Dense Wireless Networks Research Articles

Simulating the Tail of the Interference in a Poisson Network Model

Interference among simultaneous transmissions represents the main limitation factor for the capacity and connectivity of dense wireless networks. In this paper, we provide efficient simulation laws for the tail of the interference in a simple wireless ad hoc network model. Particularly, we consider node locations distributed according to a Poisson point process and various classes of light-tailed fading distributions.

OSERENA: a Coloring Algorithm Optimized for Dense Wireless Networks

The goal of this paper is to present OSERENA, a distributed coloring algorithm optimized for dense wireless sensor networks (WSNs). Network density has an extremely reduced impact on the size of the messages exchanged to color the WSN. Furthermore, the number of colors used to color the network is not impacted by this optimization. We describe in this paper the properties of the algorithm and prove its correctness and termination. Simulation results point out the considerable gains in bandwidth.

Censoring for Bayesian Cooperative Positioning in Dense Wireless Networks

Cooperative positioning is a promising solution for location-enabled technologies in GPS-challenged environments. However, it suffers from high computational complexity and increased network traffic, compared to traditional positioning approaches. The computational complexity is related to the number of links considered during information fusion. The network traffic is dependent on how often devices share positional information with neighbors. For practical implementation of cooperative positioning, a low-complexity algorithm with reduced packet broadcasts is thus necessary. Our work is built on the insight that for precise positioning, not all the incoming information from neighboring devices is required, or even useful. We show that blocking selected broadcasts (transmit censoring) and discarding selected incoming information (receive censoring) based on a Cramer-Rao bound criterion, leads to an algorithm with reduced complexity and traffic, without significantly affecting accuracy and latency.

Real Time Monitoring and Control of Wireless Networks

Adhoc sensor networks consists of dense wireless network having tiny, low-cost sensor nodes which collect the environmental data and send it to the base station. Using such networks helps in monitoring and control of physical environments remotely with ease and accuracy. Examples include military applications, and acquiring sensing information from inhospitable locations like thick forests, active volcano regions etc. Since the devices will be battery powered and are scattered in a complex network, It is very difficult to locate each node, know about its status and how the devices are connected in the wireless network. Because of their increased importance and applications, wireless networks are becoming part and parcel of our day to day life, and hence the need of developing a system to visualise , control and monitor such networks arises. This paper presents implementation issues and author's contribution to design and implement a generic framework of the 'Network Visualization tool' to monitor adhoc wireless networks. The paper also elaborates system architecture, hardware and software organizations, and integration details of the proposed system with an exemplary wireless network based on standard IEEE 802.15.4 MAC protocol[1] to monitor temperature of different rooms in a house.

On Scalability of Routing Tables in Dense Flat-Label Wireless Networks

Consider a large wireless ad hoc network that facilitates communication between random pairs of network nodes. This paper investigates the size of routing tables as the number of nodes in the network increases. A routing protocol in a flat-label network is information-efficient if the amount of information at individual nodes required to route packets does not increase with the network size. It is shown that the shortest-path and straight-line routing algorithms are not information-efficient, i.e., these protocols can be implemented only when nodes' memory increases with the network size. On the other hand, it is established that there exists an information-efficient algorithm that routes packets correctly even if each node in the network is capable of storing information on a fixed number of destinations only.

Interference Alignment in Dense Wireless Networks

We consider arbitrary dense wireless networks, in which n nodes are placed in an arbitrary (deterministic) manner on a square region of unit area and communicate with each other over Gaussian fading channels. We provide inner and outer bounds for the n × n-dimensional unicast and the n × 2 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> -dimensional multicast capacity regions of such a wireless network. These inner and outer bounds differ only by a factor O(log(n)), yielding a fairly tight scaling characterization of the entire regions. The communication schemes achieving the inner bounds use interference alignment as a central technique and are, at least conceptually, surprisingly simple.

Fault-tolerant de-Bruijn graph based multipurpose architecture and routing protocol for wireless sensor networks

As dense Wireless Sensor Networks (WSNs) are increasingly vulnerable to fault, network must continue processing data without affecting the faulty node. Fault aware routing is an effective way to mitigate such a scenario. To this end, we present a de-Bruijn graph based Multipurpose Architecture and Routing Protocol (MARP) which has all the properties of an efficient WSN. The MARP supports multicast routing, broadcasting, fault detection and efficient fault-tolerance. Its unique architecture makes it easily scalable and provides easy three-dimensional to two-dimensional mapping. Furthermore, we show that, depending on the fault-tolerance capability one wants, design requires higher redundancy. A small experiment of de-Bruijn graph based routing protocol is also presented with mica2 motes to check its feasibility in a real-life scenario.

Limit of the Transport Capacity of a Dense Wireless Network

It is known that the transport capacity of a dense wireless ad hoc network with n nodes scales like √n. We show that the transport capacity divided by √n approaches a nonrandom limit with probability 1 when the nodes are uniformly distributed on the unit square. To show the existence of the limit, we prove that the transport capacity under the protocol model is a subadditive Euclidean functional and use the machinery of subadditive functions in the spirit of Steele.

