Wireless networks: from cellular to ad hoc

2009

Outline• Wireless introduction • Wireless Ad hoc networks

– Routing• Proactive routing• On-demand routing

–TCP• Sensor networks

The three wireless “waves”• Wave #1: cellular telephony

– Still, biggest profit maker • Wave #2 : wireless Internet access

– Most Internet access on US campuses is wireless

– Hot spots are rapidly proliferating in the US; Europe and Asia to follow soon

– 2.5 G, 3G and 4G trying to keep up; competitive edge?

• Wave #3: ad hoc wireless nets (now)– Set up in an area with NO infrastructure; to

respond to a specific, time limited need

Wireless Internet Options - Cellular• 2.5 G

– GPRS: Time Division based (GSM); 100Kbps– 1xRTT: CDMA based; 144Kbps

• 3G– UMTS: Wide Band CDMA from 384 Kbps to 2Mbps– Integrates packet service with connection

oriented service (voice, video, etc)• 4 G ?

– WiMAX/IEEE802.16 (100Mbps) ->> 3G? 4G?• 上海：单路 512Kbps ～ 3Mbps

– other

Wireless Internet Option: WiFi (IEEE802.11)

• Replacement for wired Ethernet• Unlicensed spectrum (ISM)• Several options and rates

– 802.11 b: 11, 5.5, 2, 1 Mbps; @ 2.4 GHz– 802.11 a: 54 Mbps in 5.7 GHz band – 802.11 g: 54 Mbps; @ 2.4 GHz– 802.11 n, up to 500Mps with MIMO and OFDM tech.

• Range – Indoor 20 - 25 meters (more)– Outdoor: 50 – 100 meters (1 Km)

• Transmit power: 30 - 100 mW (200mW, 500 mW)

Wireless Internet options: Bluetooth (IEEE 802.15.1)

• 1998: BT SIG : Ericsson, IBM, Intel, Nokia, Toshiba• A cable replacement technology• Max rate 700Kbps @2.4 Ghz• Range 10+ meters• Single chip radio + baseband

– at low power (1mw) & low price point ($5)• Convergence of 802.15 and Bluetooth in a

single PAN standard

Cordlessheadset

Emerging Landscape

• Both 802.11 and Bluetooth will be used for access

• Complementary benefits

802.11 Bluetooth

LAN AP

802.11 for PDAs Bluetooth for LAN

access

New developments areblurring the distinction

Which Internet access to choose?

Internet

• Wireless WAN: 2G/3G cellular infrastructure

• Wireless LAN: IEEE 802.11 and Bluetooth

Wireless LAN

2G/3G WANInfrastructur

e

• Coverage– 3G: large coverage– 802.11b/a/g/n: small

• Throughput– 802.11b/a/g/n: up to 11/54/500 Mbps– 3G: up to 2.4 Mbps

• Cell size and density– 802.11: several hundred feet– 3G: up to several kilometers

• Applications supported– 802.11: mainly data, but may support VoIP– 3G: data plus voice

Comparisons of 3G and 802.11

Cost 802.11: cheaper 3G: expensive

Which Internet access to choose?

• Most portables have multiple radio interfaces– 802.11, Bluetooth, GPRS, 1xRTT, 3G , and 4G

• Dynamically select best access– Lowest connection charge– Best reception– Best power budget (must save battery power)– Suitable QoS

• Challenges:– Integrating 2G, 3G, 4G and Wi-Fi – "total seamlessness" between the technologies– Creating one multi-speed, multimedia network

集成移动通信及互联网为一体的网络集成移动通信及互联网为一体的网络• 互联网存在的问题 :

– 没有服务质量 (QoS) 控制 / 信令– 安全问题突出（没有可靠的认证、保密） – 很难支持移动，形成全网覆盖

• 移动通信存在的问题 : 3G– 价格贵 - 比无线局域网– 接入速率有限 -2Mbit/s– 很难与互联网 /IP 应用融合

• 哲学 : 集成 --- 矛盾– 通信 --- 纪律 , 有中心 , 有组织– 计算机网络 --- 自由

The 3rd Wave: Infrastructure vs Ad HocInfrastructure Network (cellular or Hot spot)

Ad Hoc, Multihop wireless Network

General Ad Hoc Network Characteristics• Instantly deployable, re-configurable (No

fixed infrastructure)• Created to satisfy a “temporary” need• Node portability (eg sensors), mobility• Limited battery power• Multi-hopping (to save power, overcome

obstacles, enhance spatial spectrum reuse, etc.)

