단일 클러스터 다중안테나 비직교 다중접속 전송

신창용 대한전기학회 2023 전기학회논문지 Vol.72 No.1

To improve spectral efficiency in multi-cell systems, we propose a multiple-input multiple-output (MIMO) non-orthogonal multiple access technique that simultaneously transmits multiple data streams to a cluster consisting of one cell-center user and one cell-edge user. Based on the MIMO channel state of the cell-center user, the proposed technique for single-cell systems finds the receive beamforming matrix for the user and performs power allocation to its data streams. Considering the MIMO channel state of the cell-edge user and interference from the cell-center user, the technique designs the receive beamforming matrix for the cell-edge user and allocates the power for the user to its data streams. By extending this technique to multi-cell systems, the proposed technique finds the receive beamforming matrix for the cell-center user and performs power allocation to its data streams according to its MIMO channel state and interference from neighboring cells. The receive beamforming matrix design and power allocation for the cell-edge user is performed based on its MIMO channel state, interference from the cell-center user, and interference from neighboring cells. Simulation results demonstrate that the proposed technique achieves better performance than the existing techniques in terms of data rates and outage probabilities for the users

여러 개의 문턱값을 이용한 Optical CDMA 부호 획득 알고리즘

정다해(Dahae Chong),이영윤(Youngyoon Lee),안상호(Sangho Ahn),이성로(Seong Ro Lee),윤석호(Seokho Yoon) 한국통신학회 2008 韓國通信學會論文誌 Vol.33 No.12C

본 논문에서는 optical orthogonal code를 (OOC) 사용하는 optical 부호 분할 다중 접속 (code division multiple access: CDMA) 시스템에 알맞은 부호 획득 알고리즘을 제안한다. 일반적으로 부호 획득 알고리즘의 평균 부호 획득 시간이 (mean acquisition time: MAT) 짧을수록 알고리즘의 성능이 뛰어나다고 말할 수 있다. 기존의 Multiple-shift (MS) 알고리즘은 부호 획득을 두 단계로 나누어 수행함으로써, serial-search (SS) 알고리즘에 비해 빠른 부호 획득이 가능하였다. 본 논문에서 제안한 enhanced multiple-shift (EMS) 알고리즘은 기존의 MS알고리즘과는 달리 여러 개의 문턱값을 씀으로써 MS 알고리즘에 비해 더 짧은 MAT를 갖는다. 모의실험을 통해 제안한 EMS 알고리즘의 MAT 성능을 MS 알고리즘의 MAT 성능과 비교해 본 결과, 단일 사용자 환경 및 다중 사용자 환경 모두에서 EMS 알고리즘이 MS 알고리즘에 비해 더 짧은 MAT를 갖는 것을 확인할 수 있었다. In this paper, we propose a code acquisition algorithm using optical orthogonal code (OOC) for optical code division multiple access (CDMA) systems. Generally, a good code acquisition algorithm offers short mean acquisition time (MAT). The conventional multiple-shift (MS) algorithm consists of two stages and has shorter MAT than that of well-known serial-search (SS) algorithm. This paper proposes a novel code acquisition algorithm called enhanced multiple-shift (EMS) algorithm. By using multiple thresholds, the proposed EMS algorithm provides shorter MAT compared with that of the MS algorithm. The simulation results show that the EMS algorithm presents shorter MAT compared with the MS algorithm in both single-user and multi-user environments.

IFDMA 시스템에서 주파수 옵셋에 의한 다중접속간섭 제거 기법

김정우,원유준,서보석 통신위성ㆍ우주산업연구회 2011 한국위성정보통신학회논문지 Vol.6 No.1

이 논문에서는 상향링크에서 분산형 직교 주파수 분할 다중 접속방식(interleaved orthogonal frequency division multiple access: IFDMA)을 이용하는 전송 시스템에서 주파수 옵셋에 의해 발생하는 다중접속간섭을 제거하는 방법을 제안하고자 한다. IFDMA 시스템에서 주파수 옵셋이 발생하면 인접한 다른 사용자의 부반송파 성분이 간섭신호로 유입되어 시스템의 성능이 크게 저하된다. 이 논문에서는 시간 영역에서 주파수 옵셋을 보상한 후 주파수 영역에서 병렬 간섭 제거기법을 적용하여 다중접속간섭을 제거하는 방법을 제안한다. 모의실험을 통하여 제안방법이 특히 사용자의 수가 많을 때 효과적으로 다중접속간섭을 제거할 수 있음을 보인다.

MISO BC 채널에서 기계학습 기반 비직교 다중 접속 구현

강민정,이정훈 한국통신학회 2022 韓國通信學會論文誌 Vol.47 No.6

Non-orthogonal multiple access (NOMA) requires successive interference cancellation at the receiver, but the optimal decoding order is not easy to find especially when the transmitter has multiple antennas. In this paper, we use machine learning to implement NOMA in downlink multiple input single output broadcast channels when data rate for each user is fixed. Our machine learning model finds the optimal decoding order for given channel states. 본 논문에서는 MISO(multiple-input single-output) 브로드캐스트 채널에서 기계학습에 기반한 비직교 다중 접속기법을 제안한다. 비직교 다중 접속 기법의 경우 수신단에서 순차적 간섭 제거(successive interference cancellation, SIC)를 수행하는데, 이때 최적의 복호 순서를 찾아야 한다. 다중 안테나를 가진 송신단의 경우 단일안테나와 달리 빔포밍과 각 채널의 상관도에 따라 각 수신단에서 수신한 유저 신호들의 세기 순서가 달라지므로최적의 복호 순서를 찾기 어렵다. 특히 다수의 유저가 존재할 경우 계산의 복잡도가 높아지므로 최적의 복호 순서를 구하기 쉽지 않다. 본 논문은 유저들이 제공받는 데이터 전송률이 고정되고, 송신 빔포밍 기법이 최대비 송신(maximum ratio transmission, MRT)으로 고정될 때, 기계학습을 활용하여 최적의 복호 순서를 찾는다. 제안하는기계학습 모델은 각 채널의 상관도와 송신 신호대 잡음비를 입력받아 최적의 복호 순서를 출력한다.

