Po-Han Wu

University of Washington Seattle, Seattle, Washington, United States

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Publications (9)4.15 Total impact

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    ABSTRACT: This paper proposes an adaptive mode and modulation coding switching (AMMCS) scheme for multiple-input multiple-output (MIMO) multicasting system. More specifically, in addition to the adaptively chosen modulation and error coding, two types of MIMO modes are adaptively switched, i.e., between spatial multiplexing (SM) mode, which can achieve higher data rate, and spatial diversity (SD) mode, which can provide higher received signal-to-noise ratio (SNR). Analytical equations for scheduling rate and average spectral efficiency are derived for both SD and SM modes in a 2×2 MIMO system. Simulation results well justify our analytical equations and also demonstrate that our proposed scheme can achieve higher scheduling rate when SNR is low and higher spectral efficiency when SNR is high.
    Circuits and Systems (ISCAS), 2013 IEEE International Symposium on; 01/2013
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    ABSTRACT: H.264/AVC video delivered through erroneous network has been reported weaker to errors when intra-refresh is used in multiple reference frame structure. This paper proposes a new reference selection method to improve this inefficient error resilience.
    Consumer Electronics (ICCE), 2013 IEEE International Conference on; 01/2013
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    ABSTRACT: We propose Opportunistic Layered Multicasting (OLM), a joint user scheduling and resource allocation algorithm that provides enhanced quality and efficiency for layered video multicast over Mobile WiMAX. This work is a lead off and complete synergy of layered video multicasting with opportunistic concept. The target application is characterized by groups of users acquiring popular video programs over a fading channel. To accommodate various bandwidth requirements and device capability, video streams are coded into base and enhancement layers using scalable video coding technology. Correspondingly, the optimization problems, which select the best subset of users to receive a specific video layer and assign the most appropriate modulation and coding scheme for this video layer, are specifically formulated for both video layer types. We also design fast and effective algorithms to bridge the gap between theoretical throughput capacity and implementation concerns. Thus, the basic video quality can be efficiently guaranteed to all subscribers while creating most utility out of limited resources on enhancement information. To overcome the inevitable packet loss in a multicast session, an FEC rate adaptation scheme to approach theoretical performance is also presented. Favorable performance of the proposed algorithms is demonstrated by simulations utilizing realistic Mobile WiMAX parameters.
    IEEE Transactions on Mobile Computing 03/2012; 11:453-463. · 2.40 Impact Factor
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    ABSTRACT: In this paper, a joint uplink (UL) and downlink (DL) framework for wireless mobile camera networks over an OFDMA-based infrastructure is proposed. On the UL, this system collects unicast real-time video streams from mobile wireless camera stations (CSs) and forwards them to a control center. On the DL, the aggregated video streams are multicast to multiple mobile stations (MSs) to facilitate monitoring of the same video scenes. A target bit rate is set for each UL video stream, based on an objective function that includes both the quality of experience (QoE) and popularity of video contents as key criteria. A QoE-driven scheduling and resource allocation policy at the MAC/PHY layers, and a real-time scalable video layer adaptation algorithm in the APP layer are proposed. On the DL, a previously published opportunistic layered multicasting scheduling algorithm is applied. Simulation results demonstrate that this proposed novel architecture can significantly enhance both the spectral efficiency and the QoE of users in both UL and DL directions.
    Circuits and Systems (ISCAS), 2012 IEEE International Symposium on; 01/2012
  • Po-Han Wu, Yu Hen Hu
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    ABSTRACT: A WiMAX radio resource allocation (WRA) problem is investigated in the context of IPTV broadcasting over mobile WiMAX multicast, broadcast services (MBS) channels. The goal is to maximize quality of services, in terms of number of subscribers served, number of IPTV channels carried, and perceived video qualities of individual viewers, subject to constraints on multicast channel capacities and space-time channel quality variations. We present an efficient heuristic algorithm based on the Pareto principle that achieves near-optimal results in polynomial time complexity. Extensive simulations are conducted to compare this new approach against state-of-the-art heuristic algorithms and consistent superior performance has been observed.
    IEEE Transactions on Multimedia 01/2011; 13:1395-1403. · 1.75 Impact Factor
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    Po-Han Wu, Jenq-Neng Hwang
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    ABSTRACT: We propose a systematic cross-layer joint scheduling and resource allocation algorithm to provide enhanced quality of service (QoS) for real-time video uplink of camera networks over WiMAX. Under the constraint of limited available OFDMA resource, how to fairly schedule all mobile camera stations (CSs) with varying channel quality and maintain system performance simultaneously is always a critical issue for practical QoS design of a WiMAX base station (BS). The proposed system uses video encoding rate adaptation in application (APP) layer of CSs and effectively incorporates with the medium access control (MAC) QoS mechanisms of the BSs, without the need of modifying existing 802.16 MAC/PHY standardized protocols, to greatly improve the spectrum efficiency of WiMAX.
    Proceedings of IEEE International Conference on Communications, ICC 2011, Kyoto, Japan, 5-9 June, 2011; 01/2011
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    ABSTRACT: A wireless resource scheduling problem is formulated in the context of IPTV multicasting streaming services over WiMAX channels. The goal is to maximize quality of services, in terms of number of subscribers served, number of IPTV channels carried, and video qualities of individual channels; subject to constraints of finite amount of multicast channel capacities as well as time and spatially varying wireless channel qualities. While a globally optimal solution is NP-hard, we present an efficient heuristic algorithm that exploits the structure of the problem formulation to yield solutions that are very close to the optimal solution.
    Proceedings of the 71st IEEE Vehicular Technology Conference, VTC Spring 2010, 16-19 May 2010, Taipei, Taiwan; 01/2010
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    ABSTRACT: Internet Protocol Television (IPTV) is an emerging and killer application for WiMAX networks, which takes advantage of multicasting mechanisms to efficiently deliver the video data to groups of subscribers. In this paper, we propose a Reception-rate-tracking Opportunistic Multicast Scheduling (ROMS) to enhance the performance of scalable IPTV layered multicasting over WiMAX networks. The proposed ROMS jointly considers the subscriber scheduling and resource allocation to achieve resource efficient multicasting. We validate our solution through theoretical analyses and empirical simulations. Our study indicates that the proposed solution outperforms the Slot-throughput-tracking Opportunistic Multicast Scheduling (SOMS) in terms of resource efficiency for 19.6%-33% in different subscriber group sizes.
    Proceedings of the 71st IEEE Vehicular Technology Conference, VTC Spring 2010, 16-19 May 2010, Taipei, Taiwan; 01/2010
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    ABSTRACT: We propose a resource allocation algorithm that provides enhanced QoS and efficiency for layered video multicast over mobile WiMAX. The application is characterized by groups of users acquiring popular video programs over a fading channel. To accommodate various bandwidth requirements and adaptive perceptual quality to different users, video streams are coded into base and enhancement layers using scalable video coding technology. Correspondingly, the optimization problems, which assign the most appropriate modulation schemes to provide best video quality to as many users, can be formulated using opportunistic multicasting concept. We maximize the minimum effective throughput across all users for mandatory (base) layer delivery through adapting modulation and coding schemes. At the same time, optional (enhancement) layers are allocated to maximize total utility. Thus the basic video quality can be efficiently guaranteed to all subscribers while making most out of limited resources on enhancement information. We further present an FEC rate adaptation scheme to approach theoretical performance. Favorable performance of the proposed algorithms is demonstrated by simulations utilizing realistic Mobile WiMAX parameters.
    Wireless Communications and Networking Conference, 2009. WCNC 2009. IEEE; 01/2009