• Title/Summary/Keyword: Multiuser communication

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Two-Way Relaying-Based Two-Hop Two-User Multiple-Input Multiple-Output System

  • Cho, Young Seek;Choi, Seyeong
    • Journal of information and communication convergence engineering
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    • v.12 no.2
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    • pp.67-74
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    • 2014
  • In multi-hop communication systems, two-way relaying is one of the solutions to mitigate the spectral efficiency loss caused by a half-duplex transmission. In this paper, a simple two-way relaying scheme is proposed for two-hop two-user multiple input multiple output (MIMO) systems. In the proposed system, a base station and a relay station (RS), both equipped with two antennas, form a point-to-point MIMO channel, while the RS and two single-antenna mobile users form a point-to-multipoint multiuser (MU)-MIMO channel. Numerical examples show that the proposed system achieves a significant sum rate gain as compared to a one-way relaying system as the distance between a relay and the two users decreases. We also show that although we can expand the proposed scheme to more than two users, its performance gain as compared to that of one-way relaying decreases with an increase in the number of users.

A Compressed Sensing-Based Signal Recovery Technique for Multi-User Spatial Modulation Systems (다중사용자 공간변조시스템에서 압축센싱기반 신호복원 기법)

  • Park, Jeonghong;Ban, Tae-Won;Jung, Bang Chul
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39A no.7
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    • pp.424-430
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    • 2014
  • In this paper, we propose a compressed sensing-based signal recovery technique for an uplink multi-user spatial modulation (MU-SM) system. In the MU-SM system, only one antenna among $N_t$ antennas of each user becomes active by nature. Thus, this characteristics is exploited for signal recovery at a base station. We modify the conventional orthogonal matching pursuit (OMP) algorithm which has been widely used for sparse signal recovery in literature for the MU-SM system, which is called MU-OMP. We also propose a parallel OMP algorithm for the MU-SM system, which is called MU-POMP. Specifically, in the proposed algorithms, antenna indices of a specific user who was selected in the previous iteration are excluded in the next iteration of the OMP algorithm. Simulation results show that the proposed algorithms outperform the conventional OMP algorithm in the MU-SM system.

Efficient Cognitive and Cooperative Communication Scheme for Multiuser OFDMA Systems using Relays (중계기를 사용하는 다중 사용자 OFDMA 시스템을 위한 효율적인 인지 협력 통신 기법)

  • Kang, Min-Gyu;Sang, Young-Jin;Ko, Byung-Hoon;Kim, Kwang-Soon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.3A
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    • pp.235-243
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    • 2009
  • In this paper, we investigate the cognitive and cooperative communication scheme to improve the spectral efficiency in multiuser OFDMA systems using wireless relays. First, we propose the frame structure in which the efficient frequency reuse scheme with the cognitive technique is performed to increase the system throughput. And in the case where the THP (Tomlinson-Harashima preceding) is used for the elimination of interference from the relay, we derive the effective signal to noise ratio of the link largely affected by the channel quantization error. From the system level simulation results, it is shown that the proposed cognitive and cooperative communication scheme increases the overall system performance including the feedback overhead.

Performance Analysis of UWB Communication System for Multiuser Communition (다중 사용자 통신을 위한 UWB 통신 시스템의 성능평가)

  • 전제훈;이민혁;변건식
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2003.10a
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    • pp.488-491
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    • 2003
  • UWB communication applications is a recent innovation due to high transmission rate and low power emission. There, we analyzed monopulse's characteristics and simulated the performance for various UWB communication applications. we introduced Time-Hopping method and simulated for MAI removal in multi-user communication.

