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Hierarchical network architectures are widely deployed to reduce routing overheads and increase scalability. In our work, we are interested in large-scale Mobile Ad-Hoc Networks (MANETs) which are formed by interconnecting smaller clusters through a backbone. To support end-to-end routing in such networks, we employ a hierarchical approach as follows. The clusters are MANETs, running OLSR locally. Each cluster has a gateway, and the gateways are interconnected through a backbone. In this paper, we study four different solutions to provide end-to-end connectivity through the backbone: flooding all data packets through the backbone, modifying an ad-hoc routing protocol such as OLSR and AODV, or using a P2P overlay for routing purposes. Running extensive simulations in OMNeT++, our results highlight the strengths and weaknesses of each approach. Flooding, albeit a very simple approach, appears to be quite competitive with more complex routing solutions, with good performance and low overheads.
Thomas Kunz. Efficient Backbone Routing in Hierarchical MANETs. Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2021, 147 -163.
AMA StyleThomas Kunz. Efficient Backbone Routing in Hierarchical MANETs. Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering. 2021; ():147-163.
Chicago/Turabian StyleThomas Kunz. 2021. "Efficient Backbone Routing in Hierarchical MANETs." Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering , no. : 147-163.
Network Function Virtualization (NFV) can lower the CAPEX and/or OPEX for service providers and allows the deployment of services quickly. The main challenge in the use of Virtualized Network Functions (VNF) is optimally placing them in the physical network in terms of deployment cost and resource consumption. The critical problem of VNF placement is inherently NP-hard and the available optimal solutions do not scale with respect to the network size. The problem of NFV placement is even more challenging in wireless networks as we are facing the issue of scarcity of BW due to the presence of interference. Therefore, this paper aims to solve the problem of VNF placement in wireless multi-hop networks by considering BW limitations and scalability. We tackle both issues at once by limiting the search space to the shortest paths. We search for the placement solution along shortest paths to minimize the BW consumption and at the same time reduce the search space to the nodes and links along the shortest path. The results are compared to a mathematical optimization model and a comparable heuristic model. They show that our proposed heuristic greatly decreases the execution time in comparison to the mathematical model and the alternative heuristic while keeping the acceptance ratio close to the optimal solution.
Zahra Jahedi; Thomas Kunz. Fast and Cost-Efficient Virtualized Network Function Placement Algorithm in Wireless Multi-hop Networks. Transactions on Petri Nets and Other Models of Concurrency XV 2020, 23 -36.
AMA StyleZahra Jahedi, Thomas Kunz. Fast and Cost-Efficient Virtualized Network Function Placement Algorithm in Wireless Multi-hop Networks. Transactions on Petri Nets and Other Models of Concurrency XV. 2020; ():23-36.
Chicago/Turabian StyleZahra Jahedi; Thomas Kunz. 2020. "Fast and Cost-Efficient Virtualized Network Function Placement Algorithm in Wireless Multi-hop Networks." Transactions on Petri Nets and Other Models of Concurrency XV , no. : 23-36.
Network Function Virtualization (NFV) can lower the CAPEX and/or OPEX for service providers and allow for quick deployment of services. Along with the advantages come some challenges. The main challenge in the use of Virtualized Network Functions (VNF) is the VNFs’ placement in the network. There is a wide range of mathematical models proposed to place the Network Functions (NF) optimally. However, the critical problem of mathematical models is that they are NP-hard, and consequently not applicable to larger networks. In wireless networks, we are considering the scarcity of Bandwidth (BW) as another constraint that is due to the presence of interference. While there exist many efforts in designing a heuristic model that can provide solutions in a timely manner, the primary focus with such heuristics was almost always whether they provide results almost as good as optimal solution. Consequently, the heuristics themselves become quite non-trivial, and solving the placement problem for larger networks still takes a significant amount of time. In this paper, in contrast, we focus on designing a simple and scalable heuristic. We propose four heuristics, which are gradually becoming more complex. We compare their performance with each other, a related heuristic proposed in the literature, and a mathematical optimization model. Our results demonstrate that while more complex placement heuristics do not improve the performance of the algorithm in terms of the number of accepted placement requests, they take longer to solve and therefore are not applicable to larger networks.In contrast, a very simple heuristic can find near-optimal solutions much faster than the other more complicated heuristics while keeping the number of accepted requests close to the results achieved with an NP-hard optimization model.
