• Title/Summary/Keyword: Slot Scheduling

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A Weight based GTS Allocation Scheme for Fair Queuing in IEEE 802.15.4 LR-WPAN (IEEE 802.15.4 LR-WPAN 환경에서 공정 큐잉을 위한 가중치 기반 GTS 할당 기법)

  • Lee, Kyoung-Hwa;Lee, Hyeop-Geon;Shin, Yong-Tae
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.9
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    • pp.19-28
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    • 2010
  • The GTS(Guaranteed Time Slot) of the IEEE 802.15.4 standard, which is the contention free access mechanism, is used for low-latency applications or applications requiring specific data bandwidth. But it has some problems such as delay of service due to FIFS(First In First Service) scheduling. In this paper, we proposes a weight based GTS allocation scheme for fair queuing in IEEE 802.15.4 LR-WPAN. The proposed scheme uses a weight that formed by how much more weight we give to the recent history than to the older history for a new GTS allocation. This scheme reduces service delay time and also guarantees transmission simultaneously within a limited time. The results of the performance analysis shows that our approach improves the performance as compared to the native explicit allocation mechanism defined in the IEEE 802.15.4 standard.

Opportunistic Precoding based on Adaptive Perturbation for MIMO Systems (다중입출력 시스템에서 적응형 섭동을 이용한 기회적 프리코딩)

  • Nam, Tae-Hwan;An, Sun-hoe;Lee, Kyungchun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.23 no.12
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    • pp.1638-1643
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    • 2019
  • In this paper, we propose an adaptive-perturbation-aided opportunistic precoding (APOP) scheme for multiple-input multiple-output (MIMO) systems. To update a precoding matrix in MIMO systems, the proposed algorithm produces a random perturbation in each time slot. Then the additional adaptive perturbation is also applied, which depends on the reports of achievable data-rates from users. If the prior random perturbation increased the data rate, the adaptive perturbation is set to be the same as the prior random perturbation, otherwise the negative value of the prior random perturbation is applied for adaptive perturbation. Furthermore, to enhance the achievable data rates, the information on the stored precoding matrices in the memory as well as the currently generated precoding matrix is used for scheduling. Simulation results show that compared to conventional opportunistic precoding schemes, higher data rates are achieved by the proposed APOP scheme, especially when there are a relatively small number of users.