BTS 기반 Coordinated SDMA와 MMSE SDMA의 평균섹터용량

정창규 忠州大學校 2011 한국교통대학교 논문집 Vol.46 No.-

In this paper, for TDD system, BTS based SDMA technique is proposed to use reciprocity between the up-down links. A BTS based coordinated SDMA select a weighting vector from a predicted up link channel without feedback from AT to BTS. A MMSE SDMA calculate a transmitted weighting vector and MCS level for all AT in sectors and perform a rank adaptation and multiuser scheduling. a system level simulation shows that a coordinated SDMA with 4 interference power have similar performance with knockdown SDMA technique and is superior to MMSE SDMA technique.

제한된 피드백을 사용하는 결합 전송 공간 분할 다중 접속기술을 위한 코드북 설계와 집중 스케줄링

문철(Cheol Mun) 한국전자파학회 2012 한국전자파학회논문지 Vol.23 No.10

본 논문에서는 협력 무선 통신 시스템의 순방향 링크에서, 각 이동국의 제한된 피드백 정보를 이용하여, 인접한 다수의 기지국들에서 동시에 코히어런트(coherent)하게 하나의 이동국에 데이터를 전송하는 결합 전송 공간분할 다중 접속(Joint Transmission Space Division Multiple Access: JT-SDMA) 기술을 제안한다. JT-SDMA 기술을 위해, 공간상관도가 높은 각 collaborative base transceiver station(C-BTS)의 하향 링크 채널과 공간상관도가 낮은 다른 C-BTS들 간의 하향 링크 채널 특성에 적합한 unitary precoding 행렬 코드북을 디자인하였다. 또한, 제안하는 JT-SDMA 기술에서, 각 이동국의 제한된 피드백 정보량을 이용하여 다중 사용자 다이버시티 이득을 증가시키는 클러스터에서 수행되는 집중 스케줄링 기술을 제안하였다. 시뮬레이션의 통해 JT-SDMA 기술이 제한된 피드백 정보량을 이용하여, 다중 사용자 다이버시티 오더가 충분하지 않은 환경에서 셀 간 간섭을 효과적으로 억제하여, 클러스터 전송 용량을 향상시킬 수 있음을 확인하였다. In this paper, joint transmission space division multiple access(JT-SDMA) scheme is proposed to mitigate inter-cell interference(ICI) in cooperative wireless communications system with limited feedback. We propose a systematic design method for a codebook consisting of a finite number of unitary matrices suitable for network multiple-input multipleoutput(MIMO) channel characteristics. A centralized cluster scheduling scheme is proposed to both mitigate ICI and maximizes multiuser diversity gain with limited feedback. It is shown that the proposed JT-SDMA scheme outperforms a existing coordinated SDMA scheme even in wireless network environments where sufficient multiuser diversity order can not be provided through efficient ICI mitigation.

TDD 무선통신 시스템을 위한 Coordinated SDMA 기술

문철(Cheol Mun),김도윤(Do-Yun Kim),정창규(Chang-Kyoo Jung) 한국정보기술학회 2008 한국정보기술학회논문지 Vol.6 No.6

This paper propose SDMA(Space Division Multiple Access) techniques using reciprocity between uplink channels and downlink channels in TDD (Time Division Duplexing) wireless communication systems. In the proposed MRT (Maximum Ratio Transmit) SDMA scheme, BTS (Base Tranceiver Station) estimates uplink channel from each AT (Access Terminal) and selects nT ATs such that maximizing multiuser diversity gain while minimizing inter-stream interferences. In the proposed coordinated SDMA scheme, BTS and AT independently determines weight vectors by estimating uplink and downlink channels, respectively, without feedback information. System level simulation shows that the proposed coordinated SDMA uses more feedback information and provides more system capacity than MRT SDMA.

협력 SDMA와 빔 성형기술의 주파수 효율성 분석

정창규 忠州大學校 2010 한국교통대학교 논문집 Vol.45 No.-

This paper propose a collaborative SDMA and collaborative beamforming technique suppressing adjacent cell interferences effectively induced by adjacent BTS, using partial channel information transferred by AT through a restricted feedback channel at reverse link in FDD collaborative wireless communication systems. Simulation shows that Channel capacity of collaborative-SDMA is superior to that of noncollaborative-SDMA.

