A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The performance of packet-level media-independent forward error correction (FEC) schemes are computed in terms of both packet loss ratio and average burst length of multimedia data after error recovery. The set of equations leading to the analytical formulation of both parameters are first given for a renewal error process. Finally, the FEC performance parameters are computed for a Gilbert (1960) model loss process and compared to various experimental data. <s> BIB001 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The problem of encoding and transmitting a video sequence over an IP-based wireless network, consisting of both wired and wireless links, is addressed. To combat the different types of packet loss in the heterogeneous network, the use of a product code forward error correction (FEC) scheme capable of providing unequal error protection is considered. At the transport layer, Reed-Solomon (RS) coding is used to provide inter-packet protection. In addition, rate-compatible punctured convolutional (RCPC) coding is used at the link layer to provide unequal intra-packet protection. Optimal bit allocation is performed in a rate-distortion optimized joint source-channel coding and power allocation framework to achieve the best video quality. Simulation results illustrate the advantage of the proposed product code FEC scheme over previously studied approaches. <s> BIB002 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> In motion-compensated video-coding schemes, such as MPEG, an I frame is normally followed by several P frames and possibly B frames in a group-of-picture (GOP). In error-prone environments, errors happening in the previous frames in a GOP may propagate to all the following frames until the next I frame, which is the beginning of the next GOP. In this paper, we propose a novel GOP structure for robust transmission of MPEG video bitstream. By selecting the optimal position of the I frame in a GOP, robustness can be achieved without reducing any coding efficiency. Experimental results demonstrate the robustness of the proposed GOP structure. <s> BIB003 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Real-time multimedia transport has stringent quality of service requirements, which are generally not supported by current network architectures. In emerging mobile ad hoc networks, frequent topology changes and link failures cause severe packet losses, which degrade the quality of received media. However, in such mesh networks, there usually exist multiple paths between any source and destination nodes. Such path diversity has been demonstrated to be effective in combating congestion and link failures for improved media quality. In this paper, we present a new protocol to facilitate multipath transport of real-time multimedia data. The proposed protocol, the multiflow real-time transport protocol (MRTP), provides a convenient vehicle for real-time applications to partition and transmit data using multiple flows. We demonstrate through analysis that data partitioning, which is an essential function of MRTP, can effectively reduce the short-range dependence of multimedia data, thus improving its queueing performance in underlying networks. Furthermore, we show that a few flows are sufficient for MRTP to exploit most of the benefits of multipath transport. Finally, we present a comprehensive simulation study on the performance of MRTP under a mobile ad hoc network. We show that with one additional path, MRTP outperformed single-flow RTP by a significant margin. <s> BIB004 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> This paper exhibits a class of universal Raptor codes: for a given integer k, and any real /spl epsiv/>0, Raptor codes in this class produce a potentially infinite stream of symbols such that any subset of symbols of size k(1 + /spl epsiv/) is sufficient to recover the original k symbols, with high probability. Each output symbol is generated using O(log(1//spl epsiv/)) operations, and the original symbols are recovered from the collected ones with O(klog(1//spl epsiv/)) operations. <s> BIB005 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> In this paper, we propose a novel transport protocol that effectively utilizes available bandwidth and diversity gains provided by heterogeneous, highly lossy paths. Our Multi-Path LOss-Tolerant (MPLOT) protocol can be used to provide significant gains in the goodput of wireless mesh networks, subject to bursty, correlated losses with average loss-rates as high as 50%, and random outage events. MPLOT makes intelligent use of erasure codes to guard against packets losses, and a Hybrid-ARQ/FEC scheme to reduce packet recovery latency, where the redundancy is adaptively provisioned into both proactive and reactive FECs. MPLOT uses dynamic packet mapping based on current path characteristics, and does not require packets to be delivered in sequence to ensure reliability. We present a theoretical analysis of the different design choices of MPLOT and show that MPLOT makes an optimal trade-off between goodput and delay constraints. We test MPLOT, through simulations, under a variety of test scenarios and show that it effectively exploits path diversity in addition to aggregating path bandwidths. We also show that MPLOT is fair to single-path protocols like TCP-SACK. <s> BIB006 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Application layer multicast (ALM) is highly expected to replace IP multicasting as the new technological choice for content delivery. Depending on the streaming application, ALM nodes will construct a multicast tree and deliver the stream through this tree. However, if a node resides in the tree leaves, it cannot deliver the stream to its descendant nodes. In this case, quality of service (QoS) will be compromised dramatically. To overcome this problem, topology-aware hierarchical arrangement graph (THAG) was proposed. By employing multiple description coding (MDC), THAG first splits the stream into a number of descriptions, and then uses arrangement graph (AG) to construct node-disjoint multicast trees for each description. However, using a constant AG size in THAG creates difficulty in delivering descriptions appropriately across a heterogeneous network. In this paper, we propose a method, referred to as network-aware hierarchical arrangement graph (NHAG), to change the AG size dynamically to enhance THAG performance, even in heterogeneous networks. Finally, we evaluate the proposed scheme by experiments using the network simulator ns-2. By comparing our proposed method to THAG and SplitStream, we show that our method provides better performance in terms of throughput and QoS. The results indicate that our approach is more reliable than other methods in heterogeneous networks. <s> BIB007 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Video streaming ranks among the most popular services offered through the Internet today. At the same time, accessing the Internet over public WiFi and 3G networks has become part of our everyday lives. However, streaming video in wireless environments is often subject to frequent periods of rebuffering and characterized by low picture quality. In particular, achieving smooth and quality-adaptive streaming of live video poses a big challenge in mobile scenarios. Building on the observation that the subjective video experience on mobile