Qian Liu

TEL: (716)-645-4768 (Office)
Curriculum Vitae

Educational Background

Research Interests

Honors and Awards


  1. Device-to-device (D2D) communication as an underlay in LTE networks
    With the explosive development on mobile multimedia, there is an increasing need under LTE networks to exploit new technologies with higher data rate support. We present in this project a new D2D communication scheme to create a quality of service (QoS) enhanced multimedia services for LTE users who are physically close to each other. This new scheme has a potential to provide higher bandwidth service with reduced delay and reduced power consumption. However, a significant challenge from such D2D opportunity is to establish the direct link between nearby devices without interference to other regular LTE users. In this research, we develop a novel user selective resource allocation scheme for D2D communication in LTE networks. In this scheme, D2D links share the same radio resources with regular LTE users while the interferences are proactively avoided with intelligent sub-channel selection.

  2. Multimedia streaming over LTE networks
    LTE represents a promising technique for ubiquitous multimedia communication because of its significant enhancement to the data transmission rate. However, the hard hand-off (HO) procedure standardized in LTE is a menace to multimedia QoS, due to the service interruption introduced by the procedure. Thus, one major challenge of such a system is to design an effective scheduler that can guarantee QoS to users under various mobility scenarios including the hard HO procedure. In this project, we develop a QoS-driven downlink scheduling scheme for video streaming that considers both QoS metrics of video packet deadline and hard HO service degradation in order to guarantee the QoS requirements of multimedia consumers. The proposed scheduler not only is able to achieve satisfactory QoS for users during HO period, but also offers fairness for both multimedia traffic and regular data traffic.

  3. Beamforming and power allocation design in multi-user MIMO (MU-MIMO) systems
    Modern wireless communications require a tremendously high transmission rate to meet with the increasing growth of multimedia services. Since MU-MIMO systems promise significant capacity improvements in rich scattering fading wireless communication links relative to single-input single-output (SISO) systems, it has become an extremely hot research topic in the past decades. Our researches in this project concentrate on two aspects: one is the fairness and QoS guaranteed user scheduling design over MU-MIMO broadcasting channels; another is the low complexity joint transceiver beamforming design and power allocation for MU-MIMO systems.

  4. Video transmission over IEEE 802.11e Networks
    IEEE 802.11e standard provides enhancement for QoS video transmission through the modification to the media access control (MAC) layer. Enhanced Distributed Channel Access (EDCA), one of channel access types provided by the standard, offers prioritized channel access, that is, high priority traffic has a higher chance of being sent than low priority traffic. The access category AC2 in EDCA is assigned for video transmission with relatively high priority. Our research in this branch mainly focuses on cross-layer design for QoS video transmission and virtual contention free EDCA for video transmission (concentrate on QoS video transmission as well as fairness to other data transmission).

  5. Scalable video transmission over MIMO wireless networks
    • Prioritized spatial multiplexing scheme for SVC video transmission over MIMO systems
      A major challenge for spatial multiplexing MIMO system is that it usually requires appropriate decomposition of both wireless channels and multimedia data bit-streams. To facilitate proper match between decomposed channels with compressed video that exhibit variable priority for different layer of bit-streams, it is necessary to proactively prioritize the decomposed MIMO channels. Our research in this project focuses on the precoding scheme capable of integrating both channel and source characteristics in order to achieve the desired prioritized spatial multiplexing.

    • High quality multimedia services over MIMO systems with fast moving terminals
      Researchers and practitioners have mainly focused their designs to cope with static or slowly evolving traffic demands, resulting in fast moving traffic conditions have not yet been taken into account in the design of broadband multimedia applications. Our research in this project mainly concentrates on how to obtain accurate channel state information (CSI), a prerequisite for channel equalization and symbol detection in order to providing high quality multimedia services over MIMO systems with fast moving terminals.

Selected Publications

  1. Qian Liu Heather Yu, and Chang Wen Chen, “Enhancing multimedia QoS with device-to-device communication,” in Proc. of IEEE International Conference on Multimedia and Expo (ICME) July 2013.
  2. Qian Liu and Chang Wen Chen, “QoS driven and fair downlink scheduling for video streaming over LTE networks with deadline and hard hand-off,” in Proc. of IEEE International Conference on Multimedia and Expo (ICME), pp.188-193, July 2012.(Best paper award)
  3. Qian Liu, and Chang Wen Chen, “Joint transceiver beamforming design and power Allocation for multiuser MIMO systems,” in Proc. of IEEE International Conference on Communications (ICC), June 2012.
  4. Qian Liu, and Chang Wen Chen, “Fairness and QoS guaranteed user scheduling for multi-user MIMO broadcasting channel,” in Proc. of IEEE international conference on Image Processing (ICIP), pp.945-948, September 2011.
  5. Qian Liu, Zixuan Zou and Chang Wen Chen, “A deadline-aware virtual contention free EDCA scheme for H.264 video over IEEE 802.11e wireless networks,” in Proc. of IEEE International Symposium on Circuit and Systems (ISCAS), pp. 625-628, May 2011. (Best student paper award finalist)
  6. Qian Liu, Deepika Bella and Chang Wen Chen, “A New Channel Simulation Model for Fast Moving Terminals15th IEEE International Workshop on Computer Aided Modeling, Analysis and Design of Communication Links and Networks (CAMAD), pp.52-56, December 2010.
  7. Qian Liu and Chang Wen Chen, “Blind Channel Equalization for Fast Moving Terminals in Prioritized Spatial Multiplexing MIMO Systems,”in Proc. of Global Telecommunications Conference (Globecom), pp.1-5, December 2010.
  8. Qian Liu Shujie Liu, and Chang Wen Chen, “A novel prioritized spatial multiplexing for MIMO wireless system with application to H.264 SVC video,”in Proc. of IEEE International Conference on Multimedia and Expo (ICME), pp. 968-973, July 2010.


Supporting Materials