Small‐block interleaving for low‐delay cross‐packet forward error correction over burst‐loss channels

By adding the redundant packets into source packet block, cross‐packet forward error correction (FEC) scheme performs error correction across packets and can recover both congestion packet loss and wireless bit errors accordingly. Because cross‐packet FEC typically trades the additional latency to combat burst losses in the wireless channel, this paper presents a FEC enhancement scheme using the small‐block interleaving technique to enhance cross‐packet FEC with the decreased delay and improved good‐put. Specifically, adopting short block size is effective in reducing FEC processing delay, whereas the corresponding effect of lower burst‐error correction capacity can be compensated by deliberately controlling the interleaving degree. The main features include (i) the proposed scheme that operates in the post‐processing manner to be compatible with the existing FEC control schemes and (ii) to maximize the data good‐put in lossy networks; an analytical FEC model is built on the interleaved Gilbert‐Elliott channel to determine the optimal FEC parameters. The simulation results show that the small‐block interleaved FEC scheme significantly improves the video streaming quality in lossy channels for delay‐sensitive video. Copyright © 2013 John Wiley & Sons, Ltd.     

Sliding‐window forward error correction using Reed‐Solomon code and unequal error protection for real‐time streaming video

Forward error correction (FEC) techniques are widely used to recover packet losses over unreliable networks in real‐time video streaming applications. Traditional frame‐level FEC encodes 1 video frame in each FEC coding window. By contrast, in the expanding‐window FEC scheme, high‐priority frames are included in the FEC processing of the following frames, so as to construct a larger coding window. In general, expanding‐window FEC improves the recovery performance of FEC, because the high‐priority frame can be protected by multiple windows and the use of a larger coding window increases the efficiency. However, the larger window size also increases the complexity of the coding and the memory space requirements. Consequently, expanding‐window FEC is limited in terms of practical applications. Sliding‐window FEC adopts a fixed window size in order to approximate the performance of the expanding‐window FEC method, but with a reduced complexity. Previous studies on sliding‐window FEC have generally adopted an equal error protection (EEP) mechanism to simplify the analysis. This paper considers the more practical case of an unequal error protection (UEP) strategy. An analytical model is derived for estimating the playable frame rate (PFR) of the proposed sliding‐window FEC scheme with a Reed‐Solomon erasure code for real‐time non‐scalable streaming applications. The analytical model is used to determine the optimal FEC configuration which maximizes the PFR value under given transmission rate constraints. The simulation results show that the proposed sliding‐window scheme achieves almost the same performance as the expanding‐window scheme, but with a significantly lower computational complexity.     

Rate-distortion based real-time wireless video streaming

This paper presents wireless video streaming techniques that exploit the characteristics of video content, transmission history, and physical layer channels to enable real-time efficient video streaming over wireless networks to a wireless client. The key contribution of the proposed video streaming techniques is the use of rate-distortion based, but simplified, low complexity packet scheduling as well as forward error correction (FEC) rate selection. To this end, we develop an optimization framework that jointly schedules the packets and selects the FEC rates. The rate-distortion optimized packet scheduling and FEC rate selection provides the optimum quality video on the receiver side albeit at a high computational cost. By some intelligent approximations, rate distortion optimized packet scheduling and FEC rate selection technique is transformed into two sub-optimal but low complexity video streaming techniques that can provide high video quality. We perform extensive simulations to understand the performance of our proposed techniques under different scenarios. Results show that, the proposed techniques improve video quality on the average by 4 dB. We conclude that significant benefits to end-user experience can be obtained by using such video streaming methods.     

Loss Tolerant Bandwidth Aggregation for Multihomed Video Streaming over Heterogeneous Wireless Networks

Bandwidth aggregation is a key research issue in integrating heterogeneous wireless networks, since it can substantially increase the throughput and reliability for enhancing streaming video quality. However, the burst loss in the unreliable wireless channels is a severely challenging problem which significantly degrades the effectiveness of bandwidth aggregation. Previous studies mainly address the critical problem by reactively increasing the forward error correction (FEC) redundancy. In this paper, we propose a loss tolerant bandwidth aggregation approach (LTBA), which proactively leverages the channel diversity in heterogeneous wireless networks to overcome the burst loss. First, we allocate the FEC packets according to the ‘loss-free’ bandwidth of each wireless network to the multihomed client. Second, we deliberately insert intervals between the FEC packets’ departures while still respecting the delay constraint. The proposed LTBA is able to reduce the consecutive packet loss under burst loss assumption. We carry out analysis to prove that the proposed LTBA outperforms the existing ‘back-to-back’ transmission schemes based on Gilbert loss model and continuous time Markov chain. We conduct the performance evaluation in Exata and emulation results show that LTBA outperforms the existing approaches in improving the video quality in terms of PSNR (Peak Signal-to-Noise Ratio).     

