Diff-Max: Separation of routing and scheduling in backpressure-based wireless networks

Original manuscript September 19, 2012Backpressure routing and scheduling, with throughput-optimal operation guarantee, is a promising technique to improve throughput in wireless multi-hop networks. Although backpressure is conceptually viewed as layered, the decisions of routing and scheduling are made jointly, which imposes several challenges in practice. In this work, we present Diff-Max, an approach that separates routing and scheduling and has three strengths: (i) Diff-Max improves throughput significantly, (ii) the separation of routing and scheduling makes practical implementation easier by minimizing cross-layer operations; i.e., routing is implemented in the network layer and scheduling is implemented in the link layer, and (iii) the separation of routing and scheduling leads to modularity; i.e., routing and scheduling are independent modules in Diff-Max, and one can continue to operate even if the other does not. Our approach is grounded in a network utility maximization (NUM) formulation and its solution. Based on the structure of Diff-Max, we propose two practical schemes: Diff-subMax and wDiff-subMax. We demonstrate the benefits of our schemes through simulation in ns-2.National Science Foundation (U.S.) (Grant CNS-0915988)United States. Office of Naval Research (Grant N00014-12-1-0064)United States. Army Research Office. Multidisciplinary University Research Initiative (Grant W911NF-08-1-0238

Some inequalities in B

Let H denote a separable Hilbert space and let B(H) be the space of bounded and linear operators from H to H. We define a subspace Δ(A,B) of B(H), and prove two inequalities between the distance to Δ(A,B) of each operator T in B(H), and the value sup{‖AnTBn−T‖:n=1,2,…}

Multi-user video streaming using unequal error protection network coding in wireless networks

In this paper, we investigate a multi-user video streaming system applying unequal error protection (UEP) network coding (NC) for simultaneous real-time exchange of scalable video streams among multiple users. We focus on a simple wireless scenario where users exchange encoded data packets over a common central network node (e.g., a base station or an access point) that aims to capture the fundamental system behaviour. Our goal is to present analytical tools that provide both the decoding probability analysis and the expected delay guarantees for different importance layers of scalable video streams. Using the proposed tools, we offer a simple framework for design and analysis of UEP NC based multi-user video streaming systems and provide examples of system design for video conferencing scenario in broadband wireless cellular networks

Network Coding-Aware Queue Management for TCP Flows Over Coded Wireless Networks

In this paper, we are interested in improving the performance of TCP flows over wireless networks with a given constructive intersession network coding scheme. We are motivated by the observation that TCP does not fully exploit the potential of the underlying network coding opportunities. In order to improve the performance of TCP flows over coded wireless networks, without introducing changes to TCP itself, we propose a network-coding aware queue management scheme (NCAQM) that is implemented at intermediate network coding nodes and bridges the gap between network coding and TCP rate control. The design of NCAQM is grounded on the network utility maximization (NUM) framework and includes the following mechanisms. NCAQM: 1) stores coded packets at intermediate nodes in order to use the buffer space more efficiently; 2) determines what fraction of the flows should be coded together; and 3) drops packets at intermediate nodes so that it matches the rates of parts of different TCP flows that are coded together. We demonstrate, via simulation, that NCAQM significantly improves TCP throughput compared to TCP over baseline queue management schemes

Separation of Routing and Scheduling in Backpressure-Based Wireless Networks

Backpressure routing and scheduling, with its throughput-optimal operation guarantee, is a promising technique to improve throughput in wireless multihop networks. Although backpressure is conceptually viewed as layered, the decisions of routing and scheduling are made jointly, which imposes several challenges in practice. In this work, we present Diff-Max, an approach that separates routing and scheduling and has three strengths: 1) Diff-Max improves throughput significantly; 2) the separation of routing and scheduling makes practical implementation easier by minimizing cross-layer operations; i.e., routing is implemented in the network layer and scheduling is implemented in the link layer; and 3) the separation of routing and scheduling leads to modularity; i.e., routing and scheduling are independent modules in Diff-Max, and one can continue to operate even if the other does not. Our approach is grounded in a network utility maximization (NUM) formulation and its solution. Based on the structure of Diff-Max, we propose two practical schemes: Diff-subMax and wDiff-subMax. We demonstrate the benefits of our schemes through simulation in ns-2.National Science Foundation (U.S.) (grant CNS-0915988)United States. Office of Naval Research (grant N00014- 12-1-0064)United States. Office of Naval Research. Multidisciplinary University Research Initiative (grant number W911NF-08-1-0238

