• Title/Summary/Keyword: multiuser MIMO-OFDM

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A Channel State Information Feedback Method for Massive MIMO-OFDM

  • Kudo, Riichi;Armour, Simon M.D.;McGeehan, Joe P.;Mizoguchi, Masato
    • Journal of Communications and Networks
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    • v.15 no.4
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    • pp.352-361
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    • 2013
  • Combining multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) with a massive number of transmit antennas (massive MIMO-OFDM) is an attractive way of increasing the spectrum efficiency or reducing the transmission energy per bit. The effectiveness of Massive MIMO-OFDM is strongly affected by the channel state information (CSI) estimation method used. The overheads of training frame transmission and CSI feedback decrease multiple access channel (MAC) efficiency and increase the CSI estimation cost at a user station (STA). This paper proposes a CSI estimation scheme that reduces the training frame length by using a novel pilot design and a novel unitary matrix feedback method. The proposed pilot design and unitary matrix feedback enable the access point (AP) to estimate the CSI of the signal space of all transmit antennas using a small number of training frames. Simulations in an IEEE 802.11n channel verify the attractive transmission performance of the proposed methods.

A New Multiuser Receiver for the Application Of Space-time Coded OFDM Systems

  • Pham, Van-Su;Le, Minh-Tuan;Mai, Linh;Lee, Jae-Young;Yoon, Gi-Wan
    • Journal of information and communication convergence engineering
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    • v.4 no.4
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    • pp.151-154
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    • 2006
  • In this work, a novel optimal multiuser detection (MUD) approach, which not only achieves the optimal maximum-likelihood (ML)-like performance but also has reasonably low computational complexity, for Space-time coded OFDM (ST-OFDM) systems is presented. In the proposed detection scheme, the signal model is firstly re-expressed into linearly equivalent one. Then, with the linearly equivalent signal model, a new jointly MUD algorithm is proposed to detect signals. The ML-like bit-error-rate (BER) performance and reasonably low complexity of the proposed detection are verified by computer simulations.

A QoS-aware Scheduling Algorithm for Multiuser Diversity MIMO-OFDM System (다중 사용자 MIMO-OFDM 시스템에서의 QoS 제공을 위한 스케줄링 기법)

  • An Se-Hyun;Yoo Myung-Sik
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.7A
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    • pp.717-724
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    • 2006
  • In order to maximize the throughput and provide the fairness between users in MIMO-OFDM system, FATM(fairness-aware throughput maximization) scheduling algorithm was proposed. In this paper, a QoS-aware scheduling algorithms for MINO-OFDM system are proposed, each of which is based on FATM. These scheduling algorithms aim to satisfy the different service requirements of various service classes. Three proposed QoS scheduling algorithms called SPQ (Strict Priority Queueing), DCBQ (Delay Constraint Based Queuing), HDCBQ (Hybrid Delay Constraint Based Queuing) are compared through computer simulations. It is shown that HDCBQ algorithm outperforms other algorithms in satisfying different requirements of various service classes.

A Multi-Dimensional Radio Resource Scheduling Scheme for MIMO-OFDM Wireless Systems

  • Li, Lei;Niu, Zhisheng
    • Journal of Communications and Networks
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    • v.8 no.4
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    • pp.401-409
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    • 2006
  • Orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO) technologies provide additional dimensions of freedom with spectral and spatial resources for radio resource management. Multi-dimensional radio resource management has recently been identified to exploit the full dimensions of freedom for more flexible and efficient utilization of scarce radio spectrum while provide diverse quality of service (QoS) guarantees. In this work, a multi-dimensional radio resource scheduling scheme is proposed to achieve above goals in hybrid orthogonal frequency division multiple access (OFDMA) and space division multiple access (SDMA) systems. Cochannel interference (CCI) introduced by frequency reuse under SDMA is eliminated by frequency division and time division between highly interfered users. This scheme maximizes system throughput subjected to the minimum data rate guarantee. for heterogeneous users and transmit power constraint. By numerical examples, system throughput and fairness superiority of the our scheduling scheme are verified.

Performance of MIMO MC-CDMA systems combining multi-beamforming algorithm with space-time coding (적응 다중 빔형성 기법과 시공간 부호가 결합된 MIMO MC-CDMA시스템의 성능)

  • Kim, Chan Kyu
    • Journal of the Institute of Electronics and Information Engineers
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    • v.50 no.8
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    • pp.53-60
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    • 2013
  • In this paper, the new multi-beamforming is proposed for Multiple-input multiple-output (MIMO) Multicarrier-Code division multiple access(MC-CDMA) systems to overcome the decrease of performance due to multiuser interference and multiple-antenna interference. Installing the number of multi-beamformer which is equal to the number of multi-transmitter antennas and exploiting the proposed approach at the receiver of MIMO MC-CDMA, the multi-beams are formed toward each multi-antenna of desired user and null beam are formed to other interference. Therefore, the performance of MIMO MC-CDMA system is improved as removing the interference signal. BER performance improvement is investigated through computer simulation by the proposed approach to MIMO MC-CDMA system.

