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Subject: search.filters.subject.IEEE 802.16

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Now showing 1 - 10 of 16
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    Adaptive point-to-point communication approach for subscriber stations in broadband wireless networks
    (2011-01-01)
    Hsu, Chung-Hsien
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    Feng, Kai-Ten
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    電機工程學系
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    Department of Electrical and Computer Engineering
    The point-to-multipoint (PMP) mode is considered the well-adopted transmission type that is supported by the IEEE 802.16 standard. The base station (BS) is served as the centralized coordinator to control and forward packets for the subscriber stations (SSs) within the network. In the case that two SSs intend to conduct packet transmission, it is required for the packets to be rerouted to the BS before arriving at the destination SS. The communication bandwidth is apparently wasted due to the rerouting processes. In this paper, an adaptive point-to-point communication (APC) approach is proposed to achieve direct communication between SSs within the PMP mode of the IEEE 802.16 standard. The BS is coordinating and arranging specific time intervals for the two SSs that are actively involved in packet transmission. Based on channel conditions among the BS and the SSs, the packet transmission operation is switched between direct communication and indirect communication in the APC approach. Both the architectural design and analytical modeling of the proposed scheme are conducted in this paper. The effectiveness of the proposed APC approach in terms of user throughput and its corresponding overhead can be observed via both the analytical and simulation results.
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    Simple and Regular Mini-Slot Scheduling for IEEE 802.16d Grid-based Mesh Networks
    (2010)
    Liang, Jia-Ming
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    Chen, Jen-Jee
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    Wu, Ho-Cheng
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    Tseng, Yu-Chee
    ;
    資訊工程學系
    This work addresses the mini-slot scheduling problem in IEEE 802.16d wireless mesh networks (WMNs). A practical mini-slot scheduling needs to take into account following issues: the transmission overhead, the scheduling complexity, and the signaling overhead to notify the scheduling results to subscriber stations. We focus in a grid-based WMN, which is the most recommended topology due to its high capacity and connectivity. In this paper, we propose scheduling schemes featured by low complexity and low signaling overhead. The proposed schemes help find periodical and regular schedules, which can balance between transmission overhead and pipeline efficiency. They can achieve near-optimal transmission latencies. Simulation results show that our schemes outperform other schemes, especially when the network size is larger.
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    A Low-Latency Scanning with Association Mechanism for Real-Time Communication in Mobile WiMAX
    (2012-10-01)
    Chen, You-Lin
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    Tsao, Shiao-Li
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    資訊工程學系
    ;
    Department of Computer Science
    In Mobile WiMAX, a mobile station (MS) scans neighboring base stations (BSs) before conducting handover. The MS may perform the association further, i.e., initial ranging, with neighboring BSs during scanning to obtain ranging parameters and/or service availability information for a potential handover to a BS and/or the selection of target BSs. However, the scanning with association scheme may introduce additional latency for handover. This study first evaluates the conventional scanning with association process, and then proposes a mechanism to reduce the association latency. The performance models of the proposed mechanism are presented and the accuracies of analytical models are verified by simulations. Results demonstrate that the proposed mechanism reduces the association latency by 61.9%-78.0% for audio services and 41.3%-65.4% for video services.
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    Managing Power Saving Classes in IEEE 802.16 Wireless MANs: A Fold-and-Demultiplex Method
    (2011-09-01)
    Tseng, Yu-Chee
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    Chen, Jen-Jee
    ;
    Yang, Yen-Chih
    ;
    資訊工程學系
    ;
    Department of Computer Science
    In IEEE 802.16, power management at the Mobile Subscriber Station (MSS) side is always an important issue. The standard defines three types of power saving classes (PSCs). A PSC can bind one or multiple traffic flows. However, given multiple flows in an MSS, the standard does not define how to form PSCs, how to organize the cooperation of multiple PSCs to obtain better energy efficiency, and how to guarantee QoS of these flows. Given a set of flows and their QoS parameters, the objective of this paper is to define multiple PSCs and their listen-and-sleep-related parameters and packet-scheduling policy such that the unavailability intervals of the MSS can be maximized and the QoS of each flow can be guaranteed. To achieve this, we propose a novel fold-and-demultiplex method for an IEEE 802.16 network with PSCs of types I and II together with an earliest-next-bandwidth-first packet scheduler. Given a set of traffic flows in an MSS, the fold-and-demultiplex method first gives each flow a tentative PSC satisfying its bandwidth requirement. Then we fold them together into one long series so as to calculate the total bandwidth requirement. Finally, we demultiplex the series into multiple PSCs, each supporting one or multiple flows. It ends up with high energy efficiency of MSSs while meets flows' bandwidth requirements. Furthermore, our packet scheduler ensures that real-time flows' delay constraints can be met. To the best of our knowledge, this is the first result offering bounded packet delays under MSS's sleep-and-listen behaviors.