ACM CoNEXT 2016 Student Workshop

12th ACM Conference on Emerging Networking Experiments and Technologies, ACM CoNEXT 2016, Irvine, US, 12-15 December 2016The ACMCoNEXT 2016 StudentWorkshop is held in Irvine, California, USA on December 12, 2016 and co-located with the ACM 12th International Conference on emerging Net- working Experiments and Technologies (CoNEXT 2016). The main objective of the workshop is to provide a platform for graduate students in the area of computer networks and communications to present their ongoing research eorts. The workshop is also a unique opportunity for students to network with other junior researchers as well as more expe- rienced ones, receive constructive feedback, guidance, tips, and learn about cutting-edge research problems being tack- led by the community. We have constructed an exciting program of 24 refereed presentations and posters, and an invited keynote talk (by Prof. Lixia Zhang, UCLA) that will give participating students an opportunity to hear from a senior researcher.Department of Computin

Graft-compatibility of rootpac rootstocks with nectarine and peach cultivars

Interspecific hybrids or clones from different Prunus species can be used as rootstocks for peaches. Recently, the Rootpac rootstocks have been released and begun to be used for peaches. Therefore, grafting aptitude and their compatibility with peach and nectarine cultivars should be examined. The aim of this study is to determine the graft-compatibility performance of different clonal Rootpac rootstocks with peach and nectarine cultivars. Graft unions of peaches and nectarines on Rootpac rootstocks were monitored at the Fruit Research Institute in Eğirdir, Isparta, Turkey. The peach cultivars 'Monroe', 'Royal Glory', 'Q'Henry', 'Vista Rich', 'Cresthaven' and the nectarine cultivar 'Venus' were T-budded on Rootpac-R, Rootpac-90, Rootpac-70, Rootpac-40 and Rootpac-20. The graft samples were evaluated with a microscope at 1, 4 and 12 months after budding. Cambial differentiation occurred after a callus bridge was formed between the two parts of the graft. The graft union and development was observed to be successful. Consequently, no evidence for histological incompatibility was found. In addition, no incompatibility visual symptoms (drying, chlorosis on the leaves, premature death of the trees, marked difference in the growth rate or vigor of scion and stock, over growth at, above or below the graft union, etc.) were observed until the third vegetative season of the budded trees. © 2020 International Society for Horticultural Science. All rights reserved.We would like to thank TAGEM (General Directorate of Agricultural Research and Policies) and Agromillora Seedling Production and Marketing Company for their support for this project

MicroCast: Cooperative video streaming using cellular and local connections

© 2015 IEEE. We consider a group of mobile users, within proximity of each other, who are interested in watching the same online video. The common practice today is that each user downloads the video independently on her mobile device using her own cellular connection, which wastes access bandwidth and may also lead to poor video quality. We propose a novel cooperative system where each mobile device uses simultaneously two network interfaces: (i) cellular to connect to the video server and download parts of the video and (ii) WiFi to connect locally to all other devices in the group to exchange those parts. Devices cooperate to efficiently utilize all network resources and to adapt to varying wireless network conditions. In the local WiFi network, we exploit overhearing, which we further combine with network coding. The end result is savings in cellular bandwidth and improved user experience. We follow a complete approach, from theory to practice. First, we formulate the problem using a network utility maximization (NUM) framework, decompose the problem, and provide a distributed solution. Then, based on the structure of the NUM solution, we design a system called MicroCast, and we implement a prototype as an Android application. We provide both simulation results of the NUM solution and experimental evaluation. We demonstrate that the proposed approach brings significant performance benefits (namely, faster download on the order of the group size) without battery penalty

MicroCast: Cooperative video streaming using cellular and local connections

© 2015 IEEE. We consider a group of mobile users, within proximity of each other, who are interested in watching the same online video. The common practice today is that each user downloads the video independently on her mobile device using her own cellular connection, which wastes access bandwidth and may also lead to poor video quality. We propose a novel cooperative system where each mobile device uses simultaneously two network interfaces: (i) cellular to connect to the video server and download parts of the video and (ii) WiFi to connect locally to all other devices in the group to exchange those parts. Devices cooperate to efficiently utilize all network resources and to adapt to varying wireless network conditions. In the local WiFi network, we exploit overhearing, which we further combine with network coding. The end result is savings in cellular bandwidth and improved user experience. We follow a complete approach, from theory to practice. First, we formulate the problem using a network utility maximization (NUM) framework, decompose the problem, and provide a distributed solution. Then, based on the structure of the NUM solution, we design a system called MicroCast, and we implement a prototype as an Android application. We provide both simulation results of the NUM solution and experimental evaluation. We demonstrate that the proposed approach brings significant performance benefits (namely, faster download on the order of the group size) without battery penalty