Adaptive quality of service
Encyclopedia
In multi-hop networks, Adaptive Quality of Service routing (AQoS or AQR) protocols have become increasingly popular and have numerous applications. One application in which it may be useful is in Mobile ad hoc network
ing (MANET).
Adaptive QoS routing is a cross-layer optimization
adaptive routing
mechanism. The cross-layer mechanism provides up-to-date local QoS information for the adaptive routing algorithm, by considering the impacts of node mobility and lower-layer link performance. The multiple QoS requirements are satisfied by adaptively using forward error correction and multipath routing mechanisms, based on the current network status. The complete routing mechanism includes three parts: (1) a modified dynamic source routing algorithm that handles route discovery and the collection of QoS related parameters; (2) a local statistical computation and link monitoring function located in each node; and (3) an integrated
decision-making system to calculate the number of routing paths, coding parity length, and traffic distribution rates.
The adaptive cooperation concept has future promisses to overcome infrastructure loaded approaches and to get rid of central facilities with autonomous networks in industrial and home applications.
The United States Air Force is determining the best way to employ QoS protocols into Airborne Networking
. Research composed shows that Adaptive QoS that uses cross-layer cooperation has provided the best results for military applications.
The emergence of multimedia applications in communications has generated the need to provide
mobile quality-of-service (QoS) support in ad hoc networks, and such applications require a stable path to guarantee QoS requirements. However, the topology of ad hoc networks is highly dynamic due to the unpredictable node mobility. In addition, wireless channel bandwidth is limited. So, QoS provisioning in such networks is complex and challenging.
QoS routing usually involves two tasks: collecting and maintaining up-to-date state information about the network and finding feasible paths for a connection based on its QoS requirements. Many approaches currently exist to perform QoS routing, most of which consist of routing across the Network layer
of the OSI model
only. Some approaches utilize both the Network and Data link layer
but do not consider the cross layer behaviors. This makes quantifying the QoS parameters difficult and leads to considerations of QoS but does not guarantee QoS.
To address this problem, appropriate cross-layer cooperation is required. Adaptive QoS schemes provide QoS information by factoring the impacts of node mobility and lower-layer link parameters into QoS performance.
Amultiobjective optimization algorithm is used to calculate routing parameters using the cross-layer mechanism. These parameters are adapted to the current network status, determining the number of routing paths and code parity lengths for Forward Error Correction
(FEC). In addition, a traffic engineering strategy is used to evenly distribute traffic over multiple paths.
routes. Second, there is a local statistical computation and link monitoring function located in each node. This function is used to support the above routing function. It will manage
and build the local routing information in each node, which includes a QoS-related table. The third function will be in charge of the final decision-making process. The adaptive
routing parameters are derived from the decision-making algorithm based on the QoS constraints. They are the number N of selected paths, parity length k of the FEC, code and the set {R} of the traffic distribution rates on each path. With these functions, adaptive multipath QoS routing is implemented.
QoS requirements can be based on either a delay or a delay and bandwidth requirement, or a packet loss requirement. FEC parity length is derived from the difference between the QoS
delay requirement and the average delay on selected paths under the packet-loss constraint. Average packet loss under this FEC scheme is achieved by using multiple routing paths.
At the same time, the packet distribution rate on each path is determined under fair packet-loss and load-balance principles. Routing maintenance under the same QoS guarantees
is achieved without increasing its computational complexity.
routing scheme are reduced. Also, since routes are discovered based on the up-to-date local information and selected by the optimization computation, routing parameters (e.g., number of paths, FEC parity length, and traffic distribution rate) are dynamic and optimized. In addition
to supporting multiple QoS requirements, traffic balancing and bandwidth resources are factored into our decisionmaking process. The distributed structure of the local QoS statistics used in the routing enables this QoS support mechanism to be scalable in mobile networks. Simulation
results indicate that the performance (i.e., packet loss and end-to-end delay) are much better and less susceptible to the state changes (i.e., node mobility, transmission power, channel characteristics, and the traffic pattern) of the network, compared to a nonadaptive routing strategy.
Mobile ad hoc network
A mobile ad-hoc network is a self-configuring infrastructureless network of mobile devices connected by wireless links. ad hoc is Latin and means "for this purpose"....
ing (MANET).
Adaptive QoS routing is a cross-layer optimization
Cross-layer optimization
Cross-layer optimization is an escape from the pure waterfall-like concept of the OSI communications model with virtually strict boundaries between layers. The cross layer approach transports feedback dynamically via the layer boundaries to enable the compensation for e.g...
adaptive routing
Adaptive routing
Adaptive routing describes the capability of a system, through which routes are characterized by their destination, to alter the path that the route takes through the system in response to a change in conditions...
mechanism. The cross-layer mechanism provides up-to-date local QoS information for the adaptive routing algorithm, by considering the impacts of node mobility and lower-layer link performance. The multiple QoS requirements are satisfied by adaptively using forward error correction and multipath routing mechanisms, based on the current network status. The complete routing mechanism includes three parts: (1) a modified dynamic source routing algorithm that handles route discovery and the collection of QoS related parameters; (2) a local statistical computation and link monitoring function located in each node; and (3) an integrated
decision-making system to calculate the number of routing paths, coding parity length, and traffic distribution rates.
The adaptive cooperation concept has future promisses to overcome infrastructure loaded approaches and to get rid of central facilities with autonomous networks in industrial and home applications.