devices decreases when quality changes are more frequent than every 1 to 2 seconds, we present a client-side scheduler that retrieves segments of several video encodings over heterogeneous network interfaces simultaneously. By extending the DAVVI streaming platform with support for multiple interfaces, the proposed scheduler's performance is experimentally evaluated. The results show that our scheduler reduces the video interruptions and achieves a higher and more stable average quality over multiple, truly heterogeneous wireless interfaces. <s> BIB008 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Devices capable of connecting to multiple, overlapping networks simultaneously are becoming increasingly common. For example, most laptops are equipped with LAN- and WLAN-interfaces, and smart phones can typically connect to both WLANs and 3G mobile networks. At the same time, streaming high-quality video is becoming increasingly popular. However, due to bandwidth limitations or the unreliable and unpredictable nature of some types of networks, streaming video can be subject to frequent periods of rebuffering and characterised by a low picture quality. In this paper, we present a client-side request scheduler that distributes requests for the video over multiple heterogeneous interfaces simultaneously. Each video is divided into independent segments with constant duration, enabling segments to be requested over separate links, utilizing all the available bandwidth. To increase performance even further, the segments are divided into smaller subsegments, and the sizes are dynamically calculated on the fly, based on the throughput of the different links. This is an improvement over our earlier subsegment approach, which divided segments into fixed size subsegments. Both subsegment approaches were evaluated with on-demand streaming and quasi-live streaming. The new subsegment approach reduces the number of playback interruptions and improves video quality significantly for all cases where the earlier approach struggled. Otherwise, they show similar performance. <s> BIB009 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Video streaming is gaining popularity among mobile users. The latest mobile devices, such as smart phones and tablets are equipped with multiple wireless network interfaces. How to efficiently and cost-effectively utilize multiple links to improve the video streaming quality needs to be investigated. In order to maintain high video streaming quality while reduce the wireless service cost, in this paper, the optimal video streaming process with multiple links is formulated as a Markov Decision Process (MDP). The reward function is designed to consider the quality of experience (QoE) requirements for video traffic, such as the interruption rate, average playback quality, playback smoothness and wireless service cost. Using dynamic programming, the MDP can be solved to obtain the optimal streaming policy. To evaluate the performance of the proposed multi-link rate adaptation (MLRA) algorithm, we implement a testbed using the Android mobile phone and the open-source X264 video codec. Experimental results demonstrate the feasibility and effectiveness of the proposed MLRA algorithm for mobile video streaming applications, which outperforms the existing state-of-the-art one. <s> BIB010 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Devices capable of connecting to multiple, overlapping networks simultaneously is becoming increasingly common. For example, most laptops are equipped with LAN- and WLAN-interface, and smart phones can typically connect to both WLANs and 3G mobile networks. At the same time, streaming high-quality video is becoming increasingly popular. However, due to bandwidth limitations or the unreliable and unpredictable nature of some types of networks, streaming video can be subject to frequent periods of rebuffering and characterized by a low picture quality. In this paper, we present a multilink extension to the data retrieval part of the DAVVI adaptive, segmented video streaming system. DAVVI implements the same core functionality as the MPEG DASH standard. It uses HTTP to retrieve data, segments video, provides clients with a description of the content, and allows clients to switch quality during playback. Any DAVVI-data retrieval extensions can also be implemented in a DASH-solution. The multilink-enabled DAVVI client divides video segments into smaller subsegments, which are requested over multiple interfaces simultaneously. The size of each subsegment is dynamic and calculated on the fly, based on the throughput of the different links. This is an improvement over our earlier subsegment approach, which divided segments into fixed size subsegments. The quality of the video is adapted based on the measured, aggregated throughput. Both the static and the dynamic subsegment approaches were evaluated with on-demand streaming and quasi-live streaming. The new subsegment approach reduces the number of playback interruptions and improves video quality significantly for all cases where the earlier approach struggled. Otherwise, they show similar performance. <s> BIB011 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The increasing number of interfaces using different access technologies in modern devices gives opportunities for enhancing the Quality of Service (QoS) delivered to multimedia and interactive data transfers involved in distributed applications. In the current Internet, the presence of "middleboxes" such as Network Address Translators (NAT) or firewalls hardly lets applications use any Transport protocol but the well-known Transmission Control Protocol (TCP). Currently under standardization at the IETF, the new Multipath-TCP (MPTCP) protocol uses several TCP flows to make use of the multiple interfaces available on the end terminals, thus improving both network availability and QoS, still being capable to cross over middle boxes. Although originally being fully reliable and fully ordered, its two sub-layers architecture gives opportunity to use QoS techniques over fully reliable paths. This paper studies the QoS benefits induced by the implementation of the "partial reliability" concept in MPTCP for interactive video applications. Two different mechanisms are experimented with the aim to enhance global quality of video transmission over paths close to 3G networks characteristics. The Internet Engineering Task Force (IETF) MPTCP working group's ns-2 implementation is used for the experimentations. The Evalvid toolkit over ns-2 is used to measure the QoS benefits expressed in terms of Peak Signal to Noise Ratio (PSNR). <s> BIB012 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Poor connectivity is common when we use wireless networks on the go. A natural way to tackle the problem is to take advantage of the multiple network interfaces on our mobile devices, and use all the networks around us. Using multiple networks at a time makes makes possible faster connections, seamless connectivity and potentially lower usage charges. The goal of this paper is to explore how to make use of all the networks with today's technology. Specifically, we prototyped a solution on an Android phone. Using our prototype, we demonstrate the benefits (and difficulties) of using multiple networks at the same time. <s> BIB013 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Known as multihoming, devices