• 전자공학회논문지A
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• 제33A권10호
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• pp.12-21
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• 1996

The trellis shaping is the method of selecting a minimum weight sequence from an equivalent class of possible transmitted sequences. It is perforemed by searching through the trellis diagram of a shaping convolutional code Cs. A shaping gain of the order of 1dB may be obtained with a simple 4-state shaping code. But when the rellis shaping is applied to multi-dimensional constellation, the shaping gain is decreased and the transmission delay is increased, which make it difficult to apply the trellis shaping to multi-dimensional constellation. In this paper, in order to solve these problems, the shell mapping algorithm is used for the mapper in the proposed trellis shaping. The simulatio result shows that the proposed trellis shaping is better than coventional trellis shaping to multi-dimensional constellation. In this paper, in order to solve these problems, the shell mapping on multi-dimensional costellation with respect to shaping gain and transmission delay. And the constellation expansion ratio (CER) and the capacity of transmitted injformation are identical to those of conventional trellis shaping on multi-dimensional constellation.

• Journal of Positioning, Navigation, and Timing
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• 제10권2호
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• pp.91-102
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• 2021

In this paper, a fully reconfigurable Software Defined Radio (SDR) for multi-constellation and multi-frequency Global Navigation Satellite System (GNSS) receivers is presented. The reconfigurability with respect to the data structure, variability of signal and receiver parameters, and receiver's internal functionality is presented. The configuration file, that is modified to lead to an entirely different operation of the SDR in response to specific target signal scenarios, directly determines the operating characteristics of the SDR. In this manner, receiver designers can effectively reduce the effort to develop many different combinations of multi-constellation and/or multi-frequency GNSS receivers. Finally, the implementation of the presented fully reconfigurable SDR is included with the experimental processing results such as acquisition, tracking, navigation for the received signals in the realistic fields.

• 방송공학회논문지
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• 제14권6호
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• pp.733-741
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• 2009

디지털 통신 시스템에서는 대역폭과 전력을 효율적으로 사용하면서 신뢰성 높은 데이터 전송을 요구한다. 본 논문에서는 다중 반송파 방식을 사용하는 시스템에서 반송파의 직교성을 이용하여 다차원 성상도를 구현하고 전력 소비가 큰 성상 포인트의 위치를 재배치하여 평균 소비 전력을 감소시킬 수 있는 기술을 제안한다. 기존의 2차원 QAM 변조 방식을 N개의 부반송파를 사용하여 다차원 QAM 형태로 단순하게 변환하면 2 N차원 큐브 형태의 성상 포인트가 구성되는데, 전력 소비가 많은 최외각 성상 포인트들을 효율적으로 재배치하면 전력 소비를 최소화할 수 있는 2 N차원 구 형태의 성상도를 구성할 수 있다. 이와 같은 방식으로 16-QAM부터 2,048-QAM까지의 2차원 성상도를 다차원으로 변환하여 구성하고 전산모의실험을 통해 얻을 수 있는 평균 소비 전력 이득 값을 비교 분석하였다. 차원을 높일수록 재배치 성상 포인트들이 증가하므로 평균 소비 전력 이득 값이 커지는 것을 알 수 있다. 하지만 차원 증가에 따른 이득의 증가비율은 로그 형태를 가지고 있기 때문에 QAM의 성상 포인트 개수에 따라 일정한 이득값에 수렴하게 되고 수렴 값을 바탕으로 적정 다차원 성상도를 유도할 수 있다. 본 논문에서 제안한 방법으로 데이터를 전송하는 것은 하드웨어 복잡도 증가가 거의 없이 소비 전력의 효율성을 높이는데 효과적이다.

• 전자공학회논문지S
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• 제35S권3호
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• pp.47-53
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• 1998

Multi-dimensional DC-free trellis codes based on two-dimensional constellation which can be omplemented more easily than conventional codes are proposed and their performances are analyzed in this paper. 2N-dimensional constellation of the proposed codes is constructed by concatenating N 2-dimensional constellation. Thus, for the proposed codes, information bits can be assigned easily to each signal point of the 2-dimensional consteellation and DC-free characteristic can be simply obtained by the symmetric structure of the constellation. In addition, since Viterbi decoder can calculate multi-dimensional Euchlidean distance between signals by simple sum of each 2-dimensional Euclidean distanc, decoding complexity can be reduced. The performance analysis shows that the proposed codes have almost same spectral characteristic and error performance as compared with conventional codes. However, the complexity is shown to be reduced further due to the construction method of contellation and the simple decoding algorithm of the proposed codes.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.11-22
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• 2023

In this paper, we propose an efficient satellite selection method for multi-constellation GNSS. The number of visible satellites has increased dramatically recently due to multi-constellation GNSS. By the increased availability, the overall GNSS performance can be improved. Whereas, due to the increase of the number of visible satellites, the computational burden in implementing advanced processing such as integer ambiguity resolution and fault detection can be increased considerably. As widely known, the optimal satellite selection method requires very large computational burden and its real-time implementation is practically impossible. To reduce computational burden, several sub-optimal but efficient satellite selection methods have been proposed recently. However, these methods are prone to the local optimum problem and do not fully utilize the information redundancy between different constellation systems. To solve this problem, the proposed method utilizes the inter-system biases and geometric assignments. As a result, the proposed method can be implemented in real-time, avoids the local optimum problem, and does not exclude any single-satellite constellation. The performance of the proposed method is compared with the optimal method and two popular sub-optimal methods by a simulation and an experiment.

