Wireless Network Topology Research Articles

Distributed Medium Access Over Time-Varying Channels

Recent studies on MAC scheduling have shown that carrier sense multiple access (CSMA) algorithms can be throughput optimal for arbitrary wireless network topology. However, these results are highly sensitive to the underlying assumption on ‘static’ or ‘fixed’ system conditions. For example, if channel conditions are time-varying, it is unclear how each node can adjust its CSMA parameters, so-called backoff and channel holding times, using its local channel information for the desired high performance. In this paper, we study ‘channel-aware’ CSMA (A-CSMA) algorithms in time-varying channels, where they adjust their parameters as some function of the current channel capacity. First, we assume that backoff rates can be arbitrary large and show that the achievable rate region of A-CSMA equals to the maximum rate region if and only if the function is exponential. Furthermore, given an exponential function in A-CSMA, we design updating rules for their parameters, which achieve throughput optimality for an arbitrary wireless network topology. They are the first CSMA algorithms in the literature which are proved to be throughput optimal under time-varying channels. Moreover, we also consider the case when back-off rates of A-CSMA are restricted compared to the speed of channel variations, and characterize the throughput performance of A-CSMA in terms of the underlying wireless network topology. Our results not only guide a high-performance design on MAC scheduling under highly time-varying scenarios, but also provide new insights on the performance of CSMA algorithms in relation to their backoff rates and underlying network topologies.

A Movement-Assisted Deployment of Collaborating Autonomous Sensors for Indoor and Outdoor Environment Monitoring.

Using mobile robots or unmanned vehicles to assist optimal wireless sensors deployment in a working space can significantly enhance the capability to investigate unknown environments. This paper addresses the issues of the application of numerical optimization and computer simulation techniques to on-line calculation of a wireless sensor network topology for monitoring and tracking purposes. We focus on the design of a self-organizing and collaborative mobile network that enables a continuous data transmission to the data sink (base station) and automatically adapts its behavior to changes in the environment to achieve a common goal. The pre-defined and self-configuring approaches to the mobile-based deployment of sensors are compared and discussed. A family of novel algorithms for the optimal placement of mobile wireless devices for permanent monitoring of indoor and outdoor dynamic environments is described. They employ a network connectivity-maintaining mobility model utilizing the concept of the virtual potential function for calculating the motion trajectories of platforms carrying sensors. Their quality and utility have been justified through simulation experiments and are discussed in the final part of the paper.

A Policy-Aware Enforcement Logic for Appropriately Invoking Network Coding

Network coding has been shown to offer significant throughput benefits over certain wireless network topologies. However, the application of network coding may not always improve the network performance. In this paper, we first provide an analytical study, which helps in assessing when network coding is preferable to a traditional store-and-forward approach. Interestingly, our study reveals that in many topological scenarios, network coding can in fact hurt the throughput performance; in such scenarios, applying the store-and-forward approach leads to higher network throughput. We validate our analytical findings via extensive testbed experiments. Guided by our findings as our primary contribution, we design and implement PACE, a Policy-Aware Coding Enforcement logic that enables network coding only when it is expected to offer performance benefits. Specifically, PACE leverages a minimal set of periodic link quality measurements in order to make per-flow online decisions with regards to when network coding should be activated, and when store-and-forward is preferable. It can be easily embedded into network-coding-aware routers as a user-level or kernel-level software utility. We evaluate the efficacy of PACE via: 1) ns-3 simulations, and 2) experiments on a wireless testbed. We observe that our scheme wisely activates network coding only when appropriate, thereby improving the total network throughput by as much as 350% in some scenarios.

Impacts of Social Relationships and Inhomogeneous Node Distribution on the Network Performance

This paper studies the impacts of social relationships and inhomogeneous node distribution on wireless network performance. Motivated by the social characteristic that makes nodes more likely to communicate with nearby nodes, we present a model that captures the small-world property, power-law distribution, and multi-clustering topology of wireless networks. We compute the average traffic distance to derive the optimal per-node capacity, which is then analyzed from the social perspective. Based on the communication pattern, we introduce the quasi-strong ties and quasi-weak ties in order to discover how system parameters control the amount of network flows with different strengths of social relationships. Moreover, we propose an indicator of information propagation speed (IIPS), and show that there is a tradeoff between the IIPS and the per-node capacity of overall nodes.