Zahra Jahedi; Thomas Kunz. The Value of Simple Heuristics for Virtualized Network Function Placement. Future Internet 2020, 12, 161 .
AMA StyleZahra Jahedi, Thomas Kunz. The Value of Simple Heuristics for Virtualized Network Function Placement. Future Internet. 2020; 12 (10):161.
Chicago/Turabian StyleZahra Jahedi; Thomas Kunz. 2020. "The Value of Simple Heuristics for Virtualized Network Function Placement." Future Internet 12, no. 10: 161.
A Multi-Beam Antenna (MBA) can be defined as a set of directional radio transceivers. These transceivers are facing different directions to prevent signal interference with each other. MBA nodes have two main characteristics: the Multi-Packet Transmission (MPT) capability and the Multi-Packet Reception (MPR) capability whereby a node can transmit/receive multiple packets at the same time. In this paper, we provide an analysis of how this MPT/MPR capability can be used to reduce the end-to-end delay for delivered packets in ad hoc networks. Taking beam considerations (determination of the beam in which neighbors are located) into account, we formulate the delay reduction issue as an optimization problem that we solve. Our results show that to maximally exploit the full potential of MBAs for delay reduction, the scheduling of links has to promote the formation of star nodes and keep the formation of bridges to a minimum; all of which leads to the selection of routes that very often are not the shortest. In fact, using only the shortest routes has a negative impact on the delay. However, the optimal link scheduling comes at the expense of a higher overhead in terms of the total number of packet transmissions. Furthermore, the beamwidth has a direct and significant impact on the end-to-end delay and the computation time.
Jean-Daniel Medjo Me Biomo; Thomas Kunz; Marc St-Hilaire. Exploiting Multi-Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks. Mobile Networks and Applications 2018, 23, 1293 -1305.
AMA StyleJean-Daniel Medjo Me Biomo, Thomas Kunz, Marc St-Hilaire. Exploiting Multi-Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks. Mobile Networks and Applications. 2018; 23 (5):1293-1305.
Chicago/Turabian StyleJean-Daniel Medjo Me Biomo; Thomas Kunz; Marc St-Hilaire. 2018. "Exploiting Multi-Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks." Mobile Networks and Applications 23, no. 5: 1293-1305.
Multi-Beam Antennas (MBAs) have two main characteristics: the Multi-Packet Transmission (MPT) capability and the Multi-Packet Reception (MPR) capability whereby a node can transmit/receive multiple packets at the same time. In this paper, we provide an analysis of how this MPT/MPR capability can be used to reduce the end-to-end delay in ad hoc networks. We formulate the delay reduction issue as an optimization problem. Simulations show that in order to exploit the full potential of MBAs for delay reduction, the scheduling of links has to promote the formation of star nodes and keep the formation of bridges to a minimum; which leads to the selection of routes that very often are not the shortest. We also show that using only the shortest routes has a negative impact on the delay.
Jean-Daniel Medjo Me Biomo; Thomas Kunz; Marc St-Hilaire. Exploiting Multiple Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks. Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2018, 143 -155.
AMA StyleJean-Daniel Medjo Me Biomo, Thomas Kunz, Marc St-Hilaire. Exploiting Multiple Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks. Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering. 2018; ():143-155.
Chicago/Turabian StyleJean-Daniel Medjo Me Biomo; Thomas Kunz; Marc St-Hilaire. 2018. "Exploiting Multiple Beam Antennas for End-to-End Delay Reduction in Ad Hoc Networks." Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering , no. : 143-155.
Ola Ashour; Marc St-Hilaire; Thomas Kunz. Multicasting in Tactical Networks: Forwarding Versus Network Coding. Proceedings of the 10th International Conference on Security and Cryptography 2018, 1 .
AMA StyleOla Ashour, Marc St-Hilaire, Thomas Kunz. Multicasting in Tactical Networks: Forwarding Versus Network Coding. Proceedings of the 10th International Conference on Security and Cryptography. 2018; ():1.
