• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.1A
• /
• pp.27-33
• /
• 2009

This paper proposes transmit power control techniques with fading channel prediction scheme based on recurrent neural network for high-speed mobile communication systems. The operation result of recurrent neural network which is derived interpretively solves complexity problems of neural network circuit, and channel gain of multiple transmit antenna is derived with maximum ratio combining(MRC) by using the operation result, and this channel gain control transmit power of each antenna. simulation results show that proposed method has a outstanding performance compared to method that is not to be controlled power based on channel prediction. Most of legacy studies are for robust receive technique of fading signals or channel prediction of fading signals limited low-speed mobility, but in open loop Power control, proposed channel prediction method decrease system complexity with removal of fading effect in transmitter.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.4
• /
• pp.395-403
• /
• 2016

This paper introduces a multi-cell search method for heterogeneous networks (HetNet), in which user equipments need to search multiple cells in its vicinity simultaneously. Due to the difficulty of acquiring channel informations for multiple cells, a non-coherent approach is preferred. In this paper, a non-coherent single-cell search scheme using a weighted vector is proposed, and the successive interference cancellation based multi-cell search algorithm is devised. In order to improve cell search performance, the weighted vector is designed in a way to exploit the general characteristic of wireless channel. Based on the fact that the performance of the proposed single-cell search scheme deviates slowly from the one using the optimal weighted vector, a universal weighted vector is also proposed, which shows the performance close to the optimal ones for various channel environments and signal-to-noise ratio regimes. Simulation results confirm that the proposed multi-cell search algorithm is capable of identifying cells more accurately with the help of the proposed single-cell search scheme, and can detect the remaining cells more effectively by removing the signals of the identified cells from the received signal.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.3 s.345
• /
• pp.84-94
• /
• 2006

In this paper, we propose the algorithm to reduce guard time of UWB MAC time slot for throughput gain. In the proposed draft by multiband ofdm alliance (MBOA), Guard time of each medium access slot (MAS) is composed of shortest inter-frame space (SIFS) and MaxDrift which is the time caused by maximum frequency offset among devices. In this paper, to reduceguard time means that we nearly eliminate MaxDrift term from guard time. Each device of a piconet computes relative frequency offset from the device initiating piconet using periodically consecutive transferred beacon frames. Each device add or subtract the calculated relative frequency offset to the estimated each MAS starting point in order to synchronize with calculated MAS starting point of the device initiating piconet. According to verification of simulations, if the frequency offset estimator is implemented with 8 decimal bit, the ratio of the wasted time to Superframe is always less than 0.0001.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.5C
• /
• pp.532-538
• /
• 2003

In this paper we have investigated a novel approach applying low-density parity-check coding to a COFDM-CDMA system, which operates in a multi-path fading mobile channel. Developed as a linear-block channel coder, the LDPC code is known for a superior signal reception capability in AWGN and/or flat fading channels with respect to increased encoding rates, however, its performance degrades when the communication channel becomes multi-path fading. For a typical multi-path fading mobile channel with a SNR of 16㏈ or lower. in order to obtain a BER lower than 1 out of 10000, the LDPC code with encoding rates below 1:3 requires not only the inherent parity check information but also the piloting information for refreshing front-end equalizer taps of COFDM-CDMA, periodically. For instance, while the 1:3-rate LDPC coded transmission symbol is consisted of data bits and parity-check bits in 1 to 3 proportion, on the other hand, in the proposed method the same rate LDPC transmission symbol contains data bits, parity check bits, and pilot bits in 1 to 2 to 1 proportion, respectively. The included pilot bits are effective not only for channel estimation and channel equalization but for symbol decoding by assisting the parity-check bits, hence, improving SNR vs BER performance over the conventional 1:3-rate LDPC code. The proposed system performance has been verified using computer simulations in multi-path, Rayleigh fading channels, and the results show us that the proposed method out-performs the general LDPC channel coding methods in terms of SNR vs BER measurements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.5
• /
• pp.445-453
• /
• 2016

This paper presents the implementation and design of the 1T-1R wireless HD video streaming systems over 28 GHz mmWave frequency using 3GPP LTE-TDD standard on NI USRP RIO SDR platform. The baseband of the system uses USRP RIO that are stored in Xilinx Kintex-7 chip to implement LTE-TDD transceiver modem, the signal that are transceived from USRP RIO up or down converts to 28 GHz by using self-designed 28 GHz RF transceiver modules and it is finally communicated HD video data through self-designed $4{\times}8$ sub array antennas. It is that communication method between USRP RIO and Host PC use PCI express ${\times}4$ to minimize delay of data to transmit and receive. The implemented system show high error vector magnitude performance above 25.85 dBc and to transceive HD video in experiment environment anywhere.