Limit of the Transport Capacity of a Dense Wireless Network

It is known that the transport capacity of a dense wireless ad hoc network with n nodes scales like √n. We show that the transport capacity divided by √n approaches a nonrandom limit with probability 1 when the nodes are uniformly distributed on the unit square. To show the existence of the limit, we prove that the transport capacity under the protocol model is a subadditive Euclidean functional and use the machinery of subadditive functions in the spirit of Steele.

Expanding Ring-Based Data Query with Delay Constraints for Dense Wireless Ad Hoc Networks

Data query is one of the most important issues in wireless ad hoc networks, since the ultimate goal of these networks is to support efficient data sharing among wireless nodes. In this paper, we study the issue of data query for delay-sensitive applications in dense wireless ad hoc networks. We focus our attention on step-by-step expanding ring-based data query, which provides an upper bound on query delay to any expanding ring based query strategies. Two replication strategies including Index Replication (IR) and Data Replication (DR) are considered, to improve the delay performance of data query. We analyze the probabilistic behavior of query delay for both DR and IR by theoretical methods, and develop analytical models to approximate the minimum number of replicas required for both query strategies if an application-specified delay bound is imposed. Our work is validated through extensive simulations.

Adaptive Probabilistic Broadcasting over Dense Wireless Ad Hoc Networks

We propose an idle probability-based broadcasting method,iPro, which employs an adaptive probabilistic mechanism to improve performance of data broadcasting over dense wireless ad hoc networks. In multisource one-hop broadcast scenarios, the modeling and simulation results of the proposediProare shown to significantly outperform the standard IEEE 802.11 under saturated condition. Moreover, the results also show that without estimating the number of competing nodes and changing the contention window size, the performance of the proposediProcan still approach the theoretical bound. We further applyiProto multihop broadcasting scenarios, and the experiment results show that within the same elapsed time after the broadcasting, the proposediProhas significantly higher Packet-Delivery Ratios (PDR) than traditional methods.

Reliable Multimedia Broadcasting over Dense Wireless Ad-Hoc Networks (Invited Paper)

Broadcasting is an essential operation for Wireless Ad Hoc Networks to perform routing path discovery, and it has become the predominant technology for message dissemination in Vehicular Ad Hoc Networks (VANETs). In the reactive routing schemes of wireless ad hoc network, Routing Request (RREQ) packets are broadcast from the source, and once received the destination traces back the broadcasting path to build an on-demand route. In VANETs, different broadcasting schemes have been proposed for safety, comfort, and commercial applications. However, broadcasting usually generates a lot of redundant messages which would cause excessive channel contention and packet collisions, especially when the density of the network becomes higher. In this survey article, we first introduce the most common data dissemination techniques used in wireless ad hoc networks. After that, we discuss techniques that have been proposed to mitigate the broadcast storm problem. Finally, we introduce an effective model for analyzing the broadcasting schemes, and based on the model we propose an adaptively adjusted probabilistic scheme that highly improves the reliability of broadcasting in dense ad hoc networks.

Performance Analysis of IEEE 802.11b Wireless Networks with Object Oriented Petri Nets

Communication protocols are often investigated using simulation. This paper presents a performance study of the distributed coordination function of 802.11 networks. Firstly, our study illustrates the different classes of Petri Nets used for modeling network protocols and their robustness in modeling based on formal methods. Next we propose a detailed 802.11b model based on Object-oriented Petri Nets that precises backoff procedure and time synchronization. Then, performance analyses are evaluated by simulation for a dense wireless network and compared with other measurements approaches. Our main goal is to propose a modular model that will enable to evaluate the impact of network performances on the performances of distributed discrete event systems.

Wireless Sensor Network Management and Functionality: An Overview

Sensor networks are dense wireless networks of small, low-cost sensors, which collect and disseminate en-vironmental data. Wireless sensor networks facilitate monitoring and controlling of physical environments from remote locations with better accuracy. They have applications in a variety of fields such as environ-mental monitoring; military purposes and gathering sensing information in inhospitable locations. Sensor nodes have various energy and computational constraints because of their inexpensive nature and adhoc method of deployment. Considerable research has been focused at overcoming these deficiencies through more energy efficient routing, localization algorithms and system design. Our survey presents the funda-mentals of wireless sensor network, thus providing the necessary background required for understanding the organization, functionality and limitations of those networks. The middleware solution is also investigated through a critical presentation and analysis of some of the most well established approaches.

Broadcasting with Randomized Network Coding in Dense Wireless Ad Hoc Networks

In this paper, we consider the broadcast storm problem in dense wireless ad hoc networks where interference among densely populated wireless nodes causes significant packet loss. To resolve the problem, we apply randomized network coding (RNC) to the networks. RNC is a completely different approach from existing techniques to resolve the problem, and it reduces the number of outstanding packets in the networks by encoding several packets into a single packet. RNC is a kind of linear network coding, and it is suited to wireless ad hoc networks because it can be implemented in a completely distributed manner. We describe a procedure for implementing the wireless ad hoc broadcasting with RNC. Further, with several simulation scenarios, we provide some insights on the relationship between the system parameters and performance and find that there is the optimal length of coding vectors for RNC in terms of packet loss probability. We also show a guideline for the parameter setting to resolve the broadcast storm problem successfully.