Chicago/Turabian StyleOla Ashour; Marc St-Hilaire; Thomas Kunz. 2018. "Multicasting in Tactical Networks: Forwarding Versus Network Coding." Proceedings of the 10th International Conference on Security and Cryptography , no. : 1.
Multicasting refers to the transmission of packets to a group of one or more destinations. It can be very useful in military applications, such as command and control, in which a commander needs to send instructions to a group of tanks, users, or planes. Broadcast is a unique case of multicast, where all the nodes in the network are intended receivers. The broadcast case has been studied quite extensively in the literature, showing that the use of Network Coding (NC) requires fewer data transmissions than Packet Forwarding (PF). That motivates us to explore whether the same result holds true when only a subset of nodes are receivers. In this paper, we developed two linear optimization models that determine lower bounds on the number of required data packet transmissions when sending data in a Mobile Ad-hoc Network (MANET) from a single source to multiple receivers. The first model determines the minimum number of required packet transmissions under the assumption that PF is used. The
Ola Ashour; Marc St-Hilaire; Thomas Kunz. Multicasting in Tactical Networks: Forwarding Versus Network Coding. Proceedings of the 10th International Conference on Security and Cryptography 2018, 42 -51.
AMA StyleOla Ashour, Marc St-Hilaire, Thomas Kunz. Multicasting in Tactical Networks: Forwarding Versus Network Coding. Proceedings of the 10th International Conference on Security and Cryptography. 2018; ():42-51.
Chicago/Turabian StyleOla Ashour; Marc St-Hilaire; Thomas Kunz. 2018. "Multicasting in Tactical Networks: Forwarding Versus Network Coding." Proceedings of the 10th International Conference on Security and Cryptography , no. : 42-51.
Yifeng Zhou; Thomas Kunz; Stefan Fischer; Zhangdui Zhong. Editorial: Ad Hoc Networking and Emerging Applications. Mobile Networks and Applications 2017, 23, 1206 -1207.
AMA StyleYifeng Zhou, Thomas Kunz, Stefan Fischer, Zhangdui Zhong. Editorial: Ad Hoc Networking and Emerging Applications. Mobile Networks and Applications. 2017; 23 (5):1206-1207.
Chicago/Turabian StyleYifeng Zhou; Thomas Kunz; Stefan Fischer; Zhangdui Zhong. 2017. "Editorial: Ad Hoc Networking and Emerging Applications." Mobile Networks and Applications 23, no. 5: 1206-1207.
In this paper, we evaluate available bandwidth as a routing metric for IEEE 802.15.4-based ad-hoc networks. The available bandwidth on a data forwarding path is an approximation of the forwarding path’s residual data relaying capacity. High available bandwidth on a data forwarding path implies low data traffic load on the path, therefore data flows may experience low delay and high packet delivery ratio (PDR). Our aim is to evaluate available bandwidth as a routing metric. We present different available-bandwidth-based routing protocols for IEEE 802.15.40-based networks, namely: end-to-end available-bandwidth-based routing protocol (ABR), available bandwidth and contention-aware routing protocol (ABCR), and shortest hop-count and available-bandwidth-based opportunistic routing protocol (ABOR). Moreover, we also present variants of ABR and ABCR capable of distributing a flow’s data packets on multiple paths by maintaining the top K downstream nodes (the downstream nodes that advertised best data forwarding paths towards a sink node) corresponding to each sink node in a routing table. We focus on both single-sink and multi-sink networks. We performed extensive simulations, and the simulation results demonstrate that the available bandwidth routing metric shows better results when combined with a routing metric that helps to limit a data forwarding path’s length, i.e., shortest hop-count or intra-flow contention count. For multi-path data forwarding towards the same sink node, and at high traffic volumes, the available bandwidth metric demonstrates best performance when combined with the shortest hop-count routing metric.
Muhammad Omer Farooq; Thomas Kunz; Cormac J. Sreenan; Kenneth N. Brown. Evaluation of available bandwidth as a routing metric for delay-sensitive IEEE 802.15.4-based ad-hoc networks. Ad Hoc Networks 2016, 37, 526 -542.