The United States Air Force is determining the best way to employ QoS protocols into Airborne Networking
Airborne Networking
An Airborne Network is defined to be the infrastructure that provides communication transport services through at least one node that is on a platform capable of flight.-Definition:...
. Research composed shows that Adaptive QoS that uses cross-layer cooperation has provided the best results for military applications.
Introduction
A wireless ad hoc network consists of a collection of mobile nodes interconnected by multihop wireless paths with wireless transmitters and receivers. Such networks can be spontaneously created and operated in a self-organized manner, because they do not rely upon any preexisting network infrastructure.The emergence of multimedia applications in communications has generated the need to provide
mobile quality-of-service (QoS) support in ad hoc networks, and such applications require a stable path to guarantee QoS requirements. However, the topology of ad hoc networks is highly dynamic due to the unpredictable node mobility. In addition, wireless channel bandwidth is limited. So, QoS provisioning in such networks is complex and challenging.
QoS routing usually involves two tasks: collecting and maintaining up-to-date state information about the network and finding feasible paths for a connection based on its QoS requirements. Many approaches currently exist to perform QoS routing, most of which consist of routing across the Network layer
Network layer
The network layer is layer 3 of the seven-layer OSI model of computer networking.The network layer is responsible for packet forwarding including routing through intermediate routers, whereas the data link layer is responsible for media access control, flow control and error checking.The network...
of the OSI model
OSI model
The Open Systems Interconnection model is a product of the Open Systems Interconnection effort at the International Organization for Standardization. It is a prescription of characterizing and standardizing the functions of a communications system in terms of abstraction layers. Similar...
only. Some approaches utilize both the Network and Data link layer
Data link layer
The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....
but do not consider the cross layer behaviors. This makes quantifying the QoS parameters difficult and leads to considerations of QoS but does not guarantee QoS.
To address this problem, appropriate cross-layer cooperation is required. Adaptive QoS schemes provide QoS information by factoring the impacts of node mobility and lower-layer link parameters into QoS performance.
Traditional QoS Approaches
Most QoS approaches tend to focus on only one QoS parameter (e.g., packet loss, end-to-end delay, and bandwidth). For example, while many of the QoS-related schemes are successful in reducing packet loss by adding redundancy in the packet, they do this at the expense of end-to-end delay. Because packet loss and end-to-end delay are inversely related, it may not be possible to find a path that simultaneously satisfies the delay, packet loss, and bandwidth constraints. Some proposed QoS routing algorithms do consider multiple metrics, but without considering cross-layer cooperation. Multipath routing is another type of QoS routing that has received much attention, since it can provide load balancing, fault tolerance, and higher aggregate bandwidth. Although this approach decreases packet loss and end-to-end delay, it is only efficient and reliable if a relationship can be found between the number of paths and QoS constraints.Adaptive QoS
Adaptive QoS is a cross-layer cooperation mechanism that supports adaptive multipath routing with multiple QoS constraints in an ad hoc network. The cross-layermechanism provides information on link performance for the QoS routing. It treats traffic distribution, wireless link characteristics, and node mobility in an integrated fashion. That is, it reflects the impacts of lower-layer parameters on QoS performance in higher layers, with emphasis on translating these parameters into QoS parameters for the higher-layer connections.Amultiobjective optimization algorithm is used to calculate routing parameters using the cross-layer mechanism. These parameters are adapted to the current network status, determining the number of routing paths and code parity lengths for Forward Error Correction
Forward error correction
In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
(FEC). In addition, a traffic engineering strategy is used to evenly distribute traffic over multiple paths.
Adaptive QoS Scheme Overview
To implement an adaptive multipath routing scheme, three functions distributed in different parts of the network are needed. First, a modified dynamic source routing function is needed. It handles route discovery and collecting the local QoS-related information along the selectedroutes. Second, there is a local statistical computation and link monitoring function located in each node. This function is used to support the above routing function. It will manage
and build the local routing information in each node, which includes a QoS-related table. The third function will be in charge of the final decision-making process. The adaptive
routing parameters are derived from the decision-making algorithm based on the QoS constraints. They are the number N of selected paths, parity length k of the FEC, code and the set {R} of the traffic distribution rates on each path. With these functions, adaptive multipath QoS routing is implemented.
QoS requirements can be based on either a delay or a delay and bandwidth requirement, or a packet loss requirement. FEC parity length is derived from the difference between the QoS
delay requirement and the average delay on selected paths under the packet-loss constraint. Average packet loss under this FEC scheme is achieved by using multiple routing paths.
At the same time, the packet distribution rate on each path is determined under fair packet-loss and load-balance principles. Routing maintenance under the same QoS guarantees
is achieved without increasing its computational complexity.
Adaptive QoS Performance
Three functions (routing function, local statistic computation and monitoring function, and integrated decisionmaking function) are implemented in the different parts of the mobile network. Due to the distributed structure, the computation and implementation complexity of therouting scheme are reduced. Also, since routes are discovered based on the up-to-date local information and selected by the optimization computation, routing parameters (e.g., number of paths, FEC parity length, and traffic distribution rate) are dynamic and optimized. In addition
to supporting multiple QoS requirements, traffic balancing and bandwidth resources are factored into our decisionmaking process. The distributed structure of the local QoS statistics used in the routing enables this QoS support mechanism to be scalable in mobile networks. Simulation
results indicate that the performance (i.e., packet loss and end-to-end delay) are much better and less susceptible to the state changes (i.e., node mobility, transmission power, channel characteristics, and the traffic pattern) of the network, compared to a nonadaptive routing strategy.