slide1 l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
9. WIRELESS ATM PowerPoint Presentation
Download Presentation
9. WIRELESS ATM

Loading in 2 Seconds...

play fullscreen
1 / 46

9. WIRELESS ATM - PowerPoint PPT Presentation


  • 147 Views
  • Uploaded on

9. WIRELESS ATM. Anywhere, Anytime Access to ATM Networks. Voice, Data, Video, and Images in Any Combination, Anywhere, Anytime with Convenience and Economy. Fixed Wireless & Mobile Users Wireless Equipment. Problems Noisy Wireless Channels High BER. Wireless Channel

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '9. WIRELESS ATM' - quasim


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

9. WIRELESS ATM

  • Anywhere, Anytime Access to ATM Networks.
  • Voice, Data, Video, and Images in Any Combination, Anywhere, Anytime with Convenience and Economy.
  • Fixed Wireless & Mobile Users Wireless Equipment.
  • Problems
    • Noisy Wireless Channels High BER.
    • Wireless Channel
        • Very bandwidth limited.
        • ATM designed for bandwidth-rich environment.
    • Overhead
        • Every ATM cell has overhead of 10%.
        • For wireless channel, we need more control information which can far exceed the overhead limit.
slide2

HLR

ATM Network

VLR

MSC

Base Station

VLR: Visitor Location Register

HLR: Home Location Register

MSC: Mobile Switching Center (also ATM switch)

Wireless ATM Network Architecture

slide3

Satellite

Fixed ATM Network

Wireless LAN

FSC: Fixed Switch Center (ATM Switch)MBS: Mobile Base Station

Wireless ATM in Digital Battlefield

slide5

Quality of Service (QoS) Parameters

  • Throughput
  • Delay
  • Jitter
  • Loss Probabilities
  • Probability of Dropping the Call
  • Expected BER; Packet Error Rate
  • Expected Disruption Time During Handoffs
  • Minimum or Maximum Level of Mobility
  • QoS Renegotiation

Also in wired ATM network

slide6

Personal Mobility vs. Terminal Mobility

User

Terminal

Network

Wired

Wireless

Terminal Mobility

Personal Mobility

slide7

Quality Critical

Applications

Time Critical

Applications

TCP

UDP

IP

AAL Layer

ATM Layer

Error Control

Medium Access Control

Physical Layer (Wireless Channel)

Protocol Stack For Wireless ATM

IP

Layer

ATM

Layer

Link

Layer

slide8

Specific Requirements for PHY Layer

Low Speed Wireless PHY

HIGH Speed Wireless PHY

Frequency Band

5.15-5.35 GHz, 5.725-5.875 GHz

59 GHz - 64 GHz

Cell Radius

80 m

10 - 15 m

Transmit Power

10 – 20 mW

100 mW

Frequency Reuse Factor

7

up to 12

Channel Bandwidth

30 MHz

150 / 700 MHz

Data Rate

25 Mbit/s

155 / 622 Mbit/s

Modulation

16 tone DQPSK

32 tone DQPSK

MAC Interface

par., transf. speed 87.5 Mbyte/s

par., transf. speed 3.127 Mbyte/s

Fixed Packet Length

PHY header + MAC header + 4*ATM cells

slide9

System Architecture and Protocol Model

Wireless Workstation

User Applications

(Quality-Critical Traffic)

Host

TCP/IP

AAL Subsystem

ATM

Backbone Network

ATM

Sonet

DL Subsystem

Wireless Workstation

Wired Line

Wireless Link

Host

slide10

Error Control

Time Critical

Applications

FEC

Hybrid ARQ

Quality Critical

Applications

slide11

Why FEC?

  • ATM HEC performance is too low for
  • wireless ATM.
  • High CLR and payload errors
  • Cell delineation problem
  • FEC (for Time-Critical Applications)
  • To correct channel errors at the expense of bandwidth by adding redundancy
slide12

Cells

RS Outer

Encoder

Symbol

Interleaver

Conv. Inner

Encoder

Bit Level

Interleaver

Transmitter FEC

Wireless

Channel

RS Outer

Decoder

Symbol

Deinterleaver

Viterbi

Decoder

Bit Level

Deinterleaver

Cells

Receiver FEC

Concatenated FEC Scheme

slide13
Why Hybrid ARQ? (for Quality Critical Traffic)

ARQ provides high reliability at good and moderate channel qualities.

The throughput drops rapidly, if the channel error rate is high as in wireless channels.

Hybrid ARQ

FEC first tries to correct the frequent error patterns. If it fails, then ARQ takes over.