Downlink media streaming with wireless fountain coding in wireline‐cum‐WiFi networks

This paper addresses the problem of streaming packetized media data in a combined wireline/802.11 network. Since the wireless channel is normally the bottleneck for media streaming in such a network, we propose that wireless fountain coding (WFC) be used over the wireless downlink in order to efficiently utilize the wireless bandwidth and exploit the broadcast nature of the channel. Forward error correction (FEC) is also used to combat errors at the application‐layer. We analytically obtain the moment generating function (MGF) for the wireless link‐layer delay incurred by WFC. With the MGF, the expected value of this wireless link‐layer delay is found and used by the access point (AP), who has no knowledge of the buffer contents of wireless receivers, to make a coding‐based decision. We then derive the end‐to‐end packet loss/late probability based on the MGF. We develop an integrated ns‐3/EvalVid simulator to evaluate our proposed system and compare it with the traditional 802.11e scheme which is without WFC capability but equipped with application‐ and link‐layer retransmission mechanisms. Through extensive simulations of video streaming, we show that streaming with WFC is able to support more concurrent video flows compared to the traditional scheme. When the deadlines imposed on video packets are relatively stringent, streaming with WFC also shows superior performance in terms of packet loss/late probability, video distortion, and video frame delay, over the traditional scheme. Copyright © 2011 John Wiley & Sons, Ltd.     

Interleaved coding and sequential transmission scheme for packet‐level forward error correction over burst loss channels

Burst packet loss is a common problem over wired and wireless networks and leads to a significant reduction in the performance of packet‐level forward error correction (FEC) schemes used to recover packet losses during transmission. Traditional FEC interleaving methods adopt the sequential coding‐interleaved transmission (SCIT) process to encode the FEC packets sequentially and reorder the packet transmission sequence. Consequently, the burst loss effect can be mitigated at the expense of an increased end‐to‐end delay. Alternatively, the reversed interleaving scheme, namely, interleaved coding‐sequential transmission (ICST), performs FEC coding in an interleaved manner and transmits the packets sequentially based on their generation order in the application. In this study, the analytical FEC model is constructed to evaluate the performance of the SCIT and ICST schemes. From the analysis results, it can be observed that the interleaving delay of ICST FEC is reduced by transmitting the source packets immediately as they arrive from the application. Accordingly, an Enhanced ICST scheme is further proposed to trade the saved interleaving time for a greater interleaving capacity, and the corresponding packet loss rate can be minimized under a given delay constraint. The simulation results show that the Enhanced ICST scheme achieves a lower packet loss rate and a higher peak signal‐to‐noise‐ratio than the traditional SCIT and ICST schemes for video streaming applications.     

Adaptive video protection in large scale peer‐to‐peer video streaming over mobile wireless mesh networks

Because video streaming over mobile handheld devices has been of great interest, the necessity of introducing new methods with low implementation cost and scalable infrastructures is a strong demand of the service. In particular, these requirements are present in popular wireless networks such as wireless mesh networks (WMN). Peer‐to‐peer (P2P) networks promise an efficient scalable network infrastructure for video streaming over wired and wireless networks. Limited resources of the peers in P2P networks and high error rate in wireless channels make it more challenging to run P2P streaming applications over WMNs. Therefore, it is necessary to design efficient and improved error protection methods in P2P video streaming applications over WMNs. In this paper, we propose a new adaptive unequal video protection method specially intended for large scale P2P video streaming over mobile WMNs. Using this method, different frames have different priorities in receivers along the recovery process. Moreover, we precisely and completely evaluate different aspects related to frame protection in these networks using five important performance metrics including video distortion, late arrival distortion, end‐to‐end delay, overhead and initial start‐up delay. The results obtained from a precise simulation in OMNeT++ show that the proposed adaptive method significantly outperforms other solutions by providing better video quality on mobile wireless nodes. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance modeling of MPEG‐4 video streaming over IEEE 802.11 using distribution coordination function

