Jonathan L. Wang

Optimal adaptive multireceiver ARQ protocols

The authors study data link error control protocols suitable for point-to-multipoint communication where data are delivered to the destinations in the order they are sent. They study a series of adaptive protocols differing in the way that the sender uses the outcomes of the previous transmissions. The protocols are based on the go-back-N schemes discussed by I.S. Gopal and J.M. Jaffe (1984), whose protocols are generalized to the case where multiple copies of a message are sent (instead of just a single copy). The optimum number of copies is determined and is found to depend on how many receivers have not yet received the message. These adaptive protocols can be applied to all three basic ARQ (automatic repeat request) schemes, namely, stop-and-wait, go-back-N, and selective-repeat. A dynamic programming technique is used to solve this optimization problem. A throughput comparison shows that, by sending the optimum number of copies of a data frame instead of just a single copy, the performance will be significantly improved. >

Maximum number of independent paths and radio connectivity

Methods for determining the network reliability of a multihop packet radio network in the presence of hostile jammers are discussed. A new connectivity parameter called radio connectivity is defined as the maximum number of disjoint communication paths that are still usable between given nodes s and d after the jammer is on or, more generally, the minimum number of jammers needed to disconnect s and d. A lower bound on the radio connectivity is computed by studying the number of jamming independent paths. The time complexity of obtaining the radio connectivity is analyzed and shown to be NP-hard except for some special cases. Greedy heuristics for developing approximate answers for general networks are described. Euclidean networks, in which the nodes and links correspond to points and line segments in the Euclidean geometry and satisfy Euclids four fundamental axioms, are also discussed. It is found that the maximum number of independent paths between a pair of source and destination nodes that can possibly exist is five. An extension in which there is a protected zone of known size around the sender and receiver is studied. >

Optimal adaptive ARQ protocols for point-to-multipoint communication

A study is made of some data-link-layer error-control protocols suitable for point-to-multipoint communication over broadcast channels where data are delivered to the destinations in the order they are sent. The authors study a series of protocols differing in the way that the sender uses the outcomes of the previous transmissions. The protocols are based on the go-back-N schemes discussed by I.S. Gopal and J.M. Jaffe (1984). The authors generalize their proposed protocols to the case where multiple copies of a message are sent (instead of just a single copy). The optimum number of copies is determined, which depends not only on the round-trip propagation delay of the channel and the error probability, but also on the number of receivers that have not yet received the message. A dynamic programming technique is used to solve this optimization problem. The throughput comparison shows that by sending the optimum number of copies of a data frame instead of just a single copy, the performance will be significantly improved.<<ETX>>

Targeting cell adhesion molecules with nanoparticles using in vivo and flow-based in vitro models of atherosclerosis:

Atherosclerosis is a leading cause of death worldwide; in addition to lipid dysfunction, chronic arterial wall inflammation is a key component of atherosclerosis. Techniques that target cell adhesion molecules, which are overexpressed during inflammation, are effective methods to detect and treat atherosclerosis. Specifically, research groups have identified vascular cell adhesion molecule-1, intercellular adhesion molecule-1, platelet endothelial cell adhesion molecule, and selectins (E-selectin and P-selectin) as correlated to atherogenesis. In this review, we discuss recent strategies both in vivo and in vitro that target cell adhesion molecules. First, we discuss peptide-based and antibody (Ab)-based nanoparticles utilized in vivo for diagnostic, therapeutic, and theranostic applications. Second, we discuss flow-based in vitro models that serve to reduce the traditional disadvantages of in vivo studies such as variability, time to develop the disease, and ethical burden, but preserve physiological relevance. The knowledge gained from these targeting studies can be translated into clinical solutions for improved detection, prevention, and treatment of atherosclerosis. Impact statement As atherosclerosis remains the leading cause of death, there is an urgent need to develop better tools for treatment of the disease. The ability to improve current treatments relies on enhancing the accuracy of in vitro and in vivo atherosclerotic models. While in vivo models provide all the relevant testing parameters, variability between animals and among models used is a barrier to reproducible results and comparability of NP efficacy. In vitro cultures isolate cells into microenvironments that fail to take into account flow separation and shear stress, which are characteristics of atherosclerotic lesions. Flow-based in vitro models provide more physiologically relevant platforms, bridging the gap between in vivo and 2D in vitro models. This is the first review that presents recent advances regarding endothelial cell-targeting using adhesion molecules in light of in vivo and flow-based in vitro models, providing insights for future development of optimal strategies against atherosclerosis.

