Sha Hua

Polytechnic Institute of New York University, Brooklyn, New York, United States

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Publications (9)4.15 Total impact

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    ABSTRACT: Cellular networks (e.g., 3G) are currently facing severe traffic overload problems caused by excessive traffic demands. Offloading part of the cellular traffic through other forms of networks, such as Delay Tolerant Networks (DTNs) and WiFi hotspots, is a promising solution. However, since these networks can only provide intermittent connectivity to mobile users, utilizing them for cellular traffic offloading may result in a nonnegligible delay. As the delay increases, the users' satisfaction decreases. In this paper, we investigate the tradeoff between the amount of traffic being offloaded and the users' satisfaction. We provide a novel incentive framework to motivate users to leverage their delay tolerance for cellular traffic offloading. To minimize the incentive cost given an offloading target, users with high delay tolerance and large offloading potential should be prioritized for traffic offloading. To effectively capture the dynamic characteristics of users' delay tolerance, our incentive framework is based on reverse auction to let users proactively express their delay tolerance by submitting bids. We further illustrate how to predict the offloading potential of the users by using stochastic analysis for both DTN and WiFi cases. Extensive trace-driven simulations verify the efficiency of our incentive framework for cellular traffic offloading.
    IEEE Transactions on Mobile Computing 01/2014; 13(3):541-555. · 2.40 Impact Factor
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    ABSTRACT: Recent progress in single channel full-duplex (SC-FD) radio design [1]–[4] has attracted the attention of many researchers. A SC-FD transceiver is capable of transmitting and receiving on the same frequency at the same time, which will have a great impact on the design and performance of current wireless networks that are based on half duplex designs. This paper analyzes the effects of adopting SC-FD enabled base stations in a cellular system with legacy mobile stations. We use a multi-cell analytical model based on stochastic geometry to derive the theoretical performance gain of such a system. To validate the performance using a realistic setting, we conduct extensive simulations for a multi-cell OFDMA system. Both sets of results show that a full-duplex design for a cellular system, while not quite doubling system capacity, does greatly increases capacity over traditional cellular systems. Our results show that the uplink, compared with the downlink, is more susceptible to the extra interference caused by using the same frequency in both directions.
    47th Annual Conference on Information Sciences and Systems (CISS), IEEE; 03/2013
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    ABSTRACT: As cellular operators are suffering from a data explosion problem, and users are consequently experiencing poor data services, the introduction of femtocells offers a cost-effective way to mitigate this problem. Femtocells enable larger network capacity by increasing spatial reuse of the spectrum and shortening the distance to the users. Existing work has shown that open access femtocells, which allow unregistered macro users to connect, are efficient in reducing inter-cell interference and offloading traffic. However, a major obstacle constraining the potential capability of femtocells and open access is the lack of incentives for privately-owned femtocells to serve unregistered users. Hence in this paper, we propose a Vickrey-Clarke-Groves (VCG) auction based incentive framework for accessing such selfish femtocells. We consider two scenarios: One scenario involves a single macro user and another scenario has multiple macro users. We design auction schemes for both scenarios and show analytically that our schemes are truthful and have low computational complexity. Extensive simulations validate these properties and show huge performance improvement to the macro users.
    10/2012;
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    ABSTRACT: As cellular networks are turning into a platform for ubiquitous data access, cellular operators are facing a severe data capacity crisis due to the exponential growth of traffic generated by mobile users. In this work, we investigate the benefits of sharing infrastructure and spectrum among two cellular operators. Specifically, we provide a multi-cell analytical model using stochastic geometry to identify the performance gain under different sharing strategies, which gives tractable and accurate results. To validate the performance using a realistic setting, we conduct extensive simulations for a multi-cell OFDMA system using real base station locations. Both analytical and simulation results show that even a simple cooperation strategy between two similar operators, where they share spectrum and base stations, roughly quadruples capacity as compared to the capacity of a single operator. This is equivalent to doubling the capacity per customer, providing a strong incentive for operators to cooperate, if not actually merge.
    11/2011;
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    ABSTRACT: Recently, a new paradigm for cognitive radio networks has been advocated, where primary users (PUs) recruit some secondary users (SUs) to cooperatively relay the primary traffic. However, all existing work on such cooperative cognitive radio networks (CCRNs) operate in the temporal domain. The PU needs to give out a dedicated portion of channel access time to the SUs for transmitting the secondary data in exchange for the SUs' cooperation, which limits the performance of both PUs and SUs. On the other hand, Multiple Input Multiple Output (MIMO) enables transmission of multiple independent data streams and suppression of interference via beam-forming in the spatial domain over MIMO antenna elements to provide significant performance gains. Researches have not yet explored how to take advantage of the MIMO technique in CCRNs. In this paper, we propose a novel MIMO-CCRN framework, which enables the SUs to utilize the capability provided by the MIMO to cooperatively relay the traffic for the PUs while concurrently accessing the same channel to transmit their own traffic. We design the MIMO-CCRN architecture by considering both the temporal and spatial domains to improve spectrum efficiency. Further we provide theoretical analysis for the primary and secondary transmission rate under MIMO cooperation and then formulate an optimization model based on a Stackelberg game to maximize the utilities of PUs and SUs. Evaluation results show that both primary and secondary users achieve higher utility by leveraging MIMO spatial cooperation in MIMO-CCRN than with conventional schemes.
