• International Journal of Internet, Broadcasting and Communication
• /
• 제12권3호
• /
• pp.39-45
• /
• 2020

The fifth generation (5G) mobile communication has been more commercialized worldwide. One of the promising 5G technologies is non-orthogonal multiple access (NOMA). We present the achievable sum rate of non-orthogonal multiple access (NOMA) with correlated superposition coding (SC). Then this paper investigates the impacts of correlation on the achievable sum rate of correlated SC NOMA. It is shown that the achievable sum rate of correlated SC NOMA is greater than that of standard independent SC NOMA, for the most of the values of the power allocation factor over the meaningful range of the user fairness. In result, correlated SC could be a promising scheme for NOMA.

• Journal of Information Processing Systems
• /
• 제13권3호
• /
• pp.630-642
• /
• 2017

In this paper, we propose the opportunistic non-orthogonal multiple access (NOMA)-based cooperative relaying system (CRS) with channel state information (CSI) available at the source, where CSI for the source-to-destination and source-to-relay links is used for opportunistic transmission. Using the CSI, for opportunistic transmission, the source instantaneously chooses between the direct transmission and the cooperative NOMA transmission. We provide an asymptotic expression for the average achievable rate of the opportunistic NOMA-based CRS under Rayleigh fading channels. We verify the asymptotic analysis through Monte Carlo simulations, and compare the average achievable rates of the opportunistic NOMA-based CRS and the conventional one for various channel powers and power allocation coefficients used for NOMA.

• 한국통신학회논문지
• /
• 제31권1C호
• /
• pp.1-7
• /
• 2006

이 논문에서는, 약한 다진 신호에 알맞도록 1부에서 제안한 검파기준을 바탕으로 간섭이 충격성일 때 초광대역 다중접속 시스템에 알맞은 검파 기법을 살펴본다. 제안한 검파기는 최대 비슷함 검파기준을 바탕으로 한 최적 검파기와 견주어 볼 때 얼개가 더 간단하고 성능이 거의 같다. 한편, 간섭이 충격성일 때, 제안한 검파기는 정규 환경에 최적화된 검파기보다 성능이 더 좋다는 것도 보인다.

• Journal of Communications and Networks
• /
• 제11권1호
• /
• pp.1-10
• /
• 2009

In this paper, we propose a chip-level detection and a spectral-slice scheme for the tunable-transmitter/fixed-receiver (TTFR)-based asynchronous spectral phase-encoded optical codedivision multiple-access (CDMA) system combined with timeencoding. The chip-level detection can enhance the tolerance of multiple access interference (MAI) because the channel collision does not occur as long as there is at least one weighted position without MAI. Moreover, the spectral-slice scheme can reduce the interference probability because the MAI with the different frequency has no adverse effects on the channel collision rate. As a result, these techniques mitigate channel collisions. We analyze the channel collision rate theoretically, and show that the proposed system can achieve a lower channel collision rate in comparison to both conventional systems with and without the time-encoding method.

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

• 전자공학회논문지A
• /
• 제32A권9호
• /
• pp.1184-1201
• /
• 1995

Two multiple access protocols are proposed for a multichannel WDM optical fibre local area network or metropolitan area network in which users are interconnected using a passive star topology. Each user has a single tunable transmitter and a single tunable receiver. A transmitter sends a control packet before its data packet transmission so that its intended receivers can tune to the proper data channel wavelength. The maximum throughput of the proposed protocols are independent of the effective normalized propagation delay which may include the transmitter and receiver tuning times and the processing delays. The maximum throughputs of the protocols are analyzed and compared with those of the existing ones by numerical examples. The message delay of the R- Aloha/synchronous N-server switch protocol which is suitable for the queued users is also analyzed.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
• /
• pp.229-233
• /
• 2003

In this paper we theoretically analyze the probability of error for M-ary pulse position modulation (PPM) ultra-wideband (UWB) multiple access system using Gaussian monopulse. The optimum detection of UWB signals using M-ary orthogonal PPM in additive white Gaussian noise (AWGN) and multiple access interference (MAI) is considered, then receiver signal to noise power ratio (SNR) and upper bound fur the bit error rate (BER) are derived. Numerical results considering some practical parameters are presented.

• 정보통신설비학회논문지
• /
• 제8권4호
• /
• pp.201-206
• /
• 2009

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference (ISI) or Multiple Access Interference (MAI) to degrade the performance of W-CDMA (Code Division Multiple Access) system. Constant Modulus Algorithm (CMA) which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. Consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye-pattern obtained from algorithm are compared.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권11호
• /
• pp.5377-5391
• /
• 2017

In this paper, we propose a new scheme to suppress the narrowband interference (NBI) in OFDM-based systems. The scheme utilizes code division multiple access (CDMA) and weighted-type fractional Fourier transform (WFRFT) domain preprocessing technologies. Through setting the WFRFT order, the scheme can switch into a single carrier (SC) or a multi-carrier (MC) frequency division multiple access block transmission system. The residual NBI can be eliminated to the maximum extent when the WFRFT order is selected properly. Final simulation results show that the proposed system can outperform MC and SC with CDMA and frequency domain preprocessing in terms of the narrowband interference suppression.

• 대한전자공학회논문지
• /
• 제20권4호
• /
• pp.61-66
• /
• 1983

본 논문에서는 대역 확산 다중통신 시스템에 쓰이는 가상 잡음 시퀀스의 설계에 관하여 연구하였다. 구형파의 일반형인 새로운 파형을 제안하여 분석한 결과 파형푹이 줄어듬에 따라 다중통신간섭 (multiple access interfererlce)이 0으로 접근하였다. 이 두항은 구형파나 정형파에 비해 훨씬 좋은 특성을 나타낸다.