Hybrid ARQ Types

Type I Hybrid ARQ scheme

Type II Hybrid ARQ scheme: only additional parity bits are retransmitted to combine with the previous packet (incremental redundancy).

slide14

MT

MT

MT

Medium Access Control for Wireless ATM Networks

slide15

Categorization of MAC Protocols

  • Based on Channel Organization
    • TDMA-Based MAC Protocols
    • CDMA-Based MAC Protocols
    • Random MAC Protocols
    • Hybrid MAC Protocols
  • Based on Duplex Mode of Uplink and Downlink
    • Time Division Duplex (TDD) (One Carrier Frequency)
    • Frequency Division Duplex (FDD) (Two Carrier Frequencies)
slide16

* Frequency Division Duplex (FDD)

(Two Carrier Frequencies)

  • Uplink frequency carries traffic from terminal to BS while downlink frequency carries traffic from BS to terminal.
  • FDD allows almost immediate feedback from the BS enabling terminal to find out quickly if its contending reservation request was unsuccessful and a retransmission is necessary.
  • Thus, FDD impacts the delay encountered by user traffic as well as the resource availability of the wireless channel.
slide17

TDMA Based MAC Methods

  • Dynamic Packet Reservation Multiple Access (DPRMA), by Dyson and Haas in 1999. FDD
  • Mobile Access Scheme Based on Contention and Reservation for ATM (MASCARA), by Bauchot et al. in 1996, and Passas et al. in 1997. TDD
  • PRMA with Dynamic Allocation (PRMA/DA), by Kim and Widjaja in 1996. FDD
  • PRMA with Adaptive TDD (PRMA/ATDD), by Priscoli in 1996. TDD
  • Dynamic TDMA with Piggyback Reservation (DTDMA/PR), by Qiu et al. in 1996. FDD
  • Distributed Queuing Request Update Multiple Access (DQRUMA), by Karol et al. in 1995. FDD
  • Dynamic TDMA with TDD (DTDMA/TDD), by Xie et al. in 1995. TDD
slide18

Packet Reservation Multiple Access (PRMA) Protocol (Goodman’91)

  • Time is divided into slots of equal duration, and slots are grouped into frames.
  • Each slot in a frame is either “reserved” or “available”.
  • BS controls the upstream traffic and broadcasts a continuous stream of packetized information through the downstream channel
  • The status of a slot is provided in feedback information supplied by BS.
  • Terminals can send two types of information: “Periodic” information such as speech or “Random” information such as data.
  • Frame rate is identical to the arrival rate of the speech packets.
  • Uses S-ALOHA for time slot reservation and TDMA for data transmission.
slide19

Packet Reservation Multiple Access (PRMA) Protocol (Goodman’91)

  • A station contends for an available slot using S-ALOHA.
  • If transmission is successful, BS responds with an ACK message and the slot is reserved in subsequent frames until the terminal relinquishes it by leaving the slot empty.
  • A terminal with “random packets” contends for slots in the same way, but cannot reserve the same slot in a subsequent frame even after a successful transmission.
  • Thus, terminal must contend again for another available time slot.
  • For unsuccessful transmission, a terminal with “periodic” packets retransmits the packet with certain probability in subsequent unreserved slots until it receives an ACK signal from BS.
  • Similarly, a terminal with “random” packets retransmits a packet in unreserved slots with certain probability.
slide20

Packet Reservation Multiple Access (PRMA) Protocol (Goodman’91)

Advantages:

  • Simple

Disadvantages:

* Upon congestion, the speech packet dropping rate and data packet delay both increase.

* Feedback information may cause waste of bandwidth.

slide21

Request packet

PRMA/DA

header

PRMA/DA

trailer

ATM cell

2

Na

Nc

Nv

1

1

2

1

1

2

Nd

2

Available slots

CBR reservation slots

ABR reservation slots

VBR reservation slots

PRMA/DA

header

PRMA/DA

trailer

ATM cell

Wireless Packet

PRMA/DA — Services and the Frame Structure

  • Supports Multimedia Traffic
    • Constant Bit Rate (CBR), Variable Bit Rate (VBR), Available Bit Rate (ABR).
  • Frame Structure
    • It is organized according to traffic types.
    • Downlink transmission is not considered. FDD

Variable

Variable

Variable

slide22

Operation Procedures of PRMA/DA

  • Send Requests in Available Slots
    • Contention-based transmission.
    • Slotted ALOHA is used.
  • Reserve Time Slots for each Successful Request
    • Dynamic allocation algorithm is used to allocate time slots for CBR, VBR, and ABR connections.
    • The allocated time slots are reserved for the lifetime of a connection.
    • Dynamic allocation algorithm is also used for updating available time slots for the transmission of requests.
  • Transmit Packets in Reserved Time Slots
    • Since time slots are reserved, contention is free in this phase.
slide23

