Transmission capacity of wireless ad hoc networks with outage constraints

In this paper, upper and lower bounds on the transmission capacity of spread-spectrum (SS) wireless ad hoc networks are derived. We define transmission capacity as the product of the maximum density of successful transmissions multiplied by their data rate, given an outage constraint. Assuming that the nodes are randomly distributed in space according to a Poisson point process, we derive upper and lower bounds for frequency hopping (FH-CDMA) and direct sequence (DS-CDMA) SS networks, which incorporate traditional modulation types (no spreading) as a special case. These bounds cleanly summarize how ad hoc network capacity is affected by the outage probability, spreading factor, transmission power, target signal-to-noise ratio (SNR), and other system parameters. Using these bounds, it can be shown that FH-CDMA obtains a higher transmission capacity than DS-CDMA on the order of M/sup 1-2//spl alpha//, where M is the spreading factor and /spl alpha/>2 is the path loss exponent. A tangential contribution is an (apparently) novel technique for obtaining tight bounds on tail probabilities of additive functionals of homogeneous Poisson point processes.     

A distributed Poisson approximation for preempt-resume clockedschedules

Many telecommunication systems with time-critical requirements use a preempt-resume clocked schedule. An approximation to the ergodic distribution of the time to completion of a low-priority task is obtained by treating the priority service time distribution as the limit of compound Poisson distributions. Explicit formulas for the mean and variance that are highly accurate are given. For random clocked loads, a stochastic bound is provided for the discrepancy between the exact and approximate distributions. For deterministic clocked loads, sample path bounds are found. Simulation results are given to demonstrate the accuracy of the model     

Throughput performance of an unslotted direct-sequence SSMA packetradio network

A spread-spectrum multiple-access (SSMA) packet radio network model is presented. The topology is a fully connected network with identical message generation processes at all radios. Packet lengths are exponentially distributed, and packets are generated from a Poisson process, resulting in a Markovian model. This network model accounts for the availability of idle receivers in a finite population network. The model also allows the performance of the radio channel to be specified in detail. The channel considered is a BPSK (binary phase-shift keying) direct-sequence SSMA radio channel with hard-decision Viterbi decoding. An analysis of the Viterbi decoder leads to a bound on its performance which is valid for a system with a varying probability of error, as is the case for the network under consideration. The approximate analysis yields lower bounds on throughput and probability of successful packet transmission. Results are given which show the effects on throughput of the received energy-to-noise density ratio, the number of chips per symbol, and the number of radios, as well as the improvement due to error control coding     

Intelligent cruise control and reliable communication of mobilestations

The reliability of a short range packet radio network for mobile stations is investigated via the probability of a successful transmission. The instantaneous power of an interfering station's transmission is described by a Rayleigh distribution. The authors determine the distribution of cumulated interference power and the probability of a successful transmission, when the number of interfering stations is random and each station transmits only with probability p. Two lower bounds of increasing complexity are given. The authors evaluate these bounds for an intelligent cruise control system, when mobile stations are lined up in a traffic jam, and one approaching vehicle should be warned by the last member of the queue     

Performance and parameter region for real-time use in IEEE 802.4token bus network

The upper and lower bounds for the mean cycle time and the mean message transmission time of class six and class four in the IEEE 802.4 token bus network, within which the minimum utilization constraint of class four is guaranteed, are derived. Stability conditions for the token bus network are also derived. These bounds and stability conditions are represented in terms of the high-priority token hold time, the token rotation time, the arrival rate, the total number of stations, etc. A parameter-tuning algorithm in a partially symmetric token bus network with two classes is suggested. This algorithm maximizes the utilization of class four for a given high-priority token hold time and at the same time meets the constraints of the stability condition of the network, the real-time constraint, and the minimum utilization of class four     

The Effect of Fading, Channel Inversion, and Threshold Scheduling on Ad Hoc Networks