Multi-Objective Topology Planning for Microwave-Based Wireless Backhaul Networks

Wireless backhaul networks provide vital infrastructure support for large public and private networks, and their efficient design is essential for smoothly handling the rapid growth of the Internet traffic. For its efficient capacity utilization, a well-planned topology would be crucial for such networks. Existing studies on planning for wireless backhaul network topologies have mostly focused on a single parameter or on a few performance aspects, e.g., to minimize the network cost or to maximize the network reliability. It would, however, be more realistic to consider multiple performance aspects jointly, subject to a variety of system constraints for a microwave-based wireless backhaul network, as proposed in this paper. For the optimization, we formulate a general cost that incorporates the various performance aspects considered, based on different weight factors. We develop an integer linear programming (ILP) optimization model and also propose an efficient heuristic algorithm to plan cost-minimized tree topologies for both single stage and multi-stage design scenarios. This paper shows that the proposed heuristic algorithm is efficient to optimize multiple system objectives jointly and performs close to the ILP model. The performances of the topologies planned with the periodic constraint and the single stage scenario are also close to each other further confirming the efficiency of the proposed heuristic algorithm.

Performance Evaluation of Two Reactive Routing Protocols for RWP Mobility Model with Different Speed

Wireless adhoc network are self creating self organizing and self administrating. The nodes within the network are free to move thus network do not rely on the preexisting infrastructure. Due to ease in deployment of mobile adhoc network wireless network are widely used. In the wireless network topology continuously changes according to the data packets to be sent at the destination path. With this so many best results in the wireless communication in this era wireless network over took wired network. In this paper we have compared the performance of two reactive MANET routing protocols AODV and DSR by using random way point mobility model. Both share similar On-Demand behavior, but the protocol's internal mechanism leads to significant performance difference. We have analyzed the performance of protocols by network load, mobility model and type of traffic (CBR). A detailed simulation has been carried out in QUALNET 6.1. The metrics used for performance analysis are Throughput, Average end-to-end Delay and Average jitter.

Ad-hoc Network Secured via Trust Computing

Ad hoc network consist of a collection of wireless nodes, all of which may be mobile, dynamically creates a wireless network topology amongst them without using any fixed infrastructure. Nodes communicate with each other by passing data and control packet from one node to another. The execution and survival of an Ad-hoc network is rely upon the co-operative and trusting nature of its nodes. Ad-hoc network are vulnerable to passive and active attacks by malicious nodes due to the independent movement of nodes. Several protocols have been developed to secure Ad-hoc networks using cryptographic schemes, but all dependent on the existence of central trust authority. The presence of central trust authority is an impractical requirement for Ad-hoc networks, so in this Paper we present a trust model that doesn’t rely on central trust authority. In our model we make use of trust agents that reside on network nodes. Each agent operates independently and maintains its individual trust value. An agent gathers data from all events & assigns weights to each event and computes different trust levels based upon them. Each trust agent basically performs the three functions: Trust Derivation, Quantification, and Computation.

A Spiderweb-Based Massive Access Management Protocol for M2M Wireless Networks

With the development of Internet of Things (IoT), a large amount of machine-to-machine (M2M) devices produce the data from a huge number of M2M communications. A massive access congestion control scheme in M2M communication is important in a wireless M2M network, where a wireless M2M network is constituted by a large number of wireless M2M devices. In this paper, we developed a spiderweb-based massive access management protocol for M2M wireless networks. The wireless M2M network topology considered, in this paper, is a spiderweb-based topology, which belongs to a regular topology. The spiderweb-based topology is split into a number of sub-spiderweb, while each sub-spiderweb can be seen as a small reservoir. The main function of the small reservoir is to temporarily store the massive access if the congestion problem is occurred due to the massive assess has been suddenly happened from the M2M devices. When the congestion problem is alleviated gradually, the temporarily-stored massive assess can be digested from these small reservoirs. The contribution of the proposed scheme is to reduce the packet loss rate and prolong the wireless M2M network lifetime. In addition, a dynamically adjustment of the different sub-spiderweb size is developed based on the amount of different data traffics. Simulation result finally illustrates that the proposed mechanism significantly reduces the packet loss rate and keeps the maximum network lifetime.

