Robust Adaptive Intra Refresh for Multiview Video

Transmission error propagation in wireless multimedia communication systems has become a recurring problem. This persistent problem has led to grave consequences on the visual quality of the decoded video. It is against this backdrop that, we present an adaptive intra refresh (AIR) error-resilient coding tool to mitigate the effect of transmission error propagation in 3D video communications. This work utilizes periodic insertion of intra macroblocks in badly error-infected frames temporally as well as related frames in the multi view video scheme. Our objective is to maximize the transmission efficiency while ensuring the transmission robustness of the coded bitstream. The selection of periodic macroblocks is based on areas with high motion above a pre-set threshold. The coding modes of the macroblocks are based on the distortion expectation due to transmission errors. Extensive simulation results show significant improvement in both objective and subjective video quality at different intra refresh rates

Error resilient packet switched H.264 video telephony over third generation networks.

Real-time video communication over wireless networks is a challenging problem because wireless channels suffer from fading, additive noise and interference, which translate into packet loss and delay. Since modern video encoders deliver video packets with decoding dependencies, packet loss and delay can significantly degrade the video quality at the receiver. Many error resilience mechanisms have been proposed to combat packet loss in wireless networks, but only a few were specifically designed for packet switched video telephony over Third Generation (3G) networks. The first part of the thesis presents an error resilience technique for packet switched video telephony that combines application layer Forward Error Correction (FEC) with rateless codes, Reference Picture Selection (RPS) and cross layer optimization. Rateless codes have lower encoding and decoding computational complexity compared to traditional error correcting codes. One can use them on complexity constrained hand-held devices. Also, their redundancy does not need to be fixed in advance and any number of encoded symbols can be generated on the fly. Reference picture selection is used to limit the effect of spatio-temporal error propagation. Limiting the effect of spatio-temporal error propagation results in better video quality. Cross layer optimization is used to minimize the data loss at the application layer when data is lost at the data link layer. Experimental results on a High Speed Packet Access (HSPA) network simulator for H.264 compressed standard video sequences show that the proposed technique achieves significant Peak Signal to Noise Ratio (PSNR) and Percentage Degraded Video Duration (PDVD) improvements over a state of the art error resilience technique known as Interactive Error Control (IEC), which is a combination of Error Tracking and feedback based Reference Picture Selection. The improvement is obtained at a cost of higher end-to-end delay. The proposed technique is improved by making the FEC (Rateless code) redundancy channel adaptive. Automatic Repeat Request (ARQ) is used to adjust the redundancy of the Rateless codes according to the channel conditions. Experimental results show that the channel adaptive scheme achieves significant PSNR and PDVD improvements over the static scheme for a simulated Long Term Evolution (LTE) network. In the third part of the thesis, the performance of the previous two schemes is improved by making the transmitter predict when rateless decoding will fail. In this case, reference picture selection is invoked early and transmission of encoded symbols for that source block is aborted. Simulations for an LTE network show that this results in video quality improvement and bandwidth savings. In the last part of the thesis, the performance of the adaptive technique is improved by exploiting the history of the wireless channel. In a Rayleigh fading wireless channel, the RLC-PDU losses are correlated under certain conditions. This correlation is exploited to adjust the redundancy of the Rateless code and results in higher Rateless code decoding success rate and higher video quality. Simulations for an LTE network show that the improvement was significant when the packet loss rate in the two wireless links was 10%. To facilitate the implementation of the proposed error resilience techniques in practical scenarios, RTP/UDP/IP level packetization schemes are also proposed for each error resilience technique. Compared to existing work, the proposed error resilience techniques provide better video quality. Also, more emphasis is given to implementation issues in 3G networks

ROBUST ADAPTIVE INTRA REFRESH FOR MULTIVIEW VIDEO

ABSTRAC

Intra-Refresh Provision for WiMAX Data-Partitioned Video Streaming

Mobile, broadband wireless access is increasingly being used for video streaming. This paper is a study of the impact of intra-refresh provision upon a robust video streaming scheme intended for WiMAX. The paper demonstrates the use of intra-refresh macroblocks within inter-coded video frames as an alternative to periodic intra-refresh video frames. In fact, the proposed scheme combines intra-refresh macroblocks with data-partitioned video compression, both error resilience tools from the H.264 video codec. Redundant video packets along with adaptive channel coding are also used to protect video streams. In harsh wireless channel conditions, it is found that all the proposed measures are necessary. This is because error bursts, arising from both slow and fast fading, as well as other channel impairments, are possible. The main conclusions from a detailed analysis are that: because of the effect on packet size it is important to select a moderate quantization parameter; and because of the higher overhead from cyclic intra macroblock line update it is better to select a low percentage per frame of intra-refresh macroblocks. The proposed video streaming scheme will be applicable to other 4G wireless technologies such as LTE

Convergence of platforms and strategies of two software vendors

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 145-157).Unified Communications: Convergence of Platforms and Strategies of Two Software Vendors by Muhammad Zia Hydari ABSTRACT Unified communication (UC) is the convergence of various modes of communication - voice telephony, email, instant messaging (IM), video conferencing and so on - used by enterprise workers. Academic literature exists that discusses digital convergence in various domains. Although UC has received considerable attention in the business press, we are not aware of any academic study within the domain of UC that explains the convergence of platforms and its links to the technology strategy of UC firms. This thesis presents an academic analysis of some platforms underlying UC and the emerging strategies of two software firms within the UC market. The theory of network effects originally developed by Rohlfs is central to the analysis in this thesis. The analysis of platform strategies of the UC firms is informed by the theoretical work on platform leadership (Gawer & Cusumano), convergence (Greenstein et al.), platform envelopment (Eisenmann et al.), and two-sided platforms (Tirole et al.). The thesis first describes four platform applications underlying UC viz. voice telephony, email, IM, and video communication. The analysis of email, IM and video communication in this thesis is unique as it takes a long term view to explain the current market situation within these domains. In particular, the thesis describes technological factors, network effects, standard battles, and competition that have led to the current market state. The thesis also links insights from these platforms to repercussions for UC supplier firms. The thesis then describes the strategies of two software vendors - Microsoft and IBM - using elements from Gawer & Cusumano's work on platform leadership.(cont.) Microsoft has defined a broad scope of innovation for its converged UC platform requiring it to enter the voice telephony market. The thesis posits that Microsoft's strategy for success is platform envelopment i.e. Microsoft is using shared components and installed user base from its email and IM platforms to create a multi-platform bundle and compete with entrenched platforms in the voice market. The thesis argues that IBM's choice for a narrower platform scope stems from its inferior market position in the email and IM markets as well as scope differences (vis-a-vis Microsoft). Convergence has created system integration opportunities that IBM's services unit has targeted. The thesis describes the implications of IBM's decisions on its ecosystem.by Muhammad Zia Hydari.S.M

Complex city systems : how cities are using technological systems to transform and compete in a global knowledge based economy

Imperial Users onl

Internet of Things From Hype to Reality

The Internet of Things (IoT) has gained significant mindshare, let alone attention, in academia and the industry especially over the past few years. The reasons behind this interest are the potential capabilities that IoT promises to offer. On the personal level, it paints a picture of a future world where all the things in our ambient environment are connected to the Internet and seamlessly communicate with each other to operate intelligently. The ultimate goal is to enable objects around us to efficiently sense our surroundings, inexpensively communicate, and ultimately create a better environment for us: one where everyday objects act based on what we need and like without explicit instructions

Journal of Telecommunications and Information Technology, 2011, nr 3

kwartalni