This paper addresses three issues in the field of ad hoc network capacity: the impact of (i) channel fading, (ii) channel inversion power control, and (iii) threshold-based scheduling on capacity. Channel inversion and threshold scheduling may be viewed as simple ways to exploit channel state information (CSI) without requiring cooperation across transmitters. We use the transmission capacity (TC) as our metric, defined as the maximum spatial intensity of successful simultaneous transmissions subject to a constraint on the outage probability (OP). By assuming the nodes are located on the infinite plane according to a Poisson process, we are able to employ tools from stochastic geometry to obtain asymptotically tight bounds on the distribution of the signal-to-interference (SIR) level, yielding in turn tight bounds on the OP (relative to a given SIR threshold) and the TC. We demonstrate that in the absence of CSI, fading can significantly reduce the TC and somewhat surprisingly, channel inversion only makes matters worse. We develop a threshold-based transmission rule where transmitters are active only if the channel to their receiver is acceptably strong, obtain expressions for the optimal threshold, and show that this simple, fully distributed scheme can significantly reduce the effect of fading.     

On minimizing the system information age in vehicular ad-hoc networks via efficient scheduling and piggybacking

Recent advances in vehicular networks have enforced researchers to focus on various information dissemination techniques. Exchanging information among the vehicles is imperative due to the ever-changing network topology in vehicular networks. However, random transmitter selection in traditional CSMA based channel access mechanism limits the delay performance. Data, such as state information, is often time critical, and hence, efficient information dissemination techniques to improve delay performance are essential. In this work, we aim to minimize the average system age which is the mean number of time slots old a vehicle’s information is at all other vehicles in the network. To achieve this, we explore the benefits of simultaneous transmission along with piggybacking of information for multi-hop communication. While allowing simultaneous transmission guarantees faster dissemination of information, piggybacking facilitates dissemination of more information per transmission, thereby keeping the network more updated. We have also analysed the relationship between piggybacked information and number of vehicles in the network. Simulation results show improvement in network performance. Our analytical results are in good agreement with the simulation results.     

Differential space–time network coding in MIMO two‐way relay channel network

This paper focuses on noncoherent detection scheme for multiple‐input multiple‐output two‐way relay channel network with two two‐antennas source nodes and one single‐antenna relay node. An orthogonal differential space–time network coding (ODSTNC) scheme based on relay detection and forward protocol is proposed. The proposed scheme combines space–time coding with network coding, and the differential modulation and detection are used in both multiple access stage and broadcast stage. The multiple‐symbol differential detection is employed at the relay. The maximum likelihood decision and its low‐complexity sphere decoding decision are given. The upper and lower bounds on the average symbol error probability for this system under differential binary phase shift keying (DBPSK) are derived, and a diversity order of 2 is confirmed to be achieved. The simulation results show that the ODSTNC scheme has good performance, and it is available for the applications of far distance signal transmission between two terminals where channel state information is unknown. Copyright © 2014 John Wiley & Sons, Ltd.     

An energy-aware deadline-constrained message delivery in delay-tolerant networks

In order to understand the message dissemination performance in delay-tolerant networks, much analysis work has been proposed in literature. However, existing work shares a common simplification that the pairwise inter-meeting time between any two mobile nodes is exponentially distributed. Not mention the fact that such assumption is only an approximation, it cannot be applied by network planners to directly control the mobile nodes for any network optimization, e.g., energy efficiency. It is quite significant to study the relationship between the network performance with the parameters that can be adjusted directly to tackle the limitations of current exponential distribution assumption based analysis. Therefore, in this paper, we are motivated to jointly consider the transmission range and messages residence time to stochastically analyze deadline-constrained message delivery ratio utilizing a controlled epidemic routing. The message propagation is considered as an age-structure process and described by a susceptible–infectious–recovered model, which is then analyzed using delay differential equations. Since both the transmission range and the message residence time are related to the mobile nodes’ energy consumption, we further apply our analysis framework to investigate the tradeoff between the energy consumption and the achievable message delivery ratio. The correctness and accuracy of our analysis are validated by extensive simulations.     