A Closed-Loop Transmission Power Control System Using a Nonlinear Approximation of Power-Time Curve

In wireless communication networks, it is desirable to achieve energy efficiency, while maintaining quality of service. Overall, energy efficiency can be achieved by minimizing the power output for each communication device. This paper presents a novel energy-saving adaptive transmit power control (TPC) algorithm based on bit error rate (BER) feedback (BER-TPC) that outperforms conventional approaches based on signal-to-interference-plus-noise ratio (SINR) feedback (SINR-TPC). It is a distributed algorithm deployed in both transmitting and receiving devices that can be applied for various wireless network topologies and protocols. This paper addresses the power efficiency of adaptive TPC, in terms of reduced total transmit power of the network by smoothing transmit power transients during adaptive iterations. It is achieved using a distributed closed-loop power control system that applies heuristically estimated dual-rate power adjustments during adaptive iterations. Because the proposed system uses a mathematical formula for power adjustment, operational bounds for stability can be provided using simple analysis. It is demonstrated that the proposed system provides adequate tradeoff between performance and complexity, in terms of reduction in sensitivities and better tracking performance in following the desired reference power curves used in the simulations. Case scenarios are simulated demonstrating approximately 1.39-dB transmit power savings compared to conventional methods.

Implementation of OpenFlow based cognitive radio network architecture: SDN&R

The static conventional network architecture is ill-suited to the growing management complexity and highly dynamic wireless network topologies. Software Defined Radio systems and their extension to cognitive and smart radio are characterized by distinct control loops for management which constantly increase network complexity and management inefficiencies, due to clear-cut between radio and core network management. Adding numerous devices and networks together will constantly increase the management cost, thus hinders scalability. Therefore, a holistic solution to synchronize radio and networks status has an elevated demand. To interconnect these systems and devices together, there is a need for a common management interface. OpenFlow is the first standard interface that enables Software Defined Networking (SDN). It can be rolled out in a variety of networking devices to enable improved automation and management by using common Application Program Interfaces to abstract the underlying networking details. The Software Defined Networking & Radio (SDN&R) framework proposed here has a potential combination between SDN and Radio networks to discover the underlying dynamism in cognitive access networks with integrated radio management. By isolating the control plane from the data plane, SDN&R enables a flexible management framework empowered by end-to-end goals through OpenFlow. In this article, we propose, validate, and evaluate the SDN&R architecture. In doing so, first we implement the OpenFlow enabled cognitive basestations (BSs) on Wireless Open-Access Research Platform. Furthermore, we develop software agents on BSs to provide radio status information to the cognitive control application implemented on the SDN controller. The results verify that the proposed framework in-lines with layer-2 or layer-3 forwarding performance. We claim that this work represents the first successful implementation results which synergizes SDN with Cognitive networks that motivates researchers towards SDN based radio resource management.

Artificial Neural Network based Cluster Head Selection in Wireless Sensor Network

The dispersed nature and vibrant topology of wireless sensor network have some basic requirements that include reduced energy utilization and extended network’s lifetime. In this paper, we have focused on hierarchical protocols. In such protocol the nodes are arranged in clusters. To synchronize action and route data, cluster head are selected one per cluster. We have introduced a new approach in wireless sensor network for selecting the cluster-head by making use of artificial neural network in order to increase network’s lifetime. We have used residual energy as a factor to make cluster-head. Radial basis function network model is used for cluster-head selection problem. The simulation results provide network’s performance on the basis of some factors including number of dead nodes, total energy consumption, cluster head formation, number of nodes dying and the number of packets transferred to base station and cluster head. The performance of the proposed algorithm is compared with LEACH and LEACH-C based on energy efficiency and improved network lifetime.

Optimization of Sensor Network Topology in Deployed in Inhomogeneous Lossy Media

This paper presents optimization of wireless sensor network (WSN) topology for forest fire detection. The sensors for this purpose are deployed in forest, grassland and open space, which have different attenuation properties in electromagnetic waves. For this reason, routers which receive signals from sensors and send them to the base station must be deployed considering these differences. In this work, we develop an optimization method for WSN topology based on simulated annealing considering the differences in the attenuation property. The vegetation data are taken from Landsat data. Using the present method, the necessary number of routers for full connection of the sensors deployed in diverse, irregular environments can be estimated.