The Battlefield

• DoD was first to understand the value of ad hoc networks for the automated battlefield

• In 1971 (two years after ARPANET), DARPA starts the Packet Radio project

• ONR (Office of Naval Research) sponsors MINUTEMAN - a 5 year program at UCLA (2000–2005)

• Goal: develop an “unmanned” , airborne ad hoc architecture

SURVEILLANCE MISSION

SURVEILLANCE MISSION

AIR-TO-AIR MISSION

STRIKE MISSION

FRIENDLY GROUND CONTROL

(MOBILE)

RESUPPLY MISSION

SATELLITE COMMS

Unmanned Control Platform

COMM/TASKING

COMM/TASKING

MannedControl Platform

COMM/TASKING

UAV-UAV NETWORK

Minuteman: Algorithms and Protocols for Network of Autonomous Agents

UAV-UGV NETWORK

Transferring Battlefield technology to civilian applications - Disaster recovery

• Flood, mud slide, earthquakes, eruption, chemical or nuclear plant disaster, snow ….

• Several rescue teams involved, with different functions

• Autonomous vehicle swarms (ground/airborne) are deployed (with sensors/actuators)

• Manned and unmanned teams cooperate in rescue

• “Ad Hoc networking” will be central to make the operation work

Ad Hoc Network Applications - Commercial• Sport events, festivals, conventions• Patient monitoring• Ad hoc collaborative computing (Bluetooth)• Networked video games at amusement parks, etc• Ad Hoc extensions (of Wireless Internet)

– Opportunistic Evolution• Vehicle Communications and Urban Surveillance

– Urban Homeland Defense• Mobile sensor platforms vs Cable TV

– Sensors on cars (car navigation safety)– Car to car communications– P2P applications

• Car Torrent, MobEyes, Autonomous evacuationCommercial Killer Application? ….stay tuned!

Vision: Opportunistic Evolution of Ad Hoc Networking

• Key issue: wired-wireless convergence: Commercial ad hoc nets must coexist with the Internet

• They will NOT follow the “military” model as isolated, self configured

• Rather, they will emerge as a “no cost” extension of the “infrastructure”

• Examples of Ad Hoc extensions (of Wireless Internet)– Indoor W-LAN extended coverage– Mesh Networks (Hot spot extensions)

• Rural networks– Group of friends sharing 3G access via Bluetooth

Alternative “All Wireless” Networks• “ All wireless” architecture: Multihop

wireless networking– Potential benefits:

•“anytime, anywhere” network setup• Self-organized, small to large scales• Minimized wiring cost

• Three architectural paradigms from resource perspective– Low-end: resource-constrained wireless

sensor networks– Middle-ground: mobile ad-hoc networks– High-end: wireless mesh networks

Multihop Wireless Networks

• Resource-constrained sensors

• Potentially large population

Wireless Sensor Networks Mobile Ad-Hoc Networks

Low-End Middle-Ground

• Nodes with reasonable amount of resources

• Data rates upto 10s Mbps

High-End: Wireless Mesh Networks 802.11s

Distribution SystemDistribution System

Mesh LinksMesh Links802.11 MAC/PHY802.11 MAC/PHY

802.11 ESS802.11 ESS

L2 Switch

Mesh PortalMesh Portal

Mesh APMesh APMesh routerMesh router

STASTA

L3 Router

Portal

• High-speed wireless backbone at >100Mbps

• Resource abundant• Promises to have both wide

coverage and high rate

Wireless Mesh Networks

Urban surveillance• CCTV surveillance

– Cameras cannot be installed at all locations– Cameras can be taken out by terrorists– The central data collection facility can be sabotaged

• Mobile video collection/storage platforms– Vehicles, People, Robots– Mobile “eyes” are an complement to CCTV

• New challenges on VEHICLES – wireless communications medium– wireless data protocols/architectures– distributed storage strategy– search of the distributed, mobile data base

Urban “opportunistic” ad hoc networking

From Wireless toWired networkVia Multihop

The Urban Vehicle Grid

• Ad hoc networking to prevent/contain accidents

Food Mart

Opportunistic piggy rides in the urban meshPedestrian transmits a large file block by block to

passing cars, bussesThe carriers deliver the blocks to the hot spot

More generally:New Vehicle Roles on the road

• Vehicle as a producer of geo-referenced data about its environment – Pavement condition– Probe data for traffic management– Weather data– Physiological condition of passengers, ….