Time synchronization over networks using convex closures

This paper presents a general time synchronization algorithm that analyzes the time offset between any two computers clocks in a network and its evolution, by using mathematical topology properties. It builds a conversion function that produces precise and guaranteed bounds for each time conversion, and which provides accurate time synchronization. It is able to automatically adjust the observation process so as to maintain the error bound within some specified limit. It does not require adjustments to local clocks, and it features a way of filtering observation data based on a criterion of usefulness to improve precision, thus discarding only useless information. Advantages over approaches using other tools to filter out and analyze observation data (mean and variance, linear regression, midpoint functions, etc.) are exposed. Special attention is given to assessing the uncertainties and errors made in the observation process, and to their propagation in the estimation processes. The developed technique allows one to globally achieve a better precision than what has been reached on each single observation, given some conditions of operation that are explained     

On the minimum distance of ternary cyclic codes

There are many ways to find lower bounds for the minimum distance of a cyclic code, based on investigation of the defining set. Some new theorems are derived. These and earlier techniques are applied to find lower bounds for the minimum distance of ternary cyclic codes. Furthermore, the exact minimum distance of ternary cyclic codes of length less than 40 is computed numerically. A table is given containing all ternary cyclic codes of length less than 40 and having a minimum distance exceeding the BCH bound. It seems that almost all lower bounds are equal to the minimum distance. Especially shifting, which is also done by computer, seems to be very powerful. For length 40⩽n⩽50, only lower bounds are computed. In many cases (derived theoretically), however, these lower bounds are equal to the minimum distance     

Sprinkler: A Reliable and Energy Efficient Data Dissemination Service for Extreme Scale Wireless Networks of Embedded Devices

We present Sprinkler, a reliable data dissemination service for wireless embedded devices which are constrained in energy, processing speed, and memory. Sprinkler embeds a virtual grid over the network whereby it can locally compute a connected dominating set of the devices to avoid redundant transmissions and a transmission schedule to avoid collisions. Sprinkler transmits O(1) times the optimum number of packets in O(1) of the optimum latency; its time complexity is O(1). Sprinkler is tolerant to fail-stop and state corruption faults. Thus, Sprinkler is suitable for resource-constrained wireless embedded devices. We evaluate the performance of Sprinkler in terms of the number of packet transmissions and the latency, both in an outdoor and indoor environment. The outdoor evaluation is based on data from project ExScal, which deployed 203 extreme scale stargazer (XSS). Our indoor evaluation is based on an implementation in the Kansei testbed, which houses 210 XSSs whose transmission power is controllable to even low ranges. We compare Sprinkler with the existing reliable data dissemination services, analytically or using simulations also. Our evaluations show that Sprinkler is not only energy efficient as compared to existing schemes, but also has less latency. Further, the energy consumption of nodes and the latency grows linearly as a function of newly added nodes as the network grows larger.     

Random access communication and graph entropy

A probabilistic problem that arises for conflict resolution in random-access communication is treated. An earlier conjecture is disproved and a technique for finding lower bounds on the number of graphs of given structure needed to cover all edges of a given graph is developed     

Design and analysis of very high-speed network architectures

Communication architectures for very-high-speed networks are dealt with. The use of high communication speed increases the ratio between the end-to-end propagation delay and the packet transmission time. This increase restricts the utilization of the high system bandwidth in broadcast channel-based systems, causing a rapid performance deterioration. A communication system architecture characterized by the use of several parallel channels and design of the nodes' channel interface is presented. The channel-division approach is introduced, showing that for a given system bandwidth the total system capacity will be increased by bandwidth division and parallel communication. An analytic model of this system is developed, from which the proposed system's performance is obtained and performance bounds determined for multichannel slotted finite systems. The results show that the architecture has a potential to improve significantly the system performance compared to conventional single-channel-based systems. Furthermore, for a given network configuration an optimal architecture can be found which simultaneously maximizes the system throughput and minimizes the average packet delay     

An analysis of the effect of multiversions on the performance oftimestamp algorithms

The performance of a multiversion conservative timestamp algorithm is evaluated by analyzing the response time of operations in a distributed database system. The random communication delay in the transmission channels of a long-haul network supporting the distributed database system causes transmitted operations to be received out of order. According to rules that are dependent on the number of versions, the scheduler reorders the operations to preserve the consistency of the database. Operations encounter extra delay in the process of reordering. The system is modeled by a queuing network. Response-time distributions are obtained analytically. Numerical results are presented to show the effect of the number of versions on the performance     