AMA StyleMuhammad Omer Farooq, Thomas Kunz, Cormac J. Sreenan, Kenneth N. Brown. Evaluation of available bandwidth as a routing metric for delay-sensitive IEEE 802.15.4-based ad-hoc networks. Ad Hoc Networks. 2016; 37 ():526-542.
Chicago/Turabian StyleMuhammad Omer Farooq; Thomas Kunz; Cormac J. Sreenan; Kenneth N. Brown. 2016. "Evaluation of available bandwidth as a routing metric for delay-sensitive IEEE 802.15.4-based ad-hoc networks." Ad Hoc Networks 37, no. : 526-542.
In this study, the impact of route length on the performance of a routing protocol and flow admission control is analysed. First, the authors present an end-to-end available-bandwidth-based proactive routing protocol for ad-hoc wireless sensor networks. The routing protocol maintains the best data forwarding path in terms of the end-to-end available bandwidth. Second, to determine the impact of route length on a routing protocol's performance, they modify the routing protocol. The modified available-bandwidth-based protocol trades-off the end-to-end available bandwidth against the route length. Third, they integrate a state-of-the-art flow admission control algorithm with the proposed protocols and a shortest hop-count-based protocol. Through simulations they evaluate the following: (i) performance of the proposed protocols and a state-of-the-art available-bandwidth-based opportunistic protocol and (ii) the effectiveness of a state-of-the-art flow admission control algorithm over proposed protocols and a shortest hop-count-based protocol. The simulation results demonstrate the following drawbacks of not considering the hop-count metric: longer data forwarding paths, higher number of retransmissions, and reduced effectiveness of the admission control algorithm. The modified available-bandwidth-based proactive protocol provides the best overall performance. Therefore, using their results they conclude that route length impacts the performance of routing and flow admission control algorithms, but is not a singularly decisive factor.
Muhammad Omer Farooq; Thomas Kunz. Impact of route length on the performance of routing and flow admission control algorithms in wireless sensor networks. IET Wireless Sensor Systems 2016, 6, 10 -16.
AMA StyleMuhammad Omer Farooq, Thomas Kunz. Impact of route length on the performance of routing and flow admission control algorithms in wireless sensor networks. IET Wireless Sensor Systems. 2016; 6 (1):10-16.
Chicago/Turabian StyleMuhammad Omer Farooq; Thomas Kunz. 2016. "Impact of route length on the performance of routing and flow admission control algorithms in wireless sensor networks." IET Wireless Sensor Systems 6, no. 1: 10-16.
A multiple model adaptive digital pre-distortion (DPD) scheme is proposed for use in a cellular base station Power Amplifier (PA). The PA is excited by rapidly changing wideband signals. The changes in the signals are caused by variations in power levels and bandwidths. These changing signals can cause a significant change in the dynamic characteristics of the PA. The proposed multiple model DPD scheme can track and compensate for the changing dynamic characteristics of the PA. The proposed scheme offers reduced computational complexity in comparison to old published methods. Experiments are performed on a Phoenix PA excited by two- and four- carrier Wideband Code Division Multiple Access (WCDMA) signals at varying power levels. The simulation results verify the efficacy of the method based on the limitations placed on the Adjacent Channel Power Ratio (ACPR) and Normalized Mean Square Error (NMSE).
Francisca Adaramola; Thomas Kunz; Howard Schwartz. Multiple Model Linearization Solution for Cellular Base Station Power Amplifiers. 2015 IEEE International Conference on Ubiquitous Wireless Broadband (ICUWB) 2015, 1 -6.
AMA StyleFrancisca Adaramola, Thomas Kunz, Howard Schwartz. Multiple Model Linearization Solution for Cellular Base Station Power Amplifiers. 2015 IEEE International Conference on Ubiquitous Wireless Broadband (ICUWB). 2015; ():1-6.
Chicago/Turabian StyleFrancisca Adaramola; Thomas Kunz; Howard Schwartz. 2015. "Multiple Model Linearization Solution for Cellular Base Station Power Amplifiers." 2015 IEEE International Conference on Ubiquitous Wireless Broadband (ICUWB) , no. : 1-6.