with more than one network interface can enhance their performance capabilities by harnessing unused resources from alternative access networks. Whether it's improved reliability or sheer throughput potential, network devices will benefit from a multihomed framework. Unfortunately, our current means of guaranteeing reliability while maintaining quality control, specifically, the transmission control protocol (TCP), does not support multihoming. Despite the latter, a relatively young transport layer standard called the stream control transmission protocol (SCTP), incorporates multihoming into its design. In this paper, we investigate state-of-the-art multihoming techniques using SCTP. A comprehensive survey of developments has brought forth three main research areas, namely: handover management, concurrent multipath transfer (CMT), and cross-layer activities. While the presented algorithms may offer sufficient results, many open problems still remain. <s> BIB014 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> This paper proposes a robust video streaming scheme for priority networks with path diversity, based on a combined approach of multiple description coding (MDC) with optimal picture classification into two priorities. A binary classification algorithm is proposed to define high (HP) and low (LP) priority network abstraction layer units (NALU), which in turn define the packet priorities. An optimisation algorithm is used to find HP pictures, based on dynamic programming and relying on minimisation of the packet loss concealment distortion. The paper shows that the proposed algorithm is able to effectively improve the decoded video without increasing the MDC stream redundancy. The overall performance evaluation, carried out by simulating MDC video streaming over lossy networks with path diversity, demonstrates that the proposed algorithm yields higher video quality for a wide range of packet loss rates (PLR). Comparing with no-priority MDC video streaming schemes, the simulation results show that the proposed algorithm can improve the average PSNR results in 0.7–3.2dB for packet loss rates between 3% and 15%. <s> BIB015 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Mobile devices equipped with multiple network interfaces can increase their throughput by making use of parallel transmissions over multiple paths and bandwidth aggregation, enabled by the stream control transport protocol (SCTP). However, the different bandwidth and delay of the multiple paths will determine data to be received out of order and in the absence of related mechanisms to correct this, serious application-level performance degradations will occur. This paper proposes a novel quality-aware adaptive concurrent multipath transfer solution (CMT-QA) that utilizes SCTP for FTP-like data transmission and real-time video delivery in wireless heterogeneous networks. CMT-QA monitors and analyses regularly each path's data handling capability and makes data delivery adaptation decisions to select the qualified paths for concurrent data transfer. CMT-QA includes a series of mechanisms to distribute data chunks over multiple paths intelligently and control the data traffic rate of each path independently. CMT-QA's goal is to mitigate the out-of-order data reception by reducing the reordering delay and unnecessary fast retransmissions. CMT-QA can effectively differentiate between different types of packet loss to avoid unreasonable congestion window adjustments for retransmissions. Simulations show how CMT-QA outperforms existing solutions in terms of performance and quality of service. <s> BIB016 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The Internet infrastructure often supports multiple routes between two communicating hosts and, today, especially mobile hosts usually offer multiple network interfaces, so that disjoint paths between the hosts can be constructed. Having a number of (partly or fully) disjoint paths available may allow applications to distribute their traffic, aggregate capacity of different paths, choose the most suitable subset of paths, and support failover if a path fails. Exploiting multipath characteristics has been explored for TCP, but the requirements for real-time traffic differs notably. In this paper, we devise a multipath communication model for Real-time Transport Protocol (RTP); present minimal set of required protocol extensions; develop algorithms for scheduling RTP traffic across multiple paths at the sender and a corresponding de-jittering algorithm at the receiver side; and evaluate our proposal in varying scenarios using media traffic across different emulated mobile access network setups. <s> BIB017 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Modern mobile devices are equipped with multiple network interfaces, including 3G/LTE and WiFi. Bandwidth aggregation over LTE and WiFi links offers an attractive opportunity of supporting bandwidth-intensive services, such as high-quality video streaming, on mobile devices. However, achieving effective bandwidth aggregation in mobile environments raises several challenges related to deployment, link heterogeneity, network fluctuation, and energy consumption. We present GreenBag, an energy-efficient bandwidth aggregation middleware that supports real-time data-streaming services over asymmetric wireless links, requiring no modifications to the existing Internet infrastructure and servers. GreenBag employs several techniques, including medium load balancing, efficient segment management, and energy-aware mode control, to resolve such challenges. We implement a prototype of GreenBag on Android-based mobile devices which hosts, to the best knowledge of the authors, the first LTE-enabled bandwidth aggregation prototype for energy-efficient real-time video streaming. Our experiment results in both emulated and real-world environments show that GreenBag not only achieves good bandwidth aggregation to provide QoS in bandwidth-scarce environments but also efficiently saves energy on mobile devices. Moreover, energy-aware GreenBag can minimize video interruption while consuming 14-25% less energy than the non-energy-aware counterpart in real-world experiments. <s> BIB018 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> This paper investigates mobile video delivery in a heterogeneous wireless network from a video server to a multi-homed client. Joint source-channel coding (JSCC) has proven to be an effective solution for video transmission over bandwidth-limited, error-prone wireless networks. However, one major problem with the existing JSCC approaches is that they consider the network between the server and the client as a single transport link. The situation becomes more complicated in the context of multiple available links because involving a low-bandwidth, highly lossy, or long-delay wireless network in the transmission will only degrade the video quality. To address the critical problem, we propose a novel flow rate allocation-based JSCC (FRA-JSCC) approach that includes three key phases: (1) forward error correction redundancy estimation under loss requirement, (2) source rate adaption under delay constraint, and (3) dynamic rate allocation to minimize end-to-end video distortion. We present a mathematical formulation of JSCC to optimize video quality over multiple wireless channels and provide comprehensive analysis for channel distortion. We