since the encoder is based on binary operations. In this paper, we propose the design and implementation of an encoder based on parallel structure for LTE systems. Through 8 bits parallel processing of the CRC attachment, code block segmentation, and parallel processor, we could perform the engines for turbo coding and rate matching of each code block in parallel fashion. Experimental results show that although the FPGA slice register, slice LUT, block ram, and clock period of the proposed scheme are 18, 19, 22, and 6% larger than those of the conventional method based on serial processing respectively, our parallel structure reduces the latency about 19 ~ 70% compared with the serial structure. In particular, our approach is more latency efficient in case the encoder processes numerous code blocks.

Design and Implementation of a Latency Efficient Encoder for LTE Systems

Abstract: The operation time of an encoder is one of the critical implementation issues for satisfying the timing requirements of Long Term Evolution (LTE) systems because the encoder is based on binary operations. In this paper, we propose a design and implementation of a latency efficient encoder for LTE systems. By virtue of 8-bit parallel processing of the cyclic redundancy checking attachment, code block (CB) segmentation, and a parallel processor, we are able to construct engines for turbo codings and rate matchings of each CB in a parallel fashion. Experimental results illustrate that although the total area and clock period of the proposed scheme are 19% and 6% larger than those of a conventional method based on a serial scheme, respectively, our parallel structure decreases the latency by about 32% to 65% compared with a serial structure. In particular, our approach is more latency efficient when the encoder processes a number of CBs. In addition, we apply the proposed scheme to a real system based on LTE, so that the timing requirement for ACK/NACK transmission is met by employing the encoder based on the parallel structure.

Optimisation of throughput of two-way buffer-aided relaying networks with wireless-assisted links

Abstract: The authors propose protocols to optimise throughput of a relay in relaying networks where two users communicate only through buffer-aided relay. Both the users randomly access finite size buffer of the relay. The protocols are developed on the basis of buffer state information (BSI) and channel state information (CSI). In their proposed scheme, half-duplex decode-and-forward (DF) concept is used for improving the spectral efficiency of two-way relaying networks. In this work, the authors derive maximum achievable relay throughput with fixed-rate transmission which is in the form of linear-fractional programming. For simplification, they transform the fractional programme into linear programme which is efficiently computed through the standard convex/linear numerical tool. The numerical results are performed with the assisted software such as CVX tool. They theoretically analyse the events to provide necessary performance endorsement. The BSI/CSI outperforms all the cases studied named as conventional relaying, BSI only, and CSI only.