In the context of the IEEE 1588 Precision Time Protocol (PTP), estimating the delay's bias is a problem that appears in both one-way (using transparent devices) or two-way message exchange mechanisms. For estimating the offset via the two-way message exchange mechanism, it is usually assumed that the expected value of delays in forward and reverse directions are equal. However, this is not a realistic assumption for packet-based wide area networks, where delays in down-link and up-link directions may have a significant difference. In this work, we propose a solution to estimate the random delay's bias and improve the synchronization accuracy of IEEE 1588. Our method is easy to implement and is compatible with the current version of the protocol. We compared our results to no bias correction and the Boot-strap method. In addition to the improvement in synchronization accuracy, our method allows us to update the slave clock recursively. The proposed method works well even in the presence of large frequency offsets and can also be implemented by using different filters.
Mohammad Javad Hajikhani; Thomas Kunz; Howard Schwartz. A Recursive Method for Clock Synchronization in Asymmetric Packet-Based Networks. IEEE/ACM Transactions on Networking 2015, 24, 2332 -2342.
AMA StyleMohammad Javad Hajikhani, Thomas Kunz, Howard Schwartz. A Recursive Method for Clock Synchronization in Asymmetric Packet-Based Networks. IEEE/ACM Transactions on Networking. 2015; 24 (4):2332-2342.
Chicago/Turabian StyleMohammad Javad Hajikhani; Thomas Kunz; Howard Schwartz. 2015. "A Recursive Method for Clock Synchronization in Asymmetric Packet-Based Networks." IEEE/ACM Transactions on Networking 24, no. 4: 2332-2342.
An unmanned aerial ad hoc network (UAANET) is a special type of mobile ad hoc network (MANET). For these networks, researchers rely mostly on simulations to evaluate their proposed networking protocols. Hence, it is of great importance that the simulation environment of a UAANET replicates as much as possible the reality of UAVs. One major component of that environment is the movement pattern of the UAVs. This means that the mobility model used in simulations has to be thoroughly understood in terms of its impact on the performance of the network. In this paper, we investigate how mobility models affect the performance of UAANET in simulations in order to come up with conclusions/recommendations that provide a benchmark for future UAANET simulations. To that end, we first propose a few metrics to evaluate the mobility models. Then, we present five random entity mobility models that allow nodes to move almost freely and independently from one another and evaluate four carefully-chosen MANET/UAANET routing protocols: ad hoc on-demand distance vector (AODV), optimized link state routing (OLSR), reactive-geographic hybrid routing (RGR) and geographic routing protocol (GRP). In addition, flooding is also evaluated. The results show a wide variation of the protocol performance over different mobility models. These performance differences can be explained by the mobility model characteristics, and we discuss these effects. The results of our analysis show that: (i) the enhanced Gauss–Markov (EGM) mobility model is best suited for UAANET; (ii) OLSR, a table-driven proactive routing protocol, and GRP, a position-based geographic protocol, are the protocols most sensitive to the change of mobility models; (iii) RGR, a reactive-geographic hybrid routing protocol, is best suited for UAANET.
Jean-Daniel Medjo Me Biomo; Thomas Kunz; Marc St-Hilaire; Yifeng Zhou. Unmanned Aerial ad Hoc Networks: Simulation-Based Evaluation of Entity Mobility Models’ Impact on Routing Performance. Aerospace 2015, 2, 392 -422.
AMA StyleJean-Daniel Medjo Me Biomo, Thomas Kunz, Marc St-Hilaire, Yifeng Zhou. Unmanned Aerial ad Hoc Networks: Simulation-Based Evaluation of Entity Mobility Models’ Impact on Routing Performance. Aerospace. 2015; 2 (3):392-422.
Chicago/Turabian StyleJean-Daniel Medjo Me Biomo; Thomas Kunz; Marc St-Hilaire; Yifeng Zhou. 2015. "Unmanned Aerial ad Hoc Networks: Simulation-Based Evaluation of Entity Mobility Models’ Impact on Routing Performance." Aerospace 2, no. 3: 392-422.
