Decisive analysis of current state of the art in congestion aware and control routing models in ad hoc networks

An important aspect that portrays a crucial position in the ad hoc network routing is congestion. Almost every research analysis is en-route in adapting this key factor in addressing congestion. This problem cannot be totally addressed by the regular TCP protocol based networks, keeping in view the special assets which include multi hop sharing etc, which is difficult to ascertain in ad hoc networks. Many attempts have been made and are in progress by researchers to provide unique solutions to the above mentioned problems. This paper projects a vital study on jamming aware and different routing standards that have been dealt with in recent times

A survey of performance enhancement of transmission control protocol (TCP) in wireless ad hoc networks

This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Springer OpenTransmission control protocol (TCP), which provides reliable end-to-end data delivery, performs well in traditional wired network environments, while in wireless ad hoc networks, it does not perform well. Compared to wired networks, wireless ad hoc networks have some specific characteristics such as node mobility and a shared medium. Owing to these specific characteristics of wireless ad hoc networks, TCP faces particular problems with, for example, route failure, channel contention and high bit error rates. These factors are responsible for the performance degradation of TCP in wireless ad hoc networks. The research community has produced a wide range of proposals to improve the performance of TCP in wireless ad hoc networks. This article presents a survey of these proposals (approaches). A classification of TCP improvement proposals for wireless ad hoc networks is presented, which makes it easy to compare the proposals falling under the same category. Tables which summarize the approaches for quick overview are provided. Possible directions for further improvements in this area are suggested in the conclusions. The aim of the article is to enable the reader to quickly acquire an overview of the state of TCP in wireless ad hoc networks.This study is partly funded by Kohat University of Science & Technology (KUST), Pakistan, and the Higher Education Commission, Pakistan

Reliable Transport Method for Hybrid Networks

Nykyaikaisten tietoverkkojen monipuolistuessa käytettyjen teknologioiden määrä tulee lisääntymään. Langattomista ja langallisista komponenteista rakentuvat liityntäverkot ovat entistä laajemmassa käytössä jo nykyään. Tämä asettaa tavoitteita paitsi laitteiden yhteistoiminnalle, myös tiedonsiirron luotettavuudelle. Erityisesti langattomalla siirtotiellä esiintyvät häiriöt ja niistä johtuvat pakettihukat ovat uhka luotettavalle tiedonsiirrolle. Näiden pakettihukkien estäminen ja niistä palautuminen ovat tärkeitä keinoja luotettavuuden parantamiseksi. Tässä työssä on mallinnettu ja simuloitu eräs menetelmä luotettavan tiedonsiirron toteuttamiseksi. Menetelmä on nimeltään HBH, ja se on hyppykohtaisiin negatiivisiin kuittauksiin perustuva menetelmä. Sen tarkoituksena on varmistaa luotettava tiedonsiirto korjaamalla linkillä tapahtuvat pakettihukat nopeasti ja tehokkaasti. Mallinnukseen on käytetty OPNET Modeler -ohjelmaa. Simulaatioiden perusteella saatiin selville, että menetelmä parantaa linkkikohtaista luotettavuutta huomattavasti. Erityisesti 10-30% pakettihukilla toiminta tehostuu huomattavasti verrattuna varmistamattomaan tilanteeseen. Kvalitatiivinen analyysi TCP:n toiminnasta menetelmän kanssa antoi erittäin lupaavia tuloksia suorituskyvyn parantumisesta erityisesti kun pakettihukkaa alkoi esiintyä huomattavasti.As modern communication networks become more diverse, the amount of utilised technologies will increase in the future. Access networks comprised of wireless and wired components are in even wider use than before. This sets goals not only for device interoperability, but also for transmission reliability. Especially wireless medium interference and packet loss caused by it is a threat to reliable communication in environments using those technologies. Avoidance of and recovery from these packet losses are key methods to improve reliability. In this Thesis a method for reliable transmission is modeled and simulated. The method is called HBH (hop-by-hop) and it is a method based on hop-by-hop negative acknowledgements. Its purpose is to secure reliable transmission by repairing link-based packet losses quickly and efficiently. The method is modeled using OPNET Modeler. Based on simulations we discovered that the method improves link-based reliability significantly. Especially when experiencing packet loss of 10 to 30 percent the communication is substantially improved compared to the case without any reliability support. Qualitative analysis on TCP operation gives very promising results on improving performance, especially when significant packet loss is present

Distributed services for mobile ad hoc networks

A mobile ad hoc network consists of certain nodes that communicate only through wireless medium and can move arbitrarily. The key feature of a mobile ad hoc network is the mobility of the nodes. Because of the mobility, communication links form and disappear as nodes come into and go out of each other's communica- tion range. Mobile ad hoc networks are particularly useful in situations like disaster recovery and search, military operations, etc. Research on mobile ad hoc networks has drawn a huge amount of attention recently. The main challenges for mobile ad hoc networks are the sparse resources and frequent mobility. Most of the research work has been focused on the MAC and routing layer. In this work, we focus on distributed services for mobile ad hoc networks. These services will provide some fundamental functions in developing various applications for mobile ad hoc networks. In particular, we focus on the clock synchronization, connected dominating set, and k-mutual exclusion problems in mobile ad hoc networks

Progetto e realizzazione di un protocollo di trasporto per reti Ad Hoc Multi-Hop

A Mobile Ad hoc Network (MANET) is a collection of mobile nodes connected together over a wireless medium, which self-organize into an autonomous multi-hop wireless network. This kind of networks allows devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. This thesis examines the problems encountered by TCP over multi-hop ad hoc networks. TCP is not able to efficiently deal with the unstable and very dynamic environment provided by multi-hop ad hoc networks. This is because TCP implicitly assumes that packet loss is almost always due to congestion phenomena causing buffer overflows at intermediate routers. Furthermore, it also assumes that nodes are static (i.e., they do not change their position over time). Unfortunately, these assumptions do not hold in MANETs, since in this kind of networks packet losses due to interference and link-layer contentions are largely predominant, and nodes may be mobile. This thesis presents a new lightweight transport protocol (TPA) designed from scratch, that provides a connection-oriented, reliable type of service. TPA differs from TCP in a number of ways. Specifically, the data transfer and the congestion control algorithms have been re-designed. Furthermore, TPA explicitly detects and deals with both route failures and route changes and it can also leverage cross-layer interactions with the routing protocol, when available. This thesis also includes a preliminary simulative evaluation of TPA