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Author: search.filters.author.Liu, Chia-LungSubject: search.filters.subject.resource allocation

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Now showing 1 - 4 of 4
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    Window-Based Frequency-Domain Packet Scheduling With QoS Support in LTE Uplink
    (2013-01-01)
    Hsu, Lung-Han
    ;
    Chao, Hsi-Lu
    ;
    Liu, Chia-Lung
    ;
    資訊工程學系
    ;
    Department of Computer Science
    Due to the power consumption issue of user equipment (UE), Single-Carrier FDMA (SC-FDMA) has been selected as the uplink multiple access scheme of 3GPP Long Term Evolution (LTE). Similar to OFDMA downlink, SC-FDMA enables multiple UEs to be served simultaneously in uplink as well. However, the single carrier characteristic requires that all the allocated subcarriers to a UE must be contiguous in frequency with each time slot. Moreover, a UE should adopt the same modulation and coding scheme at all allocated subcarriers. These two constraints do limit the scheduling flexibility. In this paper, we formulate the UL scheduling problem with proportional fairness support by taking two constraints into consideration. Since this optimization had been proven to be an NP-hard problem, we further develop one heuristic algorithm. We demonstrate that competitive performance can be achieved in terms of system throughput, which is evaluated by using 3GPP LTE system model simulations.
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    Multi-User MIMO Scheduling in LTE-Advanced Uplink Systems
    (2013-01-01)
    Hsu, Lung-Han
    ;
    Chao, Hsi-Lu
    ;
    Liu, Chia-Lung
    ;
    Huang, Kuei-Li
    ;
    資訊工程學系
    Due to the facts of wireless data usage being increasing faster now than ever before and more multimedia content being generated by users and uploaded to the network, multi-user MIMO (MU-MIMO) technology would be crucial to improve the LTE-A uplink spectral efficiency for meeting the service demands. On the other side, adopting clustered SC-FDMA technology as the uplink multiple access scheme of LTE-A means that a User Equipment (UE) can be allocated more than one cluster which consists of contiguous RBs (this is the contiguity constraint). Moreover, all allocated RBs to a UE must use the same modulation and coding scheme (this is the robust rate constraint). The two constraints make MU-MIMO UL scheduling more complicated. In this paper, we formulate the MU-MIMO UL scheduling problem with taking two constraints into consideration. Since this optimization had been proven to be an NP-hard problem, we further develop two low-complexity heuristic algorithms. We demonstrate that competitive performance can be achieved in terms of system throughput and fairness index.
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    A Novel Channel-Aware Frequency-Domain Scheduling in LTE Uplink
    (2013)
    Chao, Hsi-Lu
    ;
    Chang, Chia-Kai
    ;
    Liu, Chia-Lung
    ;
    資訊工程學系
    ;
    Department of Computer Science
    Due to the power consumption issue of user equipment (UE), Single-Carrier FDMA (SC-FDMA) has been selected as the uplink multiple access scheme of 3GPP Long Term Evolution (LTE). Similar to OFDMA downlink, SC-FDMA enables multiple UEs to be served simultaneously in uplink as well. However, the single carrier characteristic requires that all the allocated subcarriers to a UE must be contiguous in frequency with each time slot. Moreover, a UE should adopt the same modulation and coding scheme at all allocated subcarriers. These two constraints do limit the scheduling flexibility. In this paper, we formulate the UL scheduling problem with taking two constraints into consideration. Since this optimization had been proven to be an NP-hard problem, we further develop a heuristic algorithm with low complexity. We demonstrate that competitive performance can be achieved in terms of system throughput, which is evaluated by using 3GPP LTE system model simulations.
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    Item type:Item,
    Sum Throughput-Improved Resource Allocation for LTE Uplink Transmission
    (2011)
    Chang, Ching-Hsu
    ;
    Chao, Hsi-Lu
    ;
    Liu, Chia-Lung
    ;
    資訊工程學系
    ;
    Department of Computer Science
    Long Term Evolution (LTE) is a promising technology for 4G mobile networks. Due to utilize OFDMA in downlink and SC-FDMA in uplink, the LTE system is expected to provide significantly high throughput with 20 MHz spectrum allocation. To increase the cell throughput and multi-user diversity gain, channel dependent scheduling (CDS) is implemented for the OFDMA-based multi-user scenario to allocate resource blocks (RBs) to users experiencing better channel conditions. Nevertheless, CDS may not perform well in SC-FDMA due to its two inherent constraints - one is contiguous RB assignment and the other is robust modulation and coding mode. In this paper, the formulation of resource allocation for a SC-FDMA system upon considering two inherent constraints is proposed. Since the optimization problem of resource allocation in SC-FDMA is NP-hard, we further propose two heuristic algorithms to find feasible solutions. We evaluate the proposed formulation and heuristic algorithms by conducting simulation. The simulation results show that our methods achieve significant performance improvement not only in system sum throughput but also in transmission delay.