This article addresses the residential energy cost optimization problem in smart grid. To date, most of the previous research only consider a partial aspect of the cost optimization problem. As a result, they fail to analyze scenarios when the interconnected components along with their properties have to be considered simultaneously. The proposed model combines these partial models into a single unified cost optimization model. Therefore, it is able to analyze scenarios which are closer to practical implementation. Furthermore, it is useful to analyze the behavior of a population (e.g., smart buildings, smart cities, etc.) and properties of the components for specific scenarios (e.g., the impact of aggregate storage capacity, etc.). It allows energy trading in microgrid which introduces a cost fairness problem. It ensures Pareto optimality among the households which guarantees that no household will be worse off to improve the cost of others. Results show that it can maintain the user preferences and can react to a demand response program by rescheduling the household loads and sources. Finally, the paper addresses the challenge of the computational complexity of the proposed model, showing that solution time increases exponentially with the problem size and proposes possible approaches to solve this.
Muhammad Raisul Alam; Marc St-Hilaire; Thomas Kunz. A Unified Residential Energy Cost Optimization Model for Smart Grid - Significance and Challenge. 2015, 1 .
AMA StyleMuhammad Raisul Alam, Marc St-Hilaire, Thomas Kunz. A Unified Residential Energy Cost Optimization Model for Smart Grid - Significance and Challenge. . 2015; ():1.
Chicago/Turabian StyleMuhammad Raisul Alam; Marc St-Hilaire; Thomas Kunz. 2015. "A Unified Residential Energy Cost Optimization Model for Smart Grid - Significance and Challenge." , no. : 1.
Real-time multimedia applications require quality of service (QoS) provisioning in terms of bounds on delay and packet loss along with soft bandwidth guarantees. The shared nature of the wireless communication medium results in interference. Interference combined with the overheads, associated with a medium access control (MAC) protocol, and the implementation of a networking protocol stack limit the available bandwidth in IEEE 802.15.4-based networks and can result in congestion, even if the transmission rates of nodes are well below the maximum bandwidth supported by an underlying communication technology. Congestion degrades the performance of admitted real-time multimedia flow(s). Therefore, in this paper, we experimentally derive the IEEE 802.15.4 channel capacity using an unslotted CSMA-CA MAC protocol. We experimentally derive channel capacity for two cases, that is, when the CSMA-CA protocol is working without ACKs and when it is working with ACKs. Moreover, for both cases, we plot the relationship of offered data load with delay and packet loss rate. Simulation results demonstrate that the parameters that affect the choice of a CSMA-CA MAC layer protocol are end-to-end delay and packet loss requirements of a real-time multimedia flow, data load within the interference range of transmitters along the forwarding path, and length of the forwarding path.
Muhammad Omer Farooq; Thomas Kunz. Contiki-Based IEEE 802.15.4 Channel Capacity Estimation and Suitability of Its CSMA-CA MAC Layer Protocol for Real-Time Multimedia Applications. Mobile Information Systems 2015, 2015, 1 -9.
AMA StyleMuhammad Omer Farooq, Thomas Kunz. Contiki-Based IEEE 802.15.4 Channel Capacity Estimation and Suitability of Its CSMA-CA MAC Layer Protocol for Real-Time Multimedia Applications. Mobile Information Systems. 2015; 2015 (14):1-9.
Chicago/Turabian StyleMuhammad Omer Farooq; Thomas Kunz. 2015. "Contiki-Based IEEE 802.15.4 Channel Capacity Estimation and Suitability of Its CSMA-CA MAC Layer Protocol for Real-Time Multimedia Applications." Mobile Information Systems 2015, no. 14: 1-9.
In this paper, first, we present our simulation studies that help to outline key factors for a proper available-bandwidth-based flow admission control in ad-hoc Wireless Sensor Networks (WSNs). In most cases, WSNs use the IEEE 802.15.4 standard, therefore our simulation studies are based on the same standard. The identified key factors are: (i) the overheads (back-off, retransmission, contention window, ACK packet, and ACK waiting time) associated with the unslotted IEEE 802.15.4 Carrier Sense Multiple Access Collision Avoidance (CSMA-CA) MAC layer protocol reduce the amount of available bandwidth, (ii) the impact of the MAC layer overheads on a node’s available bandwidth is a function of the number of active transmitters and data traffic load within the interference range of the node, (iii) contention count on a node that is not on a flow’s data forwarding path is a function of the number of active transmitters (along the flow’s data forwarding path) within the interference range of the node, and (iv) a flow’s intra-flow contention count on a node (along the flow’s data forwarding path) depends on the hop-count distance of the node from the source and the destination nodes, and the node’s interference range. Second, we present a survey of state-of-the-art flow admission control algorithms for ad-hoc wireless networks. The survey demonstrates that the state-of-the-art flow admission control algorithms do not completely consider the key identified factors or make incorrect assumptions about them. Third, we propose techniques that an available-bandwidth-based flow admission control algorithm can use to incorporate the key identified factors. Hence, the work presented in this paper can serve as a basis of a more effective available-bandwidth-based flow admission control algorithm for ad-hoc wireless networks.
