• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권1호
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• pp.93-113
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• 2020

According to information theory, non-orthogonal transmission can achieve the multiple-user channel capacity with an onion-peeling like successive interference cancellation (SIC) based detection followed by a capacity approaching channel code. However, in multiple antenna system, due to the unideal characteristic of the SIC detector, the residual interference propagated to the next detection stage will significantly degrade the detection performance of spatial data layers. To overcome this problem, we proposed a modified power-domain non-orthogonal multiple access (P-NOMA) scheme joint designed with space-time coding for multiple input multiple output (MIMO) NOMA system. First, with proper power allocation for each user, inter-user signals can be separated from each other for NOMA detection. Second, a well-designed quasi-orthogonal space-time block code (QO-STBC) was employed to facilitate the SIC-based MIMO detection of spatial data layers within each user. Last, we proposed an optimization algorithm to assign channel coding rates to balance the bit error rate (BER) performance of those spatial data layers for each user. Link-level performance simulation results demonstrate that the proposed time-space-power domain joint transmission scheme performs better than the traditional P-NOMA scheme. Furthermore, the proposed algorithm is of low complexity and easy to implement.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권10호
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• pp.2411-2429
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• 2013

In this paper, we extend the case of information exchange error mitigation for the distributed orthogonal space-time block code (DOSTBC) for two transmit antennas to distributed quasi-orthogonal space-time block code (DQOSTBC) for four transmit antennas. A rate 1 full-diversity DQOSTBC for four transmit antennas is designed. The code matrix changes according to different information exchange error cases, so full diversity is maintained even if not all information exchange is correct. We also perform analysis of the pairwise error probability. The performance analysis indicates that the proposed rate 1 DQOSTBC outperforms rate 1/2 DOSTBC for four transmit antennas at the same transmission rate, which is confirmed by the simulation results.

• 대한전자공학회논문지TC
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• 제43권4호
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• pp.39-43
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• 2006

본 논문에서는 동기식 업링크 전송을 채용하는 직교 다중반송파 DS-CDMA 시스템의 성취가능한 성능을 고찰해보았다. 디스퍼시브 레일레이 다중경로 페이딩 조건에서 비트오류확률 (BER)로 성능을 보였으며, 그 성능은 Eb/No 및 사용자수의 함수로 표현하였다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.94-98
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• 2009

In this paper, we propose a new channel estimation scheme for amplify and forward cooperative diversity with relay selection. In order to select best relay, it is necessary to know channel state information (CSI) at the destination. Most of the previous works, however, assume that perfect CSI is available at the destination. In addition, when the number of relay is increased it is difficult to estimate CSI through all relays within coherence time of a channel because of the large amount of frame overhead for channel estimation. In a proposed channel estimation scheme, each terminal has distinct pilot signal which is orthogonal each other. By using orthogonal property of pilot signals, CSI is estimated over two pilot signal transmission phases so that frame overhead is reduced significantly. Due to the orthogonal property among pilot signals, estimation error does not depend on the number of relays. Simulation result shows that the proposed channel estimation scheme provides accurate CSI at the destination.

• ETRI Journal
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• 제35권4호
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• pp.710-713
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• 2013

We propose a new space-time block coding (STBC) for asynchronous cooperative systems in full-duplex mode. The orthogonal frequency division multiplexing (OFDM) transmission technique is used to combat the timing errors from the relay nodes. At the relay nodes, only one OFDM time slot is required to delay for a pair-wise symbol swap operation. The decoding complexity is lower for this new STBC than for the traditional quasi-orthogonal STBC. Simulation results show that the proposed scheme achieves excellent performances.

• Journal of electromagnetic engineering and science
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• 제7권1호
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• pp.1-6
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• 2007

Recently, Mc(Multi-code) modulation/demodulation(modem) technique has been explored for high speed data transmission in wireless environment. The conventional Mc modem generates some side effects such as allocating Walsh codes, which motivates to propose a novel Mc modem method with sub-code. Our proposed system should expanded the size of sub-code to provide high-rate data transmission, which also affect adversely to the performance of the system with high PAPR(Peak to Average Power Ratio). Thus, in this paper, we propose a novel pre-coded Multi-Dimensional HCOC(High Capacity Orthogonal Code) Mc modem technique to reduce the high PAPR, which enables the performance improvement. This proposed system can be easily designed by concatenating HCOC Mc modem with the generic Mc modem. The pre-coding technique that is used in this paper is CAC(Constant Amplitude Coding), that helps the system maintain the constant transmission power and reduce the maximum transmission power.