Delay minimization of the adaptive go-back-N ARQ protocols for point-to-multipoint communication

Some data-link layer error control go-back-N ARQ (automatic repeat-request) protocols are studied that are suitable for point-to-multipoint communication over broadcast channels where data are delivered to the destinations in the order they are sent. A series of protocols differing in the way that the sender uses the outcomes of the previous transmissions are studied. The system delay, rather than the throughput, is the optimization measure. The optimal number of copies that the sender should transmit to minimize the time between when the sender first transmits a data frame and when the data frame is accepted by all the receivers is determined. The results show that sending the optimum number of copies of a data frame instead of just a single copy significantly improved the delay performance.<<ETX>>

An integrated methodology for supporting network planning and traffic engineering with considerations to SMDS service

The integrated network planning system (INPLANS) is introduced. It was developed to provide a single environment to support regional network planning and traffic engineering across different networking technologies. There are four main capabilities in INPLANS: integrated network monitoring (INM), which supports planning and engineering monitoring studies; integrated network servicing (INS), which provides an integrated and interactive environment for the network servicing process; integrated capacity expansion (ICE), which provides a 1-5 year view of network demands and requirements; and integrated technology planning (ITP), which provides cost effective backbone and network access design plans. The overall network planning and traffic engineering process and how it is supported and implemented in INPLANS are described. The switched multimegabit data service (SMDS) is considered, and the impact of SMDS on the planning and engineering process is described.<<ETX>>

Establishing broadband application signatures through ATM network traffic measurement analyses

The fundamental challenge in the traffic management of high-speed networks is to describe, analyse and control complex traffic flows in ways that can be applied in practice. Our approach to this problem is experimental in nature and starts with collection and analysis of high-resolution traffic traces from working high-speed networks. This paper analyzes cell-level ATM traffic and performance modeling issues of individual connections (i.e., VPI/VCIs) based on recent traffic measurements collected from a major North American public ATM network through a custom-built ATM traffic recording prototype device. In particular, we focus on the following issues related to modeling individual ATM connections at the cell level: the existence of ON-OFF behavior, sojourn time distributions of the ON and OFF periods, traffic arrival patterns within an ON period, temporal and spatial correlations, and performance impacts. Characteristics of individual connections can be highly dependent on the applications which generate the traffic and caution should be taken in interpreting these exact results for use in other ATM networks.

Design and in vivo characterization of kidney-targeting multimodal micelles for renal drug delivery

One in three Americans is at risk for developing chronic kidney disease (CKD) and end-stage renal disease (ESRD), leading to the need for dialysis or a kidney transplant. Small-molecule drugs have been proposed as therapies to manage kidney diseases, but high dosages are often required to achieve therapeutic efficacy, generating off-target side effects, some of which are lethal. To address these limitations, we developed a novel, kidney-targeting multimodal micelle (KM) system for drug delivery applications. Specifically, we incorporated the kidney-targeting peptide (Lysine-Lysine-Glutamic acid-Glutamic acid-Glutamic acid)3-Lysine) ((KKEEE)3K) into micelles. This peptide binds to megalin, a multi-ligand cell surface receptor present on renal tubule cells. When incubated with human kidney proximal tubule cells, KMs were found to be biocompatible in vitro. In vivo, KMs showed higher accumulation in the kidneys as compared to a non-targeted (NT) control upon intravenous injection in wild-type C57BL/6J mice. Histological evaluation showed no signs of tissue damage, while blood urea nitrogen (BUN) and creatinine levels were within normal ranges, validating the preservation of kidney health upon micelle administration. To our knowledge, this is the first utilization of (KKEEE)3K in a nanoparticle formulation, and our study offers strong evidence that this novel nanoparticle platform can be used as a candidate drug delivery carrier to direct therapeutics to diseased tissue in CKD.

Throughput optimization in single commodity slotted ALOHA multi-hop packet radio networks

The authors investigate the maximum throughput that can be supported between a pair of nodes in a multihop packet radio network using slotted ALOHA. The optimization problem can be formulated as a nonlinear programming problem. The authors study different topologies where source and destination are connected with a number of independent paths and consider the cases in which the flow from source to destination is equally split among all of the independent paths connecting them or optimally split in order to maximize the throughput. For the equal split case and networks with three or more independent s-d paths, it is possible to find a closed-form expression for the maximum throughput and the optimum transmitting probabilities for each node. For optimally splitting the flow among the alternate paths, the authors solve the optimization problem for some small configurations and find a singular behavior for the network with two independent paths two hops each in length.<<ETX>>

Optimizing responses to broadcast messages in radio networks

Algorithms to optimize the performance of response traffic for broadcast messages in a packet-switched radio network are studied. The situation considered here involves a source node sending a broadcast message to all destinations and collecting positive response packets from these destinations in a fully connected packet radio network. The exact value of the number of destination nodes is unknown. A contention-based two-level protocol is described. Based on the protocol, an optimization problem is formulated in order to minimize the time for the source node to receive all the responses. Several algorithms are presented and numerical results of the corresponding optimization problems are obtained. These optimization problems are treated by the methods of dynamic programming. An extension of the basic scheme—multicast instead of full broadcast message—is also studied.