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Cross Layer Design (CLD) for Wireless Networks

Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

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Page 1: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Cross Layer Design (CLD) for Wireless Networks

Page 2: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Future Wireless Systems

Nth Generation CellularWireless Internet AccessWireless Video/Music Wireless Ad Hoc NetworksSensor Networks Smart Homes/AppliancesAutomated Vehicle NetworksAll this and more…

Ubiquitous Communication Among People and Devices

Page 3: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Next Generation Network Architecture

MobilityServices

Layer

RadioAccessLayer

MobileTerminal

Layer

InternetworkingLayer

LocalServiceLayer

NetworkServiceLayer

AccessManagement

Layer

AccessInterface

Layer

WirelessInterface

Layer

MobileApplication

Layer

Internet Wireless PSTN

Page 4: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Radio Access Network

Radio Access NetworkMobile User Equipment(e.g. Win9X, Palm OS)

Mobile User Equipment(e.g. Win9X, Palm OS)

Application

Network Server(e.g. WinNT, Unix)

Network Server(e.g. WinNT, Unix)

IP Transport(TCP, UDP, RTP)

Internet Protocol(IP)

RadioAccess

RadioAccessModemModemEthernetEthernet

Application

IP Transport(TCP, UDP, RTP)

Internet Protocol(IP)

EthernetEthernet ATMATMInternet

TransportAgents

TransportAgents

IP

RadioResourceMgmt

RadioL1

AccessL1

RadioL2

AccessL2

AccessL1

CoreL1

AccessL2

CoreL2

Radio-Optimized IP Networking• Transparent to TCP/IP protocols• Enables deployment of IP-based consumer applications in next generation wireless systems

Page 5: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Our simplified model for wireless systems

Application

Presentation

Session

Transport

Network

Data Link

Physical

(MAC sublayer)

OSI Model

Physical Layer

MAC Layer

Network Layer

Transport Layer

App. Layer

Simplified wireless network layered model

Page 6: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Separation principles Application, transport

and physical layer can be separated if : No errors at physical layer

No losses and delays at transport layer

No fluctuations in applications rate

Each layer being perfect from the point of view of other layers

Application

Transport

Physical

Signal

Packet

Bits

Page 7: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Challenges Wireless channels are a difficult and capacity-

limited broadcast communications medium

Traffic patterns, user locations, and network conditions are constantly changing

Applications are heterogeneous with hard constraints that must be met by the network

Energy and delay constraints change design principles across all layers of the protocol stack

These challenges apply to all wireless networks, but are amplified in ad hoc/sensor networks

Page 8: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Why is Wireless Hard?The Wireless Channel

Fundamentally Low Capacity: R< B log(1+SINR) bps Spectrum scarce and expensive

Received power diminishes with distance Self-interference due to multipath Channel changes as users move around Signal blocked by objects (cars, people, etc.) Broadcast medium – everyone interferes

d

Page 9: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

…And The Wireless Network

Link characteristics are dynamic Network access is unpredictable and hard to coordinate Routing often multi-hop over multiple wireless/wired channels Network topology is dynamic Different applications have different requirements

Wireline Backbone

• They are formed by nodes with radios– There is no a priori notion of “links”– Nodes simply radiate energy

Page 10: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

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 & 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

Page 11: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

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

Page 12: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Cross Layer Design

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

Page 13: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

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 algorithms

Page 14: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Cross Layer Design

General framework for cross–layer design Maintain the layered approach but exchange information between layers

and jointly optimize the performance Abstraction of layers

General models for different layers capture important parameters which influence other layers Identify the cross-layer information that has to be exchanged between layers

Implement adaptation protocols at each layer, using the information exchange between the layers

Several tools for analysis and optimization at different layers Physical layer

determine SIR as a key performance measure for the physical layer Optimize powers, receivers, antennas

MAC and Network layers QoS measures: Delay and blocking performance Optimize scheduling, routes, number of users allowed in the network

Page 15: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Cross Layer Signaling Methods

Method I – Packet headers

Method II – ICMP Messages

Method III – Local Profiles

Method IV – Networks Services

Page 16: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

CLD Design goal ? Deliver QoS

QoS measures Physical layer

BER (Bit error rate) MAC layer

Access delay, throughput Network layer

Delay, throughput, blocking probability, dropping probability Other important performance measures

Energy (power consumption, network lifetime) User capacity

Impact all layers

Page 17: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

QoS Requirements

Voice VideoData

Delay

Packet Loss

BER

Data Rate

Traffic

<100ms - <100ms

<1% 0 <1%

10-3 10-6 10-6

8-32 Kbps 1-100 Mbps 1-20 Mbps

Continuous Bursty Continuous

One-size-fits-all protocols and design do not work well

Wired networks use this approach, with poor results

Page 18: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

CLD

Hardware Link Access Network Application

Delay ConstraintsRate Constraints

Energy Constraints

Adapt across design layersReduce uncertainty through scheduling

Provide robustness via diversity

Page 19: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Examples of cross-layer integration for ad-hoc networks Physical layer + MAC

Adaptive beamforming and CSMA/CA Adaptive modulation and MAC Adaptive power control and MAC

Physical layer + network layer Adaptive power control + routing Adaptive power control + receiver optimization + routing Power control + routing + receiver optimization +

admission control Physical layer + MAC + routing

Adaptive modulation + MAC + routing Adaptive beamforming + MAC + routing

Page 20: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Case 1: Adaptive beamforming + MAC + routing In general, different MAC protocols differ

based on How RTS/CTS is transmitted (omni, directional) Transmission range of directional antennas Channel access schemes Omni or directional NAVs

The antenna gains are different for omnidirectional (Go) and directional transmission (Gd): Gd > Go

An idle node listens omnidirectionally Does not know who is going to transmit to it

Page 21: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Pros and Cons for directional antennasAdvantagesSpatial reuseMultiple transmissions in the same neighborhood

Higher gains – better links Two distant nodes may communicate with a single hop Fewer hops in a route

DisadvantagesHigher gains mean also high interference at distanced nodes

There are three types of links omnidirectional – omnidirectional : OO links – smallest range directional – omnidirectional: DO links directional –directional – largest range

Page 22: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Joint MAC and routing solution

Use the same MAC for directional antennas, but transmit RTS over multiple hops (MMAC protocol)

If source 1 wants to communicate with node 6 transmits a forwarding RTS with the profile of node 6, using DO links when node 6 gets the RTS, it beamforms in the direction of 1, forming a

DD link

Transmission from 1 to 9 on DD links requires only 2 hops

Page 23: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Performance Evaluation

Page 24: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Multilayer Design

• Hardware– Power or hard energy constraints– Size constraints

• Link Design– Time-varying low capacity channel

• Multiple Access– Resource allocation (power, rate, BW)– Interference management

• Networking.– Routing, prioritization, and congestion control

• Application– Real time media and QOS support– Hard delay/quality constraints

Multilayer Design

Page 25: Cross Layer Design (CLD) for Wireless Networks. Future Wireless Systems Nth Generation Cellular Wireless Internet Access Wireless Video/Music Wireless

Cross-layer Techniques Adaptive techniques

Link, MAC, network, and application adaptation Resource management and allocation (power

control) Synergies with diversity and scheduling

Diversity techniques Link diversity (antennas, channels, etc.) Access diversity Route diversity Application diversity Content location/server diversity

Scheduling Application scheduling/data prioritization Resource reservation Access scheduling