Multi-hop Ad-hoc Networks Research Articles

Exploring the effects of directional antennas on the secure connectivity and hop count of secure multi-hop ad-hoc wireless networks

Directional antennas can increase the received power in specific directions while reducing it in other directions. Utilizing this unique feature, we configure directional antennas at legitimate users to obtain twofold benefits for secure multi-hop ad-hoc wireless networks (AHWNs), i.e., enhancing the secure connectivity among legitimate users and lowering the hop count of the multi-hop paths. For the quantitative evaluation of these benefits, we first use a stochastic geometry graph to model the multi-hop AHWNs under the coexistence of eavesdroppers. Then, we introduce a simulation-based analysis method comprised of two algorithms: (a) the first algorithm provides the connectivity and the hop count of the shortest path between random source–destination pairs; (b) the second algorithm utilizes the results of the first one to return the average path connectivity, the probability mass function (pmf) of the hop count distribution, and the average hop count. This simulation-based analysis method helps to exhaustively study the behaviors of connectivity, hop count distribution, average hop count, and their mutual relationship in different scenarios. To the best of our knowledge, this paper is the first research work that studies the effects of directional antennas equipped at legitimate users on both secure connectivity and hop count of secure AHWNs in four combinations of two types of practical directional antennas, i.e., uniform circular array (UCA) antenna and uniform linear array (ULA) antennas, and two beamforming schemes, i.e., centralized and randomized beamforming. Moreover, comparisons with the case of using omnidirectional antennas are also provided. From the obtained simulation results, we demonstrate that using directional antennas does not always benefit the secure connectivity and hop count of secure AHWNs, i.e., only UCA-random gives higher secure connectivity and lower hop count than the omnidirectional antenna among four combinations of antenna type — beamforming scheme. Moreover, in the cases of high-density legitimate users and low-density eavesdroppers, lowering the average hop count is more remarkable than improving secure connectivity. The critical findings in this paper are valuable for deploying secure multi-hop AHWNs with directional antennas in practice.

Secure Routing in Multihop Ad-Hoc Networks With SRR-Based Reinforcement Learning

In this letter, a reinforcement learning-assisted secure routing methodology is proposed for multihop ad-hoc networks in the presence of multiple eavesdroppers. Specifically, secure relay region (SRR) is firstly proposed, which depicts the distribution of the relays forwarding the information securely. Moreover, a SRR-based on-policy Monte Carlo methodology is derived, aiming at accelerating the convergence of routing. The secrecy connection probability is also calculated, which indicates the secure performance of different routes. Simulation results show that our proposed SRR-based reinforcement learning methodology can select the secure route efficiently and fast, which is also robust to the time-varying available relays.

Smart adaptive collision avoidance for IEEE 802.11

In this paper, we introduce a novel algorithm that uses machine learning to dynamically decide whether to enable or disable IEEE 802.11 DCF’s RTS/CTS. Our algorithm continuously learns current networking conditions, namely air time, i.e. the ratio between the size of data/control information being transmitted and transmission rate, and network contention to compare the cost between using RTS/CTS or retransmitting data, and dynamically switches RTS/CTS on and off accordingly. Simulation results using a variety of WLAN- as well as wireless multi-hop ad-hoc network scenarios, including synthetic and real traffic traces, demonstrate that the proposed approach consistently outperforms current best practices, such as never enabling RTS/CTS or using a pre-specified threshold to decide whether to switch RTS/CTS on or off.

An optimized link state routing protocol for real-time application over Vehicular Ad-hoc Network

Voice over Internet Protocol (VoIP) provides good services through Vehicular Ad-hoc Networks (VANET) platform. These networks encounter various challenges to support voice calls with acceptable Quality of Service (QoS). The Optimized Link State Routing Protocol (OLSR) is used to investigate the performance of VoIP applications in the VANET network. The network was tested before and after running the OLSR algorithm, the testing focused on Quality of Service (QoS) parameters like end-to-end delay, delay variation (jitter), and probability of packet loss between two moving hops through multi-hop Ad-hoc networks in different scenarios, using the ITU G.711 VoIP codec. After measured the end-to-end delay, jitter, and probability of packet loss for two nodes the algorithm decreased delay by 18.72%, while decreased jitter by about 20.42% and decreased packet loss by about 128.6%. However, The OLSR has shown initial good performance for four hops, and then added more hops the delay exceeded 400 ms which is not acceptable according to ITU-T recommendations. This was achieved by implementing a testbed to extract the desired results as opposed to using a simulation.