• Vehicle as Information Gateway (Telematics)– Internet access, infotainment, dynamic route

guidance, ……• These roles demand efficient communications

Vehicle Roles: Vehicular Sensor Apps

• Vehicle & Vehicle, Vehicle & Roadway as collaborators– Cooperative Active Safety

• Forward Collision Warning, Blind Spot Warning, Intersection Collision Warning…….

– In-Vehicle Advisories • “Ice on bridge”, “Congestion ahead”,….

• Environment– Traffic congestion monitoring– Urban pollution monitoring

• Civic and Homeland security– Forensic accident or crime site investigations – Terrorist alerts

Urban Ad Hoc net in action: Safe DrivingVehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 65 mphAcceleration: - 5m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 45 mphAcceleration: - 20m/sec^2Coefficient of friction: .65Driver Attention: NoEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 75 mphAcceleration: + 20m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Vehicle type: Cadillac XLRCurb weight: 3,547 lbsSpeed: 75 mphAcceleration: + 10m/sec^2Coefficient of friction: .65Driver Attention: YesEtc.

Alert Status: None

Alert Status: Passing Vehicle on left

Alert Status: Inattentive Driver on Right

Alert Status: None

Alert Status: Slowing vehicle aheadAlert Status: Passing vehicle on left

Vehicular Sensor Network (VSN)IEEE Wiress Communications 2006

Uichin Lee, Eugenio Magistretti (UCLA)

VSN-enabled vehic le

Inter-vehiclecommunications

Vehic le-to-roadsidecommunications

Roadside base station

Video Chem.

Sensors

Storage

Systems

Proc.

Accident Scenario: storage and retrieval• Designated Cars:

– Continuously collect images on the street (store data locally)– Process the data and detect an event– Classify the event as Meta-data (Type, Option, Location,

Vehicle ID)– Post it on distributed index

• Police retrieve data from designated cars

Meta-data : Img, -. (10,10), V10

CRASH

- Sensing - Processing

Crash Summary Reporting

Summary Harvesting

How to retrieve the data?• “Epidemic diffusion” :

– Mobile nodes periodically broadcast meta-data of events to their neighbors

– A mobile agent (the police) queries nodes and harvests events

– Data dropped when stale and/or geographically irrelevant

• Mobility-Assist Meta-Data Harvesting– Assumption

• N disseminating nodes; each node ni advertises event ei , “k”-hop relaying

• v: average speed, R: communication range• ρ : network density of disseminating nodes• Discrete time analysis (time step Δt)

– Metrics• Average event “percolation” delay• Average delay until all relevant data is

harvested

You are driving to VegasYou hear of this new show on the radio

Video preview on the web (10MB)

CarTorrent : Opportunistic Ad Hoc networking to download large multimedia files

Highway Infostation downloading

Internet

file

Problem: Stopping at gas station to download is a nuisance

Observation: many other drivers are downloading the same files (like in the Internet)

Solution: Co-operative P2P Downloading using the Car to Car ad hoc nets (Car-Torrent)

Partial download from Infostation

Download

Internet

Co-operative P2P Download

Vehicle-Vehicle Communication

P2P Exchange of Pieces

Internet

U-Ve T: Ucla - Vehicular TestbedU-Ve T: Ucla - Vehicular Testbed - Project Goals

• Provide:– A platform to support car-to-car experiments in

various traffic conditions and mobility patterns– A shared virtualized environment to test new

protocols and applications– Remote access to U-VeT through web interface– Extendible to 1000’s of vehicles through WHYNET

emulator– potential integration in the GENI infrastructure

• Allow:– Collection of mobility traces and network statistics– Experiments on a real vehicular network

Big Picture• We plan to install our node equipment in:

– 50 Campus operated vehicles • “on a schedule” and “random” campus fleet mobility

patterns – 50 Communing Vans

• Measure freeway motion patterns– Hybrid cross campus connectivity using 10 WLAN

Access Points– The U-Box Node:

• Laptop/PC (Linux) (Windows), 2 x WLAN Interfaces, 1 Software Defined Radio (FPGA based) Interface, 1 Control Channel , 1 GPS, OLSR Used for the Demo

The C2C testbed