협력 공간 분할 다중 접속 기술을 위한 제한된 피드백과 스케줄링

문철(Cheol Mun),정창규(Chang-Kyoo Jung) 한국전자파학회 2011 한국전자파학회논문지 Vol.22 No.6

본 논문은 협력 무선 통신 시스템에서 역방향 링크의 제한된 피드백 채널을 통해 AT(Access Terminal)로부터 전달된 부분적인 채널 정보만을 이용하여, 인접 BTS(Base Transceiver Station)에 의한 타 셀 간섭을 효과적으로 억제하는 협력 공간 분할 다중 접속 기술을 제안하였다. 제안하는 협력 공간 분할 다중 접속 기술에서, AT는 각 링크별로 다중 사용자 다이버시티 이득을 최대화 하는 최적의 전송 모드를 선택하고 이를 피드백하며, 클러스터 스케줄러는 각 전송 모드별로 동일 전송 모드를 선택하는 AT들에 대해 스케줄링을 수행하고, 최대 스케줄링 우선 순위를 제공하는 클러스터의 전송 모드와 해당 AT들을 선택한다. 또한, 다중 사용자 다이버시티 이득을 증가시키기 위해, 각 AT별로 다수의 선호하는 전송 모드를 피드백하는 확장된 전송 모드 피드백 방식을 제안하였다. 시뮬레이션을 통해 제안한 기술이 시스템의 상향 링크 피드백의 허용된 용량에 따라 최적의 피드백 방식을 선택함으로써 시스템 전송 용량을 상당히 향상시킬 수 있음을 확인하였다. In this paper, coordinated space division multiple access(SDMA) technology is proposed to mitigate inter-cell interference by using partial channel state information in cooperative wireless communications system with limited feedback. Each AT selects an optimal cluster transmission mode and sends it back to a cluster scheduler, and at the cluster scheduler, ATs are scheduled within a AT group with the identical cluster transmission mode, and the optimal transmission mode and the corresponding scheduled ATs are determined to maximize scheduling priority. Also, in order to enhance multiuser diversity gain, an extended transmission feedback method is proposed to feed back multiple preferred cluster transmission modes at each AT. It is shown that the proposed coordinated SDMA scheme outperforms existing noncoordinated SDMA schemes in terms of the average system throughput.

전자파 환경 분야 : MIMO SDMA에 기반한 IMT-Advanced 시스템과 FWA 시스템간의 주파수 공유

강영흥 ( Young Heung Kang ) 한국항행학회 2010 韓國航行學會論文誌 Vol.14 No.6

무선통신시스템간의 주파수 공유는 새로운 기술의 출현 및 스펙트럼 부족으로 인해 중요한 이슈로 되고 있다. WRC-07에서 향후 4세대 이동통신(4G) 또는 IMT-Advanced 시스템을 위해 기존의 고정무선억세스(FWA) 시스템과 co-primary 기반으로 3400-3600MHz 대역을 할당함으로써 동일 주파수 대역에서 두 시스템간의 간섭문제 및 주파수 공유 문제 분석이 필요한 실정이다. 이에 본 논문에서는 셀룰러 이동통신 시스템에기반한 FWA 및 IMT-Advanced 시스템에서 다수의 기지국들에 의한 간섭 대 잡음전력비(I/N)를 구하여 간섭기준에 의한 최소 서비스 커버리지 분리거리를 파라미터로 두 시스템간의 주파수 공유기준을 제시한다. 특히 최악의 간섭 시나리오에서 비현실적인 서비스 커버리지 분리거리를 IMT-Advanced 기지국에 MIMO SDMA 기술을 적용함으로써 I/N 값을 획기적으로 개선시켜 향후 적절한 분리거리로 두 시스템의 주파수 공유가 가능함을 보인다. Spectrum sharing between wireless systems becomes a critical issue due to emerging new technologies and spectrum shortage. Since WRC-07 allocated 3400-3600MHz band for the coming fourth generation (4G) or IMT-Advanced on a co-primary basis along with existing Fixed Wireless Access (FWA), it requires spectrum sharing studies to solve the interference problems between two systems. In this paper, I propose the separation distance between service coverages as a sharing fundamental criterion based on the interference to noise power ratio (I/N) received in a FWA base station from several IMT-Advanced base stations on the cellular systems. Especially, some results imply that I/N values compared to the worst case can be greatly reduced with MIMO SDMA interference mitigation technique of IMT-Advanced base stations so that these two systems can co-exist in the same frequency with appropriate separation distance.

