A link model-driven approach toward transmission control protocol (TCP) performance over a wireless link is presented. TCP packet loss behavior is derived from an underlying two-state continuous time Markov model. The approach presented here is (to our knowledge) the first that simultaneously considers (1) variability of the round-trip delay due to buffer queueing; (2) independent and nonindependent (bursty) link errors; (3) TCP packet loss due to both buffer overflow and channel errors; and (4) the two modes of TCP packet loss detection (duplicate acknowledgments and timeouts). The analytical results are validated against simulations using the ns-2 simulator for a wide range of parameters; slow and fast fading links; small and large link bandwidth-delay products. For channels with memory, an empirical rule is presented for categorizing the impact of channel dynamics (fading rate) on TCP performance.

Choosing an appropriate type of dropping probability function is an important design issue in active queue management schemes. In this paper, we investigated the queueing performance associated with the use of different types of dropping probability function. We firstly constructed a QoS plane which can distinguish the performance limitation associated with the type of dropping probability function from the performance tradeoffs caused by the function parameter adjustment. We secondly proposed a performance measure in the QoS plane to quantify the performance limitation of different types of dropping probability function. Using the proposed performance measure, we quantitatively compared the exponential, the piecewise linear and the staircase dropping probability functions.

This paper considers the random early detection (RED) active queue management algorithm in TCP/IP networks. A stochastic framework for modeling the performance of the RED algorithm is presented. We introduce a two-dimensional second-order discrete-time Markov chain to model the feedback effect of packet dropping on the incoming traffic. The mean system occupancy, packet drop probability, and system throughput are computed from the analytical model for both marking and dropping policies. The effects of RED parameters on a selected set of performance metrics are studied.

A stochastic framework for modeling the performance of the RED algorithm is presented. A two-dimensional second-order discrete-time Markov chain is introduced to model the feedback effect of packet dropping on the incoming traffic. The mean system occupancy, packet drop probability, and system throughput are computed from the analytical model. The effects of RED parameters on a selected set of performance metrics are studied.

An analytical framework for modeling the performance of a single TCP session in the presence of random packet loss is presented. A Markovian approach is developed that allows us to study both memoryless channels (IID packet loss) and channels with memory (correlated packet loss) modeled by a two-state continuous-time Gilbert model. The analytical results are validated against results using the ns simulator. It is shown that the model predicts throughput for LAN/WAN (low and high bandwidth-delay products) with good accuracy. Further, throughput for the IID loss model is found to be relatively insensitive to the probability density function (PDF) of the loss inter-arrival process. For channels with memory, we present an empirically validated rule of thumb to categorize the channel transition frequency.

We propose a new maximum a posteriori (MAP) detector, without the need for explicit channel coding, to lessen the impact of communication channel errors on compressed image sources. The MAP detector exploits the spatial correlation in the compressed bitstream as well as the temporal memory in the channel to correct channel errors. We first present a technique for computing the residual redundancy inherent in a compressed grayscale image (compressed using VQ). The performance of the proposed MAP detector is compared to that of a memoryless MAP detector. We also investigate the dependence of the performance on memory characteristics of the Gilbert-Elliott channel as well as average channel error rate. Finally, we study the robustness of the proposed MAP detector's performance to estimation errors.

Wavelength converters increase the traffic-carrying capacity of circuit-switched optical networks by relaxing the wavelength continuity constraints. We consider the problem of optimally placing a given number of wavelength converters on a path to minimize the call-blocking probability. Using a simple performance model, we first prove that uniform spacing of converters is optimal for the end-to-end performance when link loads are uniform and independent. We then show that significant gains are achievable with optimal placement compared to random placement. For nonuniform link loads, we provide a dynamic programming algorithm for the optimal placement and compare the performance with random and uniform placement. Optimal solutions for bus and ring topologies are also presented. Finally, we discuss the effect of the traffic model on the placement decision.

We consider the problem of optimally placing a given number of wavelength converters on a path to minimize the call blocking probability. Using a simple performance model, we first prove that uniform spacing of converters is optimal for the end-to-end performance when the link loads are uniform and statistically independent. We then show that significant gains are achievable with optimal placement compared to random placement. For non-uniform link loads, we provide a dynamic programming algorithm for the optimal placement and compare the performance with random and uniform placement. Optimal solutions for bus and ring topologies are also presented.