Enhanced Bit-Loading Techniques for Adaptive MIMO Bit-Interleaved Coded OFDM Systems (적응 다중 안테나 Bit-Interleaved Coded OFDM 시스템을 위한 향상된 Bit-Loading 기법)

  • Cho, Jung-Ho;Sung, Chang-Kyung;Moon, Sung-Hyun;Lee, In-Kyu
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.2
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    • pp.18-26
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    • 2009
  • When channel state information (CSI) is available at the transmitter, the system throughput can be enhanced by adaptive transmissions and opportunistic multiuser scheduling. In this paper, we consider multiple-input multiple-output (MIMO) systems employing bit-interleaved coded orthogonal frequency division multiplexing (BIC-OFDM). We first propose a bit-loading algorithm based on the Levin-Campello algorithm for the BIC-OFDM. Then we will apply this algorithm to the MIMO system with a finite set of constellations, by reassigning residual power on each stream Simulation results show that proposed bit-loading scheme which takes the residual power into account improves the system performance especially at high signal-to-noise ratio (SNR) range.

Adaptive Multi-Antenna Channel Estimation Scheme for Uplink Multiuser Environments (다중사용자 상향링크 환경을 위한 적응형 다중안테나 채널추정 기법)

  • Kim, Kyung Jun;Choi, Kyung Jun;Lee, Jinnyeong;Kim, Kwang Soon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.7
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    • pp.1293-1295
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    • 2015
  • In this letter, an adaptive multi-antenna channel estimation scheme is proposed for uplink multiuser environments such as LTE-A systems to accurately estimate time-varying channels within an affordable complexity. It is confirmed that the proposed channel estimator can achieve accurate channel tracking performance even when various time-varying channel environments and traffic patterns are provided.

Scheduling Algorithm for Multiuser MIMO-OFDM System (MMSE-SIC 기반 상향링크 다중 사용자 MIMO-OFDM 시스템에서 공정한 스케줄링 기법)

  • Lee, Pan-Hyung;Lee, Jae-Hong
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2008.11a
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    • pp.91-94
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    • 2008
  • 본 논문에서는 준 정적(quasi-static) 레일레이 페이딩(Rayleigh fading) 채널에서 상향링크 다중 사용자 MIMO-OFDM 시스템을 위한 최소평균제곱오차-순차간섭제거(MMSE-SIC: Minimum mean square error-successive interference cancellation) 수신기에 대해 연구한다. 송신 안테나가 하나인 사용자와 수신 안테나가 다수인 기지국에서 MMSE-SIC 수신기를 기반으로 신호를 검출하는 시스템에서는 하나의 부대역 내에서 동시에 전송 가능한 사용자의 수가 기지국에서의 수신안테나 수보다 작아야 하는 제한 조건을 가지고 있다. 따라서 사용자간 공정성을 보장하고 시스템의 효율성을 높이기 위해 낮은 복잡도를 가지는 비례 공정(Proportional fair) 스케줄링 알고리즘을 제안한다. 제안된 비례 공정 스케줄링 알고리즘에서는 부대역 내에서 다중 사용자 채널 행렬을 기반으로 동시에 전송하는 사용자들의 집합을 찾는다. 평균 채널 이득이 사용자마다 다른 환경에서의 모의실험을 통해 제안된 비례 공정 스케줄링 기법의 성능을 알아본다. 제안된 비례 공정 스케줄링 기법은 기존의 공정성을 기반으로 하는 스케줄링 알고리즘보다 더 큰 일반 비례 공정(General proportional fair) 기준과 더 높은 셀 수율(Cell throughput)을 가지는 것을 보이고 있다.

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A Tradeoff of Multiplexing Gain and Pilot Overhead in Multi-User OFDM Virtual MIMO Uplink Systems (상향링크 다중 사용자 기반 가상적 MIMO-OFDM 시스템의 파일럿 오버헤드와 다중화 이득의 트레이드오프)

  • Ran, Rong;Cho, Sung-Yoon;Kim, Yo-Han;Kim, Dong-Ku
    • Journal of Advanced Navigation Technology
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    • v.12 no.5
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    • pp.437-443
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    • 2008
  • In this paper, we derive the optimum number of users which can maximize the information theoretic sum capacity in multiuser OFDM virtual MIMO uplink system. In which, there are multiple antennas at the base station and a number of users with single transmit antenna. Pilot-assisted channel state estimation is assumed for a block fading channel and time-varying fading channel. We analyze the tradeoff between the multiplexing gain and pilot overhead especially in low SNR regime and conclude that the optimum number of users is min ($N_r$,LT/2 ) in frequency nonselective block fading channel and approximately equal to min ($N_r$, ${\lfloor}{\sqrt{LT+1}}-1{\rfloor}$) in time varying fading channel. assuming the same pilot and signal pwoer.

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