Erik Jonsson School of Engineering and Computer Science
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Browsing Erik Jonsson School of Engineering and Computer Science by Subject "Access protocols"
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Item A scalable and adaptive fair access protocol for slotted WDM bus network(The University of Texas at Dallas, 2013-04-18) Fumagalli, Andrea; Grasso, Robert, 1972-; Eric Jonsson School of Engineering and Computer Science; National Science Foundation (U.S.); Centro Studi e Laboratori Telecomunicazioni (Turin, Italy) (CSELT)The recent progress of optical technologies has made it possible to increase the number of wavelengths (channels) practically available in the fiber by almost one order of magnitude. With this rapid growth, access protocols originally designed for systems with a few wavelengths may not be adequate to fully utilize the optical bandwidth that is becoming available through this technological breakthrough. This is the case with access protocols designed for unidirectional fiber bus network. The paper proposes a novel access protocol for multi-channel all-optical folded bus network whose performance scales well with the number of wavelengths. This result is achieved using a load balancing algorithm that runs independently at each node and evenly distributes the traffic among the wavelengths. With the proposed protocol, the packet average access delay at a given bandwidth utilization increases only marginally as the number of wavelengths (and proportionally the offered load) is grown in the system. In addition, at all source nodes fair access delay is guaranteed by the protocol under any stable load condition, including non uniform and bursty traffic.Item Wireless multimedia networks: cross-layer access protocols based on sequential opportunistic decoding (SOD)(The University of Texas at Dallas, 2013-05-23) Jegbefume, Onyemelem, 1977-; Saquib, M.; Tacca, Marco, 1973-; Fumagalli, Andrea; Monti, Paolo, 1973-; Eric Jonsson School of Engineering and Computer Science.Spread spectrum (SS) solutions offer well understood advantages to wireless networking, e.g., robustness to noise and interference, concurrent asynchronous transmissions, effective power and transmission rate control mechanisms. One of the authors' recent advances in this field makes it possible to take SS solutions to the next performance level, i.e., sequential opportunistic decoding, or SOD for short. SOD is based on transmitting data symbols multiple times within the frame using non-orthogonal partial signature waveforms or mini-frames. Depending on the received instantaneous signal-to-interference-plus-noise ratio (SINR), a given subset of such mini-frames may suffice to reliably decode the data symbols. The best performing subset contains mini-frames that are received under better-than-average SINR channel conditions - i.e., these are referred to as the opportunistic mini-frames. By instantaneously controlling the number of mini-frames transmitted, SOD also offers distributed adaptable processing gain. The objective of this report is to propose cross-layer medium access control (MAC) protocols based on SOD. These protocols are especially suited to operate in a crowded radio spectrum, e.g., when multiple WLANs and/or wireless sensor networks coexist in the same radio space, possibly supporting multimedia applications. This unique advantage originates from the integration of two sub-layers. The lower sub-layer (SOD-MAC) applies the SOD adaptable processing gain to contain both the level of interference in the radio channel and network latency. It also minimizes the power consumption at the node and supports multiple c1asses of service. The upper sub-layer (ARQ-MAC) enables statistical multiplexing of an unbounded number of attempts of frame transmission generated by uncoordinated active nodes and it provides the automatic retransmission request (ARQ) capabilities. In essence, the uniqueness of these cross-layer access protocols is their ability to achieve efficient statistical multiplexing of traffic generated by uncoordinated nodes while containing the level of interference in the radio channel. The challenge is to combine frame retransmission schemes and SOD adaptable processing gain strategies in the most effective way, while keeping the access protocols in the stable region. The payoff is the ability to: increase the radio channel utilization, contain network latency, reduce energy consumption at the wireless node, and provide a QoS platform for both real-time and datagram traffic.