• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.10
• /
• pp.3394-3408
• /
• 2014

Conventional mobile state (MS) and base station (BS) association based on average signal strength often results in imbalance of cell load which may require more powerful processor at BSs and degrades the perceived transmission rate of MSs. To deal with this problem, a Markov decision process (MDP) for load balancing in a multi-cell system with multi-carriers is formulated. To solve the problem, exploiting Sarsa algorithm of on-line learning type [12], ${\alpha}$-controllable load balancing algorithm is proposed. It is designed to control tradeoff between the cell load deviation of BSs and the perceived transmission rates of MSs. We also propose an ${\varepsilon}$-differential soft greedy policy for on-line learning which is proven to be asymptotically convergent to the optimal greedy policy under some condition. Simulation results verify that the ${\alpha}$-controllable load balancing algorithm controls the behavior of the algorithm depending on the choice of ${\alpha}$. It is shown to be very efficient in balancing cell loads of BSs with low ${\alpha}$.

• International journal of advanced smart convergence
• /
• v.9 no.3
• /
• pp.141-144
• /
• 2020

Iterative decision feedback equalizer (IDFE) is a recursive equalization technique that can help to achieve an additional performance gain for the system by combining iterative channel decoding and interference cancellation. In a single carrier-based system, the intersymbol interference (ISI) is a critical problem that must be resolved since it causes frequency selective fading. Based on the idea of sharing the estimated information in the process of iteration, IDFE is considered as an efficient solution to improve the robustness of the system performance on the ISI channel. In this paper, the IDFE is applied on single carrier FDMA (SC-FDMA) system to evaluate the performance under ISI channel. The simulation results illustrate that IDFE helps to improve the performance of the SC-FDMA system, especially with long delay spread channels.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
• /
• 2000.11a
• /
• pp.63-67
• /
• 2000

본 논문에서는 IEEE 802.11a 무선 LAN에 적합한 16QAM/OFDM 시스템의 성능을 AWGN과 two-ray 다중 경로 페이딩 채널에서 시뮬레이션을 통하여 분석하고 성능 향상을 위한 방법으로 비터비 복호를 하는 길쌈 부호와 단일 탭의 LMS 등화기를 사용한다. 길쌈 부호를 사용하면 AWGN과 다중 경로 페이딩 채널에서 각각 경판정(hard-decision)은 2dB, 6 dB, 연판정(soft-decision)은 4.5 dB, 10 dB의 이득을 얻는다. 또한 다중 경로 페이딩 환경에서 경판정 비터비 복호와 단일 탭의 LMS 등화기를 함께 사용하는 경우에는 경판정 복호만을 사용하는 경우보다 5 dB 향상됨을 알 수 있다.

• Proceedings of the IEEK Conference
• /
• 1999.06a
• /
• pp.61-64
• /
• 1999

The turbo code appropriate to IMT-2000 is known to have a good performance whenever the size of frame increases. But it is not appropriate to a sort of video service to need real time because of decoding complexity and long delay time by the size of frame. Therefore this paper proposes decoding decision algorithm of short frame in which soft output is weighted according to iteration number in turbo decoder. Performance of the proposed algorithm is analysed in the AWGN channel when short length of frame is 100, 256, 640. As the result. it is appeared that the proposed decoding decision algorithm has improved in BER other than in the existing MAP decoding algorithm.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.48-53
• /
• 2007

A new way to integrate various geophysical information for evaluation of RQD was developed. In this study, we did not directly define the RQD value where borehole data are not sampled. Instead, we infer the probability of RQD values with prior probability from borehole direct data, and secondary supporting probability from resistivity and seismic tomography data. For the integration, we applied the geostatstical indicator kriging to get prior probability of RQD value, and indicator kriging with soft data to get the supporting probability from resistivity and seismic data. And we finally use the permanence ratio rule to integrate these information. The finally obtained result was also analyzed to fully utilize the probabilistic features. We show the probability of wrongly classifying the RQD evaluation and vice versa. This result may be used for decision making process based on the geophysical exploration.

• Proceedings of the KIEE Conference
• /
• 1998.07g
• /
• pp.2470-2472
• /
• 1998

In this paper, we proposed the method to improve the performance of Viterbi decoder by applying Concatenated structure. Proposed decoder for Concatenated Code is designed with inner Viterbi decoder, block deinterleaver and outer Viterbi decoder. Inner Viterbi decoder (K=7, R=1/2) has 8-level soft decision, but outer decoder (K=7, R= 1/2) has 2-level hard decision. Applied interleaving scheme make decoder to have better BER performance in Concatenated code. The designed VLSI shares inner decoder with outer decoder. Because of sharing structure, complexity of decoder can be reduced to half. But it required about twice clock speed.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.6 no.1
• /
• pp.287-304
• /
• 2012

Spectrum sensing is an important functionality for cognitive users to look for spectrum holes before taking transmission in dynamic spectrum access model. Unlike previous works that assume perfect knowledge of the SNR of the signal received from the primary user, in this paper we consider a realistic case where the SNR of the primary user's signal is unknown to both fusion center and cognitive radio terminals. A Kalman filter based adaptive Takagi and Sugeno's fuzzy system is designed to make the global spectrum sensing decision based on the observed energies from cognitive users. With the capacity of adapting system parameters, the fusion center can make a global sensing decision reliably without any requirement of channel state information, prior knowledge and prior probabilities of the primary user's signal. Numerical results prove that the sensing performance of the proposed scheme outperforms the performance of the equal gain combination based scheme, and matches the performance of the optimal soft combination scheme.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.7
• /
• pp.79-81
• /
• 1998

2진 BCH 부호에 대한 새로운 연판정 복호법을 제안하였다. 후보부호어가 선출되지 않을 때의 성능 저하를 방지할 수 있는 개선된 알고리듬을 개발하여 오정정 확률과 정정 불 능 확률이 낮아지게 하였다. 또한, 복잡도를 줄이는 방안도 개발하여 알고리듬 개선으로 인 한 복잡도 증가가 거의 나타나지 않도록 하였다. (31,16) BCH 부호에 대한 시뮬레이션 결과 로 이러한 사실들을 확인할 수 있었다.

• Proceedings of the IEEK Conference
• /
• 1998.06a
• /
• pp.285-288
• /
• 1998

Viterbi docoder is a maximum likelihood decoding method for convolution coding used in satellite and mobile communications. In this paper, a Viterbi decoder with constraint length of K=7, 3-soft decision and traceback depth of $\Gamma$=96 for convolution code is implemented using VHDL. The hardware size of designed decoder is reduced by 4 bit pre-traceback in the survivor memory.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2015.11a
• /
• pp.11-12
• /
• 2015

본 논문에서는 다중 입출력 안테나 OFDM 통신시스템에서 신뢰할 만한 데이터 신호 사용하는 한 연판정 지향 채널 추정 기법을 제안한다. 기존 방식에서는 주어진 기준 신호만을 이용하여 채널을 추정하는 반면에 제안하는 기법은 기준 신호를 포함하여 신뢰할 만한 데이터 신호를 동시에 사용하여 채널을 추정한다. 모의실험을 통해 제안하는 기법이 기존 채널 추정에 비해 성능이 우수함을 확인할 수 있다.