3 research outputs found
An Extended Network Coding Opportunity Discovery Scheme in Wireless Networks
Network coding is known as a promising approach to improve wireless network
performance. How to discover the coding opportunity in relay nodes is really
important for it. There are more coding chances, there are more times it can
improve network throughput by network coding operation. In this paper, an
extended network coding opportunity discovery scheme (ExCODE) is proposed,
which is realized by appending the current node ID and all its 1-hop neighbors'
IDs to the packet. ExCODE enables the next hop relay node to know which nodes
else have already overheard the packet, so it can discover the potential coding
opportunities as much as possible. ExCODE expands the region of discovering
coding chance to n-hops, and have more opportunities to execute network coding
operation in each relay node. At last, we implement ExCODE over the AODV
protocol, and efficiency of the proposed mechanism is demonstrated with NS2
simulations, compared to the existing coding opportunity discovery scheme.Comment: 15 pages and 7 figure
Network coding: performance analysis and robust design in multi-hop wireless mesh networks
Network coding is an innovative idea to boost the capacity of wireless networks. However,
there are not enough analytical studies on throughput and end-to-end delay of network
coding in multi-hop wireless mesh network that incorporates the specifications of IEEE
802.11 Distributed Coordination Function. In this dissertation, we utilize queuing theory
to propose an analytical framework for bidirectional unicast flows in multi-hop wireless
mesh networks. We study the throughput and end-to-end delay of inter-flow network
coding under the IEEE 802.11 standard with CSMA/CA random access and exponential
back-o↵ time considering clock freezing and virtual carrier sensing, and formulate several
parameters such as the probability of successful transmission in terms of bit error rate and
collision probability, waiting time of packets at nodes, and retransmission mechanism. Our
model uses a multi-class queuing network with stable queues, where coded packets have
a non-preemptive higher priority over native packets, and forwarding of native packets
is not delayed if no coding opportunities are available. The accuracy of our analytical
model is verified using computer simulations.
Furthermore, while inter-flow network coding is proposed to help wireless networks
approach the maximum capacity, the majority of research conducted in this area is yet to
fully utilize the broadcast nature of wireless networks, and to perform e↵ectively under
poor channel quality. This vulnerability is mostly caused by assuming fixed route between
the source and destination that every packet should travel through. This assumption not only limits coding opportunities, but can also cause bu↵er overflow at some specific
intermediate nodes. Although some studies considered scattering of the flows dynamically
in the network, they still face some limitations. This dissertation explains pros and cons
of some prominent research in network coding and proposes a Flexible and Opportunistic
Network Coding scheme (FlexONC) as a solution to such issues. Moreover, this research
discovers that the conditions used in previous studies to combine packets of di↵erent flows
are overly optimistic and would a↵ect the network performance adversarially. Therefore,
we provide a more accurate set of rules for packet encoding. The experimental results
show that FlexONC outperforms previous methods especially in networks with high bit
error rates, by better utilizing redundant packets permeating the network, and benefiting
from precise coding conditions