Codebook-Based Precoding for SDMA-OFDMA with Spectrum Sharing

조한신 한국전자통신연구원 2011 ETRI Journal Vol.33 No.6

This paper focuses on codebook-based precoding for space-division multiple access/orthogonal frequency-division multiple access (SDMA-OFDMA) systems aiming to guarantee high throughput for their users as well as to mitigate interference to fixed satellite service (FSS). A systematic design of SDMA codebook for subband-based OFDMA is proposed, which forms multiple orthogonal beams with common spatial null in the direction of a victim FSS earth station (ES). The design enables both transmitter and receiver to independently construct identical codebook by sharing only on the direction angle of an FSS ES, which takes fewer overhead bits than Gram-Schmidt process, a general method satisfying our design criterion. A system-level throughput evaluation shows that the proposed precoding provides superior performance over existing spectrum sharing method, that is, subband deactivation. The spectrum sharing analysis shows that the proposed precoding, even with an estimation error of the direction angles of an FSS ES, causes lower interference than existing precoding, knockdown precoding.

Hybrid SNR‐Adaptive Multiuser Detectors for SDMA‐OFDM Systems

Uğur Yeşilyurt,Özgür Ertuğ 한국전자통신연구원 2018 ETRI Journal Vol.40 No.2

Multiuser detection (MUD) and channel estimation techniques in space‐division multiple‐access aided orthogonal frequency‐division multiplexing systems recently has received intensive interest in receiver design technologies. The maximum likelihood (ML) MUD that provides optimal performance has the cost of a dramatically increased computational complexity. The minimum mean‐squared error (MMSE) MUD exhibits poor performance, although it achieves lower computational complexity. With almost the same complexity, an MMSE with successive interference cancellation (SIC) scheme achieves a better bit error rate performance than a linear MMSE multiuser detector. In this paper, hybrid ML‐MMSE with SIC adaptive multiuser detection based on the joint channel estimation method is suggested for signal detection. The simulation results show that the proposed method achieves good performance close to the optimal ML performance at low SNR values and a low computational complexity at high SNR values.

OFDM/SDMA 기반 셀룰러 시스템에서 다양한 트래픽 데이터를 지원하기 위한 하향링크 자원할당 알고리즘

허주,박성호,장경희,이희수,안재영,Heo Joo,Park Sung-Ho,Chang Kyung-Hi,Lee Hee-Soo,Ahn Jae-Young 한국통신학회 2006 韓國通信學會論文誌 Vol.31 No.3A

최근에 OFDM 기반 셀룰러 시스템의 Throughput 및 셀 커버리지를 향상시키기 위하여 SDMA(Spatial Division Multiple Access) 방식을 적용하는 자원 할당 방식에 대한 연구가 시작되고 있으나, 대부분의 OFDM/SDMA 기반 자원 할당 방식에 대한 연구는 시스템 Throughput 만을 최적화시키거나 단일 셀 환경에서만 적응이 가능한 한계가 있다. 본 논문에서는 사용자가 요구하는 트래픽 특성에 맞는 High Layer QoS(Quality of Service) 파라미터를 고려하면서, 시스템의 Throughput의 손실을 최소화하고 인접 셀 간 간섭을 고려하여 다중 셀 환경에서도 적용이 가능한 하향 링크 OFDM/SDMA 기반 자원할당 알고리즘을 제안하고, Ped A 및 다중 안테나 채널모델인 SCME (Spatial Channel Model Extensions) 채널에서 제안된 알고리즘 성능을 분석한다. Recently, researches about downlink resource allocation algorithms applying SDMA to enhance the system throughput and cell coverage have begun. Most OFDM/SDMA based resource allocation algorithms have some limitations such that those only concentrate on maximizing the system throughput or can be applied in single cell environment. In this paper, we propose an OFDM/SDMA based downlink resource allocation algorithm which considers high layer QoS parameters suitable for the required data traffic and it also minimizes the system throughput loss and considers inter-cell interference from adjacent cells. so it can be adopted in multi-cell environment. We manifest the performance of the proposed algorithm in Ped A and SCME MIMO Channel Model.

Spectrum Sharing SDMA with Limited Feedback: Throughput Analysis

( Han-shin Jo ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.12

In the context of effective usage of a scarce spectrum resource, emerging wireless communication standards will demand spectrum sharing with existing systems as well as multiple access with higher spectral efficiency. We mathematically analyze the sum throughput of a spectrum sharing space-division multiple access (SDMA) system, which forms a transmit null in the direction of other coexisting systems while satisfying orthogonal beamforming constraints. For a large number of users , the SDMA throughput scales as log N at high signal-to-noise ratio (SNR) ((J-1 ) at loglog N at normal SNR), where J is the number of transmit antennas. This indicates that multiplexing gain of the spectrum sharing SDMA is times less than that of the non-spectrum sharing SDMA only using orthogonal beamforming, whereas no loss in multiuser diversity gain. Although the spectrum sharing SDMA always has lower throughput compared to the non-spectrum sharing SDMA in the non-coexistence scenario, it offers an intriguing opportunity to reuse spectrum already allocated to other coexisting systems.