Minimizing Expected Transmissions Multicast in Wireless Multihop Networks

We address the multicast problem in a wireless multihop network in the presence of errors. Finding the multicast schedule that minimizes the expected number of transmissions, while accounting for both the wireless broadcast advantage (WBA) and the wireless unreliable transmission (WUT) characteristics, has not been solved optimally before. We formally define the problem and propose an initial algorithm of non-polynomial complexity to obtain the optimal solution. The algorithm starts by transforming the wireless network topology into an auxiliary expanded graph that captures the WBA property, and assigning appropriate weights to the links so as to capture the WUT property. The proposed transformation is interesting on its own merit, since it permits us to consider only point-to-point transmissions (as in wireline networks) in the expanded graph, instead of the point-to-multipoint transmissions present in the original wireless network, and can also be useful in other optimization problems some of which we briefly describe. By solving the minimum Steiner tree problem on the expanded graph we obtain the optimal multicast solution for the initial graph. Since the optimal algorithm is of non-polynomial complexity, we also propose a number of heuristic algorithms. In particular, we first present a truncated graph transformation and then describe two heuristic algorithms for obtaining the multicast schedule. Simulation results show that the proposed heuristics have performance close to that of the optimal algorithm, at least for the instances for which we were able to track optimal solutions, while outperforming other heuristic multicast algorithms.

Simultaneous power control and power management algorithm with sector-shaped topology for wireless sensor networks

Abstract In this paper, we propose a topology control technique to reduce the energy consumption of wireless sensor networks (WSNs). The technique makes use of both power control and power management methods. The algorithm uses the power management technique to put as many idle nodes as possible into the sleep mode while invoking the power control method to adjust the transmission range of the active nodes. On the contrary to earlier works in which both of these methods were used separately, in this algorithm, they are utilized simultaneously to decide about the sleep nodes and the ranges of active nodes. It is an approximation algorithm which is called simultaneous power control and power management algorithm (SPCPM). The performance bound of this centralized algorithm is determined analytically. Then, to make the proposed method practical for WSNs, a distributed algorithm based on SPCPM is introduced. To assess the efficiency of the proposed algorithm, we compare its average energy consumption with those of three existing topology control algorithms for a sector-based WSN. The simulation results which were obtained for different numbers of transmitting sensor nodes reveal less average energy consumptions for SPCPM compared to other algorithms.

Strong minimum energy hierarchical topology in wireless sensor networks

Given a set of $$n$$n sensors, the strong minimum energy topology (SMET) problem in a wireless sensor network is to assign transmit powers to all sensors such that (i) the graph induced only using the bi-directional links is connected, that is, there is a path between every pair of sensors, and (ii) the sum of the transmit powers of all the sensors is minimum. This problem is known to be NP-hard. In this paper, we study a special case of the SMET problem, namely , the $$k$$k-strong minimum energy hierarchical topology ($$k$$k-SMEHT) problem. Given a set of $$n$$n sensors and an integer $$k$$k, the $$k$$k-SMEHT problem is to assign transmission powers to all sensors such that (i) the graph induced using only bi-directional links is connected, (ii) at most $$k$$k nodes of the graph induced using only bi-directional links have two or more neighbors, that is they are non-pendant nodes, and (iii) the sum of the transmit powers of all the sensors in $$G$$G is minimum. We show that $$k$$k-SMEHT problem is NP-hard for arbitrary $$k$$k. However, we propose a $$\frac{k+1}{2}$$k+12-approximation algorithm for $$k$$k-SMEHT problem, when $$k$$k is a fixed constant. Finally, we propose a polynomial time algorithm for the $$k$$k-SMEHT problem for $$k=2$$k=2.

Percolation and Scale-Free Connectivity for Wireless Sensor Networks

Based on complex network analysis and percolation theory, this letter proposes a method called LTPT to generate scale-free topology for wireless sensor networks (WSNs), with required connectivity and lifetime. The problem is divided into logical topology (LT) and physical topology (PT) analysis. With LTPT, we generate a robust logical topology of power-law degree distribution and build a physical topology of guaranteed connectivity and lifetime. This is the first time the connection between logical and physical connectivities is set up analytically.