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    On the performances of IEEE 802.16(d) mesh CDS-mode networks using Single-Switched-Beam Antennas
    (2012-03-16)
    Lin, Chih-Che
    ;
    Wang, Shie-Yuan
    ;
    Hsu, Teng-Wei
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    資訊工程學系
    ;
    Department of Computer Science
    The IEEE 802.16(d) mesh coordinated distributed scheduling (CDS) mode is a novel technology for future fixed wireless backbone networks and designed for the use of omnidirectional antennas. The use of Single-Switched-Beam Antennas (SSBAs) may have great potential to increase network capacity due to the antenna directivity. However, a network designed for omnidirectional antennas usually cannot operate well or achieve good performance with the presence of antenna directivity. In this paper, we review the designs of the IEEE 802.16 mesh CDS-mode network, study the issues of this network with the use of Single-Switched-Beam Antennas (SSBAs), and propose a complete solution to solve these issues. The performances of our proposed scheme is evaluated using simulations. The simulation results show that our proposed scheme can effectively solve the issues of using SSBAs in the IEEE 802.16 mesh CDS-mode network and greatly increase its network capacity. (C) 2011 Elsevier B.V. All rights reserved.
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    On Tile-and-Energy Allocation in OFDMA Broadband Wireless Networks
    (2011-12-01)
    Liang, Jia-Ming
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    Chen, Jen-Jee
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    Liu, Cheng-Wen
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    Tseng, Yu-Chee
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    Lin, Bao-Shuh Paul
    The Orthogonal Frequency Division Multiple Access (OFDMA) technique has been widely applied in broadband wireless networks, such as IEEE 802.16 (WiMAX) and 3GPP Long Term Evolution (LTE). Existing studies have targeted at improving network throughput by increasing the transmission rates of mobile stations (MSs). Nevertheless, this is at the cost of higher energy consumption of MSs. In the letter, we consider the tile-and-energy joint allocation problem for uplink transmissions in an OFDMA wireless network. We formulate this problem as a mixed integer programming, where the objective is to minimize MSs' energy consumption subject to satisfying their traffic demands. We show this to be NP-hard and develop a heuristic taking advantage of the water-filling technique. Simulation results show that the performance of our heuristic is close to the optimum, especially when the network is under non-saturated condition.
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    Per-flow sleep scheduling for power management in IEEE 802.16 wireless networks
    (2011-11-10)
    Chen, Jen-Jee
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    Wu, Shih-Lin
    ;
    Wang, Shiou-Wen
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    Tseng, Yu-Chee
    ;
    資訊工程學系
    Power management is a critical issue in IEEE 802.16 wireless networks. In the standard, a power saving class (PSC) of type II is defined to support real-time traffic flows. It allows a flow to switch periodically between active and sleep states to save energy. However, previous studies either consider adjusting start frames of PSCs by assuming that the PSCs are already given or assume one single PSC to accommodate all flows in a mobile station, thus leading to higher energy cost. This paper proposes two "per-flow" sleep scheduling schemes, which assign one PSC to each real-time flow according to its QoS parameters. This leads to less energy consumption, more efficient use of bandwidth, and more compact listening windows. We also prove that deciding whether a given scheduling problem is solvable can be reduced to a maximum matching problem, which is computationally tractable. Simulation results show that such a per-flow scheduling does perform much closer to the active ratio lower bound and achieve higher resource utilization than previous schemes. (C) 2011 Elsevier B.V. All rights reserved.
