A content-aware networking framework for transmitting video on the uplink of a Wideband Code Division Multiple Access (WCDMA) cellular network is studied in this article. We consider a multi-user scenario and exploit the underlying structure of the video content to optimally schedule frames in order to minimize the total distortion of video quality across all users. In particular, we propose a novel Content-Aware Distortion Fair (CADF) scheme that determines, between multiple flows, the best set of frames to schedule using optimal transmit power, while meeting interference and delay constraints. The optimization problem is considered on the time scale of a single Group of Pictures, and is formulated as a restricted Multiple Knapsack Problem. A key contribution of this study is evaluating the CADF scheme on a Qualcomm 3G emulator, called "High data rate System Emulator 2" (HSE 2), and conducting rate control experiments with different types of emulated channel conditions. Our experimental results show that the CADF scheme significantly reduces video distortion, compared to the existing Foschini-Miljanic closed-loop distributed power control algorithm implemented on the WCDMA uplink. In the Appendix section, we also use the emulator to analyze the Traffic-to-Pilot resource allocation algorithm implemented on the reverse link of Evolution-Data Optimized (EV-DO) Revision-A by profiling over different traffic classes. Keywords: Content-aware networking, Rate distortion fair, Qualcomm 3G emulator, Video delivery, Power control, Scheduling, WCDMA Introduction It is projected that mobile video traffic will comprise more than 70% of all mobile data traffic by 2016 [1] . This challenges many of our basic assumptions about designing future computer communications networks. Traditionally, network protocols have been designed to be contentoblivious, i.e., each bit is assumed to be equally important when it is transported over the network. This has given rise to the problem of content-pipe divide [2] . On the one hand, pipe-owners such as Internet Service Providers (ISPs), network infrastructure vendors, and municipalities treat all content equally as simply bits of information to be transported between given nodes. On the other hand, content-providers such as media companies, end-users who post videos online, and operators of both peer-topeer (P2P) systems and content distribution networks *Correspondence: amitabhg@princeton.edu 2 Department of Electrical Engineering, Princeton University, Princeton, NJ, USA Full list of author information is available at the end of the article (CDNs) generate content treating the network as simply a means of transportation. This gap between the pipeowners and content-providers is exacerbated especially for video content, where different frames can have different degrees of importance and can contribute differently to the distortion (i.e., quality degradation) perceived by the human eye. Content-aware networking refers to the methodology of utilizing the rate-distortion (RD) characteristics [3] of the content to design more adaptive and efficient network protocols. It advocates a cross-layer design philosophy where network resources are allocated and provisioned with optimality criteria that are reflective of the content itself [2, 4] . Content-aware techniques provide an alternative for optimizing video quality in the presence of network resource constraints. There exists a rich literature on content-aware networking, contributed by video processing, wireless, networking, and information theory communities. However, there exists a wide gap between the theory of content-aware © 2012 Pandit et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Page 2 of 14 http://jwcn.eurasipjournals.com/content/2012/1/217 networking and its practical adoption in 3G cellular systems. This article focuses on connecting the analytics of content-aware optimization with the specifics of engineering hooks and knobs in 3G cellular standards, as well as on implementing them in an industry-grade system emulator that offers a configurable and realistic test-bed to validate the theory. We study the uplink of the Wideband Code Division Multiple Access (WCDMA) [5] standard, and design techniques to make the physical layer and medium access control (MAC) layer content aware. Our proposed architecture is wrapper-based, i.e., it maintains the overall structure of the physical and MAC layer protocols in WCDMA, but provides hooks that can be implemented as wrappers. Such a wrapper-based approach can make content-aware features incrementally available in WCDMA networks without causing major disruption in services. The reason we choose to focus on the uplink is its increasing bandwidth demand. With the recent surge in data-hungry, delay-sensitive applications, such as capturing videos on mobile devices and posting them on social networking sites, online gaming, video conferencing, and Voice-over-IP (VoIP), the asymmetry in data rates between the downlink and uplink is closing. Another focus of this study is to validate our proposed algorithms using a packet-level Qualcomm 3G emulator, called "High data rate System Emulator 2" (HSE 2) [6] . HSE 2 acts as a bridge between terminal equipments by dropping and delaying IP packets to emulate 3G channels. The delay experienced by IP packets going through the emulator is faithful to that in an actual 3G system under various channel conditions. Unlike Wi-Fi networks in the unlicensed band, where software-defined radios like Wireless Open-Access Research Platform (WARP) [7] readily provide a realistic and configurable platform, experimenting with 3G cellular platforms is much more difficult. Testing the content-aware algorithms on an industry-grade emulator is much more realistic than simulation-based evaluations. Since the internal workings of most public cellular technologies are closed from public access, experimental evaluation on an emulator is a key step to faithfully capture the reality. We summarize our key contributions below: 1. Content-Aware Distortion Fair (CADF) Scheme: We propose a novel content-aware distortion fair scheme for efficiently delivering video traffic on the uplink of a WCDMA network. We formulate the problem of video delivery as a constrained optimization problem of minimizing the sum of distortion of all video streams from all users, and
The problem of joint packet scheduling and power allocation is also investigated in REF in order to minimize video quality distortion for multiple users in the uplink of a code division multiple access (CDMA) network.
Content aware optimization for video delivery over WCDMA
EURASIP Journal on Wireless Communications and Networking
Computer Science