Dongweon Yoon

Bit error probability of M-ary quadrature amplitude modulation

So far the general expression of bit error rate (BER) has not been derived for M-ary square quadrature amplitude modulation (QAM). In this paper, a generalized closed-form BER expression of M-ary square QAM with Gray code bit mapping is derived and analyzed in the presence of additive white Gaussian noise (AWGN) channel.

Error Performance Analysis of

In this paper, we derive new exact and general expressions for the symbol error rate (SER) and bit error rate (BER) of M-ary θ-quadrature amplitude modulation (QAM) for M = 2l , I ≥ 4, based on not only square-QAM (SQAM) for M = 22l, I ≥ 2 but cross-QAM (CQAM) as well, for M = 22l+1, I ≥ 2 in additive white Gaussian noise (AWGN) and various fading channels; we also present the optimum angle and constellation of M-ary θ-QAM. Through computer simulations, we confirm the results of the theoretical analysis. Because the SER and BER expressions are provided in terms of 2-D Gaussian Q-function in AWGN and various fading channels, they will be very useful for numerical evaluations in various cases of practical interest in QAM systems.

M

A zero-forcing (ZF) receiver has a quite simple structure and relatively good performance at high SNR. This paper studies the performance of a Multiple-Input Multiple-Output (MIMO) ZF receiver over continuous flat fading channels in the presence of practical channel estimation errors. We derive the bit error rate (BER) of MPSK for the MIMO ZF receiver considering the practical effects of channel estimation errors and interferences caused by Doppler spread of the channel, and analyze the effects of the number of transmit and receive antennas on the performance.

-ary

Telemetry link requires high data rate to transmit the multimedia data for lunar explorations in space communications. In this paper, we analyze a data rate with the modulation and channel coding schemes based on Consultative Committee for Space Data Systems (CCSDS) in S, X, Ku and Ka bands, respectively. Then, we suggests modulation and channel coding schemes to meet the link margins and have a maximum data rate for lunar explorations in telemetry links.

\theta

Many countries of the world have been launched the competition of space development and Korea also has a plan for the launch of Lunar orbiter in 2020 and Lunar lander in 2025 for Lunar explorations. For the success of the planned Lunar exploration, we need to enhance the required deep space communication technologies. To achieve our goals, we should develop space communications system and Korean DSN (deep space network) based on experiences and technologies through cooperation with the advanced countries in the field of deep space exploration. In this paper, we investigate overseas DSNs and deep space communication systems, and present the link margin and other technical requirements for successful DSN deployment. In addition, we propose a best strategy to secure domestic ground stations for the Korean Lunar exploration missions.

-QAM

The combination of deliberate clipping and an adaptive symbol selection scheme (ASSS) can be used to reduce the peak to average power ratio (PAPR) for Orthogonal Frequency Division Multiplexing (OFDM) signals. The probability density function (pdf) of a samples amplitude of an adaptively selected OFDM signal without over-sampling has been considered to be approximately equal to the Rayleigh pdf. In this letter, we derive the exact pdf showing the relationship between the probability distribution of the samples amplitude and the number of candidate OFDM symbols for ASSS. The use of the newly derived pdf can measure the effect of deliberate clipping on the adaptively selected OFDM signal more accurately.

Performance analysis of the MIMO zero-forcing receiver over continuous flat fading channels

대용량 데이터 전송을 위한 무선 통신 시스템에서는 높은 신뢰도를 보장하는 오류 보상 기법이 요구되며, 그러한 기법 중 하나로 재전송 방식과 터보 부호를 결합한 터보 HARQ(Hybrid Automatic Repeat Request) 기법이 여러 문헌에서 연구되어 오고 있다. 기존 터보 HARQ 기법의 경우, 수신 데이터의 일부분이 오류 정정 가능함에도 불구하고 NAK 신호 발생 시에 송신단에서는 정해진 정보 패킷 전체를 반복 전송하게 된다. 이와 같은 과정에서 재전송이 요구되는 정보 패킷 중 필요한 일부만을 송신할 경우 시스템의 전송 효율을 높일 수 있다. 본 논문에서는 전송 효율을 높이기 위한 방법으로 사후 정보 값의 부호 변화를 이용한 오류 데이터 판단 기준 및 부분 재전송 방식을 이용한 터보 HARQ 기법을 제안한다. 제안된 기법에 대한 모의 실험을 통해 전송 효율을 도출하고 성능을 분석한다.

Performance Analysis of Maximum Data Rate for Telemetry Links in Space Communications for Lunar Explorations

An -sequence (PN sequence) preestimator scheme for direct-sequence spread spectrum (DS-SS) signal acquisition by using block sequence estimation (BSE) is proposed and analyzed. The proposed scheme consists of an estimator and a verifier which work according to the PN sequence chip clock, and provides not only the enhanced chip estimates with a threshold decision logic and one-chip error correction among the first received chips, but also the reliability check of the estimates with additional decision logic. The probabilities of the estimator and verifier operations are calculated. With these results, the detection, the false alarm, and the missing probabilities of the proposed scheme are derived. In addition, using a signal flow graph, the average acquisition time is calculated. The proposed scheme can be used as a preestimator and easily implemented by changing the internal signal path of a generally used digital matched filter (DMF) correlator or any other correlator that has a lot of sampling data memories for sampled PN sequence. The numerical results show rapid acquisition performance in a relatively good CNR.

Ground Stations of Korean Deep Space Network for Lunar Explorations

We propose an improved hop-timing acquisition scheme by adding self-normalization to the conventional scheme with three envelope detectors of full, early-half, and late-half hop periods. The results of analysis and simulation show that the proposed scheme has better antijam performance than the conventional scheme against a partial-band noise jamming.

Exact Distribution of the Amplitude of Adaptively Selected OFDM Signal Samples

Many countries all over the world have been doing lunar exploration projects. Korea has also been doing basic research on lunar exploration. The development of communication systems for lunar exploration projects is one of the most important aspects of performing a successful lunar mission. In this paper, we design a DSP (Digital Signal Processor) prototype based on the requirement analysis of a communication link for lunar exploration and implement its core module considering the international standards for deep space communications to perform a basic research on baseband processor development. It is verified by comparing the bit error rate of the DSP prototype with that of a computer simulation.