Contributions and Shortcomings of PRMA/DA

  • Contributions
    • Dynamic allocation of slots for each sub-frame.
      • Variable boundary can be easily implemented.
      • Bandwidth can be utilized efficiently.
      • Collisions can be resolved quickly
    • No mini-slots; Easy for synchronization.
    • Multiple traffic classes supported.
  • Shortcomings
    • A request packet has the same length as a data packet.
      • If traffic rate high, this would cause inefficiency.
    • No mechanism is used to dynamically update VBR resources.
      • VBR bandwidth is allocated according to the average rate. The bursty requirement has to rely on the leftover bandwidth. QoS of VBR cannot be guaranteed.
slide24

Downlink Period

FH Period

ContentionPeriod

Uplink Period

… …

MPDU 1

MPDU 2

MPDU n

PHY

Hdr

MPDU

Hdr

MPDU payload: Cell train (many ATM cells)

1 time slot

n time slots

MASCARA(Mobile Access Scheme based on Contention and Reservation for ATM)

  • Supports CBR, real-time VBR (rt-VBR), non-real-time VBR (nrt-VBR), ABR, UBR traffic.
  • Demand assignment scheme with contention based reservations.
  • Uplink subframe is divided into a contention period to transmit reservation requests or some control information, and uplink period for uplink data traffic.
  • Each period within a frame has a variable length depending on the instantanous traffic to be carried.
slide25

Operation Procedures of MASCARA

  • If a terminal has cells to transmit, it sends a reservation request either piggybacked in the MPDUs uplink period or in special control MPDUs sent in the contention period.
  • Base station schedules transmissions of the next frame according to reservation requests, arriving cells for each downlink connection, traffic characteristics and QoS requirements of all connections.
  • In the Frame Header of the downlink, BS broadcasts information which contains a descriptor of the current time frame (including the lengths of each period), the results of the contention procedures from the previous frame and the position of the slot allocated to each downlink and uplink connection.
  • To minimize PHY layer overhead, MASCARA uses the concept of a CELL TRAIN (a sequence of (1-n) ATM cells belonging to a terminal and having a common header).
  • Length of overhead plus that of the MPDU header is equal to one time slot, which is defined as the length of an ATM cell.
slide26

Priority Regulated Allocation Delay-Oriented Scheduling (PRADOS)

* Assigns priorities for each connection according to its service class.

* PRADOS combines priorities with a leaky bucket traffic regulator.

  • Regulator uses a token pool introduced for each connection.
  • Tokens are generated at a fixed rate equal to the mean ATM cell rate of each VC.
  • Size of the pool is equal to the maximum number of ATM cells that can be transmitted with a rate greater than the declared mean.
  • Starting at priority 5 and ending with priority 2, scheduler satisfies requests for connections as long as tokens and slots are available.
  • For every slot allocated to a connection, a token is removed from the corresponding pool.
slide27

Contributions and Shortcomings of MASCARA

  • Contributions
    • Cell train concept is used.
    • A novel scheduling scheme - PRADOS.
    • Dynamic TDD is implicitly implemented.
    • Multiple traffic classes are supported.
  • Shortcomings
    • With each request corresponding to a time slot, too many requests are transmitted in the protocol. This results in wasting bandwidth.
    • Large size of request packet results in reduction of good throughput.
    • Connection admission control (CAC) is separate from the MAC protocol. The overall performance of the integrated system is unpredictable.
mobility management in w atm networks
Location ManagementMobility Management in W-ATM Networks
  • Handoff Management

Base Station

A

MT A is receiving a call !

How will the network

deliver the call to A ?

types of mobility
TERMINAL MOBILITY

(network should route calls to the MT

regardless of its point of attachment)

PERSONAL MOBILITY

(users should access the network wherever they are; UPT (Universal Pers. Tel #))

SERVICE PROVIDER MOBILITY

(allow user to roam beyond regional networks).

Types of Mobility
location management

Call Delivery

(Paging)

Location Update

(Registration)

Location Management
cost tradeoff

Too Many Location Updates

Too Few Location Updates

Low Paging Costs

High Update Costs

High Paging Costs

Low Update Costs

Cost Tradeoff
handoff types

Intra-Cell

Inter-Cell

Hard Handoff

Soft Handoff

Handoff Types
w atm architecture

ATM Backbone Network

ATM

Switch

ATM

Switch

Wireline connections

to ATM switch

Wireless connections to BS

MT

Cell

BS

W-ATM Architecture
slide36

LOCATION MANAGEMENT

LOCATION

SERVICE

LOCATION

ADVERTISEMENT

TERMINAL

PAGING

TWO-TIER

DATABASES

VIRTUAL

CONNECTION

TREE

INTEGRATED

LOCATION

RESOLUTION

LOCATION

REGISTERS

MOBILE PNNI

LOCATION MANAGEMENT TECHNIQUES FOR W-ATM

slide37
LOCATION SERVICE

* Use of DATABASES to maintain records of MTs.