Transmission capacity for inhomogeneous overlaid wireless Ad-hoc networks

In the analysis of overlaid wireless Ad-hoc networks, the underlying node distributions are commonly assumed to be two independent homogeneous Poisson point processes. In this paper, by using stochastic geometry tools, a new inhomogeneous overlaid wireless Ad-hoc network model is studied and the outage probability are analyzed. By assuming that primary （PR） network nodes are distributed as a Poisson point process （PPP） and secondary （SR） network nodes are distributed as a Matern cluster processes, an upper and a lower bounds for the transmission capacity of the primary network and that of the secondary network are presented. Simulation results show that the transmission capacity of the PR and SR network will both have a small increment due to the inhomogeneity of the SR network.     

Analysis for bio-inspired thrown-box assisted message dissemination in delay tolerant networks

Inspired by biological communication, the strategy of deploying communication and storage equipment called thrown box is proposed to increase message delivery probability and to reduce transmission latency in delay tolerant networks. In this paper, we study the thrown-box assisted message dissemination models by analyzing a few cases on the message delivery rate and related latency distribution. We divide such communications into two processes. We first model the message delivering process among thrown boxes and derive time related message distribution on the boxes. Then we investigate the message collection process to obtain the expected number of informed collectors as a function of time. In addition, we analyze the latency distribution for message collection. Our analysis is derived based on a discrete Markov Chain model. The numerical examples are provided to validate our model and to examine the features of message dissemination under different network scenarios. The factors such as message relay and lifetime are considered. The results show that the tradeoff exists between the number of the boxes and the message lifetime, etc. In summary, our results will help storage management and delay management in DTNs and provide guidelines for applications of search and surveillance.     

SSRC:source rate control algorithm for delay-sensitive flow in data center network

Previous work had studied how to ensure the transmission time of delay-sensitive flows,but falled short in its effectiveness for a given period.Motivated by that and based on SDN/OpenFlow framework,a SDN-based source rate control (SSRC) algorithm was proposed.With a global view of network,SSRC can quickly locate the potential congestion node,adjust the transmission rate of source and reduce the response time of SSRC.The experiment results show that compared with DCTCP and other algorithms,SSRC can shorten the completion time of flows by 75% in average,which can ensure the transmission time of delay-sensitive and solve the problem of Incast well.     

A calculus for network delay. I. Network elements in isolation

A calculus is developed for obtaining bounds on delay and buffering requirements in a communication network operating in a packet switched mode under a fixed routing strategy. The theory developed is different from traditional approaches to analyzing delay because the model used to describe the entry of data into the network is nonprobabilistic. It is supposed that the data stream entered into the network by any given user satisfies burstiness constraints. A data stream is said to satisfy a burstiness constraint if the quantity of data from the stream contained in any interval of time is less than a value that depends on the length of the interval. Several network elements are defined that can be used as building blocks to model a wide variety of communication networks. Each type of network element is analyzed by assuming that the traffic entering it satisfies bursting constraints. Under this assumption, bounds are obtained on delay and buffering requirements for the network element; burstiness constraints satisfied by the traffic that exits the element are derived     

Performance of sufficient conditions for distributed quality-of-service support in wireless networks

Given a wireless network where some pairs of communication links interfere with each other, we study sufficient conditions for determining whether a given set of minimum bandwidth quality-of-service requirements can be satisfied. We are especially interested in algorithms which have low communication overhead and low processing complexity. The interference in the network is modeled using a conflict graph whose vertices correspond to the communication links in the network. Two links are adjacent in this graph if and only if they interfere with each other due to being in the same vicinity and hence cannot be simultaneously active. The problem of scheduling the transmission of the various links is then essentially a fractional, weighted vertex coloring problem, for which upper bounds on the fractional chromatic number are sought using only localized information. We recall some distributed algorithms for this problem, and then assess their worst-case performance. Our results on this fundamental problem imply that for some well known classes of networks and interference models, the performance of these distributed algorithms is within a bounded factor away from that of an optimal, centralized algorithm. The performance bounds are simple expressions in terms of graph invariants. It is seen that the induced star number of a network plays an important role in the design and performance of such networks.