Browsing by Author "Lee, Lung-Sheng"

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A dynamic MBS zone framework for cost-effective inter-MBS zone handover in WiMAX networks
(2016-04)
Lee, Lung-Sheng
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Wang, Kuochen
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Hsu, Yi-Huai
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資訊工程學系
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Department of Computer Science
To synchronize multicast broadcast service (MBS) zone data transmissions, the WiMAX standard defines a coordination mechanism to coordinate data transmissions over the WiMAX network; however, the packet loss recovery procedures, which are parts of the coordination mechanism, enlarge packet transmission latency and packet buffer pool requirement. Therefore, we propose an in-frame control (IFC) scheme to decrease packet error rate and packet retransmission count, so as to reduce the packet transmission latency and packet buffer pool requirement. To support level-2 frame-offset coordination, we also propose a dynamic MBS zone (DMZ) framework that can provide data continuity between any two adjacent MBS zones. Based on the proposed DMZ framework, a seamless dynamic inter-MBS zone handover (called DMZ HO) scheme is proposed to resolve the data discontinuity (or packet loss) problem during inter-MBS zone HO. Compared to the WiMAX standard scheme, the proposed IFC scheme reduces packet error rate and packet retransmission count by 49.8 and 49.73 %, respectively. The proposed DMZ HO scheme also outperforms an overlapping zones (OLZ) scheme in terms of channel occupation time and channel bandwidth consumption (in terms of channel idle ratio). Therefore, by resolving data discontinuity, the proposed DMZ HO scheme is more cost-effective and more feasible in providing smooth multimedia content delivery services without disruption to multiple mobile stations (MSs) during HO, and thus will enhance user experience.
A network assisted fast handover scbeme for IEEE 802.16e networks
(2007)
Lee, Lung-Sheng
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Wang, Kuochen
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資訊工程學系
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Department of Computer Science
The IEEE 802.16e provides QoS for real-time traffic; however, the packet transmission delay due to the handover process is still a big concern. Therefore, a fast handover approach to minimize the blocking time of real-time traffic is necessary for providing QoS. In this paper, we present a novel network architecture for IEEE 802.16e, which is still compatible to the IEEE 802.16e standard. Based on this architecture, a network assisted fast handover scheme (NFHO) is proposed to shorten the handover time. Performance evaluation has shown that our proposed NFHO scheme reduces the service disruption time by 98.2% and 96.8% compared to association levels 1 and 2 / Choi et al. of the IEEE 802.16e, respectively, for scanning just one base station (BS). Our improvements will be even better if scanning more BSs. In addition, the proposed NFHO scheme reduces the service disruption time by 78.4% with five neighbouring BSs scanning compared to Lee et al.
A power efficient MAC protocol for IEEE 802.11 multihop ad hoc networks
(2006)
Wu, Hung-Jui
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Wang, Kuochen
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Lee, Lung-Sheng
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資訊工程學系
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Department of Computer Science
In this paper, we propose a power efficient MAC protocol (PEMP) for IEEE 802.11 multihop ad hoc networks. Most of related work targeted at single hop ad hoc networks. In PEMP, when a node intends to transmit data, it will piggyback a data profile, which includes data size, on ATIM* and ATIM-ACK*. ATIM* and ATIM-ACK* are ATIM and ATIM-ACK with piggybacked data profiles, respectively. In this way, senders and receivers can inform their neighbor nodes of their data profiles. Then, each node calculates its transmission priority according to the collected data profiles. Based on transmission priorities, PEMP can schedule a better transmission sequence to reduce power consumption. By decreasing the idle time in the active state and adjusting the ATIM window dynamically based on network conditions, the power consumption of PEMP is 20% and 10% similar to 30% less than that of DPSM and IEEE 802.11 PSM, respectively. PEMP is applicable to multihop ad hoc networks and can achieve a good tradeoff between power consumption, throughput and delay.
Design and Analysis of a Network-Assisted Fast Handover Scheme for IEEE 802.16e Networks
(2010-02-01)
Lee, Lung-Sheng
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Wang, Kuochen
;
資訊工程學系
;
Department of Computer Science
The IEEE 802.16e standard provides quality of service (QoS) for real-time traffic; however, packet transmission disrupted by the handover (HO) process is still a big concern, particularly when frequent HO is performed by mobile stations (MSs) with high mobility. Therefore, an HO scheme that supports frequent HO and provides short service disruption time (SDT) is necessary for providing QoS to real-time traffic. In this paper, we present a novel network architecture, which complies with the IEEE 802.16e standard, to support seamless frequent HO, particularly for MSs with high mobility. Based on this architecture, a network-assisted fast HO (NFHO) scheme is proposed to shorten SDT during the HO process. By resolving connection identifier (CID) assignment and uplink (UL) timing adjustment issues, the proposed NFHO scheme can restart both the UL and downlink (DL) packet transmissions before the MS proceeds to the HO ranging, which is a unique feature of our scheme. In addition, based on the NFHO scheme, an analytic model has been developed to investigate the expected number of buffered packets, packet loss probability, and SDT during HO. Performance evaluation results show that the NFHO scheme reduces the DL SDT by 75%, compared with the IEEE 802.16e hard HO scheme, and it also reduces the UL SDT by 55.6% and 75% compared with the work of Jiao et al. and the IEEE 802.16e hard HO scheme (also the work of Choi et al.), respectively. In addition, the proposed NFHO scheme has the best performance in terms of expected number of buffered packets and packet loss probability among existing hard HO schemes for the IEEE 802.16e. Furthermore, our analytic model can be integrated into an admission-control policy to guarantee proper QoS for ongoing HO MSs.
Efficient spatial reuse in multi-radio, multi-hop wireless mesh networks
(2007)
Guo, Da-Ren
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Wang, Kuochen
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Lee, Lung-Sheng
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資訊工程學系
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Department of Computer Science
In the paper, we propose a novel scheduling mechanism without modifying the existing IEEE 802.11 MAC, called wireless Radio-Matching Protocol (RMP). It takes account of interferences in wireless mesh networks to achieve maximum spatial reuse by using pre-specified radio transmissions. In contrast with existing random access methods, The RMP adopts decentralized controlled access to avoid nodes from unintentional packet collisions. The RMP adopts a chain topology of bidirectional transmissions, where nodes are spaced so that radios of non-neighboring nodes do not interference with each other. Simulation results indicate that the throughput of RMP is about 30% better than that of Ripple [7] and almost 200% better than that of the IEEE 802.11 DCF. Although RMP achieves higher throughput than Ripple, it still maintains the same delay time and transmission quality, as verified by our simulation results. The RMP achieved a stable throughput and a low end-to-end transmission delay in both CBR and FTP traffic compared to the IEEE 802.11 DCF. In addition, the RMP is simple, easy to implement, and it eliminates the back-off inefficiencies and the collision problem in IEEE 802.11 wireless environments.