ZTE’s perspective on applying OFDM-PON in next converged optical and wireless networks

Driven by ZTE and other telecom vendors and operators in order to meet the ever increasing bandwidth demand from fixed optical network users and mobile backhaul/fronthaul services, the latest next generation passive optical network (NGPON2) is being standardized by Full Service Access Network (FSAN) and International Telecommunication Union (ITU-T) which consists of two separated sub-systems, hybrid time- and wavelength-division multiplexing PON (TWDM-PON) and point-to-point wavelength- division multiplex (PtP WDM). The TWDM-PON will be used for traditional residential, business and wireless backhaul services which are not sensitive to time delay and delay variation, whereas the PtP WDM is mainly used for emerging wireless fronthaul service which is very sensitive to the time delay and time delay variation. However, as a main international standards’ contributor, ZTE thinks for those operators who offer multiple-level of services to both residential, business and mobile backhaul/fronthaul users, this obviously raises significant economic and power concerns by demanding to deploy two separated systems. Therefore, in this paper, for the first time, ZTE proposes a new converged optical and wireless integrated network architecture and topology by applying orthogonal frequency division multiplexing (OFDM) PON technology, which is able to simultaneously support residential, business and mobile backhaul/fronthaul services in terms of meeting the requirements of both time delay sensitive and non-sensitive services, and also address the economic and power concerns compared with conventional technologies. This architecture is further investigated and analyzed in depth on functional block, Quality-of-service (QoS), synchronization and deployment considerations. Also ZTE reports in this paper the first 40Gbps OFDMPON prototype in which eight wavelengths each with 5Gbps Ethernet data via 10G-PON encapsulation method (X-GEM) and 10G-PON transmission convergence (X-GTC) framing are demonstrated.

Analysis of wireless sensor network topology and estimation of optimal network deployment by deterministic radio channel characterization.

One of the main challenges in the implementation and design of context-aware scenarios is the adequate deployment strategy for Wireless Sensor Networks (WSNs), mainly due to the strong dependence of the radiofrequency physical layer with the surrounding media, which can lead to non-optimal network designs. In this work, radioplanning analysis for WSN deployment is proposed by employing a deterministic 3D ray launching technique in order to provide insight into complex wireless channel behavior in context-aware indoor scenarios. The proposed radioplanning procedure is validated with a testbed implemented with a Mobile Ad Hoc Network WSN following a chain configuration, enabling the analysis and assessment of a rich variety of parameters, such as received signal level, signal quality and estimation of power consumption. The adoption of deterministic radio channel techniques allows the design and further deployment of WSNs in heterogeneous wireless scenarios with optimized behavior in terms of coverage, capacity, quality of service and energy consumption.

A Flow-Weighted Scale-Free Topology for Wireless Sensor Networks

In this paper, complex network theory is used to generate robust scale-free topology for wireless sensor networks (WSNs). Nodes in WSNs consume energy in two stages: network generation and network operation. Existing scale-free models for WSNs focus on the energy in the first stage. However, sensors consume most energy in the second stage. This paper proposes a method called flow-aware scale-free (FASF) model to balance the energy consumption of sensors in the second stage. Taking into account the traffic flow in the network, a WSN is modeled as a weighted network and its energy usage is balanced. Both analysis and simulations indicate that FASF enhances connectivity and network lifetime, achieves high robustness against node failures, and at the same time maintains the scale-invariant property.

Efficient Scheduling of Packets in Wireless Sensor Networks Using Priority Based Scheduling Approach

The packet scheduling is essential and plays an important role to sense the element nodes with resource constraints in Wireless Networks. The packet scheduling scheme also scale the energy consumption and end-to-end information transmission delay in time period and non-real-time information packets during wireless transmission. The proposed Priority based Packet Scheduling (PPS) technique has a tendency to overcome the issues based on priority queues in a wireless network. The priority queue has three levels at each node, except those at the last virtual hierarchy level in the zone-based topology of wireless network. In the meantime packet square are measured and placed in the highest-priority queue and might pre-empt information packets in alternative queues. In the non-real-time period packet square are measured and placed into two alternative queues supported at a particular threshold of their calculable interval. The time period and non-real time information has two queues in a leaf node, since they did not receive information from alternative nodes which causes scale back end-to-end delay. The proposed PPS technique has affinity to evaluate performance through simulations for the time period and non-real-time information. Simulation results illustrate that the PPS Scheme outperforms typical schemes in terms of average information waiting time and end-to-end delay.