evaluate the performance of FRA-JSCC through emulations in Exata and compare it with the existing schemes. Experimental results show that FRA-JSCC outperforms the competing models in improving the video peak signal-to-noise ratio as well as in reducing the end-to-end delay. <s> BIB019 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Multiple description coding (MDC) is one of the promising solutions for live video delivery over lossy networks. In this paper, we present a review of MDC techniques based on their application domain and we explain their functionality, with the objective of giving enough insight to designers to decide which MDC scheme is best suited for their specific application based on requirements such as standard compatibility, redundancy tunability, complexity, and extendibility to n-description coding. The focus is mainly on video sources but image-based algorithms applicable to video are considered as well. We also cover the well-known and important problem of drift and solutions to avoid it. <s> BIB020 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> We consider the problem of scalable video streaming from a server to multinetwork clients over heterogeneous access networks, with the goal of minimizing the distortion of the received videos. This problem has numerous applications including: 1) mobile devices connecting to multiple licensed and ISM bands, and 2) cognitive multiradio devices employing spectrum bonding. In this paper, we ascertain how to optimally determine which video packets to transmit over each access network. We present models to capture the network conditions and video characteristics and develop an integer program for deterministic packet scheduling. Solving the integer program exactly is typically not computationally tractable, so we develop heuristic algorithms for deterministic packet scheduling, as well as convex optimization problems for randomized packet scheduling. We carry out a thorough study of the tradeoff between performance and computational complexity and propose a convex programming-based algorithm that yields good performance while being suitable for real-time applications. We conduct extensive trace-driven simulations to evaluate the proposed algorithms using real network conditions and scalable video streams. The simulation results show that the proposed convex programming-based algorithm: 1) outperforms the rate control algorithms defined in the Datagram Congestion Control Protocol (DCCP) by about 10-15 dB higher video quality; 2) reduces average delivery delay by over 90% compared to DCCP; 3) results in higher average video quality of 4.47 and 1.92 dB than the two developed heuristics; 4) runs efficiently, up to six times faster than the best-performing heuristic; and 5) does indeed provide service differentiation among users. <s> BIB021 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The massive proliferation of wireless infrastructures with complementary characteristics prompts the bandwidth aggregation for Concurrent Multipath Transfer (CMT) over heterogeneous access networks. Stream Control Transmission Protocol (SCTP) is the standard transport-layer solution to enable CMT in multihomed communication environments. However, delivering high-quality streaming video with the existing CMT solutions still remains problematic due to the stringent quality of service (QoS) requirements and path asymmetry in heterogeneous wireless networks. In this paper, we advance the state of the art by introducing video distortion into the decision process of multipath data transfer. The proposed distortion-aware concurrent multipath transfer (CMT-DA) solution includes three phases: 1) per-path status estimation and congestion control; 2) quality-optimal video flow rate allocation; 3) delay and loss controlled data retransmission. The term ‘flow rate allocation’ indicates dynamically picking appropriate access networks and assigning the transmission rates. We analytically formulate the data distribution over multiple communication paths to minimize the end-to-end video distortion and derive the solution based on the utility maximization theory. The performance of the proposed CMT-DA is evaluated through extensive semi-physical emulations in Exata involving H.264 video streaming. Experimental results show that CMT-DA outperforms the reference schemes in terms of video peak signal-to-noise ratio (PSNR), goodput, and inter-packet delay. <s> BIB022 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Video streaming is gaining popularity among mobile users. The latest mobile devices, such as smart phones and tablets, are equipped with multiple wireless network interfaces. How to efficiently and cost-effectively utilize multiple links to improve video streaming quality needs investigation. In order to maintain high video streaming quality while reducing the wireless service cost, in this paper, the optimal video streaming process with multiple links is formulated as a Markov Decision Process (MDP). The reward function is designed to consider the quality of service (QoS) requirements for video traffic, such as the startup latency, playback fluency, average playback quality, playback smoothness and wireless service cost. To solve the MDP in real time, we propose an adaptive, best-action search algorithm to obtain a sub-optimal solution. To evaluate the performance of the proposed adaptation algorithm, we implemented a testbed using the Android mobile phone and the Scalable Video Coding (SVC) codec. Experiment results demonstrate the feasibility and effectiveness of the proposed adaptation algorithm for mobile video streaming applications, which outperforms the existing state-of-the-art adaptation algorithms. <s> BIB023 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Forward error correction (FEC) is a common error control technique to improve the quality of video streaming over lossy channels. To optimize the data recovery performance, frame-level FEC schemes have been proposed for streaming video to maximize playable frame rate (PFR) within transmission rate constraint on a random binary symmetric channel (BSC). However, burst loss is a commonplace in current Internet architecture, and the FEC efficacy c an be degraded since the burst data losses easily exceed the error correction capacity of FEC. Accordingly, an estimated video quality model over burst loss channels is proposed in this paper to evaluate the impact of burst loss for FEC-based video applications. In addition to th e model analysis, the simulation experiments on the NS-2 network simulator are conducted at a given estimate of the packet loss probability and average burst length. The results suggest a useful reference in designing the FEC scheme for video applications, and as the video coding and channel parameters are given, the proposed model can provide the optimal FEC solution to achieve a better reconstructed video quality than the FEC model based on a random BSC channel. <s> BIB024 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The growing availability of various wireless access technologies promotes increasing demand for mobile video applications. Stream control transmission protocol (SCTP)-based concurrent multipath transfer (CMT) improves the wireless video delivery performance with its parallel transmission and bandwidth (BW) aggregation features. However, the existing CMT solutions deployed at