Simulation study on the impact of the transmission power on the performance of routing protocols under different mobility models

© 2014 IEEE. the dynamic topology of a mobile ad hoc network poses a real challenge in designing the routing protocol. This paper examine through simulation the fundamental factors, mobility models and transmission power which have a major impacts on the performance of position based routing protocols. We analyse the effect of the transmission power of on the performance of protocols under two different mobility models. Using OPNET simulation tool, results show the evaluation and performance of the proposed protocol under a unified simulation environment for different scenarios

Enhanced collision avoidance mechanisms for wireless sensor networks through high accuracy collision modeling

Wireless channel and multi-hop communications cause a significant number of packet collisions in Wireless Sensor Networks (WSNs). Although a collision may cause packet loss and reduce network performance, low-power wireless transceivers allow packet reception in the presence of collisions if at least one signal can provide a sufficiently high power compared with other signals. Therefore, with respect to the large number of nodes used in WSNs, which necessitates the use of simulation for protocol development, collisions should be addressed at two layers: First, collisions should be modeled at the physical layer through a high-accuracy packet reception algorithm that decides about packet reception in the presence of collisions. Second, collision avoidance mechanisms should be employed at the Medium Access Control (MAC) layer to reduce packet losses caused by collisions. Unfortunately, the existing packet reception algorithms exhibit low accuracy and impede the development of efficient collision avoidance mechanisms. From the collision avoidance perspective, existing contention-based MAC protocols do not provide reliable packet broadcasting, thereby affecting the initialization performance of WSNs. In addition, despite the benefits of schedule-based MAC protocols during the data-gathering phase, the existing mechanisms rely on unrealistic assumptions. The first major contribution of this work is CApture Modeling Algorithm (CAMA), which enables collision modeling with high accuracy and efficiency at the physical layer. The higher accuracy of CAMA against existing approaches is validated through extensive comparisons with empirical experiments. The second major contribution includes mechanisms that improve the reliability of packet broadcasting. In particular, adaptive contention window adjustment mechanisms and the Geowindow algorithm are proposed for collision avoidance during the initialization phases. These mechanisms considerably improve the accuracy of the initialization phases, without violating duration and energy efficiency requirements. As the third major contribution, a distributed and concurrent link-scheduling algorithm (called DICSA) is proposed for collision avoidance during the data-gathering phase. DICSA provides faster slot assignment, higher spatial reuse and lower energy consumption, compared with existing algorithms. Furthermore, evaluating DICSA within a MAC protocol confirms its higher throughput, higher delivery ratio, and lower end-to-end delay

A survey on Bluetooth multi-hop networks

Bluetooth was firstly announced in 1998. Originally designed as cable replacement connecting devices in a point-to-point fashion its high penetration arouses interest in its ad-hoc networking potential. This ad-hoc networking potential of Bluetooth is advertised for years - but until recently no actual products were available and less than a handful of real Bluetooth multi-hop network deployments were reported. The turnaround was triggered by the release of the Bluetooth Low Energy Mesh Profile which is unquestionable a great achievement but not well suited for all use cases of multi-hop networks. This paper surveys the tremendous work done on Bluetooth multi-hop networks during the last 20 years. All aspects are discussed with demands for a real world Bluetooth multi-hop operation in mind. Relationships and side effects of different topics for a real world implementation are explained. This unique focus distinguishes this survey from existing ones. Furthermore, to the best of the authors’ knowledge this is the first survey consolidating the work on Bluetooth multi-hop networks for classic Bluetooth technology as well as for Bluetooth Low Energy. Another individual characteristic of this survey is a synopsis of real world Bluetooth multi-hop network deployment efforts. In fact, there are only four reports of a successful establishment of a Bluetooth multi-hop network with more than 30 nodes and only one of them was integrated in a real world application - namely a photovoltaic power plant. © 2019 The Author