Muhammad Omer Farooq; Thomas Kunz. Key Factors for a Proper Available-Bandwidth-Based Flow Admission Control in Ad-Hoc Wireless Sensor Networks. Transactions on Petri Nets and Other Models of Concurrency XV 2015, 8629, 246 -260.
AMA StyleMuhammad Omer Farooq, Thomas Kunz. Key Factors for a Proper Available-Bandwidth-Based Flow Admission Control in Ad-Hoc Wireless Sensor Networks. Transactions on Petri Nets and Other Models of Concurrency XV. 2015; 8629 ():246-260.
Chicago/Turabian StyleMuhammad Omer Farooq; Thomas Kunz. 2015. "Key Factors for a Proper Available-Bandwidth-Based Flow Admission Control in Ad-Hoc Wireless Sensor Networks." Transactions on Petri Nets and Other Models of Concurrency XV 8629, no. : 246-260.
Clock synchronization in many protocols such as IEEE 1588 is achieved by exchanging timing information between a master and slave node. Packet delay variation (PDV) is a major source of inaccuracy in packet-based synchronization systems. When the expected values of the delays from master to slave and from slave to master are not equal, the synchronization problem can be modeled as a biased estimation problem. In this paper we propose a solution to estimate the delay bias and use this estimate to improve the synchronization accuracy. Our method is easy to implement and is compatible with the current version of the protocol. Moreover, this method allows us to update the slave clock recursively rather than after collecting many samples. The proposed method works well in the presence of frequency offset and does not require any assumption on the filter which is used in the synchronization process.
Mohammadjavad Hajikhani; Thomas Kunz; Howard Schwartz; Maryam Hajikhani. A recursive method for bias estimation in asymmetric packet-based networks. 2014 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication (ISPCS) 2014, 47 -52.
AMA StyleMohammadjavad Hajikhani, Thomas Kunz, Howard Schwartz, Maryam Hajikhani. A recursive method for bias estimation in asymmetric packet-based networks. 2014 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication (ISPCS). 2014; ():47-52.
Chicago/Turabian StyleMohammadjavad Hajikhani; Thomas Kunz; Howard Schwartz; Maryam Hajikhani. 2014. "A recursive method for bias estimation in asymmetric packet-based networks." 2014 IEEE International Symposium on Precision Clock Synchronization for Measurement, Control, and Communication (ISPCS) , no. : 47-52.
This paper proposes a Delay Asymmetry Correction (DAC) Model to enhance clock synchronization protocols based on a Master-Slave arrangement such as the IEEE 1588 PTP protocol. The purpose of this work is to mitigate the effects of unpredictable packet delay variations (PDV), which may aggravate asymmetric link delays on timing packets, in order to improve the synchronization accuracy of the slave clock with respect to the master clock. The key idea in our work is to filter clock updates derived from the master-slave message exchange, using only good samples for slave clock updates. The proposed solution is implemented in Network Simulator 2 (NS-2.34). NS-2 test cases are implemented according to the ITU-T G.8261 document covering various network loads and network conditions. Our simulation results indicate that the proposed solution improves the slave accuracy significantly, achieving almost perfect synchronization accuracy in the presence of a wide range of network traffic loads, network congestions, and temporary network outage. Furthermore, when there is a routing path change due to the failure in the network, the solution also maintains high slave clock accuracy with respect to the master clock.
Arifur Rahman; Thomas Kunz; Howard Schwartz. Delay Asymmetry Correction Model for Master-Slave Synchronization Protocols. 2014 IEEE 28th International Conference on Advanced Information Networking and Applications 2014, 1 -8.