the transport layer only are not accurate enough due to lower layer uncertainties, such as variations of the wireless channel. In addition, CMT-based video transmission may use excessive BW in comparison with the popular Transmission Control Protocol (TCP)-based flows, which results in unfair sharing of network resources. This paper proposes a novel cross-layer fairness-driven (CL/FD) SCTP-based CMT solution (CMT-CL/FD) to improve video delivery performance, while remaining fair to the competing TCP flows. CMT-CL/FD utilizes a cross-layer approach to monitor and analyze path quality, which includes wireless channel measurements at the data-link layer and rate/BW estimations at the transport layer. Furthermore, an innovative window-based mechanism is applied for flow control to balance delivery fairness and efficiency. Finally, CMT-CL/FD intelligently distributes video data over different paths depending on their estimated quality to mitigate packet reordering and loss, under the constraint of TCP-friendly flow control. Simulation results show how CMT-CL/FD outperforms existing solutions in terms of both video delivery performance and TCP-friendliness. <s> BIB025 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Owing to the increase in consumption of multimedia content and the improvement of device capacity, user demand for high-quality content has increased. However, it is difficult to transport such large amounts of content over the existing broadcasting network with limited bandwidth. To provide high-definition broadcasting, some studies suggest methods of transporting multimedia over heterogeneous networks after encoding content hierarchically. MPEG Media Transport (MMT), standardized by Moving Picture Experts Group (MPEG), is a solution that enables large-volume media transport over heterogeneous networks such as digital broadcasting networks and packet-switched networks. In the case of delivering a scalable encoded video over different networks, synchronization of each stream is an important issue. MMT defines a synchronization scheme, but does not contain sufficient functions to implement it. In this paper, we propose a synchronization scheme for media streams that are encoded hierarchically, divided into layers, and transported over heterogeneous networks. We implement our scheme using MMT and HTTP, and experimented using three encapsulated video streams with different durations. As a result, we show that the proposed scheme can reduce the waiting time to display high-quality video, relative to Dynamic Adaptive Streaming over HTTP-Scalable Video Coding (DASH-SVC) by requesting segments of enhanced layers after calculating the transmission time. Additionally, we find out that the selection of durations have a relation to the characteristics of the video. <s> BIB026 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Layered video coding creates multiple layers of unequal importance, which enables us to progressively refine the reconstructed video quality. When the base layer (BL) is corrupted or lost during transmission, the enhancement layers (ELs) must be dropped, regardless whether they are perfectly decoded or not, which implies that the transmission power assigned to the ELs is wasted. For the sake of combating this problem, the class of inter-layer forward error correction (IL-FEC) solutions, also referred to as layer-aware FEC (LA-FEC), has been proposed for layered video transmissions, which jointly encode the BL and the ELs, thereby protecting the BL using the ELs. This tutorial aims for inspiring further research on IL-FEC/LA-FEC techniques, with special emphasis on the family of soft-decoded bit-level IL-FEC schemes. <s> BIB027 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Load distribution is a key research issue in deploying the limited network resources available to support traffic transmissions. Developing an effective solution is critical for enhancing traffic performance and network utilization. In this paper, we investigate the problem of load distribution for real-time traffic over multipath networks. Due to the path diversity and unreliability in heterogeneous overlay networks, large end-to-end delay and consecutive packet losses can significantly degrade the traffic flow’s goodput , whereas existing studies mainly focus on the delay or throughput performance. To address the challenging problems, we propose a G oodput- A ware L oad distribu T i ON (GALTON) model that includes three phases: (1) path status estimation to accurately sense the quality of each transport link, (2) flow rate assignment to optimize the aggregate goodput of input traffic, and (3) deadline-constrained packet interleaving to mitigate consecutive losses. We present a mathematical formulation for multipath load distribution and derive the solution based on utility theory. The performance of the proposed model is evaluated through semi-physical emulations in Exata involving both real Internet traffic traces and H.264 video streaming. Experimental results show that GALTON outperforms existing traffic distribution models in terms of goodput, video Peak Signal-to-Noise Ratio (PSNR), end-to-end delay, and aggregate loss rate. <s> BIB028 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Delivering high-definition (HD) wireless video under stringent delay constraint is challenging with regard to the limited network resources and high transmission rate. Concurrent multipath transfer (CMT) using stream control transmission protocol (SCTP) exploits the multihoming feature of mobile devices to establish associations with different access networks. In this paper, we study the multihomed HD video communication with SCTP over heterogeneous wireless networks. The existing CMT schemes mainly treat the traffic data in a content-agnostic fashion, and thus cannot effectively leverage the scarce wireless resources to maximize the perceived video quality. To address this critical issue, we propose a content-aware CMT (CMT-CA) solution that featured by the unequal frame-level scheduling based on estimated video parameters and feedback channel status. First, we develop an analytical framework to model the total distortion of parallel video transmission over multiple wireless access networks. Second, we introduce a joint congestion control and data distribution scheme to minimize the total distortion based on online quality evaluation and Markov decision process (MDP). The performance of CMT-CA is evaluated through extensive semi-physical emulations in Exata involving HD video encoded with H.264 codec. Experimental results show that CMT-CA outperforms the reference schemes in terms of video peak signal-to-noise ratio (PSNR), end-to-end delay, and goodput. Or conversely, CMT-CA achieves the same video quality with $20$ percent bandwidth conservation. <s> BIB029 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> End-users in online video services are sensitive to the overall quality of the video at screen, but also, and more importantly, to other factors, including the latency between the video generation and the playback for live videos. If the improvement of the quality of the perceived video has been well investigated by the multimedia community, the impact of delay, latency, and re-buffering has not received a significant attention. Adaptive streaming technologies, which have been widely adopted in the recent years, contribute to this