1

Metropolitan-Area

Regional-Area

Concept

In-Building

Campus-AreaPacket Relay

Wide-Area Testbed

Bay Area Research Wireless Access Network:Towards a Wireless Overlay Internetworking Architecture

Randy H. Katz, Eric A. Brewer, UC Berkeley

Bandwidth Adaptive API

Network Monitor

Physical Subnet

Network Management Layer

Application Support Layer

Application DataTypes

ServiceKinds

Subcontractor:Hughes MalibuResearch Labs

2

Project Vision

“Access is the Killer App”• Goals

– Be connected anywhere, anytime via the “best” available (wireless/wireline) network

– Adapt the application to the available bandwidth and latency

• Strategies– Wireless Overlay Internetworking Architecture– Network- and Type-Aware Applications Building Blocks

3

Wireless Overlay Concept

In-Building

Campus-Area Packet Relay

Metropolitan-Area

Regional-Area

Theatre of Operations

Rear Echelons

Bases, Depots, Ranges

Command CentersTraining Centers

4

Proxy Architecture

Proxy

• Proxy– Mediates between wireless and wireline environment– Ideally executes at “well-connected” boundary of internetwork– Changes data representations on-the-fly– Trade-off in transcoding time and communications time

Well Connected Poorly Connected

5

Bandwidth Adaptive Application Interfaces

Network Monitor

Physical Subnet

Network Management Layer

Application Support Layer

Application DataTypes

ServiceKinds

When to switch from one overlay network to another?

Strategy: – Monitor network state – Detect edge of coverage – Initiate vertical h/o

6

Applications Support Services

Audio Video Image Maps

Data-type Specific Data Transmissions

Processor Resource Allocation

NavigationCollaboration Image ExchangeAudio/Video Conferencing Digital Library Access

Mobile Multimedia Applications

Agent-based backend processing

Compression/Decompression Multi-layer representations

Session Management

Overlay Network Management

Transaction combining to reduce latency

Wireless TCPAdaptive QOS Support

ApplicationsQOS Needs

NetworkCapabilities

Wireless Overlay Subnets

SatelliteIn-building Campus-Area Wide-Area

Mobile IPUser Tracking Low Latency Handoff

Physical Layer

Data Link Layer

Network Layer

Transport LayerConnection-Oriented Mechanisms

Network load-balancing across cooperative overlays

Policy-based Network Selection Scalable Network Management

Layered Architecture

Eric

Randy

7

Soda Hall

BaseStation DirecPC

Basestation

InternetGateway

Hughes DBSBasestation

GatewayMetricom "WAP"

WLAN RFIBM IR

MetricomWide Area

Circuit Switched Cellular &Cellular Digital Packet Data

Bay Area Research Wireless Access Network Testbed

+ Ethernet

8

Wireless Networking Challenges

MobilityMobilityUnreliabilityUnreliability

Low Data RateLow Data RateHigh LatencyHigh Latency

Adaptability

9

Mobility Meets Multimedia: Low Latency Handoff

HomeAgent

BaseStation

BaseStation

Multicast Group• Use hints about terminal trajectory to assist in handoffs

• Multicast packets to adjacent base stations to smooth handoffs

Handoffs every 10 seconds

Code release 1st Quarter 19960

2e+06

4e+06

6e+06

8e+06

1e+07

1.2e+07

1.4e+07

0 10 20 30 40 50 60 70 80 90

Packet Sequence Numbers

Time (seconds)

10

Web Browsing on the Move: Reliable Wireless Transport

Local retransmissionsTCP acksNack lost packets

Retransmit

0

2e+06

4e+06

6e+06

8e+06

1e+07

1.2e+07

0 50 100 150 200 250 300 350

Snoop Regular TCP

Packet Sequence Numbers

Time (seconds)

• Cache unacknowledged TCP data; Snoop on TCP acks, do local rexmit

• BS explicitly NACKs MH’s lost pkts

• Maintain end-to-end TCP semantics

20X speed-up in presence of bit errors

Aggregate b/w 1 Mbps vs. 0.25 Mbps

Code release integrated with handoff

3.8 x 10-6 BER(1/256 kbps)

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Proxy Architecture:Image Proxy

78 colors,49K bytes

4 grays, 530 bytes

~2 sec.

• Distillation: lossy compression that preserves semantic content

• Works in R/T on desktop PC

• Client can request refinement of distilled image

Mobileclient

Servers(Internet)

Orig. size (bytes) New size

New size as % of original

Pixel dimensions

Scaled by

Time (sec.)

34K 2022 0.058 320x200 2 1848K 5938 0.007 1280x1024 4 13848K 1676 0.002 1280x1024 8 10361K 24311 0.066 1022x703 2 8361K 6240 0.017 1022x703 4 7173K 4974 0.028 640x480 2 4173K 1644 0.009 640x480 4 3

Orig. size (bytes) New size

New size as % of original

Pixel dimensions

Scaled by

Time (sec.)

34K 2022 0.058 320x200 2 1848K 5938 0.007 1280x1024 4 13848K 1676 0.002 1280x1024 8 10361K 24311 0.066 1022x703 2 8361K 6240 0.017 1022x703 4 7173K 4974 0.028 640x480 2 4173K 1644 0.009 640x480 4 3

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Proxy Architecture:Video Gateway

Motion Full Dec/Enc DCT Dec/Enc

Low

High

26 fps 30 fps

15 fps 27 fps

JPEGEncoder

H.261Encoder

NVDecoder

JPEG

H.261

IpadVQEncoder

Decoder

Decoder

Transcoder

Gateway Architecture

E-1 Q-1DCT -1

CR/MCDCTQE

JPEG

H.261

CR

JPEG to H.261 Transcoder

1/4 NTSC JPEG to CIF H.261 on SparcStation 20

• Another early instance of a proxy

• R/T transcode from high b/w video to low bandwidth video formats

• Integrated with existing Internet MM infrastructure via RTP

13

Research Plan as ProposedYear 1 Year 2 Year 3

T1: Overlay InternetworkManagement Services

T2: Mobile ApplicationSupport Services

O1: Wide-Area Deploymentand Demonstration

O2: Pilot ApplicationDemonstrations

Measure & Eval Ovly NetsDesign for In-Building Ovly

Design for Wide-Area OvlyDemo In-Building Ovly Net

Demo Wide-Area OvlyDemo Scaled Net Perfor

Design API & Appl Toolkit Demo API for In-BuildingDevelop Simple Collab Apps

Integrate with NOW ServersDemo Scaled Apps Perf

Accelerate Design for Wide-Area Ovly Integration

Demo Wide-Area OverlayDesign for Multiple Ovlys

Demo Extension to MultipleWide-Area Overlays

Design Libr Nav & MedImage Distr Apps using API

Large Scale Demo of Nav& Med Image Distr Apps

Deploy In-Build Net@UCSFEval Med Image Apps Reqs

9/95 - 8/96 9/96 - 8/97 9/97 - 8/98

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Fit with GloMo Program GoalsARPA GloMoFY 96Adaptive Mobile Internet Services

Location Transparent Computing

FY 97Demo B/W Adaptive MM Node

Demo Advanced Mobile Networking

FY 98Demo Multimedia ConferencingDemo Continuous Mobility

Daedalus/BARWAN Program

Measure/eval overlay networking techDesign overlay network architectureDesign proxy architecture, API, toolkitPrototype proxies for image, video, maps

Demo first impl of proxy API & toolkitPrototype apps for A/V conferencingDemo in-building coop vertical handoffExtend design for metro/wide-area ovlys

Demo scalable processing for proxiesDemo seamless roaming over in-building,wide-area wireless overlays