    INFOCOM, 2011 Proceedings IEEE; 05/2011
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    ABSTRACT: Mobile video broadcasting service, or mobile TV, is expected to become a popular application for 3G wireless network operators. Most existing solutions for video Broadcast Multicast Services (BCMCS) in 3G networks employ a single transmission rate to cover all viewers. The system-wide video quality of the cell is therefore throttled by a few viewers close to the boundary, and is far from reaching the social-optimum allowed by the radio resources available at the base station. In this paper, we propose a novel scalable video broadcast/multicast solution, SV-BCMCS, that efficiently integrates scalable video coding, 3G broadcast, and ad-hoc forwarding to balance the system-wide and worst-case video quality of all viewers at 3G cell. We solve the optimal resource allocation problem in SV-BCMCS and develop practical helper discovery and relay routing algorithms. Moreover, we analytically study the gain of using ad-hoc relay, in terms of users' effective distance to the base station. Through extensive real video sequence driven simulations, we show that SV-BCMCS significantly improves the system-wide perceived video quality. The users' average PSNR increases by as much as 1.70 dB with slight quality degradation for the few users close to the 3G cell boundary.
    IEEE Transactions on Multimedia 05/2011; · 1.75 Impact Factor
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    ABSTRACT: The upcoming vehicular communication standard IEEE 802.11p adopts a Carrier Sense Multiple Access (CSMA) based MAC protocol, in which the mobile nodes listen to the wireless channel before transmission. In this paper, we show the disadvantages of the CSMA for Vehicular Ad Hoc Network (VANET): 1) lack of the assurance of the delivery delay for the emergent safety messages; 2) poor performance on periodically broadcasting routine safety messages. A real-time MAC protocol is demanded for VANET. Some recent studies suggest designing the protocol based on Time Division Multiple Access (TDMA). The major challenge of designing a TDMA based MAC protocol for VANET with high mobility is to provide efficiently decentralized scheduling. For TDMA, if a node occupies a slot, it will keep the slot until detecting a collision. Thus, by reducing the chance of the encountered nodes occupying the same slot, the efficiency of TDMA can be significantly improved. The vehicular traffic trace shows that in VANET, the majority of the encounters happen in the opposite direction rather than the same direction. According to our theoretical analysis and simulations, we demonstrate that the ratio of the number of encounters from the opposite direction to the total number of encounters exceeds 80%. We further propose an innovative direction-based TDMA scheduling strategy by exploiting this property to cope with fast-changing vehicular topology. Through extensive simulations, we show that the proposed strategy can reduce over 80% of collisions with an acceptable overhead.
    01/2011;
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    A. Rath, Sha Hua, S.S. Panwar
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    ABSTRACT: The ever increasing user demand for highly data-intensive applications is motivating cellular operators to provide more data services. However, the operators are suffering from the heavy budgetary burden of upgrading their infrastructure. Most macrocell Base Stations still connect to backhauls with capacities of less than 8 Mbps, much too low to be able to serve all voice and data users in the cell. This so-called macrocell backhaul bandwidth shortage problem is encumbering the growth of cellular data services. In this paper, we propose a novel solution, FemtoHaul , which efficiently exploits the potential of femtocells to bear the macrocell backhaul traffic by using relays, enhancing the data rates of cellular subscribers. We design a system architecture and its related signaling and scheduling strategies. Extensive simulations demonstrate that FemtoHaul can effectively serve more users and support higher data demand with the existing macrocell backhaul capacity.
    INFOCOM IEEE Conference on Computer Communications Workshops , 2010; 04/2010
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    ABSTRACT: Mobile video broadcasting service, or mobile TV, is a promising application for 3G wireless network operators. Most existing solutions for video broadcast/multicast services in 3G networks employ a single transmission rate to cover all viewers. The system-wide video quality of the cell is therefore throttled by a few viewers close to the boundary, and is far from reaching the social-optimum allowed by the radio resources available at the base station. In this paper, we propose a novel scalable video broadcast/multicast solution, SV-BCMCS, that efficiently integrates scalable video coding, 3G broadcast and adhoc forwarding to balance the system-wide and worst-case video quality of all viewers in a 3G cell. We study the optimal resource allocation problem in SV-BCMCS and develop practical helper discovery and relay routing algorithms. Through analysis and extensive OPNET simulations, we demonstrate that SV-BCMCS can significantly improve the system-wide video quality at the price of slight quality degradation of a few viewers close to the boundary.
    Global Telecommunications Conference, 2009. GLOBECOM 2009. IEEE; 01/2010