lack of consideration since vendors usually recommend the introduction of significant extra-latency. In this paper, we address the problem of low-latency live video streaming. We propose an implementation of multi-path video delivery at the applicative level, which exploits the information provided in the latest version of the video delivery standards. We present an implementation of a video player, which takes advantage of multi-path networking to enable video playback using TCP with a latency below 100 ms. By initiating the multi-path delivery from the client side, our mechanism is compatible with current network equipments and does not require any change neither at the server nor in the middleboxes. <s> BIB030 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> The proliferating wireless infrastructures with complementary characteristics prompt the bandwidth aggregation for concurrent video transmission in heterogeneous access networks. Multipath TCP (MPTCP) is an important transport-layer protocol recommended by IETF to integrate different access medium (e.g., Cellular and Wi-Fi). This paper investigates the problem of mobile video delivery using MPTCP in heterogeneous wireless networks with multihomed terminals. To achieve the optimal quality of real-time video streaming, we have to seriously consider the path asymmetry in different access networks and the disadvantages of the data retransmission mechanism in MPTCP. Motivated by addressing these critical issues, this study presents a novel quAlity-Driven MultIpath TCP (ADMIT) scheme that integrates the utility maximization based Forward Error Correction (FEC) coding and rate allocation. We develop an analytical framework to model the MPTCP-based video delivery quality over multiple communication paths. ADMIT is able to effectively integrate the most reliable access networks with FEC coding to minimize the end-to-end video distortion. The performance of ADMIT is evaluated through extensive semi-physical emulations in Exata involving H.264 video streaming. Experimental results show that ADMIT outperforms the reference transport protocols in terms of video PSNR (Peak Signal-to-Noise Ratio), end-to-end delay, and goodput. Thus, we recommend ADMIT for streaming high-quality mobile video in heterogeneous wireless networks with multihomed terminals. <s> BIB031 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> One major concern when applying Multipath TCP (MPTCP) to the real-time multimedia applications is related to MPTCP's fully-reliable and fully-ordered service nature, which will inevitably degrade users' Quality of Experience (QoE) for multimedia streaming services in a heterogeneous wireless network environment because asymmetric wireless links are commonly with different transmission characteristics and sensitive to variations. In this paper, we first discuss the design considerations of partially reliable-MPTCP associated with the real-time constraint of multimedia streaming. Then we propose a context-aware QoE-oriented MPTCP Partial Reliability extension (PR-MPTCP+) for providing partially reliable multimedia streaming service to an upper layer protocol. Finally, we evaluate the proposed PR-MPTCP+ solution using a wide range of multimedia quality metrics. <s> BIB032 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Video streaming has already become the main portion of data traffic over the Internet. However, it is hard to guarantee the user-perceived video quality in single access networks due to the limitation in available bandwidth. Multihomed systems enable concurrent multipath data transfer over multiple network paths. Path control can be implemented at the transport layer such as in Stream Control Transport Protocol (SCTP). SCTP has built-in support for multihoming, but offers only a limited standard path selection mechanism. In this paper a new method for video streaming over SCTP is proposed. Secondary paths are used to send redundant information to prevent degradation of viewer's perceived quality. The efficiency of the proposed method is demonstrated by computer simulations using video coded with H.264/MPEG-4 AVC (Advanced Video Coding). The results show that the proposed method can prevent degradation of video quality at the cost of small extra bandwidth usage. <s> BIB033 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> In order to improve the Quality-of-Service (QoS) of latency sensitive applications in next-generation cellular networks, multi-path is adopted to transmit packet stream in real-time to achieve high-quality video transmission in heterogeneous wireless networks. However, multi-path also introduces two important challenges: out-of-order issue and reordering delay. In this paper, we propose a new architecture based on Software Defined Network (SDN) for flow aggregation and flow splitting, and then design a Multiple Access Radio Scheduling (MARS) scheme based on relative Round-Trip Time (RTT) measurement. The QoS metrics including end-to-end delay, throughput and the packet out-of-order problem at the receiver have been investigated using the extensive simulation experiments. The performance results show that this SDN architecture coupled with the proposed MARS scheme can reduce the end-to-end delay and the reordering delay time caused by packet out-of-order as well as achieve a better throughput than the existing SMOS and Round-Robin algorithms. <s> BIB034 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Transport protocols that can exploit multiple paths, especially MPTCP, do not match the requirements of video streaming: high average transmission delay, too strict reliability, and frequent head-of-line phenomenons resulting in abrupt throughput drops. In this paper, we address this mismatch by introducing a cross-layer scheduler, which leverages information from both application and transport layers to re-order the transmission of data and prioritize the most significant parts of the video. Our objective is to maximize the amount of video data that is received in time at the client. We show that current technologies enable the implementation of this cross-layer scheduler without much overhead. We then demonstrate the validity of our approach by studying the performance of an optimal cross-layer scheduler. The gap between the performance of the traditional scheduler versus the optimal scheduler justifies our motivation to implement a cross-layer scheduler in practice. We propose one implementation with basic cross-layer awareness. To evaluate the performance of our proposal, we aggregate a dataset of real MPTCP sessions and we use video stream encoded with HEVC. Our results show that our cross-layer proposal outperforms the traditional scheduler. Viewers not only benefit from the inherent advantages of using MPTCP (such as a better resilience to path failure) but also get a better QoE compared to the traditional scheduler. <s> BIB035 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Making networks aware of applications and vice versa is a current trend in the design of emerging network management and service architectures. Additionally, new protocols and application adaptation approaches have been proposed in order to enhance the transmission of Quality of Service (QoS) sensitive data in the best effort Internet. This paper contributes to the field by studying means to improve the quality and availability of video streaming