A Holistic Survey of Wireless Multipath Video Streaming <s> 2) Proxy solutions: <s> A variety of wireless interfaces are available for today's mobile user to access Internet content. When coverage areas of these different technologies overlap, a terminal equipped with multiple interfaces can use them simultaneously to improve the performance of its applications. In this paper, we motivate the advantages that can be had through simultaneous use of multiple interfaces and present a network layer architecture that enables diverse multiaccess services. In particular, we explore in depth one such service provided by the architecture: Bandwidth Aggregation (BAG) for real-time applications. An important aspect of the architecture when providing BAG services for real-time applications is the scheduling algorithm that partitions the traffic onto different interfaces such that the QoS requirements of the application are met. We propose one such algorithm Earliest Delivery Path First (EDPF), that ensures packets meet their playback deadlines by scheduling packets based on the estimated delivery time of the packets. We show through analysis that EDPF performs close to an idealized Aggregated Single Link (ASL) discipline, where the multiple interfaces are replaced by a single interface with same aggregated bandwidth. A prototype implementation and extensive simulations carried using video and delay traces show the performance improvement BAG with EDPF scheduling offers over using just the Highest Bandwidth Interface (HBI) and other scheduling approaches based on weighted round robin. <s> BIB001 </s> A Holistic Survey of Wireless Multipath Video Streaming <s> 2) Proxy solutions: <s> Smart devices equipped with multiple network interfaces are becoming commonplace. Nevertheless, even though multiple interfaces can be used to connect to the Internet, their capabilities have not been fully utilized yet because the default TCP/IP stack supports only a single interface for communication. This situation is now changing due to the emergence of multipath protocols on different network stack layers. For example, many IP level approaches have been proposed utilizing tunneling mechanisms for hiding multipath transmission from the transport protocols. Several working groups under IEEE and IETF are actively standardizing multipath transmission on the link layer and transport layer. Application level approaches enable multipath transmission capability by establishing multiple transport connections and distributing data over them. Given all these efforts, it is beneficial and timely to summarize the state-of-the-art, compare their pros and cons, and discuss about the future directions. To that end, we present a survey on multipath transmission and make several major contributions: 1) we present a complete taxonomy pertaining to multipath transmission, including link, network, transport, application, and cross layers; 2) we survey the state-of-the-art for each layer, investigate the problems that each layer aims to address, and make comprehensive assessment of the solutions; and 3) based on the comparison, we identify open issues and pinpoint future directions for multipath transmission research. <s> BIB002
It is possible to use proxy at one side (client/server) or at both sides. Using proxy at one side hides multipath transmission from the other side. In the case of using proxy on both sides, each endpoint communicates with the proxy via a normal connection without awareness of the multipath communication. In proxy-based applications, a tunneling IP-in-IP mechanism (to encapsulate one IP packet as a payload in a new IP packet) is used to redirect data to different paths over routing level. Consequently, proxy-based approaches are transparent to both transport and application layers and do not require any changes in them BIB002 . Chebrolu et al. designed a network layer architecture, Bandwidth Aggregation (BAG) BIB001 , to utilize bandwidth aggregation for real-time applications. In BAG, server streams video data to the client by using a UDP socket. In particular, there is a proxy at the client side, which is aware of client interfaces and splits flow over these network interfaces by using IP-in-IP tunneling (see Figure 11 ). The proposed scheduling algorithm, Earliest Delivery Path First (EDPF), estimates the delivery time of each packet over each path and spreads packets over the fastest path in order to avoid packets from missing their deadlines and minimizing packet reordering. Delay and wireless bandwidth between the proxy and the client are used for delivery time estimation. As a result, EDPF is more efficient than Round Robin in avoiding HOL BIB002 . The advantage of using proxy at the client side is that no change is required at the server side BIB002 .