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Cross Layer Design


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Title: Cross Layer Design

Cross Layer Design
  • -Suparna

  • Introduction
  • Signaling Methods
  • Architecture
  • Applications
  • Issues
  • Proposed solutions
  • Conclusion Future Work
  • References

What lead to CLD?
  • Advanced applications like VOIP, Web browsing ,
    multimedia conferences video streaming demanded
  • Widely varying and diverse QoS guarantees
  • Adaptability to dynamically varying networks
  • 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?
  • The approach of any layered network is to treat
    different layers as different entities and
    perform layer specific operation independent of
    other layers
  • 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
  • QoS was not an issue for the application using
    Layered approach for providing multi vendor
  • FIFO buffers were used for resource handling and

Cross Layer Design
  • 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
  • This approach allows upper layers to better adapt
    their strategies to varying link and network
  • 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
  • Wireless Networking
  • Architecture Connection Vs Connectionless
  • Energy efficient analysis of manets
  • Traffic theory protocols
  • Signal processing
  • Increasing the spectral efficiency
  • Reducing Bit Error Rate
  • Reducing transmission energy
  • Information Theory
  • Developing capacity limits
  • Designing efficient source coding and channel

Cross Layer Signaling Methods
  • Method I Packet headers
  • Method II ICMP Messages
  • Method III Local Profiles
  • Method IV Networks Services

Method I Packet headers
  • 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

Method I Packet Headers Method II ICMP
Method II ICMP Messages
  • 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
  • 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
  • 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

Method IV Networks Services
Some applications of CLD
  • 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
  • Link Layer Adaptive techniques are used to
    maximize the link rates under varying channel
  • 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
  • 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
  • The optimal packet length L is calculated as

PSNR performance for video Streaming for two
different Networks
Issue 1Video Delivery in Wireless Networks (Link
layer, Transport Layer Application Layer)
  • 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
  • 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 link-layer
    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
  • 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
  • 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
  • Create all the possible branches in order to
    account for all the accumulated buffer
  • 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
  • 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
  • The transmission module requests the video coding
    module to adjust itself to the lower value.

Solution for Priority Transmission and Video
Application Module
  • 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

Issue2 Providing Multi User Gain
  • 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
Related Issues
  • 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

Proposed Solution
  • 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
  • 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
  • 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

Rate Adaptive MAC and Minimum Hop Routing Problem
  • 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
  • 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
  • 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
  • Since hello packets are broadcast packets, they
    are sent at the base rate, and thus have a large
  • 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
Conclusion Future Work
  • 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.

  • Introduction
  • http//
    041.pdf http//
  • Architecture
  • http//
  • http//
  • issue1 http//
  • http//

  • Issue2 http//
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  • Issue3 http//