services in multi-access networks through controlled bitrate adaptation and multipath capabilities. The paper proposes a network management system to achieve advanced control and improved performance for multipath adaptive HTTP video streaming in multi-access networks. The management system builds upon the Distributed Decision Engine (DDE) framework and it is partially implemented and evaluated in the paper using a multi-access network testbed. <s> BIB036 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Compared with using only a single wireless path such as WiFi, leveraging multipath (e.g., WiFi and cellular) can dramatically improve users' quality of experience (QoE) for mobile video streaming. However, Multipath TCP (MPTCP), the de-facto multipath solution, lacks the support to prioritize one path over another. When applied to video streaming, it may cause undesired network usage such as substantial over-utilization of the metered cellular link. In this paper, we propose MP-DASH, a multipath framework for video streaming with the awareness of network interface preferences from users. The basic idea behind MP-DASH is to strategically schedule video chunks' delivery and thus satisfy user preferences. MP-DASH can work with a wide range of off-the-shelf video rate adaptation algorithms with very small changes. Our extensive field studies at 33 locations in three U.S. states suggest that MP-DASH is very effective: it can reduce cellular usage by up to 99% and radio energy consumption by up to 85% with negligible degradation of QoE, compared with off-the-shelf MPTCP. <s> BIB037 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> MPTCP (MultiPath TCP) boosts application network performance by aggregating bandwidth over multiple paths. However, it may cause poor performance due to the large number of out-of-order packets especially when the paths have different delays. To resolve this issue, we propose to dynamically add or remove MPTCP paths with the leverage of software-defined networking (SDN). The key idea is to track the available capacity of connected paths and pick the most appropriate paths depending on varying network conditions. To show the feasibility of our approach, we create an SDN platform using Mininet over Wi-Fi networks. Our analysis shows that a faster download and improved quality of experience (QoE) in adaptive rate video streaming is possible with our dynamic MPTCP path control mechanism using SDN. <s> BIB038 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> B. How to protect the packet? <s> Recent technological advancements in wireless infrastructures and handheld devices enable mobile users to concurrently receive multimedia contents with different radio interfaces (e.g., cellular and Wi-Fi). However, multipath video transport over the resource-limited and error-prone wireless networks is challenged with key technical issues: 1) conventional multipath protocols are throughput-oriented, and video data are scheduled in a content-agnostic fashion and 2) high-quality real-time video is bandwidth-intensive and delay-sensitive. To address these critical problems, this paper proposes a bandwidth-efficient multipath streaming (BEMA) protocol featured by the priority-aware data scheduling and forward error correction-based reliable transmission. First, we present a mathematical framework to formulate the delay-constrained distortion minimization problem for concurrent video transmission over multiple wireless access networks. Second, we develop a joint Raptor coding and data distribution framework to achieve target video quality with minimum bandwidth consumption. The proposed BEMA is able to effectively mitigate packet reordering and path asymmetry to improve network utilization. We conduct performance evaluation through extensive emulations in Exata involving real-time H.264 video streaming. Compared with the existing multipath protocols, BEMA achieves appreciable improvements in terms of video peak signal-to-noise ratio, end-to-end delay, bandwidth utilization, and goodput. Therefore, BEMA is recommended for streaming high-quality real-time video to multihomed terminals in heterogeneous wireless networks. <s> BIB039
Providing packet protection techniques to the scheduler leads to data loss rate decreases, and consequently, better video streaming throughput and QoE. In fact, inter-dependency among video frames causes a compressed video to be very sensitive to data loss. By this idea  , individual frames of pictures are grouped together, which is called GoP. Each GoP consists of one initial Intra (I)-frame, several Predicted (P)-frames and possibly Bidirectional (B)-frames BIB003 . While an I-frame is encoded without reference to any other video frames, but a P-frame is encoded with reference to previous I or P-frames, and a B-frame is encoded with reference to both immediate previous and forward I or P-frames. Therefore, in the decoding process, loss of some frames may preclude a proper decoding, especially in the miss of I-frames. Thus, it is important to protect frames (especially I-frames) in lossy wireless channels. For this purpose, some JSCC/Channel Level and Error Resilience/Source Level techniques have been implemented. These techniques will be discussed in this subsection. Tables V, VI , VII, and VIII present each category of such techniques divided by the protocol layer. Automatic Repeat reQuest (ARQ) retransmits requests to provide reliable data transmission. The retransmission occurs in case of packets lost or received with bit error. Inherently, all protocols atop or extensions of TCP (e.g., HTTP, DASH, MPTCP) use ARQ. However, the retransmission wastes bandwidth, causing network congestion, and consequently, increasing End-to-End delay. For example, in efforts to mitigate these problems: CMT-QA BIB016 retransmits packets over the path with minimum transfer delay; CMT-DA BIB022 and CMT-CA BIB029 retransmit only the estimated packets to arrive at the destination within the deadline; and CMT-CL/FD BIB025 selects the path with the largest cwnd for the retransmission, which sends the lost packet before all the other packets that exist in the path buffer. In addition, considering the existence of many clients in multicast communications, responding to the retransmission requests of all clients might be difficult for the server. Other surveyed works, which utilize ARQ as JSCC technique are MRTP BIB004 , MPRTP BIB017 , BIB030 , BIB010 , RTRA BIB023 , BIB026 , BIB008 , BIB009 , BIB011 , Greenbag BIB018 , MPLOT BIB006 , ADMIT BIB031 , MPTCP-SD BIB012 , MPTCP-PR BIB012 , PR-MPTCP + BIB032 , SRMT BIB033 , BIB013 , MARS BIB034 , BIB035 , BIB036 , MP-DASH BIB037 , and BIB038 . Forward Error Correction (FEC) appeared to remedy the shortcoming of packet retransmission and delay constraints, especially for live video streaming. Such a technique is also applied in multicast communication and whenever retransmission is costly or impossible, for instance, in one-way communication links BIB027 . FEC can be applied to circumvent packet erasures/loss by cross-packets FEC in the application or transport layer (inter-packet FEC), and/or to handle bit errors in the physical layer BIB002 (intra-packet FEC). In wired networks, it can have packet loss and packet truncation due to congestion. Therefore, either the packets are dropped by the network routers or the receiver due to excessive delay. In wireless