Article Free Access Share on Optimal location management algorithms for mobile networks Authors: Govind Krishnamurthi Department of Electrical and Computer Engineering, Iowa State University, Ames, IA Department of Electrical and Computer Engineering, Iowa State University, Ames, IAView Profile , Murat Azizoğlu Department of Electrical Engineering, University of Washington, Seattle WA Department of Electrical Engineering, University of Washington, Seattle WAView Profile , Arun K. Somani Department of Electrical and Computer Engineering, Iowa State University, Ames, IA Department of Electrical and Computer Engineering, Iowa State University, Ames, IAView Profile Authors Info & Claims MobiCom '98: Proceedings of the 4th annual ACM/IEEE international conference on Mobile computing and networkingOctober 1998 Pages 223–232https://doi.org/10.1145/288235.288300Online:25 October 1998Publication History 20citation622DownloadsMetricsTotal Citations20Total Downloads622Last 12 Months7Last 6 weeks4 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF

The information-theoretic capacity of continuous-time queues was analyzed recently by Anantharam and Verdu (see ibid. vol.42, p.4-18, 1996). Along similar lines, we analyze the information-theoretic capacity of two models of discrete-time queues. The first model has single packet arrivals and departures in a time slot and independent packet service times, and is the discrete-time analog of the continuous-time model analyzed by Anantharam and Verdu. We show that in this model, the geometric service time distribution plays a role analogous to that of the exponential distribution in continuous-time queues, in that, among all queues in this model with a given mean service time, the queue with geometric service time distribution has the least capacity. The second model allows multiple arrivals in each slot, and the queue is modeled as serving an independent random number of packets in each slot. We obtain upper and lower bounds on the capacity of queues with an arbitrary service distribution within this model, and show that the bounds coincide in the case of the queue that serves a geometrically distributed number of packets in each slot. We also discuss the extremal nature of the geometric service distribution within this model.

We consider routing and wavelength assignment in wavelength-routed all-optical networks (WAN) with circuit switching. The conventional approaches to address this issue consider the two aspects of the problem disjointly by first finding a route from a predetermined set of candidate paths and then searching for an appropriate wavelength assignment. We adopt a more general approach in which we consider all paths between a source-destination (s-d) pair and incorporate network state information into the routing decision. This approach performs routing and wavelength assignment jointly and adaptively, and outperforms fixed routing techniques. We present adaptive routing and wavelength assignment algorithms and evaluate their blocking performance. We obtain an analytical technique to compute approximate blocking probabilities for networks employing fixed and alternate routing. The analysis can also accommodate networks with multiple fibers per link. The blocking performance of the proposed adaptive routing algorithms are compared along with their computational complexity.

This paper considers the transmission of uniform deterministic traffic in an optical broadcast-star network using wavelength division multiplexing. Lower bounds are established on the minimum time to exchange information between every node pair in such a network with tunable transmitters and fixed-tuned receivers. Three different scheduling algorithms are developed that are strictly optimal in three regimes of system parameters. The results are applicable to arbitrary tuning delays and arbitrary numbers of wavelength channels, and indicate the existence of a well-defined transition regime from tuning-limited operation to bandwidth-limited operation.

This paper formulates the wavelength assignment issues an interconnecting optical broadcast-star local area networks (LANs) through a wavelength routing bridge. Static and dynamic approaches to partitioning of wavelengths for local and global traffic are compared using analysis and simulations. It is found that static wavelength assignment, the easiest algorithm to implement, is significantly outperformed by dynamic algorithms. Several dynamic assignment algorithms are developed, and architectural issues in interconnecting optical networks are discussed. The dependence of the call blocking performance on system parameters, such as the traffic rate, the local and global traffic statistics, and the number of available wavelengths is examined in detail. A simple, yet accurate approximation is also developed to predict the blocking performance with an arbitrary number of LANs.

This paper makes the first known attempt to study wavelength-routing networks and the effects of wavelength conversion under dynamic non-Poisson traffic. An approximation that characterizes any non-Poisson traffic by its first two moments is utilized. The arrival occupancy distribution of busy wavelengths for this approximate process is derived and is used to analyze the effects of wavelength conversion. The model predicts that traffic peakedness plays an important role in determining the blocking performance, and also that wavelength conversion gain is insensitive to traffic peakedness over a large range.

We study image transmission on a lossy packet network in which the loss mechanism is modeled as buffer overflows. A simple error concealment strategy involving table lookups and a buffer allocation scheme with an optimally chosen virtual boundary for a 2 priority class system are described. Significant improvements are achieved by combining these two strategies.

Wavelength-routing networks offer the advantages of wavelength re-use and scalability over broadcast-and-select networks and are therefore suitable for wide area networks (WANs). We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks. An approximate blocking analysis of such network is performed. We first propose an improved framework for the analysis of networks with arbitrary topology. We introduce a simple model for networks with a variable number of converters and analyze the effect of wavelength converter density on blocking probability. We then apply this framework to two sparse network topologies, the ring and the mesh-torus, and obtain the blocking performance. The results show that, in most cases, only a fraction of the network nodes need to be equipped with wavelength conversion capability for good performance. Finally, the tradeoff between physical connectivity, wavelength conversion, and the number of available wavelengths is studied through networks with random topologies.