Simulation based comparison of routing protocols in wireless multihop adhoc networks

Routing protocols are responsible for providing reliable communication between the source and destination nodes. The performance of these protocols in the ad hoc network family is influenced by several factors such as mobility model, traffic load, transmission range, and the number of mobile nodes which represents a great issue. Several simulation studies have explored routing protocol with performance parameters, but few relate to various protocols concerning routing and Quality of Service (QoS) metrics. This paper presents a simulation-based comparison of proactive, reactive, and multipath routing protocols in mobile ad hoc networks (MANETs). Specifically, the performance of AODV, DSDV, and AOMDV protocols are evaluated and analyzed in the presence of varying the number of mobile nodes, pause time, and traffic connection numbers. Moreover, Routing and QoS performance metrics such as normalized routing load, routing packet, packet delivery ratio, packet drop, end-to-end delay, and throughput are measured to conduct a performance comparison between three routing protocols. Simulation results indicate that AODV outperforms the DSDV and AOMDV protocols in most of the metrics. AOMDV is better than DSDV in terms of end-to-end delay. DSDV provides lower throughput performance results. Network topology parameters have a slight impact on AODV Performance.

Cross-Layer Routing for Outage Minimization in Multihop Ad-Hoc Networks

In this study, cross-layer approach for joint routing and power allocation problem is formulated in an optimization framework for end-to-end outage minimization under the constraint of total permissible transmission power. A closed form solution for optimal transmission power is obtained following the extraction of routing metric. The scheme is referred as minimum end-to-end outage probability (MEO) strategy. A distributed implementation of the proposed strategy is also presented. Simulation results prove that our proposed MEO routing and power allocation strategy succeeds in achieving significant improvement of end-to-end outage probability over MEO routing and equal power allocation scheme.

Modeling and simulation of secure connectivity and hop count of multi-hop ad-hoc wireless networks with colluding and non-colluding eavesdroppers

Connectivity and hop count are two crucial attributes of dynamic wireless networks such as ad-hoc wireless networks (AHWNs). When the security issue is considered, establishing a secure multi-hop path in AHWNs is challenging because an intermediate node having a wireless link with previous nodes may not be secure to receive data from those nodes, and vice versa. In this paper, stochastic geometry graphs is used to model the AHWNs with eavesdroppers’ presence, then a simulation-based analysis method is proposed to investigate the characteristics of connectivity, hop count distribution, average hop count, and their relations in various scenarios. The proposed simulation-based analysis method consists of two algorithms. The first one finds all possible secure communication paths between two arbitrary legitimate users selected as source and destination and returns the shortest path’s hop count. This algorithm utilizes the random locations of legitimate users and eavesdroppers, the wireless channel condition, and the eavesdropper’s operating mode as input data. The second one provides the hop count distribution and the connection probability of the obtained multi-hop path of the first algorithm by averaging a huge number of network topology trials. So far, this paper is the first work that investigates both connectivity and hop count of security-aware multi-hop AHWNs. Moreover, these characteristics of multi-hop AHWNs with colluding eavesdroppers are compared with those of multi-hop AHWNs with non-colluding eavesdroppers and without eavesdroppers. Simulation results show that putting more legitimate users does not greatly improve the quality of the multi-hop path in the non-colluding case compared with that in colluding case. Furthermore, the shape parameter of Nakagami fading has a more substantial effect on the connectivity and hop count than the spread parameter. The results in this paper provide valuable insights in designing and evaluating security-aware multi-hop AHWNs.