Delivering video streaming over wireless Internet is becoming increasingly popular. However, most of the research studies focused on the modeling analysis of system performance such as saturation throughput and channel utilization. Perceived quality of video streaming cannot be assessed solely based on the results of analytical models. In this paper, we propose a model to assess the perceived quality of MPEG‐4 video streaming over IEEE 802.11 distribution coordination function (DCF)‐based wireless local area networks. The analysis of our proposed model considers not only effects of losses such as collision loss from channel access competition but also wireless loss caused by wireless interferences. Moreover, the impact of the loss of specific MPEG‐4 video frames is also taken into account in the performance analysis. The model was validated by comparing our performance results with results obtained from simulation and analytical models. The results show that our proposed model is able to predict the perceived quality of MPEG‐4 video streaming over DCF‐based WLAN more accurately than other models. Copyright © 2010 John Wiley & Sons, Ltd.     

Error repair for broadcast transmissions in DVB‐H systems

People travelling in public transportation vehicles are foreseen to be a relevant use case of future Digital Video Broadcast—Handhelds (DVB‐H) systems. However, it is also one of the critical user cases, since, besides the vehicle penetration loss, the received signal quality is strongly affected by the high mobility of the users, which is accompanied by temporary shadowing and fast fading. On the other hand, mobility can be also beneficial thanks to the bursty character of DVB‐H transmissions, as additional repair data can be sent in the time intervals between original service bursts in order to hide the coverage discontinuities from the users' perception. In this way, users which miss the original transmission have more chances to receive the information correctly. By managing the amount of repair data the network operator can trade system capacity and network latency for improved vehicular user satisfaction in a DVB‐H network with imperfect coverage of the service area (as perceived by the vehicular users). To illustrate the potential of this approach, we evaluate the mentioned trade‐off in a DVB‐H system dimensioned for pedestrian outdoor users, for both streaming and filecasting services. To enable an easy and efficient implementation of the repair mechanisms, we adopt application layer forward error correction (FEC), as it can provide a multi‐burst protection of the transmission. Copyright © 2008 John Wiley & Sons, Ltd.     

Hierarchical Optimization of Cascading Error Protection Scheme for H.264 Scalable Video Streaming

Forward error correction (FEC) coding has been shown to offer a feasible solution to fulfill the need for Quality of Service for multimedia streaming over the fluctuant channels, especially in terms of the reduction of end-to-end delay. In this paper, we propose the Dynamic FEC-Distortion Optimization Algorithm to efficiently utilize the network bandwidth for better visual quality by means of hierarchical coding structure with the cascading error protection scheme. The optimization criteria are based on the unequal error protection by taking account of the error drifting problems from both temporal motion compensation and inter-layer prediction of the H.264/MPEG-4 AVC scalable video coding so that the priorities of each video components can be differentiated for the calculation of the distribution of parity packets. It is shown that the cascading error protection scheme makes the hierarchical structure of error erasure code more efficient. Also, the proposed algorithm works particularly well for fast motion videos and the performance does not depend on accurate estimation of packet loss rate.     

A retransmission‐based scheme for video streaming over wireless channels

Efficient resource allocation is a key factor to improve the efficiency of video transmission over wireless channels. To increase the number of correctly received video frames at the decoder, it is desirable to reduce the video source rate while increasing error protection when the wireless channel is anticipated to be bad or when the receiver buffer is approaching starvation. In this study, we introduce a retransmission‐based adaptive source‐channel rate control scheme for video transmission over wireless packet networks. In this scheme, the level of adaptiveness is optimized to reduce the bandwidth requirement while guaranteeing delay and loss bounds. The proposed scheme has the advantage of providing closed‐form expressions of the near‐optimum parameters of the proposed model, which are then fed back to the transmitter to scale both the source and channel rates adaptively. Simulation and numerical investigations are carried out to verify the adequacy of the analysis and study the impact of the adaptive process on the continuity of the video playback process. Copyright © 2009 John Wiley & Sons, Ltd.     

A distributed utility‐based scheduling for peer‐to‐peer video streaming over wireless networks

