Large Number Of Hops Research Articles

Secure Connectivity Probability of Multi-hop Clustered Randomize-and-Forward Networks

This work investigates secure cluster-aided multi-hop randomize-and-forward networks. We present a hop-by-hop multi-hop transmission scheme with relay selection, which evaluates for each cluster the relays that can securely receive the message. We propose an analytical model to derive the secure connectivity probability (SCP) of the hop-by-hop transmission scheme. For comparison, we also analyze SCPs of traditional end-to-end transmission schemes with two relay-selection policies. We perform simulations, and our analytical results verify that the proposed hop-by-hop scheme is superior to end-to-end schemes, especially with a large number of hops or high eavesdropper channel quality. Numerical results also show that the proposed hop-by-hop scheme achieves near-optimal performance in terms of the SCP.

Exploiting mm-Wave Communications to Boost the Performance of Industrial Wireless Networks

This work explores the potentiality of millimeter waves (mmW) as physical layer in industrial wireless networks. Innovative models and a link design method are proposed to achieve reliable communication, at a distance of tens of meters for a single hop, even in harsh environments. By exploiting the worldwide-free band of several GHz, available around 60 GHz, mmW links allow to achieve a performance boosting of up to two orders of magnitude, w.r.t. conventional sub-6-GHz wireless links, in indoor industrial environments. Time slotted channel hopping and frequency-diversity can be implemented with a large number of channels, and with high bit rate (several Mb/s per channel). This allows for robust networking of high data-rate sensors, such as cameras, radars, or laser scanners. Featuring a low bit error rate, mmW communication allows for low-latency link and large number of hops in networks with a large radius. Finally, it ensures interference separation from operating frequencies of electrical machines, switching converters, and other industrial wireless networks (e.g., 802.11 or 802.15). Implementation results for key HW blocks in low-cost technologies show the feasibility of mmW communication nodes with low-power and compact size.

Extensible time synchronisation protocol for wireless sensor networks

One important aspect in many applications of wireless sensor networks WSNs is time synchronisation. There are still some problems to be solved for time synchronisation, such as error and imbalance of time synchronisation precision, causing the fluctuations among nodes' time and being even worse for those with a larger number of hops, producing unstable communication links for the network. In this paper, we introduce an extensible time synchronisation protocol ETSP for WSNs and nodes get synchronised through time stamps from the root node directly or indirectly. We improve the least square method for linear regression to get better performance of time drift and spread the time information from the root node to the whole network. The proposed method reduces fluctuations in terms of time among nodes especially for the nodes far from the root, enhancing stability in large-scale networks. Simulation and experimental results show good performance of our method.

How network monitoring and reinforcement learning can improve tcp fairness in wireless multi-hop networks

Wireless mesh network (WMN) is an emerging technology for the last-mile Internet access. Despite extensive research and the commercial implementations of WMNs, there are still serious fairness issues in the transport layer, where the transmission control protocol (TCP) favors flows with a smaller number of hops to flows with a larger number of hops. TCP unfair behavior is a known anomaly over WMN that attracts much attention in recent years and is the focus of this paper. In this article, we propose a distributed network monitoring mechanism using a cross-layer approach that deploys reinforcement learning techniques (RL) to achieve fair resource allocation for nodes within the wireless mesh setting. In our approach, we deploy Q-learning, a reinforcement learning mechanism, to monitor the dynamics of the network. The Q-learning agent creates a state map of the network based on the medium access control (MAC) parameters and takes actions to enhance TCP fairness and throughput of the starved flows in the network. The proposal creates a distributed cooperative mechanism where each node hosting a TCP source monitors the network and adjusts its TCP parameters based on the network dynamics. Extensive simulation results and testbed analysis demonstrate that the proposed method significantly improves the TCP fairness in a multi-hop wireless environment.

