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Cross Layer Design
-Suparna
Agenda
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Introduction
Signaling Methods
Architecture
Applications
Issues
Proposed solutions
Conclusion & Future Work
References
What lead to CLD?
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Advanced applications like VOIP, Web browsing ,
multimedia conferences & video streaming
demanded
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Widely varying and diverse QoS guarantees
Adaptability to dynamically varying networks & traffic
Modest Buffer requirements
High and effective Capacity utilization
Low processing overhead per packet
Video streaming high bandwidth requirements are coupled with
tight delay constraints
What lead to CLD?
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The approach of any layered
network is to treat different layers
as different entities and perform
layer specific operation independent
of other layers
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TCP is a point-to-point protocol that
sets up a connection bet two
endpoints using a handshake signal,
hence it cannot be used in multicast
environment
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QoS was not an issue for the
application using Layered approach
for providing multi vendor interface
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FIFO buffers were used for resource
handling and sharing
Cross Layer Design
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CLD is a way of achieving information sharing
between all the layers in order to obtain highest
possible adaptivity of any network.
This is required to meet the challenging Data rates,
higher performance gains and Quality of Services
requirements for various real time and non real time
applications.
CLD is a co-operation between multiple layers to
combine the resources and create a network that is
highly adaptive
Cross Layer Design
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This approach allows upper layers to better adapt
their strategies to varying link and network
conditions.
This helps to improve the end-to-end performance
given networks resources.
Each layer is characterized by some key parameters,
that are passed to the adjacent layers to help them
determine the best operation modes that best suit the
current channel, network and application conditions
Cross Layer Design
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Wireless Networking
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Signal processing
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Architecture: Connection Vs
Connectionless
Energy efficient analysis of manets
Traffic theory & protocols
Increasing the spectral efficiency
Reducing Bit Error Rate
Reducing transmission energy
Information Theory
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Developing capacity limits
Designing efficient source coding and
channel algorithms
Cross Layer Signaling Methods
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Method I – Packet headers
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Method II – ICMP Messages
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Method III – Local Profiles
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Method IV – Networks Services
Method I – Packet headers
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Interlayer signaling pipe stores the cross layer
information of the Headers of theIPv6 packets
It makes use of IP data packets as in-band
message carriers
There is no need to use a dedicated message
protocol
Method I – Packet Headers
Method II – ICMP Messages
Method II – ICMP Messages
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A message can be generated at any layer and propagated to
any upper layer, thus a message is transferred using these
holes rather than a pipe as in method I
The messages are propagated through the layers using the
“Internet Control Message Protocol (ICMP)”
This is more flexible and efficient method.
But, ICMP encapsulated message have to pass by network
layer even if the signaling is requires between link and
application layer.
Only upward ICMP messages are reported
Method III – Local Profiles
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Cross layer information is abstracted from
related layer and stored in separate profiles
within a Mobile Host (MH).
Interested layers can select profiles to fetch
desired information.
This is not suitable for time-stringent tasks
like real time applications.
Method III – Local Profile
Method IV – Networks Services
Channel and link information from physical
layer and link layer are gathered, abstracted
and managed by WCI – Wireless channel
Information Servers.
Method IV – Networks Services
Some applications of CLD
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QoS support in the 3Gpp2 Wireless Systems
AD-HOC networks for real-time video
streaming
QoS mapping architecture for video delivery
in wireless network
Multimedia over wireless
Multi hop wireless networks
Application of CLD in AD-HOC Networks for
Real time Video Streaming
CLD for Real Time Video Streaming
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Link Layer: Adaptive techniques are used to maximize the link
rates under varying channel conditions.
MAC Layer: Assigns time slots, codes or frequency bands to
each links.
Network Layer: Network layer operates jointly with MAC layer
to determine the set of network flows that minimizes
congestion.
Transport Layer: Congestion-Distortion optimized scheduling is
performed to control the transmission and retransmission of
packets. It uses a CoDiO Scheduler which selects the most
important packet in terms of video distortion and transmits it in
an order that minimizes congestion. It avoids transmitting
packets in large bursts.
Application Layer: It determines the most efficient encoding
rate that will suite the given requirements for that application
Adaptive Link Layer Technique
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The data rate of the link is improved by adapting
the link layer variation to the variation of the
channel like transmitter power, target BER and
Symbol rate.
Adapting the Packet length depending on the
SINR and the link layer parameters to optimize
throughput.
The optimal packet length L is calculated as
PSNR performance for video Streaming for two
different Networks
Issue 1:Video Delivery in Wireless Networks
(Link layer, Transport Layer & Application Layer)
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Providing better quality of service QoS mapping
techniques so that each video layer is optimally
mapped to its corresponding priority class.
There should be a proper coordination mechanism
between priority transmission system and video
applications. This is because in transmission layer
the QoS is expressed in terms of probability of
buffer overflow and the probability of delay
violation at the link layer. Whereas, in Video
application layer QoS is measured by mean squared
error (MSE) and Peak signal-to-noise ratio (PSNR).
Architecture of a cross layer QoS Management
for video delivery over wireless
QoS Mapping Technique
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The QoS mapping and the Adaptation Module
are the key factors of the cross layer design.
It has to be designed to optimally match
application layer QoS and the link
(Transmission layer) QoS.
The video application layer QoS and linklayer QoS are allowed to interact with each
other and adapt along with the wireless
channel condition.
GOP structure of MPEG video file
QoS Mapping Issues
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Packets from the same GOP structure have to
placed on the same QoS class.
The video playback frame rate at the end user
is F frames/sec. And if the mobile terminal
starts to play back the first video frame of
GOP at time Tp, then for uninterrupted
playback the video frame n in the same GOP
should be received before
Td(n) = Tp + ((n-1)/F)
Solution: Tree search approach
Tree approach for optimal Mapping
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Find out the number of the video layers and mark
them as the stages of the tree
Mark the priority classes as the nodes of the stages
Create all the possible branches in order to account
for all the accumulated buffer occupancies.
