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In hybrid datacenter networks, wired connections are augmented with wireless links to facilitate data transfers between racks. The usage of mmWave/FSO wireless links enables dynamic bandwidth/capacity allocation with extremely small reconfiguration delay. Also, on-demand workload distribution, where the workload of a job is divided into multiple tasks that can be distributed/routed to different racks to be processed in parallel, allows better utilization of computational resources in data centers. In prior work, the dynamic wireless capacity augmentation and workload distribution decisions were mostly made independently and in a heuristic manner for serving distributed and parallel computing jobs. In this paper, we propose a novel analytical framework and algorithms to jointly optimize both the wireless capacity augmentation and the workload distribution, to minimize the job completion time. We consider workload that is not amenable to pipelining, fully amenable to pipelining, and partially amenable to pipelining. With extensive simulation studies, we show that the gain (in terms of the reduction in the job completion time) can be very substantial when allowing such joint optimization. [ABSTRACT FROM AUTHOR]

Local (single-hop) broadcasting is widely employed in distributed protocols (e.g., neighbor discovery, local information exchange in distributed network optimization and gossip-based algorithms) in wireless ad hoc networks. The performance of local broadcasting is characterized by the mean number of neighbors and the probability distribution of the number of neighbors of a broadcasting node. In this paper, we study the performance of local broadcasting in heterogeneous wireless ad hoc networks in which inter-system interference dominates signal reception quality, considering general fading distributions of both the desired signal and the interfering signals. In addition, we investigate the impacts of different error control techniques (e.g., simple retransmission, Chase combining, and incremental redundancy) on the performance of local broadcasting. The increase in the mean number of neighbors of a broadcasting node with respect to the number of retransmissions of a message is clarified, facilitating QoS provisioning in reliable local broadcasting in interference-limited heterogeneous wireless ad hoc networks. [ABSTRACT FROM AUTHOR]

We investigate the mean degree and the isolation probability of a network node sustaining intrasystem interference and intersystem interference from multiple coexisting wireless ad hoc networks. Under general fading of the desired signal and interfering signals, a closed-form upper bound on the mean node degree and a lower bound on the node isolation probability are obtained by thoroughly considering dominating interferers and second-order interferers. A closed-form lower bound on the mean node degree is further computed. The ratio between the upper bound and lower bound is bounded, and they are asymptotically tight as the path-loss exponent approaches infinity. Moreover, a nearly closed-form expression for the mean node degree is derived in terms of inverse Laplace transform of the fading distribution of the desired signal. Our derived local network quantities could find application in the approximate study of a number of metrics related to connectivity and delay of information propagation in wireless ad hoc networks. [ABSTRACT FROM PUBLISHER]

The concept of introducing network-coded packets as redundancy was proposed to improve the reliability of end-to-end packet transmissions in wireline/wireless networks, and the corresponding rate–reliability tradeoff has been studied in the literature. However, little attention has been focused on how to design a network code to reduce end-to-end packet transmission delay and even further on analyzing the corresponding rate–delay tradeoff. In this paper, we propose a packet-combining scheme based on network coding to reduce packet transmission delay between a source and destination pair connected by multiple disjoint paths. Improving the reliability of packet transmission is also addressed. Moreover, both rate–delay tradeoff and rate–reliability tradeoff of the proposed scheme are studied. New tradeoff points with fine granularity are achieved compared with the traditional repetition-based approach. Quality-of-service (QoS) provisioning is facilitated by our analysis because the network code can be adjusted to operate at the tradeoff point closest to the system QoS requirement. Finally, design of network codes that can provide multilayered reliability and delay guarantees for packets with different priority levels is investigated. [ABSTRACT FROM PUBLISHER]

In two-tier networks consisting of a macrocell overlaid with femtocells in cochannel deployment and closed-access policy, spatial reuse is achieved at the price of severe intratier and cross-tier interference from concurrent transmissions. The interference causes significant performance degradation, particularly when coordination among base stations (BSs) is infeasible. Cognitive radio (CR) is a promising technique for interference mitigation, where femto-BSs with cognitive information accomplish concurrent transmissions while meeting a per-tier outage constraint. This paper studies the role of information sensed at femto-BSs on the transmission capacity. By exploiting different cognitive information, we propose spectrum-sharing schemes between macrocell and femtocell, as well as among femtocells, to improve spatial reuse gain. Bounds on the maximum intensity of simultaneously transmitting femtocells that satisfy a given per-tier outage constraint in these schemes are theoretically derived via a stochastic geometry model. We conduct simulations to evaluate the performance of the proposed schemes in terms of transmission capacity. The results confirm that, when femto-BSs acquire the knowledge of user channel statistics or user location information, significant spatial reuse gain can be achieved by exploiting the avoidance region and multiuser diversity. [ABSTRACT FROM PUBLISHER]