Distributed Resource Allocation for Multihop Decode-and-Forward Relay Systems

In multihop relay networks with a large number of hops, it is challenging to allocate the available resources optimally among the relay nodes due to the large number of required control signals between the controller and the relay nodes. In addition, the latency caused by this signaling can result in using outdated resource-allocation information as the channels are time varying. Hence, a distributed resource-allocation scheme is proposed for multihop decode-and-forward (DF) relay systems, with low complexity in analytical computation and practical implementation. Based on the type of division multiplexing in time or frequency, this scheme can be used to obtain the optimal per-hop time slot length or bandwidth, respectively. This distributed iterative scheme needs no additional resource for optimization. The required communication to fulfill this optimization is only with the adjacent nodes of each relay and can be performed through the forwarding and acknowledgment packets (ACKs). It is shown that this scheme converges to the global optimal solution with an exponential convergence rate. The performance of this scheme is also investigated for the time-variant transmission channels by computer simulations.

Multi-Hop Relaying Using Energy Harvesting

In this letter, the performance of multi-hop relaying using energy harvesting is evaluated. Both amplify-and-forward and decode-and-forward relaying protocols are considered. The evaluation is conducted for time-switching energy harvesting as well as power-splitting energy harvesting. The largest number of hops given an initial amount of energy from the source node is calculated. Numerical results show that, in order to extend the network coverage using multi-hop relaying, time-switching is a better option than power splitting and in some cases, decode-and-forward also supports more hops than amplify-and-forward.

A novel framework to mitigate the negative impacts of green techniques on BGP

Green networking techniques usually shut down the least utilized links and/or routers during off-peaks hours. In a prior work, we showed conclusively that these actions trigger what is known as hot-potato routing changes. These changes are well known to negatively impact the operation of the Border Gateway Protocol (BGP). Critically, they may cause packet loss due to slow BGP convergence and increased congestion. In order to overcome such negative impacts, in this paper, we propose a novel framework that allows Ingress Routers (IRs) to work collaboratively to determine the set of links that should be carrying their respective traffic to Egress Routers (ERs). IRs exchange information about their established paths with each other, and each IR determines whether to shift their existing paths to ERs to optimize a given objective, e.g., energy savings. The IRs repeat the process until convergence. Unused links are then shut down, and thereby, lowering the energy consumption rate of a network. In this framework, we study a number of key issues: first, we study the order in which IRs establish paths, namely (i) most savings, (ii) round robin, and (iii) random order. Our results show that similar performance is achieved regardless of employed method. However, in some cases, IRs that establish paths using round robin took up to 23% more time to converge than IRs that used the most savings method. Second, we study path selection metrics. In particular, IRs select paths according to (i) shortest path, where paths with the minimum number of hops are selected, (ii) longest path, where paths with the largest number of hops are preferred, and (iii) random, where paths are randomly selected. Our experimental results over five topologies show that using shortest paths is the most efficient where IRs use as little as 25% more active links than a global optimal solution. However, IRs establishing paths in a robin manner are able to utilize 5% fewer number of links than when they employ the shortest path to each ER.

First-Passage-Time Kinetic Monte Carlo Simulation of Nucleation and Growth in Electrodeposition