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Multiuser Precoding and Power Allocation with Sum Rate Matching for Full-duplex MIMO Relay (전이중 MIMO 릴레이를 위한 다중 사용자 Precoding 및 Sum Rate 정합 기반 전력 할당 기법)

  • Lee, Jong-Ho;Shin, Oh-Soon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.12C
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    • pp.1020-1028
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    • 2010
  • Relay has attracted great attention due to its inherent capability to extend the service coverage and combat shadowing in next generation mobile communication systems. So far, most relay technologies have been developed under the half-duplex (HD) constraint that prevents relays from transmitting and receiving at the same time. Although half-duplex relay (HDR) is easy to implement, it requires partitioning of resource for transmission and reception, reducing the whole system capacity. In this paper, we propose a multinser precoding and power control scheme with sum rate matching for a full-duplex (FD) multiple-input multiple-output (MIMO) relay. Full-duplex relay (FDR) can overcome the drawback of HDR by transmitting and receiving on the same frequency at the same time, while it is crucial to reduce the effect of self-interference that is caused by its own transmitter to its own receiver. The proposed precoding scheme cancels the self-interference of the FDR as well as to support multiuser MIMO. Moreover, we suggest a power allocation scheme for FD MIMO relay with the constraint that the sum rate of the relay's received data streams is equal to that of the relay's transmit data streams.

Improved Subcarrier Allocation Algorithm for Multiuser OFDM Systems (다중 사용자 OFDM 시스템을 위한 개선된 부반송파 할당 알고리즘)

  • Lee, Jae-Yoon;Yoon, Dong-Weon;Park, Sang-Kyu;Hyun, Kwang-Min
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.44 no.9
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    • pp.9-16
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    • 2007
  • In the multiuser OFDM systems, an efficient resource allocation is necessary in order to provide the service to more users. This paper proposes u improved subcarrier allocation algorithm, satisfying each user's QoS under the limited resources, to maximize total transmission data rate and spectral efficiency. The proposed algorithm is divided into two steps. In the first step, users who are eligible for services are determined by using BER, user's minimum data rate requirement, and channel information. In the second step, first, subcarriers are allocated to users on the basis of channel state. And then, reallocation is fulfilled so that the total transmission data rate is maximized and the least reduction in the overall throughput is caused.

A Hybrid Multiuser Detection Algorithm for Outer Space DS-UWB Ad-hoc Network with Strong Narrowband Interference

  • Yin, Zhendong;Kuang, Yunsheng;Sun, Hongjian;Wu, Zhilu;Tang, Wenyan
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.5
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    • pp.1316-1332
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    • 2012
  • Formation flying is an important technology that enables high cost-effective organization of outer space aircrafts. The ad-hoc wireless network based on direct-sequence ultra-wideband (DS-UWB) techniques is seen as an effective means of establishing wireless communication links between aircrafts. In this paper, based on the theory of matched filter and error bits correction, a hybrid detection algorithm is proposed for realizing multiuser detection (MUD) when the DS-UWB technique is used in the ad-hoc wireless network. The matched filter is used to generate a candidate code set which may contain several error bits. The error bits are then recognized and corrected by an novel error-bit corrector, which consists of two steps: code mapping and clustering. In the former step, based on the modified optimum MUD decision function, a novel mapping function is presented that maps the output candidate codes into a feature space for differentiating the right and wrong codes. In the latter step, the codes are clustered into the right and wrong sets by using the K-means clustering approach. Additionally, in order to prevent some right codes being wrongly classified, a sign judgment method is proposed that reduces the bit error rate (BER) of the system. Compared with the traditional detection approaches, e.g., matched filter, minimum mean square error (MMSE) and decorrelation receiver (DEC), the proposed algorithm can considerably improve the BER performance of the system because of its high probability of recognizing wrong codes. Simulation results show that the proposed algorithm can almost achieve the BER performance of the optimum MUD (OMD). Furthermore, compared with OMD, the proposed algorithm has lower computational complexity, and its BER performance is less sensitive to the number of users.

Performance Analysis of Multiuser Detection Scheme for Turbo Encoded DS-CDMA over Rayleigh Fading Channel (레일레이 페이딩 채널에서 터보 부호화 DS-CDMA를 위한 다중 사용자 검출 시스템의 성능 분석)

  • 박재오;이정재
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2000.10a
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    • pp.235-238
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    • 2000
  • In this paper the MUD(Multi-User Detection) schemes and turbo codes are utilized in DS-CDMA mobile communication systems. Theses schemes effectively mitigate the effects of MAI(Multiple Access Interference) and Rayleigh fading. Using Monte Carlo simulation, the performance of the proposed schemes is analyzed for various channel conditions.

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