Implementation of the Friis Free Space Propagation Model in the Dynamic Source Routing (DSR) Routing Protocol in the Vehicular Ad-hoc Network (VANET) with Variations of Road Models

The use of VANET technology is to create better traffic management. Different road conditions and high mobility of vehicles cause problems in VANET such as efficient search processes, network routes that need to be maintained, and data transmission problems. DSR (Dynamic Source Routing) predefines and generates routes on demand and is designed to work on multihop ad-hoc networks without centralized control. The Friis Free Space propagation model is used to model the Line of Sight (LOS) that occurs in a free space environment. The variation of road models in Indonesia is grouped into four groups, namely express roads, intercity roads, urban roads, and residential roads. In each of these road models, simulation testing is carried out based on different vehicle number scenarios. Network Simulator v3.27 (NS-3.27) and SUMO as a mobility generator were used for the simulation. The parameters of average throughput, packet delivery ratio and MAC/PHY overhead sequentially measure the DSR performance. The results on the express roads with Friis Free Space propagation produce values of 6.52 KBps, 7.71%, 39.59 KBytes. Test results on intercity roads 5.72 KBps, 11.17%, 5.48 KBytes. Test results on urban roads 16.50 KBps, 32.22%, 0.0016 KBytes. While the test results on residential roads were 12.66 KBps, 24.72%, 0.779 KBytes. The test results show that the road model in Indonesia with the performance of the DSR routing protocol with Friis Free Space propagation on the VANET network from the best to the worst, respectively, is the urban road model, residential road model, intercity road model, and express road model.

Cross Layer Approach and ANFIS based Optimized Routing in Wireless Multi-Hop Ad Hoc Networks

Mobile ad hoc networks are non-dependent on any wired infrastructure and provide exceptional benefits during typical situations like conference, fair/exhibition, disaster recovery and emergency rescue operations. But these networks have to deal with several open issues, since they are battery operated and the dynamic topology can change due to mobility. Thus, multi-hop wireless ad hoc networking needs an energy efficient routing protocol that discovers/maintains routes to any other member node in the network, minimizing computation/communication overhead and battery power consumption. An adaptive neuro fuzzy inference system (ANFIS) based ad hoc routing approach has not been investigated before. In this paper, an ANFIS and cross layer approach-based energy efficient routing protocol for wireless multi-hop networks is proposed and its performance is compared with the Ad Hoc On-demand Distance Vector (AODV) Routing Protocol and fuzzy based AODV, using the network simulator ns2. Using remaining battery power, hop count and link stability as the input variables, the ANFIS module computes the optimum path cost, as the output. The proposed ANFIS based approach produces better results when compared using the metrics: average throughput, packet delivery ratio, average end-to-end delay in packet delivery between source and destination and average routing overhead.

A Framework for Multi-Hop Ad-Hoc Networking over Wi-Fi Direct with Android Smart Devices

The wide diffusion of mobile devices that natively support ad hoc communication technologies has led to several protocols for enabling and optimizing Mobile Ad Hoc Networks (MANETs). Nevertheless, the actual utilization of MANETs in real life seems limited due to the lack of protocols for the automatic creation and evolution of ad hoc networks. Recently, a novel P2P protocol named Wi-Fi Direct has been proposed and standardized by the Wi-Fi Alliance to facilitate nearby devices’ interconnection. Wi-Fi Direct provides high-performance direct communication among devices, includes different energy management mechanisms, and is now available in most Android mobile devices. However, the current implementation of Wi-Fi Direct on Android has several limitations, making the Wi-Fi Direct network only be a one-hop ad-hoc network. This paper aims to develop a new framework for multi-hop ad hoc networking using Wi-Fi Direct in Android smart devices. The framework includes a connection establishment protocol and a group management protocol. Simulations validate the proposed framework on the OMNeT++ simulator. We analyzed the framework by varying transmission range, number of hops, and buffer size. The results indicate that the framework provides an eventual 100% packet delivery for different transmission ranges and hop count values. The buffer size has enough space for all packets. However, as buffer size decreases, the packet delivery decreases proportionally.

A Study of Named Data Networking as Communication Protocol for Multi-hop Wireless Ad Hoc Network

Named Data Networking (NDN) has been repeatedly quoted in numerous past and existing literature reviews to have replaced Host Centric Networking (HCN) due to its ability to solve energy efficiency issues inherent in Multi-hop Wireless Ad-hoc Networks (WAHN). However, this claim is proven to be wholly unsubstantiated and is not justified by academic proof in said articles. Therefore, this study take the initiative to fill in this gap by presenting a comparative study of NDN based MWAHN and HCN based MWAHN through the use of real implementation by measuring two parameter metric that are related to energy efficiency, namely energy consumption and file transfer completion time. For this study, NDN-based MWAHN is compared with two type of actively developed HCN routing protocol implementation, namely Babeld and BMX6. The results obtained from this experiment is crucial for MWAHN researchers to gain better understanding of the real potential of the NDN based routing that can be used as a solution for energy consumption issues that exist in wireless multi-hop ad-hoc network.

