Martin Fleury

Interval Type-2 Fuzzy Logic Congestion Control for Video Streaming Across IP Networks

Intelligent congestion control is vital for encoded video streaming of a clip or film, as network traffic volatility and the associated uncertainties require constant adjustment of the bit rate. Existing solutions, including the standard transmission control protocol (TCP) friendly rate control equation-based congestion controller, are prone to fluctuations in their sending rate and may respond only when packet loss has already occurred. This is a major problem, because both fluctuations and packet loss affect the end-users perception of the delivered video. A type-1 (T1) fuzzy logic congestion controller (FLC) can operate at video display rates and can reduce packet loss and rate fluctuations, despite uncertainties in measurements of delay arising from congestion and network traffic volatility. However, a T1 FLC employing precise T1 fuzzy sets cannot fully cope with the uncertainties associated with such dynamic network environments. A type-2 FLC using type-2 fuzzy sets can handle such uncertainties to produce improved performance. This paper proposes an interval type-2 FLC that achieves a superior delivered video quality compared with existing traditional controllers and a T1 FLC. To show the response in different network scenarios, tests demonstrate the response both in the presence of typical Internet cross-traffic as well as when other video streams occupy a bottleneck on an All-Internet protocol (IP) network. As All-IP networks are intended for multimedia traffic, it is important to develop a form of congestion control that can transfer to them from the mixed traffic environment of the Internet. It was found that the proposed type-2 FLC, although it is specifically designed for Internet conditions, can also successfully react to the network conditions of an All-IP network. When the control inputs were subject to noise, the type-2 FLC resulted in an order of magnitude performance improvement in comparison with the T1 FLC. The type-2 FLC also showed reduced packet loss when compared with the other controllers, again resulting in superior delivered video quality. When judged by established criteria, such as TCP-friendliness and delayed feedback, fuzzy logic congestion control offers a flexible solution to network bottlenecks. These findings offer the type-2 FLC as a way forward for congestion control of video streaming across packet-switched IP networks.

Improving Propagation Modeling in Urban Environments for Vehicular Ad Hoc Networks

Developing applications, particularly real-time applications, for wireless vehicular ad hoc networks (VANETs) requires a reasonable assurance of the likely performance of the network, at the least in terms of packet loss ratios and end-to-end delay. Because wireless propagation strongly influences performance, particularly in an urban environment, this paper improves on simpler propagation models for simulations by augmenting ray-tracing-derived models of propagation. In the non-line-of-sight (NLOS) component, the propagation distance is more closely calculated according to the reflection distance, the effect of roadside obstacles is included, and for the modeling of fast fading, a phase factor is introduced, all without necessarily overly increasing the computational load. In the line-of-sight (LOS) component, as well as the roadside obstacle modeling, single and double reflections from roadside buildings are added to the standard two-ray ground-propagation model, the distribution of vehicles within a street segment is used to more closely model the ground reflection ray, and the reflection coefficient is also accordingly adjusted to account for reflections from vehicles. The results have been compared with widely used measurement studies of city streets in the literature, which have confirmed the overall advantage of the improvements, particularly in the case of the NLOS component. A simulation case study shows that, in general, optimistic performance predictions of packet loss occur with the two-ray ground-propagation model when indiscriminately applied. This paper therefore represents a way forward for VANET wireless channel modeling in simulations.

Robust Video Streaming over an Urban VANET

Because of restricted mobility patterns, multi-hop routing, and wireless channel conditions, streaming video over a Vehicular Ad Hoc Network (VANET) is a daunting task. This paper demonstrates that H.264 codec Flexible Macroblock Ordering (FMO) with receiver error concealment is capable of streaming good-quality video across a VANET. FMO is shown to be superior to other error resilience techniques but attention should be given to packet size, choice of protocol and the rate the video is released into the network if there are multiple destinations. Settings close to those of the emerging IEEE 802.11p standard for VANETs were emulated for a Manhattan grid mobility model.

H.264 video streaming with data-partitioning and Growth codes

This paper demonstrates that Growth codes, based on Raptor channel coding, allow incremental protection of H.264 video codec data-partitioned Network Adaption Layer units. When combined with increased protection of video reference frames, in an ADSL erasure channel up to 10 dB in video quality (PSNR) can be gained through this scheme compared to equal error protection with rateless codes. Equivalent gains occur in a wireless channel from combining data-partitioning with error protection. The bitrate overhead from data-partitioning is also shown to be less than from other H.264 error resilient tools.

