Tae-Doo Park

Analysis of Turbo Coding and Decoding Algorithm for DVB-RCS Next Generation

This paper analyzed performance of three dimensional turbo code and turbo codes proposed in the next generation DVB-RCS systems. In the view of turbo codes, we proposed the optimal permutation and puncturing patterns for triple binary input data. We also proposed optimal post-encoder types and interleaving algorithm for three dimensional turbo codes. Based on optimal parameters, we simulated both turbo codes, and we confirmed that the performance of turbo codes are better than that of three dimensional turbo codes. However, the complexity of turbo is more complex than that of three dimensional turbo codes by 18%.

A Study on layered Space Time Trellis codes for MIMO system based on Iterative Decoding Algorithm

The next-generation wireless communication requires fast transmission speeds with various services and high reliability. In order to satisfy these needs we study MIMO system used layered space time coded system (LST) combining space time trellis codes (STTC) with turbo codes. In LST, two codes that are inner and outer codes are concatenated in the serial fashion. The inner codes are turbo Pi codes suggested in DVB-RCS NG system, and outer codes are STTC codes proposed by Blum. The interleaver technique is used to efficiently combine two codes. And we proposed and simulated that a full iteration method between turbo decoder and BCJR decoder to improve the performance instead of only processing inner-iteration turbo decoder. The simulation results of proposed effective layered method show improving BER performance about 1.3~1.5dB than conventional one.

Alternative Approach for Combination of Fingers in Underwater Acoustic Communication

An underwater acoustic communication channel is time varying and has multipath propagation with bottom and surface reflection. A rake receiver has time diversity effects in multipath propagation environments. We have to recognize the correct path for a rake receiver, as this affects communication performance in the underwater acoustic channel. In this paper, we propose a more reliable rake receiver based on BER (bit error rate) of training sequence duration. We conducted simulations and lake trials to evaluate the performance of the proposed method. When the channel coding technique was not applied, the uncoded BER performances of the proposed method, the conventional method, and the nonrake method in the lake trial were 0.016, 0.088, and 0.141, respectively.

Influence of Underwater Channel Time-Variability on Communication Throughput Efficiency

Underwater acoustic channel has time-variability. Time varying channel which disturbs the continuous transmission of information data reduces the underwater acoustic communication performance. In this paper, we show the temporal coherence as time-variability of channel and indicate throughput efficiency in accordance with transmission time of information data. Then we analyzed influence of underwater channel time-variability on communication throughput efficiency. We confirmed that the throughput efficiency reduced when the time-variability of the channel increased via lake trial.

Optimizing of iterative turbo equalizer for underwater acoustic channel

Underwater acoustic communications have multipath errors because of reflection by sea-level and sea-bottom. The multipath of underwater channel causes signal distortion and error floor. In order to improve the performance, it is necessary to employ an iterative coding scheme. Among the iterative coding schemes, turbo codes and LDPC codes are dominant channel coding schemes in recent. This paper concluded that turbo coding scheme is optimal one for underwater communications system in aspect to performance, coded word length, and equalization applications. Also, we confirmed that iterative equalization using soft information from the turbo decoder further enhances the receiver performance in the environment of oceanic experimentation with distance of 5Km and data rate of 1Kbps.

Performance Analysis of Underwater Communication Channel Using LDPC Codes in the MISO Channel

Due to reflect at surface of the water and limit bandwidth, it is difficult to design underwater acoustic communication systems with high-reliability and high transmission rate. Therefore the trends of underwater communication is transformed from single sensor to multiple sensor studies. However, underwater MIMO communication techniques have a high correlation value between multiple sensors on transmitters and receivers in underwater environments, it is difficult to expect space diversity gain on muli-path channels. Therefore, this paper proposed the MISO communications system with two transmit sensors and single receiver sensor, and analyzed its performance using the LDPC codes and channel compensation algorithm.

A cooperative communication system using cross-layer coding method base on Hybrid-ARQ

MIMO system generally requires more than one antenna at the communication device. However, many wireless devices are limited by size, cost or hardware complexity to one antenna. To overcome such restrictions, we used a new technique, called cooperative communication. We propose a new cooperative transmission strategy system using cross-layer coding method base on H-ARQ for optimal communication. And we confirmed simulation result better performance than general one by one communication in using proposed cooperative communication system.

Turbo equalization for covert communication in underwater channel

The design of optimal covert underwater acoustic communication systems is required from an analysis of the impact on communication performance by applying the low probability of interception (LPI) techniques for reducing the probability of intercept information transmitted. In this paper, we propose a transceiver model using a spread spectrum based on turbo equalization in order to improve performance in low SNR(signal-to-noise ratio). We analyzed the performance of proposed method and confirmed performance enhancement by simulation and lake experiments.

Design of orthogonal code for covert underwater acoustic communication

The use of orthogonal waveform can offer many advantages in covert underwater acoustic communication, including improved symbol detection ability. In this paper, we derive a new orthogonal code design. The proposed code has a good autocorrelation property compared to other codes. We present some results of a lake trial to evaluate the performance of the proposed method.

Performance Analysis of Underwater Acoustic Communication Systems with Turbo Equalization in Korean Littoral Sea

The performance of underwater acoustic communication system is sensitive to the ISI(Inter-Symbol Interference) due to delay spread develop of multipath signal propagation. The equalizer is used to combat the ISI. In this paper, the performances of underwater acoustic communication with turbo equalizer were evaluated by real data collected in Korean littoral sea. As a result, when one iterative decoding using turbo equalizer is applied, the performance was improved 1.5 dB than the case of the non-iterative equalizer at BER . In the case of two or three iterations the performance was enhanced about 3.5 dB, but the performance wasn`t improved any more in the case of more than three times.