Nucleation and growth are the fundamental processes in electrochemical phenomena, which are influenced by many factors in solution and electrode surface. Important issues in electrochemical engineering such as controlling dendrite formation or single crystal production must be considered based on the understanding of nucleation process since precursors of large scale structures of deposited films are expected to appear in the early stage of nucleation.Kinetic Monte Carlo (KMC) method is widely used to study electrodeposition and crystal growth, which are categorized as “diffusion-reaction system”. This system consists of many diffusing particles (reactants). When two (or more) particles collide with each other, some reaction occurs. In crystal growth, for example, the reactants are adatoms deposited on crystal surface and the reaction is the nucleation as a result surface diffusion. KMC method is a direct and commonly used simulation method for diffusion-reaction systems. The direct KMC method, however, becomes inefficient when the concentration of the reactants becomes low and a large number of hops have to be simulated before a reaction occurs. In order to overcome this problem, a first-passage-time KMC (FPKMC) method has been developed by Oppelstrup, et. al. [1] In the FPKMC method, an area is assigned to each particle which includes only one reactant, and an analytical solution is used to derive the distribution function of the first-passage time which is defined as the time when the particle reaches the boundary of the area for the first time. A particle is moved to the boundary of the area following the FPT distribution function skipping many hops. The FPKMC is an efficient and exact method to realize fast simulation of diffusion-reaction systems. In the work of Oppelstrup et. al., a continuous diffusion model is used to derive the FPT distribution function. [1, 2] Bezzola et. al. extended the FPKMC method to a discrete lattice to simulate crystal growth. [3, 4] In Bezzola’s work, solution is not explicitly included in the model.The purpose of the present work is to study the nucleation and growth in the electrochemical systems by developing the hybrid method of FPKMC and ordinary KMC methods. The reactants are metal ions which are electrodeposited on the electrode surface. The nucleation occurs when the surface adatoms collide after surface diffusion. The mass transport of ions in solution is also taken into account. The surface diffusion and nucleation, which are the time-consuming part of the simulation, are simulated by the FPKMC method. The mass transport and reaction in solution are simulated by the ordinary KMC method. We first confirmed that the computing time is greatly reduced by applying FPKMC compared to conventional KMC method. Using the hybrid method, we study the correlation between the microscopic nucleation process and the resulting large scale crystal structure. The influence of solution structure on nucleation and growth is also discussed.

Coded packets over lossy links: A redundancy-based mechanism for reliable and fast data collection in sensor networks

In wireless sensor networks (WSNs), many applications require a high degree of reliability with low delay. Due to the lossy nature of wireless channels, achieving reliable communication can be very challenging. The most commonly adopted approach for achieving reliability is the acknowledgment based retransmission mechanism; however, this approach is inefficient in terms of end-to-end delay especially when there are a large number of hops from a sensor to the sink node. In this paper, we propose a redundancy-based approach that achieves high reliability and low end-to-end delay. The proposed protocol employs a network coding-based approach to improve packet redundancy when a link is unreliable or there is a strict end-to-end delay requirement. The protocol adaptively changes the redundancy level according to the application requirements and link loss rate. The protocol can be implemented easily because modification of the application layer at the source node and destination node is the only mandatory requirement. We implement the proposed mechanism on a real testbed which consists of IRIS motes, and evaluate the performance of the proposed mechanism using real-world experiments, network simulations and theoretical analysis.

Efficient Performance Analysis of Spectrum Sensing for Cascaded Multihop Network over Nagakami-m Fading Channels

Performance evaluation of spectrum sensing in infrastructure based multihop network is very hard to achieve because of the adverse effects of channel fading. In this paper, performance of a multihop link is studied over Nakagami-m distribution. It provides the exact theoretical methodology for the performance analysis of spectrum sensing by evaluating detection probability. Using a cascaded multihop model, the end-to-end Signal to Noise Ratio (SNR) is given over Nakagami-m distribution. In the analysis, multihop model based on relays are considered over independent and not identically distributed (i.n.i.d) wireless channels. Simulation results show the effect of increase in number of hops on probability of detection for multihop links. Subsequent to the thorough fading severity analysis, it has been accomplished that spectrum hole detection is more crucial at lower SNR values with large number of hops.

BUFE-MAC: A Protocol With Bandwidth Utilization and Fairness Enhancements for Mesh-Backbone-Based VANETs

Vehicular ad hoc network technologies can improve traffic safety for drivers and provide comfort services for passengers. Because the hardware of a roadside unit (RSU) is costly, in most previous research, vehicles might exchange data with an RSU through multihop transmissions. However, the vehicle with a larger number of hops to the RSU has fewer opportunities and longer time to exchange its data with the RSU because the contentions and collisions increase with the number of hops. This paper proposes the bandwidth utilization and fairness enhancements medium access control (BUFE MAC) protocol, which considers a vehicular ad hoc network that accesses the Internet through fixed Internet Gateways along the road. BUFE-MAC aims at increasing bandwidth utilization, maintaining fairness, and avoiding collision. The performance study reveals that the proposed MAC protocol not only avoids the collision problem but improves the performance in terms of end-to-end throughput and fairness as well.