• Journal of Positioning, Navigation, and Timing
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• 제8권1호
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• pp.1-12
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• 2019

In this paper, we implement a navigation software of a Global Navigation Satellite System (GNSS) receiver based on a commercial purpose GNSS software receiver platform and verify its performance by performing experimental tests for various GNSS signals available in Korea region. The SX3, employed in this paper, is composed of an application program and a Radio Frequency (RF) frontend, and can capture and process multi-constellation and multi-frequency GNSS signals. All the signal processing procedure of SX3 is accessible by the receiver software designer. In particular for an easy research and development, the Application Programing Interface (API) of the SX3 has a flexible architecture to upgrade or change the existing software program, equipped with a real-time monitoring function to monitor all the API executions. Users can easily apply and experiment with the developed algorithms using a form of Dynamic Link Library (DLL) files. Thus, by utilizing this flexible architecture, the cost and effort to develop a GNSS receiver can be greatly reduced.

• Journal of Positioning, Navigation, and Timing
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• 제12권3호
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• pp.295-306
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• 2023

This paper presents a multi-frequency and multi-constellation Global Navigation Satellite System (GNSS) signal generator that simulates intermediate frequency level digital signal samples for testing GNSS receivers. GNSS signal generators are ideally suited for testing the performance of GNSS receivers and algorithms under development in the laboratory for specific user locations and environments. The proposed GNSS signal generator features a fully-reconfigurable structure with the ability to adjust signal parameters, which is beneficial to generate desired signal characteristics for multiple scenarios including multi-constellation and frequencies. Successful signal acquisition, tracking, and navigation are demonstrated on a verified Software Defined Radio (SDR) in this study. This work has implications for future studies and advances the research and development of new GNSS signals.

• 한국산학기술학회논문지
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• 제17권4호
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• pp.567-572
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• 2016

GPS의 도입과 함께 위성항법시스템과 관련된 많은 연구들이 수행되었으며 이를 통해 위성항법시스템을 이용한 위치 결정의 활용성이 충분히 제시되었다. 하지만 대부분의 연구가 정확도 부분에 초점을 맞추고 있으며 현재 빠르게 발전하고 있는 위성항법시스템과 관련 국가 인프라에 대한 분석적 연구는 부족한 실정이다. 이에 본 연구에서는 현재 다중 위성항법 시스템과 국토지리정보원의 위성기준점의 현황을 파악하고, 실험을 통해 측위성능 향상을 위한 위성측량 인프라 고도화의 방향과 이에 따른 기대효과를 제시하고자 하였다. 연구를 통해 GPS, GLONASS 뿐만 아니라 Galileo, COMPASS, QZSS 등 다중 위성항법시스템이 측량에 적용할 수 있을 정도로 운영되고 있음을 알 수 있었다. 또한 기존 GPS와 GLONASS만을 이용한 VRS 서비스와 다중 위성항법 시스템을 활용하는 경우의 비교를 통해 가용 위성 수, 정밀도, PDOP 등 다중 위성항법시스템 활용에 대한 정량적인 개선점을 제시하고, 위성측량 인프라 고도화를 위해 우선적으로 고려해야할 사항들을 도출하였다. 향후 VRS에서 다중 위성항법 서비스가 가능해 진다면 도심에서 GNSS 측량 요구가 증가하고 있는 현재 대민서비스 만족도를 크게 재고할 것이며, 측량 인프라 선진화에 크게 기여할 것이다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2012년도 추계학술대회
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• pp.75-76
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• 2012

본 논문에서는 MIMO(multi-input multi-output) RQD(rotation constellation and Q-delay) 시스템을 적용하여 지상파 UHDTV 시스템을 구현하기 위한 전송 시스템의 성능을 분석한다. 차세대 UHDTV 시스템이 필요로 하는 높은 전송량을 달성하기 위하여 STBC(space time block code)를 사용하는 기존의 MISO(multi-input single-output)와 MIMO(multi-input multi-output) 시스템에 RQD 기술을 더하여 성능을 개선한다. 개선된 MISO RQD 기법과 MIMO RQD 기법의 성능을 컴퓨터 시뮬레이션을 통하여 비교 분석하였다. 또한 실험 결과를 통하여 앞으로 차세대 지상파 UHDTV를 위한 방향을 제시한다.