The Impact of IEEE 802.11 Contention Window on The Performance of Transmission Control Protocol in Mobile Ad-Hoc Network

A Mobile Ad-hoc Network (MANET) is a group of nodes connected via ad-hoc fashion for communicating with each other through wireless interface. The communication among the nodes in such network take place by using multi-hop in the absence of fixed infrastructure. TCP faces some hurdles and complexities in multi-hop ad-hoc networks particularly congestion and route failures. The incompatibility between the MAC and TCP are previously noticed by the research community. This research study focuses on the impact of MAC layer contention window on TCP in MANET by using variation in network density and velocity of nodes respectively. Simulation has been carried out to quantify and analyze the impact of Contention Window (CW) sizes that affects the performance of TCP by using NS-2 simulator. The impact of CW is investigated on TCP in multi-hop networks by means of performance evaluation parameters i.e. average delay, average packet drops and average throughput.

An Upper Bound Capacity Algorithm for Multi-hop Wireless Ad Hoc Networks

The upper bound capacity based on the SINR model is a very important parameter when evaluating the performance of the multi-hop wireless ad hoc networks. In this paper, a new upper bound capacity algorithm is proposed. Firstly, we analyzed the classical physics SINR model over the Rayleigh fading channels to establish the relationship between density of nodes and path outage probability. Then, we developed the closed-form expression of the upper bound transmission capacity based on the Weber model for the random networks. Finally, we evaluated effects of parameters in the communication range, density, SINR threshold and fading factors, and consequently transmission capacity of the network by sensitivity analysis. The numerical simulation showed that the optimum density of nodes was existed to obtain the upper bound transmission capacity. The capacity increased firstly and then decreased over the density of nodes increasing. It affected by channel fading factor and communication range sensitively.

Spectral Examination in Cognitive Adhoc Multihop Networks

The issue of range need & inefficiency in go use will be tended to by the beginning late making energetic radio perspective that empowers radios to astutely transmit in the unfilled pieces of the range starting at now doled out to asserted customers. For this, the limit as for run perceiving, go sharing, picking the best range among the available decisions, & industriously changing transmission parameters reliant on the activity of the embraced range owners must be made inside adroit radio customers. Unequivocally in mental radio particularly named structures, dispersed multihop plan, center point versatility, & spatio-ordinary contrast in go availability are the bit of the key explicit components. In this article the tremendous features of CRAHNs are shown, close to the game-plan approaches & research bothers that must be tended to. Range the executives in CRAHNs consolidates expand recognizing, sharing, decision, & flexibility. In this paper, these limits are depicted in detail from the point of view of multihop infrastructureless structures requiring support among customers.

A reactive algorithm for deducing nodal forwarding behavior in a multihop ad-hoc wireless network in the presence of errors

novel algorithm is presented to deduce individual nodal forwarding behavior from standard end-to-end acknowledgments. The algorithm is based on a well-established mathematical method and is robust to network related errors and nodal behavior changes. The proposed solution was verified in a network simulation, during which it achieved sound results in a challenging multihop ad-hoc network environment.

Optimized Energy Consumption for Slotted Aloha and CSMA/CA Multihop Ad Hoc Networks

Ad hoc and wireless sensor networks are characterized by their ability to monitor phenomena in the most adverse scenarios. However, to perform well, these networks need to be self-adjusting and save energy. In general, these networks operate without human interference and require strategies to provide longer operating life. This paper investigates the energy consumption in a random multihop ad hoc network, comparing the slotted Aloha with the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) implemented in the IEEE 802.11 Distributed Coordination Function (DCF) as medium access control (MAC) protocols. We obtain the optimal transmission power as a function of physical and link layers parameters which results the optimized energy consumption per successfully transmitted bit. In this paper, we find that there are values of these parameters that can be used to extend the battery life of wireless communication devices comparing the Aloha and CSMA/CA performance.

