• Title, Summary, Keyword: User scheduling

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Scheduling with Heterogeneous QoS Provisioning for Indoor Visible-light Communication

  • Dong, Xiaoli;Chi, Xuefen;Sun, Hongliang;Zhu, Yuhong
    • Current Optics and Photonics
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    • v.2 no.1
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    • pp.39-46
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    • 2018
  • Visible-light communication (VLC) combined with advanced illumination can be expected to become an integral part of next-generation communication networks. One of the major concerns in VLC implementation is developing resource-allocation schemes in a multi-user scenario. However, the scheduling for heterogeneous quality of service (QoS) traffic has not been studied so far, for the indoor VLC downlink system. In this paper, we creatively introduce effective-bandwidth and effective-capacity theory into the multi-user scheduling (MUS) problem, to guarantee the user's statistical delay QoS. We also take account of the aggregate interference (AI) in the indoor VLC downlink system, and analyze its impact on the user-centric MUS problem for the first time. Simulations show that the AI has a nonnegligible influence on the scheduling result, and that the proposed scheduling scheme could guarantee the user's QoS requirement under the premise of ensuring sum capacity.

Efficient Channel State Feedback Scheme for Opportunistic Scheduling in OFDMA Systems by Scheduling Probability Prediction

  • Ko, Soomin;Lee, Jungsu;Lee, Byeong Gi;Park, Daeyoung
    • Journal of Communications and Networks
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    • v.15 no.6
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    • pp.589-600
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    • 2013
  • In this paper, we propose a new feedback scheme called mode selection-based feedback by scheduling probability prediction (SPP-MF) for channel state feedback in OFDMA downlink system. We design the scheme such that it determines the more desirable feedback mode among selective feedback by scheduling probability prediction (SPP-SF) mode and bitmap feedback by scheduling probability prediction (SPP-BF) mode, by calculating and comparing the throughputs of the two modes. In both feedback modes, each user first calculates the scheduling probability of each subchannel (i.e., the probability that a user wins the scheduling competition for a subchannel) and then forms a feedback message based on the scheduling probability. Specifically, in the SPP-SF mode, each user reports the modulation and coding scheme (MCS) levels and indices of its best S subchannels in terms of the scheduling probability. In the SPP-BF mode, each user determines its scheduling probability threshold. Then, it forms a bitmap for the subchannels according to the scheduling probability threshold and sends the bitmap along with the threshold. Numerical results reveal that the proposed SPP-MF scheme achieves significant performance gain over the existing feedback schemes.

Multi-Parameter Based Scheduling for Multi-user MIMO Systems

  • Chanthirasekaran, K.;Bhagyaveni, M.A.;Parvathy, L. Rama
    • Journal of Electrical Engineering and Technology
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    • v.10 no.6
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    • pp.2406-2412
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    • 2015
  • Multi-user multi-input multi-output (MU-MIMO) system has attracted the 4th generation wireless network as one of core technique for performance enrichment. In this system rate control is a challenging problem and another problem is optimization. Proper scheduling can resolve these problems by deciding which set of user and at which rate the users send their data. This paper proposes a new multi-parameter based scheduling (MPS) for downlink multi-user multiple-input multiple-output (MU-MIMO) system under space-time block coding (STBC) transmissions. Goal of this MPS scheme is to offer improved link level performance in terms of a low average bit error rate (BER), high packet delivery ratio (PDR) with improved resource utilization and service fairness among the user. This scheme allows the set of users to send data based on their channel quality and their demand rates. Simulation compares the MPS performance with other scheduling scheme such as fair scheduling (FS), normalized priority scheduling (NPS) and threshold based fair scheduling (TFS). The results obtained prove that MPS has significant improvement in average BER performance with improved resource utilization and fairness as compared to the other scheduling scheme.

User Scheduling Algorithm Based on Signal Quality and Inter-User Interference for Outage Minimization in Full-Duplex Cellular Networks (전이중 셀룰라 네트워크에서 아웃티지 최소화를 위한 신호 품질과 사용자간 간섭량 기반의 사용자 스케쥴링 알고리즘)

  • Choi, Hyun-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.11
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    • pp.2576-2583
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    • 2015
  • In a full-duplex (FD) wireless cellular network, uplink (UL) users induce the severe inter-user interference to downlink (DL) users. Therefore, a user scheduling that makes a pair of DL user and UL user to use the same radio resource simultaneously influences the system performances significantly. In this paper, we first formulate an optimization problem for user scheduling to minimize the occurrence of outage, aiming to guarantee the quality of service of users, and then we propose a suboptimal user scheduling algorithm with low complexity. The proposed scheduling algorithm is designed in a way where the DL user with a worse signal quality has a higher priority to choose its UL user that causes less interference. Simulation results show that the FD system using the proposed user scheduling algorithm achieves the optimal performance and significantly decreases the outage probability compared with the conventional half-duplex cellular system.

Energy Efficient Transmit and Receive Strategy for Green Communications: K users extension

  • Oh, Changyoon
    • Journal of the Korea Society of Computer and Information
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    • v.21 no.10
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    • pp.37-42
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    • 2016
  • We investigate multi user joint rate scheduling and power allocation problem for a delay sensitive CDMA systems. First, we characterize the existing two user joint rate scheduling and power allocation. We then extend the problem to the case of the multi user systems. In general, there is no simple optimum solution for the multi user scheduling problem. To that end, we propose a sub optimum solution, termed 'virtual user approach'. We show the performance of the virtual user approach to verify the benefit of complexity.

