Alicia Triviño

Type-2 fuzzy decision support system to optimise MANET integration into infrastructure-based wireless systems

Mobile ad hoc networks are able to extend the coverage area of Internet access points by establishing multihop communication paths. Due to diverse factors such as the mobility of the nodes, the propagation conditions or the traffic status, the communication paths present a lifetime. In fact, the quality of the Internet connection mainly depends on the durability of the employed communication routes. In order to improve the network performance, the nodes should select the best route in terms of its remaining lifetime. Since the factors impacting the route lifetime are unpredictable, the route remaining lifetime cannot be analytically derived. Under these circumstances, a fuzzy-logic system outstands as a potential solution to estimate the stability of the routes. This paper analyses the potentiality of this kind of solution. In particular, the paper presents a fuzzy logic system which should be installed in the mobile nodes to distributedly identify the stable routes. In particular, the system is supported by an interval-based type-2 fuzzy logic. Being a type-2 fuzzy logic system, it is able to cope with inexact estimations. This ability is necessary to avoid the use of additional messages which will occupy the scarce wireless medium. On the other hand, an interval-based fuzzy system provides the simplicity demanded by the energy-constrained mobile devices. As a novelty, the two outputs of the interval-based fuzzy system are employed. The use of each output depends on the traffic state of the mobile node. By means of extensive simulations, we demonstrate the goodness of the proposed system.

An adaptive gateway discovery for mobile ad hoc networks

One of the main aspects that affect the performance of hybrid ad hoc networks is the discovery and selection of Internet gateways. Similar to conventional ad hoc route discovery, this procedure could be accomplished employing three different strategies: proactive, reactive and hybrid. In the proactive gateway discovery, the gateway periodically generates Modified Router Advertisement (MRA) messages. The election of the time between two consecutive MRAs (T) may greatly impact on the network performance (a low T could lead to unnecessary control packets meanwhile a high T could induce nodes keep invalid routes to external hosts). The optimum value of T depends on the network conditions as the load, the node density or the node mobility. In order to dynamically adjust the T interval, in this work we present a new adaptive scheme which is supported by a control system based on a genetic algorithm. The simulation results show that the proposed algorithm is able to decrease the network congestion and achieve lower end-to-end delay.

Improved Scheme for Adaptive Gateway Discovery in Hybrid MANET

This paper presents an adaptive scheme for gateway discovery in MANETs connected to the Internet. Basically, the proposed scheme reduces the flooding processes related to gateway discovery. To do so, the algorithm dynamically adjusts the interval of emission of the gateway advertisement messages to the need for updated routes to the gateway. The tuning is supported by the analysis of the spatial distribution of nodes in the MANET and by the impact that the relative position of nodes has on the route lifetimes. The simulations show that the proposed adaptive mechanism outperforms the conventional schemes: it decreases network saturation while it achieves lower end-to-end delay and it minimizes the routing overhead.

Adaptive gateway discovery for mobile ad hoc networks based on the characterisation of the link lifetime

Mobile ad hoc networks (MANETs) connected to the Internet require a gateway to operate. The gateway is responsible for providing the configuration parameters to the nodes by means of message exchanges. These messages are also necessary to create and/or update the route to the gateway in the mobile nodes. As MANET nodes move freely, these messages are generated at the beginning of the connections (to obtain the configuration parameters), when the route to the gateway breaks or when the gateway proactively sends them. This message exchange, also known as the gateway discovery procedure, has to be optimised in order to release wireless resources for the data transmissions. In this sense, this study proposes a novel technique by which the messages that the gateway periodically generates are exclusively forwarded in the areas where the links are expected to remain stable. By this, nodes are able to learn stable routes and, in turn, the messages generated because of the breakages of used links are avoided. From this parameter setting, the network performance is improved. The main difficulty of the technique is to determine the paths that are stable. For this purpose, the statistical characterisation of link duration in MANETs is employed in this study. The simulation results show the goodness of applying the proposed technique in terms of packet delivery ratio, protocol overhead and end-to-end delay.

People-Centric Internet of Things—Challenges, Approach, and Enabling Technologies

Technology now offers the possibility of delivering a vast range of low-cost people-centric services to citizens. Internet of Things (IoT) supporting technologies are becoming robust, viable and cheaper. Mobile phones are increasingly more powerful and disseminated. On the other hand, social networks and virtual worlds are experiencing an exploding popularity and have millions of users. These low-cost technologies can now be used to create an Internet of People (IoP), a dynamically configurable integration platform of connected smart objects that allows enhanced, people-centric applications. As opposed to things-centric ones, IoP combines the real, sensory world with the virtual world for the benefit of people while it also enables the development of sensing applications in contexts such as e-health, sustainable mobility, social networks enhancement or fulfilling people’s special needs. This paper identifies the main challenges, a possible approach, and key enabling technologies for a people-centric society based on the Internet of Things.