Building Realistic Mobility Models for Mobile Ad Hoc Networks

A mobile ad hoc network (MANET) is a self-configuring wireless network in which each node could act as a router, as well as a data source or sink. Its application areas include battlefields and vehicular and disaster areas. Many techniques applied to infrastructure-based networks are less effective in MANETs, with routing being a particular challenge. This paper presents a rigorous study into simulation techniques for evaluating routing solutions for MANETs with the aim of producing more realistic simulation models and thereby, more accurate protocol evaluations. MANET simulations require models that reflect the world in which the MANET is to operate. Much of the published research uses movement models, such as the random waypoint (RWP) model, with arbitrary world sizes and node counts. This paper presents a technique for developing more realistic simulation models to test and evaluate MANET protocols. The technique is animation, which is applied to a realistic scenario to produce a model that accurately reflects the size and shape of the world, node count, movement patterns, and time period over which the MANET may operate. The animation technique has been used to develop a battlefield model based on established military tactics. Trace data has been used to build a model of maritime movements in the Irish Sea. Similar world models have been built using the random waypoint movement model for comparison. All models have been built using the ns-2 simulator. These models have been used to compare the performance of three routing protocols: dynamic source routing (DSR), destination-sequenced distance-vector routing (DSDV), and ad hoc n-demand distance vector routing (AODV). The findings reveal that protocol performance is dependent on the model used. In particular, it is shown that RWP models do not reflect the performance of these protocols under realistic circumstances, and protocol selection is subject to the scenario to which it is applied. To conclude, it is possible to develop a range of techniques for modelling scenarios applicable to MANETs, and these simulation models could be utilised for the evaluation of routing protocols

Delay tolerant networking in a shopping mall environment

The increasing popularity of computing devices with short-range wireless offers new communication service opportunities. These devices are small and may be mobile or embedded in almost any type of object imaginable, including cars, tools, appliances, clothing and various consumer goods. The majority of them can store data and transmit it when a wireless, or wired, transmitting medium is available. The mobility of the individuals carrying such short-range wireless devices is important because varying distances creates connection opportunities and disconnections. It is likely that successful forwarding algorithms will be based, at least in part, on the patterns of mobility that are seen in real settings. For this reason, studying human mobility in different environments for extended periods of time is essential. Thus we need to use measurements from realistic settings to drive the development and evaluation of appropriate forwarding algorithms. Recently, several significant efforts have been made to collect data reflecting human mobility. However, these traces are from specific scenarios and their validity is difficult to generalize. In this thesis we contribute to this effort by studying human mobility in shopping malls. We ran a field trial to collect real-world Bluetooth contact data from shop employees and clerks in a shopping mall over six days. This data will allow the informed design of forwarding policies and algorithms for such settings and scenarios, and determine the effects of users' mobility patterns on the prevalence of networking opportunities. Using this data set we have analysed human mobility and interaction patterns in this shopping mall environment. We present evidence of distinct classes of mobility in this situation and characterize them in terms of power law coefficients which approximate inter-contact time distributions. These results are quite different from previous studies in other environments. We have developed a software tool which implements a mobility model for "structured" scenarios such as shopping malls, trade fairs, music festivals, stadiums and museums. In this thesis we define as structured environment, a scenario having definite and highly organised structure, where people are organised by characteristic patterns of relationship and mobility. We analysed the contact traces collected on the field to guide the design of this mobility model. We show that our synthetic mobility model produces inter-contact time and contact duration distributions which approximate well to those of the real traces. Our scenario generator also implements several random mobility models. We compared our Shopping Mall mobility model to three other random mobility models by comparing the performances of two benchmark delay tolerant routing protocols, Epidemic and Prophet, when simulated with movement traces from each model. Thus, we demonstrate that the choice of a mobility model is a significant consideration when designing and evaluating delay-tolerant mobile ad-hoc network protocols. Finally, we have also conducted an initial study to evaluate the effect of delivering messages in shopping mall environments by exclusively forwarding them to customers or sellers, each of which has distinctive mobility patterns