Interactive multimedia applications such as peer‐to‐peer (P2P) video services over the Internet have gained increasing popularity during the past few years. However, the adopted Internet‐based P2P overlay network architecture hides the underlying network topology, assuming that channel quality is always in perfect condition. Because of the time‐varying nature of wireless channels, this hardly meets the user‐perceived video quality requirement when used in wireless environments. Considering the tightly coupled relationship between P2P overlay networks and the underlying networks, we propose a distributed utility‐based scheduling algorithm on the basis of a quality‐driven cross‐layer design framework to jointly optimize the parameters of different network layers to achieve highly improved video quality for P2P video streaming services in wireless networks. In this paper, the quality‐driven P2P scheduling algorithm is formulated into a distributed utility‐based distortion‐delay optimization problem, where the expected video distortion is minimized under the constraint of a given packet playback deadline to select the optimal combination of system parameters residing in different network layers. Specifically, encoding behaviors, network congestion, Automatic Repeat Request/Query (ARQ), and modulation and coding are jointly considered. Then, we provide the algorithmic solution to the formulated problem. The distributed optimization running on each peer node adopted in the proposed scheduling algorithm greatly reduces the computational intensity. Extensive experimental results also demonstrate 4–14 dB quality enhancement in terms of peak signal‐to‐noise ratio by using the proposed scheduling algorithm. Copyright © 2015 John Wiley & Sons, Ltd.     

Quality-aware cross-layer scheduling for robust video streaming over wireless channels

In the case of video streaming over wireless channels, burst errors may lead to serious video quality degradation. By jointly exploiting the scheduling mechanism on different communication layers, this paper proposes a quality-aware cross-layer scheduling scheme to achieve unequal error control for each Latency-constraint Frame Set (LFS) of a video stream. After a network-layer agent at base station firstly utilizes the network-layer packet scheduling to provide packet-granularity importance classification for the current LFS, a link-layer agent at base station further utilizes the Radio-Link-Unit (RLU) scheduling to implement finer selective retransmission of the current LFS. Under scheduling delay and bandwidth constraints, the proposed scheme can be aware of the application-layer quality and time-varying channel conditions, and hence burst errors can simply be shifted to lower-priority transmission units in the current LFS. Simulation results demonstrate that the proposed scheme has strong robustness against burst errors, and thus improves the overall received quality of the video stream over wireless channels.     

Per-packet rate adaptation for wireless video

Streaming video over error-prone wireless channels is a challenge as the dynamic network conditions and slow adaptation to channel degradations may affect the quality of the streamed video. Unequal error protection (UEP) can potentially address this issue by considering the importance of each video packet and its impact on the quality of reconstructed video. This paper proposes a cross-layer UEP solution for wireless video streaming over IEEE 802.11 networks. Video packets are prioritized based on the relative importance of the video packet. UEP is achieved by adapting the link layer parameters on a per-packet basis, using inherent forward error correction and adaptive modulation capabilities of the 802.11n network. Experimental results revealed that the proposed solution achieves comparable performance to the state-of-the-art methods at a lower complexity.     

SVC-based multisource streaming for robust video transmission in mobile ad hoc networks

Emerging noninfrastructure-based network types like mobile ad-hoc networks (MANETs) are becoming suitable platforms for exchanging/sharing real-time video streams, because of recent progress in routing algorithms, throughput and transmission bit-rate. MANETs are characterized by highly dynamic behavior of the transmission routes and path outage probabilities. In this article a multisource streaming approach is presented to increase the robustness of real-time video transmission in MANETs. For that, video coding as well as channel coding techniques on the application layer are introduced, exploiting the multisource representation of the transferred media. Source coding is based on the scalable video coding (SVC) extension of H.264/MPEG4-AVC with different layers for assigning importance for transmission. Channel coding is based on a novel unequal packet loss protection (UPLP) scheme, which is based on Raptor forward error correction (FEC) codes. While in the presented approach, the reception of a single stream guarantees base quality only, the combined reception enables playback of video at full quality and/or lower error rates. Furthermore, an application layer protocol is introduced for supporting peer-to-peer based multisource streaming in MANETs     

Joint source/FEC rate selection for quality-optimal MPEG-2 videodelivery

This paper deals with the optimal allocation of MPEG-2 encoding and media-independent forward error correction (FEC) rates under a total given bandwidth. The optimality is defined in terms of minimum perceptual distortion given a set of video and network parameters. We first derive the set of equations leading to the residual loss process parameters. That is, the packet loss ratio (PLR) and the average burst length after FEC decoding. We then show that the perceptual source distortion decreases exponentially with the increasing MPEG-2 source rate. We also demonstrate that the perceptual distortion due to data loss is directly proportional to the number of lost macroblocks, and therefore decreases with the amount of channel protection. Finally, we derive the global set of equations that lead to the optimal dynamic rate allocation. The optimal distribution is shown to outperform classical FEC scheme, thanks to its adaptivity to the scene complexity, the available bandwidth and to the network performance. Furthermore, our approach holds for any standard video compression algorithms (i.e., MPEG-x, H.26x).     