Environmental controls and the influence of vegetation type, fine roots and rhizomorphs on diel and seasonal variation in soil respiration.

Characterization of spatial and temporal variation of soil respiration coupled with fine root and rhizomorph dynamics is necessary to understand the mechanisms that regulate soil respiration. A dense wireless network array of soil CO2 sensors in combination with minirhizotron tubes was used to continuously measure soil respiration over 1 yr in a mixed conifer forest in California, USA, in two adjacent areas with different vegetation types: an area with woody vegetation (Wv) and an area with scattered herbaceous vegetation (Hv). Annual soil respiration rates and the lengths of fine roots and rhizomorphs were greater at Wv than at Hv. Soil respiration was positively correlated with fine roots and rhizomorphs at Wv but only with fine roots at Hv. Diel and seasonal soil respiration patterns were decoupled with soil temperature at Wv but not at Hv. When decoupled, higher soil respiration rates were observed at increasing temperatures, demonstrating a hysteresis effect. The diel hysteresis at Wv was explained by including the temperature-dependent component of soil respiration and the variation dependent on photosynthetically active radiation. The results show that vegetation type and fine root and rhizomorph dynamics influence soil respiration in addition to changes in light, temperature and moisture.

The Impact of Channel Feedback on Opportunistic Relay Selection for Hybrid-ARQ in Wireless Networks

This paper presents a decentralized relay selection protocol for a dense wireless network and describes channel feedback strategies that improve its performance. The proposed selection protocol supports hybrid automatic repeat request transmission where relays forward parity information to the destination in the event of a decoding error. Channel feedback is employed for refining the relay selection process and to select an appropriate transmission mode in a proposed adaptive modulation transmission framework. An approximation of the throughput of the proposed adaptive modulation strategy is presented, and the dependence of the throughput on system parameters such as the relay contention probability and the adaptive modulation switching point is illustrated via maximization of this approximation. Simulations show that the throughput of the proposed selection strategy is comparable with that yielded by a centralized selection approach that relies on geographic information.

On Loss Differentiation for CSMA-Based Dense Wireless Network

In this paper, we propose a novel method to differentiate packet loss based on interference energy and timing relative to desired signal in CSMA-based dense wireless networks. All measurements are conducted locally at transmitters without any additional over-the-air overhead. Our method can estimate PER (packet error rate) due to interference prior to or after the beginning of the desired signal separately, allowing for more efficient MAC(media access control) adaptation design.

On Traffic Load Distribution and Load Balancing in Dense Wireless Multihop Networks

We study the load balancing problem in a dense wireless multihop network, where a typical path consists of a large number of hops, that is, the spatial scales of a typical distance between source and destination and mean distance between the neighboring nodes are strongly separated. In this limit, we present a general framework for analyzing the traffic load resulting from a given set of paths and traffic demands. We formulate the load balancing problem as a minmax problem and give two lower bounds for the achievable minimal maximum traffic load. The framework is illustrated by considering the load balancing problem of uniformly distributed traffic demands in a unit disk. For this special case, we derive efficient expressions for computing the resulting traffic load for a given set of paths. By using these expressions, we are able to optimize a parameterized set of paths yielding a particularly flat traffic load distribution which decreases the maximum traffic load in the network by 40% in comparison with the shortest-path routing.

On the power efficiency of cooperative broadcast in dense wireless networks

A fundamental problem in large scale wireless networks is the energy efficient broadcast of source messages to the whole network. The energy consumption increases as the network size grows, and the optimization of broadcast efficiency becomes more important. In this paper, we study the optimal power allocation problem for cooperative broadcast in dense large-scale networks. In the considered cooperation protocol, a single source initiates the transmission and the rest of the nodes retransmit the source message if they have decoded it reliably. Each node is allocated an-orthogonal channel and the nodes improve their receive signal-to-noise ratio (SNR), hence the energy efficiency, by maximal-ratio combining the receptions of the same packet from different transmitters. We assume that the decoding of the source message is correct as long as the receive SNR exceeds a predetermined threshold. Under the optimal cooperative broadcasting, the transmission order (i.e., the schedule) and the transmission powers of the source and the relays are designed so that every node receives the source message reliably and the total power consumption is minimized. In general, finding the best scheduling in cooperative broadcast is known to be an NP-complete problem. In this paper, we show that the optimal scheduling problem can be solved for dense networks, which we approximate as a continuum of nodes. Under the continuum model, we derive the optimal scheduling and the optimal power density. Furthermore, we propose low-complexity, distributed and power efficient broadcasting schemes and compare their power consumptions with those-of-a traditional noncooperative multihop transmission.