Wireless Mesh Network

homuskratNetworking and Communications

Nov 20, 2013 (3 years and 9 months ago)

85 views

Wireless Mesh Network


指導教授:吳和庭教授、柯開維教授

報告:江昀庭


Source reference:

Akyildiz
, I.F.

and
Xudong

Wang “
A survey on
wireless mesh
networks


IEEE Communications
Magazine,
Sep., 2005, p23
-
30.

1

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


2

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


3

Introduction


Wireless Mesh
Network(WMNs)


WMNs are comprised of two types of nodes:


mesh routers


mesh clients


Wireless can access without NICs by connecting to
wireless mesh router


WMNs will be always
-
on
-
line anywhere, anytime


WMNs can use IEEE802.11 IEEE802.15 IEEE802.16




4

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


5

Network Architecture



Client
meshing provides
peer
-
to
-
peer
networks
among
client
devices.



The mesh
routers form
a mesh of
self
-
configuring
,
self
-
healing

links
among themselves
.

6

7

Network Architecture


Hybrid WMNs


WMNs are multi
-
hop wireless networks.


Mesh clients can access the network through mesh routers
as well as directly meshing with other mesh
clients


Routing
capabilities of clients provide improved
connectivity and coverage inside WMNs.

//

!


WMNs support
ad hoc
networking, and have the capability



of
self
-
forming, self
-
healing, and self
-
organization
.

8

9

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


10

Critical Design Factors



Radio
Techniques


Scalability


Mesh Connectivity


Broadband and
QoS


Security


Ease of Use


Compatibility and Inter
-
operability


11

Radio
Techniques



Directional
and smart antennas, multiple input multiple output
(MIMO) systems, and multi
-
radio/multi
-
channel systems
.



To
further improve the
performance

of a wireless
radio,
reconfigurable
radios
,
frequency agile/cognitive
radios
, and
even
software radios
, have
been used
for wireless
communication.

12

Scalability



Mesh
= high
scalability



All protocols from the MAC layer to the application layer need
to be scalable

13

Mesh Connectivity


To
ensure reliable mesh connectivity, network self
-
organization and topology control
algorithm
s are needed
.


Topology
-
aware
MAC and routing protocols
can significantly
improve the performance of
WMNs

14

Broadband and
QoS



Most applications of WMNs are broadband services


with heterogeneous
QoS

requirements

Security


It’s
a problem and one of the future work in this paper because
most of the security solutions for ad hoc networks are still
not
mature enough to be implemented
practically.

15

Ease of Use



Network management tools need to be developed to efficiently
maintain the operation
,
monitor the performance
, and
configure the parameters
of WMNs.

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


16

Network
Capacity



A
node should only communicate with
nearby
nodes
(cost)



Throughput capacity can be increased by deploying relaying
nodes
.



Nodes need to be grouped into clusters.

17

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


18

Physical layer



Advanced Physical
-
Layer Techniques



Orthogonal frequency multiple access (OFDM
)


Ultra
-
wide band (UWB) techniques

19

Mac layer


MAC for WMNs is concerned with more than one
-
hop
communication.


MAC is distributed, needs to be collaborative, and works for
multipoint
-
to
-
multipoint communication.


Network self
-
organization is needed for better collaboration
between neighboring nodes and nodes in multi
-
hop distances.


Mobility is low but still affects the performance of MAC.


A MAC protocol for WMNs can be designed to work on a
single channel or multiple channels simultaneously.

20

Routing layer


Many existing routing protocols use minimum hop
-
count as a
performance metric to select the routing path.


Scalability
. Setting up or maintaining a routing path in a very
large wireless network may take a long time. Thus, it is critical
to have a scalable routing protocol in WMNs.


Robustness
. To avoid service disruption, WMNs must
be
robust
to link failures or congestion. Routing protocols
also
need
to perform load balancing
.


Efficient Routing with Mesh Infrastructure


21

Transport layer

TCP variants improve the performance of the classical

TCPs by tackling the following problems.


Non
-
Congestion Packet Losses.


Unknown Link Failure.


Network Asymmetry


Large RTT Variations

22

Application Layer


Numerous
applications supported by WMNs can be categorized
into several classes.



Internet Access



Distributed Information Storage and Sharing

23

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


24

Network Management




Mobility
Management



Power
Management



Network
Monitoring


25

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


26

Security



Two
more strategies need to be considered
:

o
Embedding
security mechanisms
into network protocols
such as secure
routing
MAC
protocols

o
Developing
security monitoring
and
response systems
to
detect
attacks.

27

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


28

Cross
-
Layer Design



Cross
-
layer
design can be performed in two ways
.



The first approach is to improve the performance of a
protocol layer by
taking into account parameters in other
protocol layers
. Typically, parameters in the lower protocol
layers are reported to higher
layers.


The
second approach of

is
to
merge several protocols into
one component
. For
example, in
ad hoc networks, MAC
and routing protocols can
be combined
into one protocol in
order to closely consider
their interactions
.

29

Overview


Introduction


Network Architecture


Critical Design Factors


Advances and Research Challenges


Network Capacity


Layered Communication Protocols


Network Management


Security


Cross
-
Layer Design


Conclusion


30

Conclusion


Scalability
. Based on existing MAC, routing, and transport
protocols, network performance is not scalable with either the
number of nodes or the number of hops in the network
.



Security
. WMNs are vulnerable to security attacks in various
protocol layers. Current security approaches may be effective
to a
particular
attack in a specific protocol layer
.



Self
-
organization

and
self
-
configuration

capability is
a desired
feature in WMNs. It requires protocols
in WMNs
to be
distributive and collaborative.

31

Reference

[1]
J. So and N.
Vaidya
, “Multi
-
Channel MAC for ad hoc
Networks:
Handling Multi
-
Channel
Hidden Terminals using a
Single Transceiver,”
ACM Int’l
.
Symp
. Mobile Ad Hoc Net. and
Comp. (MOBIHOC), May 2004,
pp. 222

33.

[2
] Markus Winter and Steffen
Prusseit

and Gerhard P.
Fettweis

“Hierarchical Routing Architectures in Clustered
2D
-
MeshNetworks
-
on
-
Chip”



32

Q & A


33

Thanks for your listen

34