AMA StyleArifur Rahman, Thomas Kunz, Howard Schwartz. Delay Asymmetry Correction Model for Master-Slave Synchronization Protocols. 2014 IEEE 28th International Conference on Advanced Information Networking and Applications. 2014; ():1-8.
Chicago/Turabian StyleArifur Rahman; Thomas Kunz; Howard Schwartz. 2014. "Delay Asymmetry Correction Model for Master-Slave Synchronization Protocols." 2014 IEEE 28th International Conference on Advanced Information Networking and Applications , no. : 1-8.
Network Coding is a relatively new forwarding paradigm where intermediate nodes perform a store, code, and forward operation on incoming packets. Traditional forwarding approaches, which employed a store and forward operation, have not been able to approach the limit of the max-flow min-cut throughput wherein sources transmitting information over bottleneck links have to compete for access to these links. With Network Coding, multiple sources are now able to transmit packets over bottleneck links simultaneously, achieving the max-flow min-cut through-put and increasing network capacity. While the majority of the contemporary literature has focused on the performance of Network Coding from a capacity perspective, the aim of this research has taken a new direction focusing on two Quality of Service metrics, e.g., Packet Delivery Ratio (PDR) and Latency, in conjunction with Network Coding protocols in Mobile Ad Hoc Networks (MANETs). Simulations are performed on static and mobile environments to determine a Quality of Service baseline comparison between Network Coding protocols and traditional ad hoc routing protocols. The results show that the Random Linear Network Coding protocol has the lowest Latency and Dynamic Source Routing protocol has the highest PDR in the static scenarios, and show that the Random Linear Network Coding protocol has the best cumulative performance for both PDR and Latency in the mobile scenarios.
Michael Hay; Basil Saeed; Chung-Horng Lung; Thomas Kunz; Anand Srinivasan. Network Coding and Quality of Service for Mobile Ad Hoc Networks. International Journal of Communications, Network and System Sciences 2014, 07, 409 -422.
AMA StyleMichael Hay, Basil Saeed, Chung-Horng Lung, Thomas Kunz, Anand Srinivasan. Network Coding and Quality of Service for Mobile Ad Hoc Networks. International Journal of Communications, Network and System Sciences. 2014; 07 (10):409-422.
Chicago/Turabian StyleMichael Hay; Basil Saeed; Chung-Horng Lung; Thomas Kunz; Anand Srinivasan. 2014. "Network Coding and Quality of Service for Mobile Ad Hoc Networks." International Journal of Communications, Network and System Sciences 07, no. 10: 409-422.
A two-way message exchange mechanism is at the core of many clock synchronization protocols. The basic concept of this method has been designed for symmetrical links, otherwise, depending on the level of asymmetric delays, large synchronization errors may occur. Many estimation based methods have been proposed so far for estimating the degree of asymmetry and reducing this error. However, many of them are solved for a specific distribution of link random delays. Moreover, imposing a high level of computational complexity upon network nodes is another problem of them. In this paper we introduce a recursive solution for improving the performance of the basic two-way message exchange mechanism. The advantage of this method is that it keeps the protocol simple and therefore easily implementable. The proposed method does not make any specific assumption about the distribution of the random delays. It also provides the network designer with some deployment flexibility, trading off convergence speed against stability.
Mohammadjavad Hajikhani; Thomas Kunz; Howard Schwartz; Maryam Hajikhani. A recursive solution for improving the synchronization accuracy in wireless sensor networks. 2013 9th International Wireless Communications and Mobile Computing Conference (IWCMC) 2013, 1325 -1330.
AMA StyleMohammadjavad Hajikhani, Thomas Kunz, Howard Schwartz, Maryam Hajikhani. A recursive solution for improving the synchronization accuracy in wireless sensor networks. 2013 9th International Wireless Communications and Mobile Computing Conference (IWCMC). 2013; ():1325-1330.
Chicago/Turabian StyleMohammadjavad Hajikhani; Thomas Kunz; Howard Schwartz; Maryam Hajikhani. 2013. "A recursive solution for improving the synchronization accuracy in wireless sensor networks." 2013 9th International Wireless Communications and Mobile Computing Conference (IWCMC) , no. : 1325-1330.