User Scheduling Algorithm for Cell Capacity Maximization in Full Duplexing Wireless Cellular Networks (전이중 무선 셀룰라 네트워크에서 셀 용량 최대화를 위한 사용자 스케쥴링 방식)

  • Choi, Hyun-Ho
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.18 no.11
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    • pp.2613-2620
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    • 2014
  • In this paper, we consider a full duplexing (FD) wireless cellular network where a central base station (BS) works in the FD mode while the downlink (DL) and uplink (UL) users work in the time division duplexing (TDD) mode. Since this FD system induces the inter-user interference from UL user to DL user, the main challenge for maximizing the system performances is user scheduling that makes a pair of DL user and UL user to use the same radio resource simultaneously. We formulate an optimization problem for user pairing to maximize the cell capacity and propose a suboptimal user scheduling algorithm with low complexity. This scheduling algorithm is designed in a way where the DL user with a better signal quality has a higher priority to choose its UL user that causes less interference. Simulation results show that the FD system using the proposed user scheduling algorithm achieves the optimal performance and significantly outperforms the conventional TDD system in terms of the cell capacity.

Packet Scheduling for Cellular Relay Networks by Considering Relay Selection, Channel Quality, and Packet Utility

  • Zhou, Rui;Nguyen, Hoang Nam;Sasase, Iwao
    • Journal of Communications and Networks
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    • v.11 no.5
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    • pp.464-472
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    • 2009
  • In this paper, we propose a packet scheduling algorithm for cellular relay networks by considering relay selection, variation of channel quality, and packet delay. In the networks, mobile users are equipped with not only cellular but also user relaying radio interfaces, where base station exploits adaptive high speed downlink channel. Our proposed algorithm selects a user with good cellular channel condition as a relay station for other users with bad cellular channel condition but can get access to relay link with good quality. This can achieve flexible packet scheduling by adjusting transmission rates of cellular link. Packets are scheduled for transmission depending on scheduling indexes which are calculated based on user's achieved transmission rate, packet utility, and proportional fairness of their throughput. The performance results obtained by using computer simulation show that the proposed scheduling algorithm is able to achieve high network capacity, low packet loss, and good fairness in terms of received throughput of mobile users.

Delay Determination of Cyclic Delay Diversity for Multi-user Scheduling in OFDMA Systems (OFDMA 시스템의 다중 사용자 스케줄링을 위한 순환지연 다이버시티의 지연값 결정)

  • Rim, Min-Joong;Hur, Seong-Ho;Song, Hyun-Joo;Lim, Dae-Woon;Jeong, Byung-Jang;Noh, Tae-Gyun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.3A
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    • pp.248-255
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    • 2008
  • In an OFDMA system the performance of multi-user scheduling in the frequency domain is affected by the frequency selectivity of the channel. If the channel is too flat in the frequency domain, the multi-user scheduling gain might be degraded. On the contrary, if the frequency selectivity is too high and the magnitude of the frequency response severely fluctuates on the allocation bandwidth, it is also hard to get sufficient scheduling gain. For maximizing the multi-user scheduling gain, a cyclic delay diversity technique can be used to adjust the frequency selectivity of the channel. This paper proposes a method to determine the optimal delay value of cyclic delay diversity according to the allocation bandwidth and the channel characteristics.

Performance of Two-User Two-Way Amplify-and-Forward Relaying Systems with Scheduling

  • Fang, Zhaoxi;Li, Guosheng;Li, Jun
    • ETRI Journal
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    • v.33 no.5
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    • pp.689-694
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    • 2011
  • In this paper, we study scheduling schemes for two-user two-way wireless relaying systems. Two transmission modes are considered: point-to-point direct transmission and two-way amplify-and-forward relaying. An optimal scheduling scheme that opportunistically selects the best transmission mode for each user is proposed to minimize the sum bit error rate (BER). The performance lower bound of the optimal scheduling scheme is analyzed, and closed-form expression of the lower-bound BER is derived. However, for optimal scheduling, the scheduler requires the knowledge of channel state information (CSI) of all links. To reduce the feedback information of CSI, we also propose a suboptimal scheduling scheme that selects the transmission mode using only the CSI of two direct links. Simulation results show that there are 4 dB to 8 dB gains for the proposed optimal and suboptimal schemes over the fixed direct transmission and fixed two-way relayed transmission scheme. The performance gap between the optimal and suboptimal scheduling schemes is small, which implies a good trade-off between implementation complexity and system performance.

SLNR-based User Scheduling in Multi-cell networks: from Multi-antenna to Large-Scale Antenna System

  • Li, Yanchun;Zhu, Guangxi;Chen, Hua;Jo, Minho;Liu, Yingzhuang
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.8 no.3
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    • pp.945-964
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    • 2014
  • In this paper, we investigate the performance of Signal to Leakage and Noise Radio (SLNR) based user scheduling in uplink of multi-cell with large-scale antenna system. Large antenna array is desired to improve the performance in future system by providing better beamforming capability. However, some studies have found that the signal channel is 'hardened' (becomes invariant) when the antenna number goes extremely large, which implies that the signal channel aware user scheduling may have no gain at all. With the mathematic tool of order statistics, we analyzed the signal and interference terms of SLNR in a homogeneous multicell network. The derived distribution function of signal and interference shows that the leakage channel's variance is much more influential than the signal channel's variance in large-scale antenna regime. So even though the signal channel is hardened, the SLNR-based scheduling can achieve remarkable multiuser diversity (MUD) gain due to the fluctuation of the uplink leakage channel. By providing the final SINR distribution, we verify that the SLNR-based scheduling can leverage MUD in a better way than the signal channel based scheduling. The Monte Carlo simulations show that the throughput gain of SLNR-based scheduling over signal channel based scheduling is significant.