Compute the accumulated distortion reduction to
each mapping and after that the optimal mapping
solution will be the route from the leaf node to the
tree root which had the minimum accumulated
distortion reduction.
Solution for Priority Transmission and
Video Application Module
Solution for Priority Transmission and
Video Application Module
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Video coding module sets up a QoS bound r(t) in terms of
expected video distortion (PSNR). It then send a transmit
request (Txreq) to transmission module
Transmission Module offers a set of statistical Qos guarantees
for each priority class. The QoS parameters that provide the
lowest distortion and satisfy the range of video quality
requirement r(t) will be chosen as the QoS parameters for the
transmission.
The transmission module requests the video coding module to
adjust itself to the lower value.
Solution for Priority Transmission and
Video Application Module
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The video coding module sends the selected QoS
parameters to set up the QoS parameters for each
priority class of the network. In the next step the
transmission module acknowledges this after set up
is complete.
The prioritized video bit stream is uploaded onto the
network based on the QoS parameters and the video
layer mapping policy.
Upon the change of the channel service rate,
parameters have to rearranged by using the same
procedure.
Issue:2 Providing Multi User Gain
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In cross Layer Design for wireless networks
on of the important issue is related to
providing multi user gain without
compensating for the QoS requirements of the
users.
CLD Architecture for a Wireless Network
Scheduler
Related Issues
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How to support real time data users simultaneously
with good QoS, with packet delays not exceeding
given thresholds ?
How to support a mixture of real time and non real
time data users simultaneously with real time user
receiving their desired QoS and non real time users
receiving maximum throughput ?
How to fairly allocated Bandwidth among various
user?
Proposed Solution
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The optimal scheduling for a wireless networks
consists of N queues and a single server is serving all
the queues.
The arrival process to each of the queues is assumed
to be i.i.d (independent n identical distribution)
bernoulli process and the channel perceived by each
queue is also i.i.d ON-OFF process.
Then it has been proved that the policy which
minimizes the number of packets in the system is
when the server serves the user whose channel is On
and has the longest queue.
Simulation Results for Traffic Mix Parameters
Issue: 3
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Whenever Cross Layer design is implemented
problems like Time Separation, Stability and
unintended interactions between the layers
have to be taken care of.
This issue deals with these problems with the
help of some examples like Adaptive Rate
MAC Layer.
Rate Adaptive MAC and Minimum
Hop Routing Problem
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The rate adaptive protocol is a simple
variation of IEEE 802.11 MAC Protocol.
The idea behind rate-adaptive MAC protocols
is to send data at higher rates when the
channel quality is good. And such higher rates
can be achieved by changing the modulation
scheme.
Rate Adaptive MAC and Minimum
Hop Routing Problem
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The transmission rate can be set as required
depending on the Modulation scheme
The RTS/CTS are always transmitted at Base rate
At receiver, it measures the signal strength and
figures out the maximum rate at which the Data
can be received given that signal strength
This rate is then communicated through CTS
Then the transmitter send the subsequent ACK
and DATA packets at this data rate.
Plain IEEE 802.11 protocol
Rate Adaptive Mac Protocol
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Using minimum Hop Routing Protocol with higher layers
protocol like Destination Sequenced Distance Vector
(DSDV), then it had some undesirable effects.
DSDV builds routing tables by sending hello packets to
neighbors. Hello packets are broadcast packets that contain
cumulative routing information.
Since hello packets are broadcast packets, they are sent at the
base rate, and thus have a large range.
Minimum-hop routing thus chooses the longest possible hops
on the path, which causes low received signal strength, which
in turn implies a low data rate.
Destination Sequence Distant Vector
Comparison of Adaptive Rate MAC and Plain
IEEE 802.11
Conclusion & Future Work
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CLD is one of the most rapidly growing technologies which
involves cooperation and state information sharing between all
layers, thus bringing a revolutionary approach.
CLD creates some interactions between the layers. Some of these
are intentional but some are unintentional resulting into the poor
performance of the system which is contradictory to why CLD is
used in first place?
As the CLD architecture is not a modular one, everything is
interconnected to other, more complex algorithms have to be
designed.
A system wide CLD can lead to “spaghetti” implementations which
in turn will hamper further innovations and it becomes difficult to
maintain.
Questions?
References
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Introduction:
http://www.iet.ntnu.no/projects/cuban/archive/1812041.pdf
http://www.tech.plym.ac.uk/see/research/cdma/Papers/QWang%20EPMC
C03%20paper.pdf
Architecture:
http://www.stanford.edu/~esetton/Wcomm.pdf
http://ieeexplore.ieee.org/iel5/7742/32173/01497859.pdf?tp=&arnumber=
1497859&isnumber=32173
issue:1
http://ieeexplore.ieee.org/iel5/9692/30597/01417549.pdf?tp=&arnumber=
1417549&isnumber=30597
http://140.98.193.112/iel5/49/28068/01254584.pdf?tp=&arnumber=12545
84&isnumber=28068
References
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Issue2:
http://140.98.193.112/iel5/49/28068/01254584.pdf?tp=&arnumber=1254584&isn
umber=28068
http://www.tech.plym.ac.uk/see/research/cdma/Papers/QWang%20EPMCC03%20
paper.pdf
http://ieeexplore.ieee.org/iel5/35/27698/01235598.pdf?tp=&arnumber=1235598&
isnumber=27698
Issue3:
http://ieeexplore.ieee.org/iel5/7742/30466/01404568.pdf?tp=&arnumber=1404568
&is%20%20%20number=30