• ETRI Journal
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• 제28권1호
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• pp.17-30
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• 2006

In time division duplex (TDD) code division multiple access (CDMA) systems, chip-synchronous transmission in the uplink is obtainable, thus leading to free multiple access interference in flat Rayleigh fading channels plus additive white Gaussian noise. This motivates us to develop a novel cooperative transmission strategy that allows single-antenna devices to benefit from spatial diversity using orthogonal signature sequences. The proposed cooperation is applicable to many digital modulation methods and achieves the fullest diversity level, low implementation complexity, and a full data rate. Closed-form bit-error-rate expressions were also derived and compared to simulation results in order to evaluate its validity. A variety of numerical results demonstrated the cooperation's superiority over single transmission under the same transmit power constraint.

• Journal of information and communication convergence engineering
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• 제22권3호
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• pp.181-188
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• 2024

Herein, an innovative transmission technique that utilizes the satellite aerial terrestrial integrated network (SATIN) architecture in combination with non-orthogonal multiple access (NOMA) communications is proposed. This approach is designed to significantly enhance communication rates, which is critical for modern and future combat capabilities. The effectiveness of the proposed transmission system is validated by conducting a comparative analysis of the sum-throughput results, considering various numbers of transmission nodes within the SATIN structure. The results and analyses reveal that the proposed method outperforms traditional methods such as spatial division multiple access (SDMA) and time division multiple access (TDMA), especially in terms of reducing data loss. This superior performance is primarily due to the advanced capability of NOMA in minimizing interference between signals, resulting in improved sum-throughput outcomes. The implementation of this method is expected to significantly enhance command communications in manned-unmanned combat systems, thereby bolstering overall combat effectiveness through improved transmission rates.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 I
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• pp.19-22
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• 2003

본 논문에서는 비전송을 갖는 OFDM 전송을 위한 직교 부호화기와 복호화기를 사용하는 새로운 주파수 diversity 기술을 제안하였다. 기존의 주파수 diversity 방식이 하나의 데이터를 여러 개의 부반송파들을 이용하여 전송하는 반면, 제안한 주파수 diversity 방식은 직교적으로 부호화된 여러 데이터를 여러 개의 부반송파를 통하여 전송한다. 따라서, 제안한 방식은 하나의 데이터가 여러 부반송파를 통하여 전송되므로, diversity 에 의한 성능의 이득을 유지하면서도 하나의 부 반송파에 직교적으로 혼합된 또 다른 전송 심벌을 전송하므로 기존 주파수 diversity 의 단점인 주파수 대역폭의 비효율성을 만들지 않는 장점을 갖게 된다.

• 한국ITS학회 논문지
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• 제5권3호
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• pp.29-39
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• 2006

본 논문에서는 SOSTTC를 다중 안테나 시스템에 적용하고 ST SF STF 복호화 기법을 통해 효과적으로 신호를 검출하는 방법을 연계하여 주파수 선택적인 채널에서 성능 평가를 한다. 또한 성능 향상을 위해 제안된 시스템에 OFDM을 적용한다. 먼저 기본적인 두 개의 전송 안테나를 가진 SOSTTC-OFDM 시스템을 설명하고 기존의 시 공간 부호화된 OFDM과 성능을 비교한다. 이 시스템을 네 개의 전송 안테나 시스템으로 확장하고 기존의 ST SF STF-OFDM 기법에 SOSTTC를 적용하여 SOSTTC ST SF STF-OFDM 시스템을 설계한다. 이 시스템에 적합한 복호화 기법을 사용하여 효과적으로 신호가 검출됨을 평가하고, 또한 주파수 선택적 채널에서 도플러 주파수가 변화함에 따라 제안된 시스템의 성능을 확인한다.