networks, besides packet loss and packet truncation, there exists also bit errors due to noisy channels. Next, more details about inter-and intra-packet FEC techniques are provided. In inter-packet FEC, redundant/parity packets are commonly generated in addition to source packets to perform crosspacket FEC, which is usually achieved by erasure codes. These allow the receiver to detect error packets and correct data without retransmission. The capability of FEC to recover the lost data depends on the added redundant symbols. Among the many existent erasure codes, the most commonly studied ones are Reed-Solomon (RS) BIB001 , Low-Density Generator Matrix (LDGM)  and Raptor codes BIB005 . In our surveyed works, ADMIT BIB031 , GALTON BIB028 and FRA-JSCC BIB019 utilize RS due to stringent delay constraint. MPEG-H part 10 defines several MMT AL-FEC algorithms, including RS codes and LDGM. Raptor coding is used in BEMA BIB039 due to low processing time and high error correction capability. Such erasure codes could be applied at frame level, GoP level, or subGoP level for video protection BIB019 . In frame level BIB024 , the frames in each GoP are classified in terms of their type and their distance from the leading I-frame. Then, FEC is applied on the frames according to their priority. Besides, low priority frames can be dropped based on network conditions. In GoP level (see Figure 13 ), each GoP packetizes in k source packets. Then, FEC encoding maps source packets to some encoded packets. A FEC block of n data packets contains of k source packets, and (n − k) redundant packets. Redundancy in FEC is calculated as (n − k)/k, and the code rate is equal to k/n. In SubGoP level BIB039 , each GoP consists of several subgroups, each mapped to a source block. In our surveyed works, GoP level is used in ADMIT BIB031 , GALTON BIB028 , FRA-JSCC BIB019 , and SubGoP level is used in BEMA BIB039 . A trade-off between bandwidth/End-to-End delay and FEC redundancy is required. In particular, a smaller FEC packet size indicates a larger FEC block size due to the larger number of redundant packets BIB031 . While higher redundancy leads to better recoverability, it also increases overhead rate and bandwidth consumption. Consequently, congestion, packet reordering, FEC decoding delay and End-to-End delay have their probability increased, especially in the presence of burst losses. Therefore, an adaptive FEC is required to minimize these problems (e.g., bandwidth consumption and End-toEnd delay), and maximize the recoverability by adaptively changing FEC parameters (e.g., adequate FEC packet size and FEC redundancy) according to the network channel status, application delay characteristics, or based on the importance of content data. For example, a stronger FEC would be used in a more lossy channel while not required in a more stable channel with less loss rate percentage, or more robust FEC could also be used only for I-frames rather than B or P-frames. In our surveyed works, adaptive FEC is used in several works, like FRA-JSCC BIB019 and GALTON BIB028 to find FEC redundancy, ADMIT BIB031 to adjust FEC redundancy and code rate, and BEMA BIB039 to set code rate and symbol size. Moreover, MPLOT BIB006 also adaptively chooses block sizes, considering the usage of large block sizes in order to reduce bursty loss for delay-tolerant applications. We also identified FEC usage in MRTP BIB004 . Besides using FEC method, an adequate technique is also requested to distinguish losses due to traffic congestion with the ones caused by wireless channel disturbances and impairments. It is based on the fact that FEC redundancy in wireless lossy networks leads to better packet recovery; however, adding more FEC redundancy in a congested network worsens network situation since it pushes higher congestion and more losses BIB014 due to bit stuffing operations. More technical details on packet loss differentiation are provided in Section VI-A. In intra-packet FEC, channel coding is applied to correct bit errors in the physical layer. Turbo Codes (parallel Concatenated Constitutional coding) and Low-Density Parity-Check (LDPC) codes are generally used. Error detection is performed at the link layer, based on Cyclic Redundancy Check (CRC). Due to this approach, only packets passing CRC stage are visible on the network/Internet layer. Therefore, FEC provides reliable access network and End-to-End video distortion minimization. Moreover, a joint-ARQ and FEC usage approach can enhance efficiency, depending on the adopted strategy to couple both techniques. For example, in our surveyed works, ADMIT BIB031 utilizes FEC for reconstructing data, and consequently, it leads to delay reduction, making video data ready for fast video playback. However, there is no additional help to mitigate the number of retransmissions and bandwidth consumption increases drawbacks, since there is no ACK message sending to inform the server that the data is successfully reconstructed. Therefore, the MPTCP protocol on the server keeps sending retransmission of each lost packet until it receives the ACK from the receiver. This scenario outlines a motivation for a proper ARQ-and-FEC joint approach, using FEC for data protection, while retransmitting events only occur when there is no way to perform data reconstruction. 2) Error Resilience/Source Level: Besides employing JSCC techniques to recover from packet loss and bit errors, increasing the error resilience of the video sequence itself is also an important task. To provide this functionality, error resilience techniques embrace, among others, the usage of Scalable Video Coding (SVC) and Multiple Description Coding (MDC) methods. In SVC BIB020 , source video is encoded in one base layer and several enhancement layers. These layers are hierarchically dependent to each other. This means that, at the receiver, each layer can be decoded only when its lower layers have been correctly received. Therefore, video quality is improved based on the number of received enhancement layers. In order to improve the efficiency of SVC, base layer is often protected by FEC or it is transmitted through more reliable paths, due to its importance. In the proposed approach BIB021 , each packet is transmitted to the network only if all other related packets in lower layers have been sent before. Other surveyed works, which utilize SVC as Error Resilience are MRTP BIB004 , RTRA BIB023 , BIB026 , CMT-DA BIB022 , GALTON BIB028 and FRA-JSCC BIB019 . In MDC BIB020 , source video is encoded into several independent compressed streams which are called descriptions. Each description can be decoded independently and shall provide acceptable quality. When one or more descriptions arrive at the receiver, a video with a certain quality level would be made by the decoder. MDC is a good alternative to retransmission in order to remedy the delay constraint in real-time video streaming. According to a reviewed work about MDC techniques for video streaming BIB020 , MDC is more useful than FEC in the case of high lossy networks, since FEC uses long code block sizes, increasing bandwidth consumption as well. MDC also outperforms SVC in high lossy networks, but SVC is more proper than MDC in low loss rate networks, due to overhead reduction. MDC is also recommended for multicast with heterogeneous receivers BIB007 . Accordingly, works like BIB015 and MRTP BIB004 utilize MDC as error resilience technique.