Study on the need for adaptive gateway discovery in MANETs

The integration of MANET into external networks is achieved by Internet Gateways. These Gateways are responsible for propagating the information necessary to make mobile nodes autoconfigure. This information can be generated on demand (reactively), periodically (proactively) or in a hybrid way. When a hybrid gateway discovery is used, the Gateway periodically generates MRA messages each interval of time TMRA. In opposition to the proactive schemes, the messages are propagated in a restricted area close to the Gateway. The area is defined by the number of hops that these messages are broadcast (the TTL value). The optimum value for TMRA and TTL depends on the network conditions such as the network load, the position of sources, etc. In this work, we analyze the benefits of dynamically adjusting the interval of emission of the MRA messages in a hybrid gateway discovery.

An Adaptive Genetic Fuzzy Control Gateway Discovery to Interconnect Hybrid MANETs

In wireless communication, Mobile Ad Hoc NETwork (MANET) is a set of mobile nodes that are dynamically and randomly located in such a manner that the wireless link among nodes are often changing due to MANET dynamic features. In this MANET environment, if a device wants to connect to Internet, it must establish a communication with an Internet Gateway. The network performance between mobile nodes and Internet Gateway is affected by the stability, connectivity and network traffic load. The complex interactions among these parameters can be modelled using fuzzy set theory. This paper uses Artificial Intelligence (genetic algorithm and fuzzy system) to tune, adaptively, the control system that uses the gateway discovery schemes. The performance of fuzzy control is evaluated using simulation, and it is compared to others adaptive schemes explained in literature.

Connectivity Gateway Discovery in MANETs

The integration of mobile ad hoc networks into IP-based access networks demands the presence of a gateway which is responsible for propagating some configuration parameters by means of Modified Router Advertisement (MRA) messages. This function may be accomplished on demand by the mobile nodes (reactively), periodically activated by the gateway (proactively) or by combining the two approaches. In the proactive mechanisms, the interval of emission of the MRA messages (T ) may significantly affect the network performance. The optimum value for T depends on the network conditions such as the position of the sources, the mobility of nodes, etc. Therefore, an autonomous and adaptive technique to dynamically configure T is strongly recommended. In this sense, a new adaptive gateway discovery mechanism is proposed in this paper. The adaptation is achieved by a control system which has been conveniently configured by means of an analytical model. Simulation results show that the proposed adaptive mechanism improves the conventional proactive schemes.

Cooperative layer-2 based routing approach for hybrid wireless mesh networks

In a Wireless Mesh Network (WMN), the convenience of a routing strategy strongly depends on the mobility of the intermediate nodes that compose the paths. Taking this behaviour into account, this paper presents a routing scheme that works differently accordingly to the node mobility. In this sense, a proactive routing scheme is restricted to the backbone to promote the use of stable routes. Conversely, the reactive protocol is used for searching routes to or from a mobile destination. Both approaches are simultaneously implemented in the mesh nodes so that the routing protocols share routing information that optimises the network performance. Aimed at guaranteeing the IP compatibility, the combination of the two protocols in the core routers is carried out in the Medium Access Control (MAC) layer. In contrast to the operation in the IP layer where two routing protocols cannot work concurrently, the transfer of the routing tasks to the MAC layer enables the use of multiple independent forwarding tables. Simulation results show the advantage of the proposal in terms of packet losses and data delay.

Assessing the impact of Link Layer Feedback mechanisms on MANET routing protocols

Mobile Ad Hoc Networks have a highly dynamic topology due to terminal mobility. Ad hoc routing protocols can cope with this mobility as they search for an alternative route when a currently-in-use path breaks. Despite of their ability to recover from path failures, the time elapsed until the route is reestablished deteriorates network performance. MANET routing protocols can detect link breakages faster when Link Layer Feedback (LLF) mechanisms are used. In this paper we evaluate the advantages and drawbacks of using feedback mechanisms. Our simulation results show that these mechanisms are appropriate for low mobility conditions. In contrast, feedback is not adequate for scenarios where terminals move faster due to frequent collisions mistaken as link breakages.