• Journal of Information Technology Services
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• v.13 no.1
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• pp.125-134
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• 2014

Device discovery for D2D (device-to-device) communication enables a device to discover other devices in order to initiate communication with them. Devices should perform the discovery phase using a small quantity of radio resource in a short time and be able to reduce the load of the base station. Legacy device discovery schemes have focused on discovering as many target devices as possible. However, it is not appropriate for peer-to-peer D2D communication scenario. Further, synchronization problems are an important issue for discovery signal transmission. This paper proposes a discovery method that one requesting device discovers a specific target for communication. Multiple antenna beamforming is employed for the synchronization between the base station and a target device. The proposal can reduce the load of the base station using the information that it already maintains and improve the reliability of the device discovery because two times of synchronizations using beamforming among the base station and devices can make the exact discovery of a target device with mobility possible.

• ETRI Journal
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• v.42 no.4
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• pp.562-574
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• 2020

Quadrature spatial modulation (QSM) utilizes the in-phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.720-726
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• 2008

In this paper, we propose a multi-cell cooperation method for broadcast packet data services in the orthogonal frequency division multiplexing (OFDM)-based cellular system with multiple transmit antennas. In the proposed method, to transmit two streams of spatially demultiplexed or transmit diversity coded symbols over a number of transmit antennas, we divide a coded packet into multiple subparts to which different cell groups and antenna pairs are assigned. The proposed method enhances the diversity order by transforming the channel frequency responses of two symbol streams in each subpart of the broadcast packet. The increase in diversity of the proposed method is shown with the outage probability under various configurations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.70-76
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• 2009

In this paper, we propose the design criteria of the pre-processing scheme used in ABAB type quasi-orthogonal space-time block code(QOSTBC) and derive. The proposed design criteria show how to obtain full-diversity and full-rate (FDFR) property, single-symbol decodability, and increased coding gam. We design an improved ABAB type QOSTBC using the proposed design criteria. The desinged QOSTBC has a superior performance to Dalton's QOSTBC and inherits the merits of Dalton's QOSTBC, which are FDFR property, and single symbol decodability for PAM signal constellation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.1
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• pp.62-69
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• 2011

A novel QEGT codebook index searching algorithm for long tenn evolution (LTE) system is proposed. The proposed algorithm divides the Q precoding vectors into M groups, and selects the optimal precoding vector from the selected group at the receiver. This algorithm reduced the calculation for searching the optimal precoding vector index compared to the previous algorithms. The index searching algorithm is implemented for TI's TMS320C6713 DSP board. When the number of transmit antenna is 4, the number of clock cycles is reduced to 25%.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.423-428
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• 2004

In this paper, STBC (Space Time Block Code) is applied to the WB system and frequency repeated diversity is used to get the 4-th order space time diversity gain. The performance of が STDB-OFDM system is analyzed by computer simulation. As a result of simulation, proposed W system can reduce the complexity that is introduced by increasing number of transmit antenna and show the same performance of 4 antennas with only using 2. Proposed system shows the enhancement of 7.1 dB compared to the general UWB OFDM and 1.9 dB compared to UWB STBC-OFDM.

• Journal of Satellite, Information and Communications
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• v.3 no.2
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• pp.48-53
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• 2008

In the future, satellite communication systems, such as ISDB in Japan and DVB in Europe, are required to support higher transmission date rate for providing multimedia services including HDTV, high rate data communication etc. Considering the effectiveness of OFDM technique in efficient usage of frequency bandwidth and its robustness to the multi-path fading, several OFDM based standards have been proposed for satellite communication. However, the problem of high Peak to Average Power Ratio is one of the main obstacles for the implementation of OFDM based system. Many PAPR reduction schemes have been proposed for OFDM systems. Among these, the partial transmit sequences (PTS) is attractive as they obtain better PAPR property by modifying OFDM signals without distortion. In this paper, considering the complexity issue, we present a simplified minimum maximum (minimax) criterion and Sub-Optimal PTS algorithm to optimize the phase factor. This algorithm can be dynamically made tradeoff`f between performance and complexity on demand. In addition, we integrate guided scrambling (GS) with this method. Simulation in multiple antenna based OFDM system proves that the proposed Hybrid schemes can get much more PAPR reduction and do not require transmission of side information (SI). Thus it is helpful when implementing OFDM technique in satellite communication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.637-645
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• 2015

Recently, a spatial modulation (SM) scheme achieving high throughput based on quaternary quasi-orthogonal sequences (Q-QOSs), referred to as Q-QOS-SM, is presented for $N_t=2^n(n=1,2,{\cdots})$ transmit antennas. In this paper, based on the design approach of the conventional Q-QOS-SM, new improved QO-SM (I-QO-SM) schemes are proposed for 8 transmit antennas. The new schemes employ Q-QOSs of length 4 or 2 unlike of 8 in the original one, which guarantees more information bits to be allocated for antenna index parts compared to the conventional Q-QOS-SM. By computer simulation results, the proposed scheme are shown to enjoy much higher throughputs compared to the conventional other SM schemes for all simulation environments. Finally, we also examine and compare analytically the performances of the new and conventional SM schemes by calculating upper-bounds on BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7C
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• pp.644-651
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• 2007

In multiple antenna systems, vertical Bell Labs Layered Space-Time (V-BLAST) systems enable very high throughput by nulling and cancelling at each layer detection. In this paper, we propose a V-BLAST system which combines with signal space diversity technique. The benefit of the signal space diversity is that we can obtain an additional gain without extra bandwidth and power expansion by applying inphase/quadrature interleaving and the constellation rotation. Through simulation results, it is shown that the performance of the proposed system is less than 0.5dB away from the ideal upper bound.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.4
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• pp.295-301
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• 2011

A triple-band transceiver module for 2.3/2.5/3.5 GHz mobile WiMAX, IEEE 802.16e, applications is introduced. The suggested transceiver module consists of RFIC, reconfigurable/multi-resonance MIMO antenna, embedded PCB, mobile WiMAX base band, memory and channel selection front-end module. The RFIC is fabricated in $0.13{\mu}m$ RF CMOS process and has 3.5 dB noise figure(NF) of receiver and 1 dBm maximum power of transmitter with 68-pin QFN package, $8{\times}8\;mm^2$ area. The area reduction of transceiver module is achieved by using embedded PCB which decreases area by 9% of the area of transceiver module with normal PCB. The developed triple-band mobile WiMAX transceiver module is tested by performing radio conformance test(RCT) and measuring carrier to interference plus noise ratio (CINR) and received signal strength indication (RSSI) in each 2.3/2.5/3.5 GHz frequency.