1140 IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 11, NO. 6, OCTOBER 2009 A Quality-Driven Cross-Layer Solution for MPEG Video Streaming Over WiMAX Networks Ehsan Haghani, Student Member, IEEE, Shyam Parekh, Senior Member, IEEE, Doru Calin, Senior Member, IEEE, Eunyoung Kim, and Nirwan Ansari, Fellow, IEEE Abstract—Extensive efforts have been focused on deploying broadband wireless networks. Providing mobile users with high speed network connectivity will let them run various multimedia applications on their wireless devices. Satisfying users with dif- ferent quality-of-service requirements while optimizing resource allocation is a challenging problem. In this paper, we discuss the challenges and possible solutions for transmitting MPEG video streams over WiMAX networks. We will briefly describe the MPEG traffic model suggested by the WiMAX Forum. A cross-layer solution for enhancing the performance of WiMAX networks with respect to MPEG video streaming applications is explained. Our solution uses the characteristics of MPEG traffic to give priority to the more important frames and protect them against dropping. Besides, it is simple and compatible with the IEEE 802.16 standards and thus easily deployable. It is shown that the proposed solutions will improve the video quality over WiMAX networks. Index Terms—Cross layer, MPEG, quality-of-service, video, wireless, WiMAX. I. INTRODUCTION T HE excessive demand for ubiquitous broadband wire- less access has attracted tremendous investment from the telecommunications industry in the development and de- ployment of WiMAX networks. The WiMAX technology is promising to provide broadband wireless access to mobile users in the near future. It is expected that video streaming will be a very attractive application for the rapid deployment of WiMAX networks. The stringent quality-of-service (QoS) requirements including high bitrate and low latency are some of the challenges the service providers and network designers are confronting. Furthermore, the popularity of many online video servers such as YouTube will encourage an increasing number of users to watch video clips on their mobile devices. The scarcity of available bandwidth in wireless networks has called for efficient resource management. WiMAX networks are Manuscript received October 01, 2008; revised April 21, 2009. Current ver- sion published September 16, 2009. This work was conducted when E. Haghani was an intern at Bell Laboratories in 2008. The associate editor coordinating the review of this manuscript and approving it for publication was Prof. Aggelos K. Katsaggelos. E. Haghani and N. Ansari are with the Department of Electrical and Com- puter Engineering, New Jersey Institute of Technology, Newark, NJ, 07102 USA (e-mail: Ehsan@njit.edu; Nirwan.Ansari@njit.edu). S. Parekh, D. Calin, and E. Kim are with Bell Laboratories, Alcatel-Lucent, Murray Hill, NJ 07974 USA (Tel.: (e-mail: Sparekh@alcatel-lucent.com; Calin@alcatel-lucent.com; Ekim@alcatel-lucent.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TMM.2009.2026099 based on the IEEE 802.16 standards which have defined dif- ferent QoS classes to support a broad range of applications with varying service requirements. The IEEE 802.16 standards pro- vide true QoS classes for different types of applications. As a result, in WiMAX networks, each traffic flow is mapped into an appropriate service class based on its service requirements and the user’s service level agreements (SLAs). Selecting ap- propriate service classes with proper parameters to support the required QoS while not wasting the scarce resources is the key challenge that we address in this paper. We study the traffic char- acteristics of video streaming applications and will show that an application driven, traffic aware service classification will provide the WiMAX subscriber stations (SSs) with better video quality. The importance of efficient resource management has prompted a keen interest in the research community on sup- porting video streaming applications in wireless networks. Reference [1] has reviewed the challenges of video streaming in wireless networks. It has also proposed a network adaptive rate control and cross-layer design for enhancing the overall received video quality. Many other research works have also considered feedback based video rate control [2]–[6]. In most of the rate adaptive methods, the server receives some informa- tion such as the available bandwidth, loss rate, buffer size at the receiver, or the end-to-end delay to adapt to the optimum video coding rate. One of the main drawbacks for the rate adaptive methods is caused by the channel variations in the wireless networks. Owing to the fast variation in the wireless physical channels, the adaptation methods may not be able to track the fast changes in radio channel conditions and adapt to the op- timum rate accordingly. Furthermore, selecting the appropriate rate increases the computational complexity at the video server which can result in overloading the video streaming servers. Moreover, sending feedback is not a feasible option in some multicasting applications such as IPTV or MobileTV. In such cases, a video server transmits the same content to multiple receivers with different physical channels. The heterogeneity of receivers in these applications makes it very complicated for the server to attain the flexibility and sustain the efficiency. In order to reduce the complexity at the server side and sup- port various types of clients, scalable video coding (SVC) has been introduced in [7]. The goal of this method is to encode high quality video streams into some groups of bit streams in- cluding one base sublayer and multiple enhancement sublayers. All clients register to receive the base sublayer. The addition of enhancement sublayers improves the video quality. Thus, 1520-9210/$26.00 © 2009 IEEE Authorized licensed use limited to: New Jersey Institute of Technology. Downloaded on October 27, 2009 at 13:01 from IEEE Xplore. Restrictions apply.