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    A Cross-layer Approach of Link Adaptation in IEEE 802.16 Broadband Wireless Access Systems
    (2007)
    Yu, Yu-Ting
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    Chao, Hsi-Lu
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    資訊工程學系
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    Department of Computer Science
    IEEE 802.16 Broadband Wireless Access system (BWA) is a promising emerging technology. In the IEEE 802.16 standard, multiple data transmission rates are defined by employing different modulation and channel coding schemes. How to select a proper mode affects the system performance significantly. In this paper, an efficient link adaptation scheme with QoS support is proposed The proposed scheme takes both QoS demand and channel condition into consideration to determine a proper transmission mode. The QoS demand of a connection is represented as an expected packet error rate (PER). Based on this expected PER, the BS calculates the required signal-to-noise ratio (SNR) threshold of each mode. By comparing the measured SNR and all modes' SNR thresholds, the BS then suggests the SS a proper transmission mode. We evaluate the proposed scheme by simulations. The simulation results show that the link adaptation scheme improves the average system throughput and guarantees each connection's QoS demand
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    An LDPC decoder chip based on self-routing network for IEEE 802.16e applications
    (2008-03-01)
    Liu, Chih-Hao
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    Yen, Shau-Wei
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    Chen, Chih-Lung
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    Chang, Hsie-Chia
    ;
    Lee, Chen-Yi
    An LDPC decoder chip fully compliant to IEEE 802.16e applications is presented. Since the parity check matrix can be decomposed into sub-matrices which are either a zero-matrix or a cyclic shifted matrix, a phase-overlapping message passing scheme is applied to update messages immediately, leading to enhance decoding throughput. With only one shifter-based permutation structure, a self-routing switch network is proposed to merge 19 different sub-matrix sizes as defined in IEEE 802.16e and enable parallel message to be routed without congestion. Fabricated in the 90 nm 1P9M CMOS process, this chip achieves 105 Mb/s at 20 iterations while decoding the rate-5/6 2304-bit code at 150 MHz operation frequency. To meet the maximum data rate in IEEE 802.16e, this chip operates at 109 MHz frequency and dissipates 186 mW at 1.0 V supply.
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    A Cross-Layer Framework for Overhead Reduction, Traffic Scheduling, and Burst Allocation in IEEE 802.16 OFDMA Networks
    (2011-05-01)
    Liang, Jia-Ming
    ;
    Chen, Jen-Jee
    ;
    Wang, You-Chiun
    ;
    Tseng, Yu-Chee
    ;
    資訊工程學系
    IEEE 802.16 orthogonal frequency-division multiple access (OFDMA) downlink subframes have a special 2-D channel-time structure. Allocation resources from such a 2-D structure incur extra control overheads that hurt network performance. Existing solutions try to improve network performance by designing either the scheduler in the medium access control layer or the burst allocator in the physical layer, but the efficiency of overhead reduction is limited. In this paper, we point out the necessity of "codesigning" both the scheduler and the burst allocator to efficiently reduce overheads and improve network performance. Under the partial-usage-of-subcarriers model, we propose a cross-layer framework that covers overhead reduction, real-time and non-real-time traffic scheduling, and burst allocation. The framework includes a two-tier priority-based scheduler and a bucket-based burst allocator, which is more complete and efficient than prior studies. Both the scheduler and the burst allocator are tightly coupled together to solve the problem of arranging resources to data traffic. Given available space and bucket design from the burst allocator, the scheduler can well utilize the frame resource, reduce real-time traffic delays, and maintain fairness. On the other hand, with priority knowledge and resource assignment from the scheduler, the burst allocator can efficiently arrange downlink bursts to satisfy traffic requirements with low complexity. Through analysis, the cross-layer framework is validated to give an upper bound to overheads and achieve high network performance. Extensive simulation results verify that the cross-layer framework significantly increases network throughput, maintains long-term fairness, alleviates real-time traffic delays, and enhances frame utilization.