5,077 research outputs found
Improving the performance of QoS models in MANETs through interference monitoring and correction
Mobile Ad hoc Networks (MANETs) have been proposed for a wide variety of applications, some of which require the support of real time and multimedia services. To do so, the network should be able to offer quality of service (QoS) appropriate for the latency and throughput bounds to meet appropriate real time constraints imposed by multimedia data. Due to the limited resources such as bandwidth in a wireless medium, flows need to be prioritised in order to guarantee QoS to the flows that need it. In this research, we propose a scheme to provide QoS guarantee to high priority flows in the presence of other high as well as low priority flows so that both type of flows achieve best possible throughput and end-to-end delays. Nodes independently monitor the level of interference by checking the rates of the highest priority flows and signal corrective mechanisms when these rates fall outside of specified thresholds. This research investigates using simulations the effects of a number of important parameters in MANETs, including node speed, pause time, interference, and the dynamic monitoring and correction on system performance in static and mobile scenarios. In this report we show that the dynamic monitoring and correction provides improved QoS than fixed monitoring and correction to both high priority and low priority flows in MANETs
Multipath routing and QoS provisioning in mobile ad hoc networks
PhDA Mobile Ad Hoc Networks (MANET) is a collection of mobile nodes that can
communicate with each other using multihop wireless links without utilizing any
fixed based-station infrastructure and centralized management. Each mobile node
in the network acts as both a host generating flows or being destination of flows
and a router forwarding flows directed to other nodes.
Future applications of MANETs are expected to be based on all-IP
architecture and be capable of carrying multitude real-time multimedia
applications such as voice and video as well as data. It is very necessary for
MANETs to have an efficient routing and quality of service (QoS) mechanism to
support diverse applications.
This thesis proposes an on-demand Node-Disjoint Multipath Routing protocol
(NDMR) with low broadcast redundancy. Multipath routing allows the
establishment of multiple paths between a single source and single destination
node. It is also beneficial to avoid traffic congestion and frequent link breaks in
communication because of the mobility of nodes. The important components of
the protocol, such as path accumulation, decreasing routing overhead and
selecting node-disjoint paths, are explained. Because the new protocol
significantly reduces the total number of Route Request packets, this results in an
increased delivery ratio, smaller end-to-end delays for data packets, lower control
overhead and fewer collisions of packets.
Although NDMR provides node-disjoint multipath routing with low route
overhead in MANETs, it is only a best-effort routing approach, which is not
enough to support QoS. DiffServ is a standard approach for a more scalable way
to achieve QoS in any IP network and could potentially be used to provide QoS
in MANETs because it minimises the need for signalling. However, one of the
biggest drawbacks of DiffServ is that the QoS provisioning is separate from the
routing process. This thesis presents a Multipath QoS Routing protocol for
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supporting DiffServ (MQRD), which combines the advantages of NDMR and
DiffServ. The protocol can classify network traffic into different priority levels
and apply priority scheduling and queuing management mechanisms to obtain
QoS guarantees
QoS in Node-disjoint Routing for Ad Hoc Networks
PhDA mobile ad hoc network (MANET) is a collection of mobile nodes that
can communicate with each other without using any fixed infrastructure.
It is necessary for MANETs to have efficient routing protocol and quality
of service (QoS) mechanism to support multimedia applications such as
video and voice.
Node-Disjoint Multipath Routing Protocol (NDMR) is a practical protocol
in MANETs: it reduces routing overhead dramatically and achieves
multiple node-disjoint routing paths.
Because QoS support in MANETs is important as best-effort routing is
not efficient for supporting multimedia applications, this thesis presents a
novel approach to provide that support.
In this thesis NDMR is enhanced to provide a QoS enabled NDMR that
decreases the transmission delay between source and destination nodes.
A multi-rate mechanism is also implemented in the new protocol so that
the NDMR QoS can minimise the overall delays. It is shown that these
approaches lead to significant performance gains. A modification to
NDMR is also proposed to overcome some of the limitations of the
original
Managing Shared Access to a Spectrum Commons
The open access, unlicensed or spectrum commons approach to managing shared access to RF spectrum offers many attractive benefits, especially when implemented in conjunction with and as a complement to a regime of marketbased, flexible use, tradable licensed spectrum ([Benkler02], [Lehr04], [Werbach03]). However, as a number of critics have pointed out, implementing the unlicensed model poses difficult challenges that have not been well-addressed yet by commons advocates ([Benjam03], [Faulhab05], [Goodman04], [Hazlett01]). A successful spectrum commons will not be unregulated, but it also need not be command & control by another name. This paper seeks to address some of the implementation challenges associated with managing a spectrum commons. We focus on the minimal set of features that we believe a suitable management protocol, etiquette, or framework for a spectrum commons will need to incorporate. This includes: (1) No transmit only devices; (2) Power restrictions; (3) Common channel signaling; (4) Mechanism for handling congestion and allocating resources among users/uses in times of congestion; (5) Mechanism to support enforcement (e.g., established procedures to verify protocol is in conformance); (6) Mechanism to support reversibility of policy; and (7) Protection for privacy and security. We explain why each is necessary, examine their implications for current policy, and suggest ways in which they might be implemented. We present a framework that suggests a set of design principles for the protocols that will govern a successful commons management regime. Our design rules lead us to conclude that the appropriate Protocols for a Commons will need to be more liquid ([Reed05]) than in the past: (1) Marketbased instead of C&C; (2) Decentralized/distributed; and, (3) Adaptive and flexible (Anonymous, distributed, decentralized, and locally responsive)
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