Real-time communication over unreliable wireless links: A theory and its applications

IEEE Wireless Communications (Impact Factor: 5.42). 02/2012; 19(1):48-59. DOI: 10.1109/MWC.2012.6155876
Source: DBLP


Wireless networks are increasingly used to serve real-time flows. We provide an overview of an emerging theory on real-time wireless communications and some of its main results. This theory is based on a model that jointly considers the delay bounds and throughput requirements of clients, as well as the unreliable and heterogeneous nature of wireless links. This model can be further extended in several aspects. It provides solutions to three important problems, namely, admission control, packet scheduling, and utility maximization. The theory can also be extended to consider broadcast of real-time flows, and to incorporate network coding.

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    • "Scheduling the wireless links and controlling their transmission power and rate in Spatial-reuse Time Division Multiple Access (STDMA) wireless networks has been investigated to minimize the detrimental effects of the interference for various objectives including maximizing total throughput [1], [2], maximizing minimum throughput [3], [4], minimizing total transmit power [5], [6] and minimizing schedule length [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22]. Among these objectives, minimizing schedule length given the traffic demands of the links is increasingly used with the proliferation of the time critical applications of wireless networks such as real-time surveillance, networked control [23]. Moreover, minimum length schedule determines the traffic-carrying capability of the wireless network since minimization of the total time required for a set of links to transmit their data packets is effectively maximizing the total data transmission rate while providing fairness among Yalcin Sadi and Sinem Coleri Ergen are with the department of Electrical and Electronics Engineering, Koc University, Istanbul, Turkey, email: ysadi, "
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    ABSTRACT: Traditional approach to the minimum length scheduling problem ignores the packet level details of transmission protocols, meaning that a packet transmission can be divided into several data chunks each of which is transmitted at a different rate due to the difference in the set of concurrently transmitting nodes. This solution requires including packet headers for each data chunk resulting in both an increase in the system overhead and underutilization of the time slots. In this paper, we extend the previous works on minimum length scheduling by considering the transmission of the packets of arbitrary sizes in the time slots of arbitrary lengths. Given the packet traffic demands on the links, we formulate the joint optimization of the power control, rate adaptation and scheduling for minimizing the schedule length of a wireless ad hoc network and demonstrate the hardness of this problem. Upon solving the power control and rate adaptation problem separately, we formulate the scheduling problem as an integer programming (IP) problem where the number of variables is exponential in the number of the links. In order to solve this large-scale IP problem fast and efficiently, we propose Branch and Price Method and Column Generation Method based heuristic algorithms.
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    ABSTRACT: This paper studies minimum-energy packet forwarding over multi-hop lossy networks under deadline and reliability constraints. We assume a routing topology in the form of a directed graph with packet loss processes on links described by finite-state Markov chains, and formulate the forwarding problem as a finite-horizon constrained Markov decision process. We show that the minimum energy forwarding policy under hard deadline and reliability constraint can be computed using dynamic programming, and that the optimal forwarding policy is a randomized policy over two history-independent and deterministic policies. Closed-form optimal policies are derived for some particular scenarios. Numerical examples show that the transmission energy cost of achieving reliabilities close to the maximum can be significant when links are bursty. In addition, transmission power adjustments can further reduce energy cost. Finally, we develop simple heuristic policies with a good balance between transmission energy cost and reliability.
    Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks (WiOpt), 2012 10th International Symposium on; 05/2012
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    ABSTRACT: The current military and civil ground based surveillance and reconnaissance is characterized by a large number of sensor assets, feeding resource constrained analysis nodes, and constrained by extremely limited transport bandwidth. The complexity of such systems is captured by the Networks of Systems (NoS) concept which use tools from wireless engineering and control theory. In this paper, the role of perceptual quality constraints on video-based NoS is investigated. An algorithm to determine the feasible set of nodes and optimal packet schedule via a Markov decision process, given their perceptual constraints and channel qualities is proposed. The H.264/SVC codec is used for compression, while the visual information fidelity pixel-domain (VIFP) full-reference image quality assessment model is used to measure perceptual quality. The algorithm is implemented in custom C;; software with over-the-air transmissions using 802.11 WLAN hardware. Real-time encoding is done for over-the-air transmission of the video. The results indicate that gains of 10-30% can be realized for a three node system.
    2013 Asilomar Conference on Signals, Systems and Computers; 11/2013


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