Broadcast/multicast MPEG-2 video over broadband fixed wirelessaccess networks

With the emergence of broadband fixed wireless access networks, there is an increasing interest in providing broadband video services over outdoor wireless networks. We investigate some fundamental issues related to the broadcasting or multicasting of CBR MPEG-2 videos over fixed wireless channels in B-FWANs using FEC strategies. In B-FWANs, high-frequency wireless channels are used and a direct or indirect LOS propagation path is usually required between a transmitter and a receiver. The wireless channel is modeled by a K factor Rician fading model instead of a Rayleigh fading model. The unique characteristics of the physical channel require special consideration at the system design level. In order to evaluate the overall system performance properly, a set of parameters for objective video quality assessment is introduced and used in our simulation studies, including a definition of the objective grade point value, the number of reconstructed frames, and the conventional peak signal-to-noise ratio value. The feasibility of cell interleaving is also addressed. MPEG-2 control information (i.e., the control blocks) plays a critical role in the decoding process and can influence the reconstructed video quality dramatically; special consideration and excess protection should be given to this information. The concept of a new FEC strategy, header redundancy FEC, is introduced to address this issue. In HRFEC, selected important (high-priority) MPEG-2 control blocks (such as sequence header, sequence extensions, and picture header and corresponding extensions) are replicated before transmission, and duplicate copies are transmitted over the wireless link. Our results indicate that HRFEC is a simple, flexible, and effective error control strategy for broadcasting or multicasting MPEG-2 videos over error-prone and time-varying wireless channels     

Scene content driven FEC allocation for video streaming

Unequal error protection schemes applied on video data streams, considering varying importance of data packets over a group of pictures (GOP), are more efficient in terms of rate-distortion performance at different loss rates. Importance ordering policy adopted so far, mostly considered frame positions within a GOP. In the present work, we offer significant importance to the packets containing scene-transition frames, as these should be better error protected. We adopt a strategy of Forward Error Correcting (FEC) Code allocation, based on the minimization of end-to-end distortion up to the decoder, assuming that error concealment is adopted at the decoder. Two FEC allocation strategies are proposed within the Block of Packets (BOP) structure — one is an iterative modified hill climbing approach and the other is a reduced complexity heuristic approach. The Gilbert–Elliot model is used for the modeling of transmission channel. The proposed FEC allocation schemes outperform existing FEC allocation schemes in terms of PSNR for sequences with and without transitions, when transmitted over lossy channels.     

Error resilience in video and multiplexing layers for very lowbit-rate video coding systems

The transmission of audio-visual services on low-bit-rate, wireless telecommunications systems requires the use of coding techniques that are both efficient in their use of bits and robust against errors introduced in transmission. In this paper, we present efficient techniques for improving the error resilience of audio-visual services. These techniques are based on coding simultaneously for synchronization and error protection or detection. We apply the techniques to improve the performance of the multiplexing protocol (which combines the video and audio streams so that they can be transmitted on a single circuit), and also to improve the robustness of the coded video. We show through simulations that the techniques are efficient in their use of bits and effective against bursty errors common in wireless channels. For a simulation of the DECT channel at a bit-error rate of 10^-3, the techniques give an order of magnitude improvement in the probability of lost packets in the multiplexer layer over more conventional techniques. In the video layer, the techniques give an improvement of between 1-2 dB over ITU-T Recommendation H.263. The techniques proposed for the video layer also have the advantage of permitting simple transcoding with bit streams complying with H.263     

Performance evaluation of HDAF relaying systems for pilot and data symbol burst transmission over quasi‐static Rayleigh fading channels

This paper analyzes averaged symbol error probabilities of burst transmission consisting of pilot and data symbols for hybrid adaptive decode‐or‐amplify‐forward (HDAF) relaying systems. Under the assumption of quasi‐static Rayleigh fading channels with independent and non‐identically distribution, we consider a channel estimation scheme based on pilot symbols and show how channel estimation error affects received signal‐to‐noise ratio (SNR) and symbol error probability (SEP). Firstly, all the possible detection error‐events are presented for all the relay nodes, and their probabilities are derived as forms related with data symbol burst transmission. For the given error event, we analyze the conditional SEP as an exact form and then, the averaged SEP (ASEP) is approximately derived as a closed‐form. The simulation results verify that our derived ASEP expression is accurate over all the regions of SNR. Utilizing the proposed expressions, we can evaluate ASEP performance of HDAF relay systems easily and fast. Copyright © 2015 John Wiley & Sons, Ltd.