Position-Based Packet Forwarding for Vehicular Ad-Hoc Networks

Mobile Ad-Hoc Networks, or MANETs, are data communication networks between (potentially) mobile computer systems equipped with wireless communication devices and — in their purest form — in complete absence of communication infrastructure. Usage scenarios for these systems include communication during disaster recovery or battlefield communications. One of the great research challenges concerning MANETs is the Packet Forwarding Problem, i.e., the question to which neighbor node a data packet should be handed over to reach non-neighboring nodes. While this problem has been previously solved by the adaption of classic routing algorithms from wired networks, the availability of GPS enables to include information about the geographic position of nodes into the routing decision, by selecting forwarders that are geographically closest to the destination. While these algorithms have been shown to improve communication performance in networks with a high degree of node mobility, they require (a) a beaconing service that allows every node to build a table of its neighbors and (b) a so-called Location Service that allows to acquire the current position of non-neighboring nodes in the network. In this thesis, we propose Contention-Based Forwarding (or CBF), a greedy routing heuristic that is no longer in need of a beaconing service. Moreover, a forwarding node running CBF does not at all select the next forwarder explicitly but broadcasts the packet containing its own position and the position of the destination. The selection of the forwarding is now done in a contention period, where every possible forwarder, i.e., every receiver of the packet, considers its own suitability to forward by calculating the geographical progress for the packet if forwarded by itself. Then it waits for a time reciprocal to this suitability before simply retransmitting. If the retransmission of a packet is overheard, the own postponed retransmission process is canceled. In this thesis, we demonstrate that CBF outperforms beacon and position-based routing by delivering packets with constant overhead, almost ignorant of mobility. Also, we introduce two strategies to cope with the problem of packet duplication. A problem left open by greedy routing heuristics is routing in the presence of local optima, or voids. Voids are node placement situations, where — in spite of an existing route — no neighboring node is geographically closer to the destination than the current forwarder. In these situations, greedy forwarding fails and standard graph-based recovery well known from classical Position-Based Forwarding cannot be applied due to the lack of the beacon-based construction of neighbor tables. As a solution, we propagate Contention-Based Distance Vector Routing, a contention-based adaption of AODV that acquires topology information in the area of the void and does contention on the topological distance to the forwarder. Besides the forwarding algorithms, we extend position-based routing by two location services. The first, the Reactive Location Service or RLS is simple, purely on-demand and very robust to mobility, the second Hierarchical Location Service, is more complex but outperforms RLS in scalability. The second big column in this thesis is ad-hoc multi-hop communication in the context of Vehicular Ad-Hoc Networks , or VANET, i.e., networks where the communication system is carried by vehicles. These systems very elegantly fit into the propositions and requirements for our more general routing approaches since they have (a) easy access to position information an (b) "suffer" from high mobility. For VANETs, we separate the routing problem into highway and city scenarios and study various routing algorithms in both. In the end, we advocate the usage of position-based routing in both scenarios; moreover, the contention-based approaches are most promising. While a lot of ad-hoc research has been deemed to be theoretical, we have also built a multi-car communication system. For this system, we provided the network and system architecture and provided the communication software. In this thesis, we will describe these efforts as a proof-of-concept and provide measurement results

Delay tolerant networking in a shopping mall environment

The increasing popularity of computing devices with short-range wireless offers new communication service opportunities. These devices are small and may be mobile or embedded in almost any type of object imaginable, including cars, tools, appliances, clothing and various consumer goods. The majority of them can store data and transmit it when a wireless, or wired, transmitting medium is available. The mobility of the individuals carrying such short-range wireless devices is important because varying distances creates connection opportunities and disconnections. It is likely that successful forwarding algorithms will be based, at least in part, on the patterns of mobility that are seen in real settings. For this reason, studying human mobility in different environments for extended periods of time is essential. Thus we need to use measurements from realistic settings to drive the development and evaluation of appropriate forwarding algorithms. Recently, several significant efforts have been made to collect data reflecting human mobility. However, these traces are from specific scenarios and their validity is difficult to generalize. In this thesis we contribute to this effort by studying human mobility in shopping malls. We ran a field trial to collect real-world Bluetooth contact data from shop employees and clerks in a shopping mall over six days. This data will allow the informed design of forwarding policies and algorithms for such settings and scenarios, and determine the effects of users' mobility patterns on the prevalence of networking opportunities. Using this data set we have analysed human mobility and interaction patterns in this shopping mall environment. We present evidence of distinct classes of mobility in this situation and characterize them in terms of power law coefficients which approximate inter-contact time distributions. These results are quite different from previous studies in other environments. We have developed a software tool which implements a mobility model for "structured" scenarios such as shopping malls, trade fairs, music festivals, stadiums and museums. In this thesis we define as structured environment, a scenario having definite and highly organised structure, where people are organised by characteristic patterns of relationship and mobility. We analysed the contact traces collected on the field to guide the design of this mobility model. We show that our synthetic mobility model produces inter-contact time and contact duration distributions which approximate well to those of the real traces. Our scenario generator also implements several random mobility models. We compared our Shopping Mall mobility model to three other random mobility models by comparing the performances of two benchmark delay tolerant routing protocols, Epidemic and Prophet, when simulated with movement traces from each model. Thus, we demonstrate that the choice of a mobility model is a significant consideration when designing and evaluating delay-tolerant mobile ad-hoc network protocols. Finally, we have also conducted an initial study to evaluate the effect of delivering messages in shopping mall environments by exclusively forwarding them to customers or sellers, each of which has distinctive mobility patterns