Hop-Based Burst-Cluster Transmission: Fairness Improvement in High-Performance OBS Networks

In order to improve the fairness in terms of the number of hops for high-performance optical burst switching networks, we propose a method called hop-based burst-cluster transmission. In this method, bursts with different numbers of hops are assembled simultaneously, and a hop-based burst-cluster is generated so that the bursts within the cluster are arranged in order from the smallest to the largest number of hops. Then the hop-based burst-cluster is transmitted along with multiple control packets. Here, within the same cluster, a burst whose number of hops is small is transmitted before a burst whose number of hops is large. The control packets are processed according to the modified processing algorithm, and hence a burst whose number of hops is large has more chances in the wavelength reservation than a burst whose number of hops is small. As a result, the burst loss probability of many hops decreases and the burst loss probability of few hops increases, improving the fairness. In addition, hop-based burst-cluster transmission can also decrease the overall burst loss probability. We evaluate the performance of hop-based burst-cluster transmission for the 14-node NSFNET and ARPA2 with simulation. In numerical examples, we compare the performance of the proposed method with conventional burst transmission, and we investigate the impacts of the amount of traffic, the processing time of a control packet, the switching time of an optical switch, and the number of wavelengths. We show that the proposed method can not only improve the fairness but also decrease the overall burst loss probability in both the networks.

A Random Ant-Like Unicast Routing Protocol for Wireless Ad Hoc Sensor Networks and Performance Evaluation

A random ant-like unicast routing (RAUR) protocol is proposed for wireless ad hoc sensor networks. In RAUR, when a source node needs to find a routing path to a destination, it does not flood the network. Instead, the source selects one of its neighbors to send out a route request packet. And the selected neighbor will also select one of its neighbors to forward the packet. The number of nodes to forward the searching message will be reduced. Hence, it could help to save the energy. In addition, the control overhead will be less. In this paper, our approximated mathematical analysis shows that the successful rate in finding a path with only one attempt is considerably high. Our research also shows that the RAUR will get higher successful rate through the larger number of hops. We study the performance of the network using the proposed RAUR by simulation of Glomosim and compare it with the routing protocols, DSR and AODV. The results show that RAUR could outperform in many metrics.

Impact of the Gauss-Markov Mobility Model on Network Connectivity, Lifetime and Hop Count of Routes for Mobile Ad hoc Networks

The high-level contribution of this paper is a simulation based analysis of the network connectivity, hop count and lifetime of the routes determined for mobile ad hoc networks (MANETs) using the Gauss-Markov mobility model. The Random Waypoint mobility model is used as a benchmark in the simulation studies. Two kinds of routes are determined: routes with the longest lifetime (stable paths) and routes with the minimum hop count. Extensive simulations have been conducted for different network density, node mobility values and different values of the degree of randomness parameter for the Gauss-Markov model. In low-density network scenarios, we observe that the network connectivity under the Gauss-Markov model is significantly lower than that obtained under the Random Waypoint model. In moderate and high density network scenarios, the network connectivity obtained under the two mobility models is almost equal. The minimum hop paths determined under the Gauss-Markov model have a larger number of hops than those computed under the Random Waypoint model. The lifetime of stable paths determined under the Gauss-Markov model is smaller than those determined under the Random Waypoint model. Low-density networks using the Gauss-Markov mobility model attain larger connectivity for intermediate values of the degree of randomness parameter, while the connectivity of moderate and high-density networks is not significantly dependent on the degree of randomness parameter. The minimum hop count of the paths is not much affected by different values of the degree of randomness parameter, while maximum lifetime stable paths are obtained for larger intermediate values of the degree of randomness parameter, but not for unity.

A CDMA/TDD approach for wireless mesh networks

Wide band mesh or star oriented networks have recently become a subject of greater interest. Providing wideband multimedia access for a variety of applications has led to the inception of mesh networks. Classic access techniques such as FDMA and TDMA have been the norm for such networks. CDMA maximum transmitter power is much less than TDMA and FDMA counter parts, which is an important asset for mobile operation. In this paper we introduce a code division multiple access/time division duplex technique CDMA/TDD for such networks. The CDMA approach is an almost play and plug technology for wireless access, making it amenable for implementation by the mesh network service station, SS. Further it inherently allows mesh network service stations to use a combination of turbo coding and dynamic parallel orthogonal transmission to improve network efficiency. We outline briefly the new transmitter and receiver structures then evaluate the efficiency, delay and delay jitter. By analysis we show the advantages over classic counter parts with respect to the total network efficiency achievable especially for larger number of hops.