Evaluating optical-flow algorithms on a parallel machine

Abstract Algorithmic development of optical-flow routines is hampered by slow turnaround times (to iterate over testing, evaluation, and adjustment of the algorithm). To ease the problem, parallel implementation on a convenient general-purpose parallel machine is possible. A generic parallel pipeline structure, suitable for distributed-memory machines, has enabled parallelisation to be quickly achieved. Gradient, correlation, and phase-based methods of optical-flow detection have been constructed to demonstrate the approach. The prototypes enabled comparisons to be made between the speed when parallelised and (already known) accuracy of the three methods when parallelised, on balance favouring the correlation method.

Parallel entropic auto-thresholding

In this paper, we examine a multi-level thresholding algorithm based on a number of phases including peak-search, fuzzy logic and entropy of the fuzzy membership function. Analysis of the algorithm is presented to show its properties and behaviours at the various cascaded stages. The fuzzy entropy function of the image histogram is computed using S-function membership and Shannons entropy function. To establish a suitable fuzzy region bandwidth, we have used a peak-search method based on successive clipping of the image histogram. Location of the valleys in the entropy function correspond to the certainties within the fuzzy region of the image. These certainties are used to indicate an optimal segmentation pattern for multi-level image thresholding. We compare and contrast this method of thresholding with a maximum entropy method. We have implemented the technique in parallel on a transputer-based machine as well as on a cluster of SUN4 workstations, availing ourselves of the PVM communication kernel. A parallel algorithm for the maximum entropy method is given, which significantly reduces computation times. An objective method is used to evaluate the resulting images.

Adaptive packet-level interleaved FEC for wireless priority-encoded video streaming

Packet-level Forward Error Control (FEC) for video streaming over a wireless network has received comparatively limited investigation, because of the delay introduced by the need to assemble a group of packets. However, packet-level interleaving when combined with FEC presents a remedy to time-correlated error bursts, though it can further increase delay if this issue is not addressed. This paper proposes adapting the overall degree of interleaved packet-level FEC according to the display deadlines of packets, transmit buffer occupation, and estimated video input to the wireless channel, all of which address the issue of delay. To guard against estimation error, the scheme applies a conservative adaptation policy, which accounts for picture type importance to ensure that display deadlines are met, thus avoiding this defect of interleaving. The paper additionally introduces a greedy algorithm that effectively groups packet-level FEC protection according to packet priority. Priority encoding adds extra protection during deep fades. As feedback is not required, the interleaving scheme is suitable for all forms of video broadcast. A Bluetooth piconet demonstrates the packet-level FEC interleaving scheme, which provides higher quality delivered video compared to the industry-standard Pro-MPEG Cop#3r2 interleaving scheme.

Fuzzy-Logic Congestion Control of Transcoded Video Streaming Without Packet Loss Feedback

Congestion control of a variable bit-rate video stream crossing the Internet is crucial to ensuring the quality of the received video. When a fuzzy-logic congestion controller (FLC) changes the sending rate of a video transcoder, it does so without feedback of packet loss, using packet dispersion instead. Compared with the well-known TFRC and RAP controllers, the FLCs sending rate is significantly smoother, allowing it to more closely take up available bandwidth at a bottleneck link. There is an accompanying order of magnitude reduction in packet losses. Due to better utilization of the available bandwidth, video quality is improved over time by several decibels in low-packet-loss conditions. The strength of the FLC solution is demonstrated by the resulting video quality when typical Web traffic forms the background traffic. The FLC avoids any risk of congestion collapse through fairness to coexisting TCP flows and is robust to changes in path delay and router buffer configuration.

Delay-based congestion avoidance for video communication with fuzzy logic control

Early detection of network congestion is important in streaming video, as packet loss has a recurring impact on video quality. Packet delay itself, rather than packet loss, can give early notice of congestion provided it can accurately reflect the congestion level at the network path’s tight link. In this paper, the one-way delay of video packets serves as an incipient network congestion indicator, which acts as one input to fuzzy logic control of congestion avoidance to help optimize the response to network congestion. The fuzzy logic models are shown to be robust under: changes in the complexity and motion content of the video stream under control; a wide range one way end-to-end link delays up to 120 ms; and variations in available bandwidth. Tests reported that the fuzzy logic approach compares favorably to standard TFRC congestion control.

Hardware compilation for software engineers: an ATM example

Forthcoming technology such as single-chip RISC/FPGA combinations make hardware compilation, fast prototyping and FPGA replacement of ASICs all more likely. FPGAs have made a software-oriented approach to digital design feasible. Remaining obstacles to this approach are reviewed. The trade-offs between use of an HDL and a C-variant, Handel-C, for logic synthesis are considered, particularly with regard to programmability and the overall design process. A simple example in a likely application area, simulation/emulation of telecommunications switches, illustrates the analysis.