Spelling suggestions: "subject:"netwerkkodering"" "subject:"netzwerkkodierung""
1 |
Comparing network coding implementations on different OSI layers / Jacobus Leendert van WykVan Wyk, Jacobus Leendert January 2010 (has links)
Network coding is a technique used to increase the capacity of a network by combining messages
sent over the network. The combined messages could be separated by using sufficient original
messages which were used to combine the messages. Network coding can be implemented in
different layers of the 051 stack, but to date a complete comparison between different
implementations of network coding has not been done.
The goal of this dissertation is to implement a wireless node model with network coding in the MAC
layer and evaluate the performance characteristics of reference networks that implement the new
node model. This will serve as the first step of a greater goal, namely finding the most favourable
position in the 051 stack to implement network coding. The characteristics of the different
implementations of network coding are presented in this dissertation. Simulations were done in
OPNET® to find further attributes concerning the implementation of network coding in the MAC
layer.
The simulation process used is presented and explained, and the results from the simulations are
analysed. Network coding in the simulations was implemented opportunistically. The results show
that the more often different nodes send frames to the coding node, the better network coding
performs.
The work contributes to finding the best layer for implementing network coding for its increased
throughput. A benchmark network was created so that network coding could be implemented in all
the layers of the 051 stack, and then be compared to each other. An implementation of network
coding in the MAC layer was simulated and analyzed.
We conclude that, because there are so many different purposes for which networks are used, a
single instance of network coding is unlikely to be similarly beneficial to all purposes. There still
remains work to find the most favourable position for network coding in the 051 stack for all the
different types of network coding. / Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011
|
2 |
Comparing network coding implementations on different OSI layers / Jacobus Leendert van WykVan Wyk, Jacobus Leendert January 2010 (has links)
Network coding is a technique used to increase the capacity of a network by combining messages
sent over the network. The combined messages could be separated by using sufficient original
messages which were used to combine the messages. Network coding can be implemented in
different layers of the 051 stack, but to date a complete comparison between different
implementations of network coding has not been done.
The goal of this dissertation is to implement a wireless node model with network coding in the MAC
layer and evaluate the performance characteristics of reference networks that implement the new
node model. This will serve as the first step of a greater goal, namely finding the most favourable
position in the 051 stack to implement network coding. The characteristics of the different
implementations of network coding are presented in this dissertation. Simulations were done in
OPNET® to find further attributes concerning the implementation of network coding in the MAC
layer.
The simulation process used is presented and explained, and the results from the simulations are
analysed. Network coding in the simulations was implemented opportunistically. The results show
that the more often different nodes send frames to the coding node, the better network coding
performs.
The work contributes to finding the best layer for implementing network coding for its increased
throughput. A benchmark network was created so that network coding could be implemented in all
the layers of the 051 stack, and then be compared to each other. An implementation of network
coding in the MAC layer was simulated and analyzed.
We conclude that, because there are so many different purposes for which networks are used, a
single instance of network coding is unlikely to be similarly beneficial to all purposes. There still
remains work to find the most favourable position for network coding in the 051 stack for all the
different types of network coding. / Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011
|
3 |
An optimisation approach to improve the throughput in wireless mesh networks through network coding / van der Merwe C.Van der Merwe, Corna January 2011 (has links)
In this study, the effect of implementing Network Coding on the aggregated throughput in Wireless
Mesh Networks, was examined. Wireless Mesh Networks (WMNs) are multiple hop wireless networks,
where routing through any node is possible. The implication of this characteristic, is that messages
flow across the points where it would have been terminated in conventional wireless networks. User
nodes in conventional wireless networks only transmit and receive messages from an Access Point
(AP), and discard any messages not intended for them.
The result is an increase in the volume of network traffic through the links of WMNs. Additionally,
the dense collection of multiple RF signals propagating through a shared wireless medium, contributes
to the situation where the links become saturated at levels below their capacity. The need exists to
examine methods that will improve the utilisation of the shared wireless medium in WMNs.
Network Coding is a coding and decoding technique at the network level of the OSI stack, aimed to
improve the boundaries of saturated links. The technique implies that the bandwidth is simultaneously
shared amongst separate message flows, by combining these flows at common intermediate nodes.