Routing strategies in multihop cooperative networks

The fading characteristics and broadcast nature of wireless channels are usually not fully considered in the design of routing protocols for wireless networks. In this paper, we combine routing and cooperative diversity, with the consideration of a realistic channel model. We focus on a multihop network with multiple relays at each hop, and three routing strategies are designed to achieve the full diversity gain provided by cooperation among the relays. In particular, an optimal routing strategy is proposed to minimize the end-to-end outage, which requires the channel information of all the links and serves as a performance bound. An ad-hoc routing strategy is then proposed based on a hop-by-hop relay selection, which can be easily implemented in a distributed way. As expected, ad-hoc routing performs worse than optimal routing, especially with a large number of hops. To achieve a good complexity-performance tradeoff, an N-hop routing strategy is further proposed, where a joint optimization is performed every N hops. Simulation results are provided which verify the outage analyses of the proposed routing strategies.

All-Optical Label Swapping, Clock Recovery, and 3R Regeneration in 101-Hop Cascaded Optical-Label Switching Router Networks

This paper experimentally demonstrates the cascaded operation of an optical-label switching router for up to 101 hops, with optical label swapping, optical clock recovery, and 3R regeneration (re-amplification, reshaping, and retiming) at each hop. The optical label swapping utilizes all-optical payload/label separation and label rewriting with subcarrier label. An interferometer wavelength converter enables the reshaping function, while the synchronous modulation driven by the optically recovered packet clock performs the retiming function. The optical label swapping and 3R regeneration enable the packets to traverse a large number of hops while maintaining the signal quality to support the scalability of the optical-label switching network

Last-hop preemptive scheme based on the number of hops for optical burst switching networks

We propose a preemptive scheme based on the hop number of a burst for optical burst switching (OBS) networks. In the proposed scheme, when a burst fails in reserving a wavelength at its last hop, the burst can preempt another burst transmission. We consider a tandem network with four OBS nodes and analyze the burst loss probability for the proposed scheme with a continuous-time Markov chain. We also evaluate by simulation the performance of our proposed scheme for a unidirectional ring network. Numerical examples show that our proposed method effectively decreases the loss probability of the burst with a large number of hops.

Outage probability of multihop transmission over Nakagami fading channels

We present a general analytical framework for the evaluation of the end-to-end outage probability of multihop wireless communication systems with nonregenerative relays over Nakagami fading channels. It is shown that the presented results can either be exact or tight lower bounds on the performance of these systems depending on the choice of the relay gain. More specifically, we obtain a closed-form expression for the moment generating function of the reciprocal of the end-to-end signal-to-noise ratio (SNR) and we then use this expression to calculate the outage probability via numerical inversion of the Laplace transform. Numerical examples show that regeneration is more crucial at low average SNR and for multihop systems with a large number of hops.

Analytical study of FFH systems with square-law diversity combining in the presence of multitone interference

An analytical study of the performance of fast frequency-hopped (FFH), M-ary orthogonal frequency-shift keyed noncoherent modulation with linear combining of square-law envelopes in the presence of multitone interference is presented. The multiple equal-power interference tones are assumed to correspond to some of the possible FFH/M-ary orthogonal signaling tones. It is also assumed that the channel fading characteristics of the signal and interference tones are independent. We evaluate the effect of the channel fading on the system's performance as a function of various parameters, such as the number of hops per symbol, the signal power to multitone interference power ratio, and the number of interference tones. Our numerical results indicate that by use of square-law time diversity combining, a large number of hops per symbol make the bit-error probability of the system more sensitive to the fading of multitone interference. Finally, the analysis has been proven valid by simulation.