Wireless Atm Cs

7/31/2019 Wireless Atm Cs

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WATM


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ATMAsynchronous Transfer

Mode It is a high speed, connection oriented

switching and multiplexing technology capableof transmitting voice, video and data and

interconnecting LANs. ATM is asynchronous because information

streams can be sent independently without theneed of a common clock.


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A networking technology developed by thetelephone companies to handle all types of data

using fixed 53-byte cells, or packets. Creates virtual point-to-point circuit connections

between the source and the destination.

Data rates from 25 to 622 Mbps.

The small cell size allows ATM to transmit video,audio, and computer data over the same network,while guaranteeing a preset QoS level for each.


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ATM Cell Structure


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Why 53 bytes?

US wanted 64 payload bytes

Europe wanted 32Compromised on 48

+5 header = 53


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Features of ATM

The service is connection-oriented, with datatransferred over a VC.

The data is transferred in 53-byte packets calledcells.

Cells from different VCs that occupy the samechannel or link are statistically multiplexed.

High speed switching at hardware level.

Bandwidth on demand Superior Management features

Scalability in network size and speed

Ease of integration with other technologies


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ATM Interfaces ATM is a connection

oriented techniquedesigned to transportboth connection andconnection-less

services Operations at the

boundary of anetwork are

connection oriented Within the network

the operation isconnectionless

User to Network Interface

(UNI) : Connection existingbetween the user equipmentand ATM equipment.

Network to NetworkInterface (NNI) :

Connection via which traffictravels between ATMdevices in the samenetwork.

Intercarrier Interface (ICI) :Used to send traffic acrossintermediate networks

Data Exchange Interface(DXI) : Used to transmitpackets rather than cells tothe ATM interface when

nonATM equipment isused


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ATM Service Categories Allow for traffic to be buffered and queued for

later transmission Can permit asynchronous operations between

sender and receiver


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ATM Virtual paths and

Channels Virtual Channel (VC)

provides a fixed pathway orroute between 2 points. Setupacross an ATM networkwhenever data transfer begins.

Virtual Path (VP)groups ofVCs used to tell a switch how

to forward an ATM cell throughan ATM network

Virtual Path Identifier (VPI)

in the ATM header used toidentify route established in theATM Switch

Virtual Channel Identifier(VCI) - in the ATM header used

to identify a channel within aVP


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ATM Applications


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Extension of LAN for mobile user

Simplified wiring and configuration

Provide high-speed data access for users withoutneed for a new wired infrastructure

Create unforeseen opportunities for future

applications

The Promise of W-ATM


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THE NEED FOR WATM

New developments of wireless networks areneeded to enable wireless technologies tointerwork with existing wired networks.

In order for ATM to be successful, it must offer awireless extension, otherwise it cannot participate in therapidly growing field of mobile communications.

Other wireless technologies are implemented inspecific environments: IEEE 802.11 only covers local area access methods.

Bluetooth only builds up piconets.

Mobile IP only works on the network layer.


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WATM tries to build up a comprehensive systemcovering many different networking scenarios, such asprivate and public, local and global, mobility and

wireless access. Other wireless technologies do not provide as

many QoS parameters as ATM networks do.

WATM could offer QoS for adequate support of

multimedia data streams. WATM will be more complex than most of the

other wireless technologies.


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W-ATM


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Benefits of ATM made mobile

Free to roam

Flexible bandwidth allocation

Efficient multiplexing of traffic

Availability of existent ATM switching

Flexibility of reusing same frequency

Soft handoff without any data loss

Advantages of W-ATM


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Delay to multi-path interference

Hop-by-hop routing method not adequate

Virtual connection takes longer

Poor physical level characteristics

High noise interference

Finding a suitable wireless channel

Disadvantages of W-ATM


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Physical Layer

Infrared vs. Radio

Circuit-switched vs. Packet-switched

Channel Coding

Multiple Antennas

Operating Frequency Licensed vs. Unlicensed Frequency

Transition Issues


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Data Link Layer

Encapsulation

Header CompressionARQ (Automatic Repeat Request) vs. FEC

(Forward Error Correction)

Quality-of-Service Issues

Split Functionality

Transition Issues


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HIPERLAN

HIPERLAN - HIgh PErformance Radio LAN

HIPERLAN is an interoperability standard which

specifies a common air interface MAC and PHYlayers in OSI model

HIPERLAN will be a family of standards

HIPERLAN 1 is described in detail


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HIPERLAN REFERENCEMODEL

Medium Access Control

(MAC) Sublayer

Channel Access Control

(CAC) Sublayer

Physical (PHY) Layer

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer

higher layer protocols

OSI

Reference Model

HIPERLAN

Reference Model

Documents

Wireless Atm Cs