Channel Capacity for NOMA Weak Channel User and Capacity Region for NOMA with Gaussian Mixture Interference

정규혁 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.1

Non-orthogonal multiple access (NOMA) has been considered for the fifth generation (5G) mobile networks toprovide high system capacity and low latency. We calculate the channel capacity for the weak channel user inNOMA and the channel capacity region for NOMA. In this paper, Gaussian mixture channel is compared to theadditive white Gaussian noise (AWGN) channel. Gaussian mixture channel is modeled when we assume thepractical signal modulation for the inter user interference, such as the binary phase shift keying (BPSK)modulation. It is shown that the channel capacity with BPSK inter user interference is better than that withGaussian inter user interference. We also show that the channel capacity region with BPSK inter user interferenceis larger than that with Gaussian inter user interference. As a result, NOMA could perform better in the practicalenvironments.

Channel Capacity for NOMA Weak Channel User and Capacity Region for NOMA with Gaussian Mixture Interference

Chung, Kyuhyuk Institute of Korean Electrical and Electronics Eng 2019 전기전자학회논문지 Vol.23 No.1

Non-orthogonal multiple access (NOMA) has been considered for the fifth generation (5G) mobile networks to provide high system capacity and low latency. We calculate the channel capacity for the weak channel user in NOMA and the channel capacity region for NOMA. In this paper, Gaussian mixture channel is compared to the additive white Gaussian noise (AWGN) channel. Gaussian mixture channel is modeled when we assume the practical signal modulation for the inter user interference, such as the binary phase shift keying (BPSK) modulation. It is shown that the channel capacity with BPSK inter user interference is better than that with Gaussian inter user interference. We also show that the channel capacity region with BPSK inter user interference is larger than that with Gaussian inter user interference. As a result, NOMA could perform better in the practical environments.

Channel Capacity for NOMA Weak Channel User and Capacity Region for NOMA with Gaussian Mixture Interference

Kyuhyuk Chung 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.1

Non-orthogonal multiple access (NOMA) has been considered for the fifth generation (5G) mobile networks to provide high system capacity and low latency. We calculate the channel capacity for the weak channel user in NOMA and the channel capacity region for NOMA. In this paper, Gaussian mixture channel is compared to the additive white Gaussian noise (AWGN) channel. Gaussian mixture channel is modeled when we assume the practical signal modulation for the inter user interference, such as the binary phase shift keying (BPSK) modulation. It is shown that the channel capacity with BPSK inter user interference is better than that with Gaussian inter user interference. We also show that the channel capacity region with BPSK inter user interference is larger than that with Gaussian inter user interference. As a result, NOMA could perform better in the practical environments.

Iterative Interstream Interference Cancellation for MIMO HSPA+ System

Yu, Hyoug-Youl,Shim, Byong-Hyo,Oh, Tae-Won The Korea Institute of Information and Commucation 2012 Journal of communications and networks Vol.14 No.3

In this paper, we propose an iterative interstream interference cancellation technique for system with frequency selective multiple-input multiple-output (MIMO) channel. Our method is inspired by the fact that the cancellation of the interstream interference can be regarded as a reduction in the magnitude of the interfering channel. We show that, as iteration goes on, the channel experienced by the equalizer gets close to the single input multiple output (SIMO) channel and, therefore, the proposed SIMO-like equalizer achieves improved equalization performance in terms of normalized mean square error. From simulations on downlink communications of $2{\times}2$ MIMO systems in high speed packet access universal mobile telecommunications system standard, we show that the proposed method provides substantial performance gain over the conventional receiver algorithms.

해석적 최적 칩파형의 BER과 전송성능(Throughput) 분석

유흥균,정기호,이동훈 한국전자파학회 2002 한국전자파학회논문지 Vol.13 No.7

The study on the chip waveform design to minimize multiple-access interference (MAI) and its performance evaluation are very important since chip waveform decides the signal quality and system capacity of the direct-sequence CDMA wireless communication system. This paper suggests the analytical chip waveform to minimize the MAI. The BER and throughput performances achieved by the proposed analytical optimum chip waveform are compared with those of the conventional chip waveforms in the Nakagami-m distribution frequency selective channel when the differential phase shift keying (DPSK) is employed in DS-CDMA system. From the numerical results, capacity and throughput are improved about 2 times and 1.4 times respectively when it is compared with the Kaiser chip waveform that is considered as one of the best in the conventional ones.

Mitigation Techniques of Channel Collisions in the TTFR-Based Asynchronous Spectral Phase-Encoded Optical CDMA System

Miyazawa, Takaya,Sasase, Iwao The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.1

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.