The number of transmissions needed to convey information through the network, is decreased by
Network Coding. The result is in an improvement of the aggregated throughput.
The research approach followed in this dissertation, includes the development of a model that
investigates the aggregated throughput performance of WMNs. The scenario of the model, followed a
typical example of indoors WMN implementations. Therefore, the physical environment representation
of the network elements, included an indoors log–distance path loss channel model, to account for the
different effects such as: power absorption through walls; and shadowing.
Network functionality in the model was represented through a network flow programming problem.
The problem was concerned with determining the optimal amount of flow represented through the
links of the WMN, subject to constraints pertaining to the link capacities and mass balance at each
node. The functional requirements of the model stated that multiple concurrent sessions were to
be represented. This condition implied that the network flow problem had to be a multi–commodity
network flow problem.
Additionally, the model requirements stated that each session of flow should remain on a single path.
This condition implied that the network flow problem had to be an integer programming problem.
Therefore, the network flow programming problem of the model was considered mathematically
equivalent to a multi–commodity integer programming problem. The complexity of multi–commodity
integer programming problems is NP–hard. A heuristic solving method, Simulated Annealing, was implemented to solve the goal function represented by the network flow programming problem of the model.
The findings from this research provide evidence that the implementation of Network Coding in
WMNs, nearly doubles the level of the calculated aggregated throughput values. The magnitude of
this throughput increase, can be further improved by additional manipulation of the network traffic
dispersion. This is achieved by utilising link–state methods, rather than distance vector methods, to
establish paths for the sessions of flow, present in the WMNs. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.
|
4 |
An optimisation approach to improve the throughput in wireless mesh networks through network coding / van der Merwe C.Van der Merwe, Corna January 2011 (has links)
In this study, the effect of implementing Network Coding on the aggregated throughput in Wireless
Mesh Networks, was examined. Wireless Mesh Networks (WMNs) are multiple hop wireless networks,
where routing through any node is possible. The implication of this characteristic, is that messages
flow across the points where it would have been terminated in conventional wireless networks. User
nodes in conventional wireless networks only transmit and receive messages from an Access Point
(AP), and discard any messages not intended for them.
The result is an increase in the volume of network traffic through the links of WMNs. Additionally,
the dense collection of multiple RF signals propagating through a shared wireless medium, contributes
to the situation where the links become saturated at levels below their capacity. The need exists to
examine methods that will improve the utilisation of the shared wireless medium in WMNs.
Network Coding is a coding and decoding technique at the network level of the OSI stack, aimed to
improve the boundaries of saturated links. The technique implies that the bandwidth is simultaneously
shared amongst separate message flows, by combining these flows at common intermediate nodes.
The number of transmissions needed to convey information through the network, is decreased by
Network Coding. The result is in an improvement of the aggregated throughput.
The research approach followed in this dissertation, includes the development of a model that
investigates the aggregated throughput performance of WMNs. The scenario of the model, followed a
typical example of indoors WMN implementations. Therefore, the physical environment representation
of the network elements, included an indoors log–distance path loss channel model, to account for the
different effects such as: power absorption through walls; and shadowing.
Network functionality in the model was represented through a network flow programming problem.
The problem was concerned with determining the optimal amount of flow represented through the
links of the WMN, subject to constraints pertaining to the link capacities and mass balance at each
node. The functional requirements of the model stated that multiple concurrent sessions were to
be represented. This condition implied that the network flow problem had to be a multi–commodity
network flow problem.
Additionally, the model requirements stated that each session of flow should remain on a single path.
This condition implied that the network flow problem had to be an integer programming problem.
Therefore, the network flow programming problem of the model was considered mathematically
equivalent to a multi–commodity integer programming problem. The complexity of multi–commodity
integer programming problems is NP–hard. A heuristic solving method, Simulated Annealing, was implemented to solve the goal function represented by the network flow programming problem of the model.
The findings from this research provide evidence that the implementation of Network Coding in
WMNs, nearly doubles the level of the calculated aggregated throughput values. The magnitude of
this throughput increase, can be further improved by additional manipulation of the network traffic
dispersion. This is achieved by utilising link–state methods, rather than distance vector methods, to
establish paths for the sessions of flow, present in the WMNs. / Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2012.
|
Page generated in 0.0788 seconds