Latency Reduction in Probabilistic Broadcast Protocols for Ad Hoc Networks

This letter introduces a strategy to reduce broadcast latency in multi-hop ad-hoc networks; this overall reduction is the result of the accumulation of a series of per-node delay reductions. Current broadcasting protocols employ uniformly distributed random delays on a per-node basis, while the proposed strategy consists of using a truncated-exponential distribution to determine these delays. Such an approach can reduce latency significantly while maintaining broadcasting reachability, yet it entails minimal additional overhead in relation to existing protocols.

Modeling the Impact of Heterogeneous Transmission Powers on the Throughput of IEEE 802.11 Multi-Hop Ad Hoc Networks

Transmission power control (TPC) leads to heterogeneous transmission power levels of the nodes in multi-hop wireless ad hoc networks. This eventually results in a quite complicated collision scenario due to hidden and exposed terminal problems, and brings a big challenge for analyzing the saturation throughput of the flows. This paper presents a saturation throughput model for IEEE 802.11 multi-hop ad hoc networks with heterogeneous transmission powers. In the model, one tagged node goes through with three processes, i.e., backoff, freezing and transmission, and each of which is composed of a certain number of continuous fixed length time slots. We put forward a four-dimensional Markov chain model for the behavior of the tagged node in each fixed-length time slot. Under the condition of heterogeneous transmission powers, we consider two types of collisions, i.e., the instantaneous and persistent collisions. Their probabilities are characterized by the one-step transition probability matrix of the Markov chain. The per-flow saturation throughput of the flow is eventually derived through an iterative way. Finally, the accuracy of our model is validated by comparing the analytical values and the simulation results, and the impact of the heterogeneous power levels on the performance of the wireless multi-hop ad hoc networks is effectively analyzed.

A Gibbsian model for message routeing in highly dense multihop networks

We investigate a probabilistic model for routeing of messages in relay-augmented multihop ad-hoc networks, where each transmitter sends one message to the origin. Given the (random) transmitter locations, we weight the family of random, uniformly distributed message trajectories by an exponential probability weight, favouring trajectories with low interference (measured in terms of signal-to-interference ratio) and trajectory families with little congestion (measured in terms of the number of pairs of hops using the same relay). Under the resulting Gibbs measure, the system targets the best compromise between entropy, interference and congestion for a common welfare, instead of an optimization of the individual trajectories. In the limit of high spatial density of users, we describe the totality of all the message trajectories in terms of empirical measures. Employing large deviations arguments, we derive a characteristic variational formula for the limiting free energy and analyse the minimizer(s) of the formula, which describe the most likely shapes of the trajectory flow. The empirical measures of the message trajectories well describe the interference, but not the congestion; the latter requires introducing an additional empirical measure. Our results remain valid under replacing the two penalization terms by more general functionals of these two empirical measures.

Secure Routing for Multihop Ad Hoc Networks With Inhomogeneous Eavesdropper Clusters

This paper studies finding the secure path according to the secrecy connectivity probability (SCP) in the multihop ad hoc networks in the presence of inhomogeneous eavesdropper clusters. We consider both random and fixed eavesdropper clusters, where the former case assumes that there is no knowledge of the locations of the clusters and the latter case assumes that the locations of the clusters can be estimated accurately. First, we derive the end-to-end SCP to characterize the secrecy performance of a given path in a general multihop wireless network with half-duplex randomize-and-forward relaying. Then, we consider a full-duplex scheme at the legitimate receiver, which receives the useful information while broadcasting a jamming signal to the potential eavesdroppers to further enhance the secrecy connectivity. Then, a novel secure routing algorithm that can provide the maximum SCP for any legitimate transmitter/receiver pair in a distributed manner is proposed. The theoretical analysis is verified by Monte Carlo simulation results. The results show that our secure routing algorithm provides similar results compared to an exhaustive search. For the random eavesdropper cluster case, the optimal route is independent of the knowledge of the cluster, which is the same as the homogeneous eavesdropper case. However, for the case where eavesdropper clusters are fixed and their locations are known a priori , the optimal path selection depends on the radii and locations of the eavesdropper clusters and the average number of eavesdroppers in each cluster.