This paper studies the effects of tuning delay of transmitters in packet-based optical broadcast networks. We consider scheduling of random traffic with tunable transmitters and fixed-tuned receivers and obtain the degradation imposed by tuning delay using several performance criteria, such as schedule completion time, average packet delay, and session blocking rates. We show that for off-line scheduling the effects of tuning delay are small even if the tuning time is as large as the packet duration. We provide a lower bound to the expected completion time of any off-line schedule with an arbitrary number of wavelengths. We then describe a near-optimal schedule which is based on the principle of having idle transmitters tune to wavelengths just-in-time to start their transmissions. Stability and capacity issues in the transmission of real-time traffic are considered and a queueing-theoretic analysis of average packet delay is given. The packet delay is found to be insensitive to tuning delay under near-optimal transmission scheduling. Finally we extend the model to connection-oriented networks and evaluate the session blocking performance for scheduled circuit connections.

The author investigates the convexity properties of error probability in the detection of binary-valued scalar signals corrupted by additive noise. It is shown that the error probability of the maximum-likelihood receiver is a convex function of the signal power when the noise has a unimodal distribution. Based on this property, the results of the optimal time-sharing strategies of transmitters and jammers, and of the optimal use of multiple channels are obtained.

All-optical networks (AONs) with a broadcast-star based physical topology offer the possibility of transmission scheduling to resolve channel and receiver conflicts. This paper considers the problem of scheduling packet transmissions in a wavelength-division multiplexed (WDM) optical network with tunable transmitters and fixed-tuned receivers. The scheduling problem is complicated by tuning latency, a limited number of channels, and arbitrary traffic demands. We first analyze scheduling all-to-all packet transmissions and obtain a new lower bound for the schedule length. The lower bound is achieved by an algorithm proposed by Pieris and Sasaki (1994). We then extend the analysis to the case of arbitrary traffic demands and obtain lower bounds for the schedule length. Two constructions for scheduling algorithms are provided through list scheduling and multigraphs. The upper bounds so obtained not only provide performance guarantees with arbitrary demands, but also nearly meet the lower bound in simulations.

Unlike broadcast-and-select networks, wavelength-routing networks offer the advantages of wavelength reuse and scalability and are thus suitable for wide-area networks (WANs) We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks. A blocking analysis of such networks is given. We first propose an analytical framework for accurate analysis of networks with arbitrary topology. We then introduce a model for networks with a variable number of converters and analyze the effect of wavelength converter density on the blocking probability. This framework is applied to three regular network topologies that have varying levels of connectivity: the ring, the mesh-torus, and the hypercube. The results show that either a relatively small number of converters is sufficient for a certain level of performance or that conversion does not offer a significant advantage. The benefits of conversion are largely dependent on the network load, the number of available wavelengths, and the connectivity of the network. Finally, the tradeoff between physical connectivity, wavelength conversion, and the number of available wavelengths is studied through networks with random topologies.

We consider the effects of tuning delay in optical broadcast networks. We show that for off-line scheduling these effects are small even if the tuning time is as large as the packet duration. In particular, we consider scheduling of random traffic with tunable transmitters and fixed-tuned receivers. We provide a lower bound to the completion time of any off-line schedule with an arbitrary number of wavelengths. We then describe a near-optimal schedule which is based on the principle of having idle transmitters tune to wavelengths just-in-time to start their transmissions. Stability and capacity issues in the transmission of real-time traffic are considered. We show that the scheduling problem admits a single stable equilibrium point, and point out how the traffic capacity of a broadcast network can be reached. We also consider the implications in connection-oriented networks.

We consider an optical communication system where a reference signal is transmitted along with a phase modulated information carrying signal. This system has the potential of alleviating the effect of phase noise considerably. We perform a joint optimization of the receiver bandwidth and the powers of the two signals. The scheme achieves a performance that is close to that of ideal phase modulation systems when the ratio of bit rate to laser linewidth is large, and a performance that is identical to that of frequency modulation when the ratio is small. We also introduce a centered filter structure which achieves a far better performance than traditional filters due to increased the phase coherence.>

The authors provide an analysis of the performance of optical orthogonal codes in an optical code division multiple access (CDMA) network by considering the probability distribution of the interference patterns. It is shown that the actual performance is close to a previous estimate. A less structured temporal code in which the code words are allowed to overlap at two pulse positions is also considered. The bit error probability for this class of codes is obtained for two cases: with and without optical hard-limiting at the receivers. It is shown that this code may increase the number of users in the network considerably without a significant loss in the performance.>