* When location information is obtained from DATABASE, TERMINAL PAGING is used to deliver calls to MTs.

* Requires signaling, querying and paging.

LOCATION ADVERTISEMENT

* No databases but location information is broadcast throughout the network.

location service method 1 two tier database akyol cox 96

(3)

HOME

ZONE

(4)

Home

Tier

Home

Tier

Home

Tier

Zone

Manager

(5)

Visitor

Tier

Visitor

Tier

Visitor

Tier

(2)

(1)

CURRENT

ZONE

Location Service: Method 1: Two Tier Database (Akyol/Cox’96)

PREVIOUS

ZONE

slide39
Explanation:

* Bi-level databases are distributed to ZONES throughout the network.

* Each zone is maintained by a ZONE MANAGER controlling the zone’s location update procedures.

* Each MT has a home zone where it is permanently registered.

MT transmits a location registration request message to the new zone. Message contains User ID Number, authentication data and ID of the previous zone.

Current zone manager determines the home zone of the MT from the previous zone ID.

Current and home zone managers authenticate the user and update home user profile with the new location information.

Home zone sends a copy of the profile to the current zone manager which stores the profile in the visitor tier of its database.

Current zone manager sends a purge message to the previous zone manager so that user’s profile is deleted from the visitor tier before.

slide40

Location Advertisement: Method 1:

Virtual Connection Tree (Veeraraghavan et.al.’97)

Portable

Base Station (PBS)

Cell

Boundary

De-registration

message

MT’s Former

position

Registration

message

slide41
VCT advertises location information via provisioned virtual paths.

A collection of PBSs connected via provisioned VPs forms a connection tree.

PBSs are equipped with switching capabilities and limited buffering capabilities.

Trees are based on the mobility indications of the MT.

Each PBS maintains a running list of resident MTs in its coverage area.

Location registration occurs when MT is on/off or it moves to a new service area.

On/Off case, MT sends a message to its local (current) PBS which then adds/deletes the MT to/from the service list.

When MT moves to a new service area of a PBS, the PBS sends a de-registration message to the old PBS on behalf of the MT and enters the MT’s ID into its current list.

comparison of location management techniques

Location Service

Location Advertisement

Advantages Disadvantages

Flexibility Database Admin

Scalability Signaling Load

Advantages Disadvantages

No Paging No Scalability

No Database Wasted

Admin Bandwidth

Comparison of LocationManagement Techniques
slide43

Handoff Management

Multicast

Connection

Re-Routing

Partial

Connection

Re-Routing

Full

Connection

Re-Routing

Route

Augmentation

InterWorking

Devices

Connection Extension

Virtual

Connection

Tree Re-Routing

Nearest

Connection

Node Re-Routing

Hybrid

Connection

Re-Routing

InterWorking

Devices

Connection Re-Routing

Homing Base

Station

Re-Routing

slide44
Full Connection Re-Routing:

Maintains the connection by establishing a completely new route for each handoff as if it were brand new call.

Route Augmentation:

Extends the original connection with a hop to the MTs next location.

Partial Connection Re-Routing:

Re-establishes certain segments of the original connection, while preserving the remainder.

Multicast Connection Re-Routing:

Combines the 3 techniques but includes the maintenance of potential handoff connection routes to support the original connection, reducing the time spent in finding a new route for handoff.

slide45

Comparison of Handoff Management

Approaches

Full

Extension

Partial

Multicast

Advantages

Optimal

route;

existing

methodology

Fast;

maintains

cell

sequence

Maintains cell

sequence;

reduced

resourceutilization

Fast;

maintains

cell

sequence

Disadvantages

Slow;

inefficient resource

re-assignment

Wastes bandwidth;

inefficient

connection route

Complex;

added switch

processing reqs

Added buffering

requirements;

bandwidth

pre-allocation

slide46
References:

J. McNair, “Mobility Management Protocols for Wireless ATM

Networks”,BWN Lab Technical Report, 1997. (Available on the

WEB).

I.F. Akyildiz, J. McNair, J. Ho, H. Uzunalioglu, W. Wang,

“Mobility Management in Next Generation Wireless Systems”,

Proceedings of the IEEE Journal, Vol, 87, No.8, pp.1347-1384,

August 1999.