Bt Overview

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Networking over Bluetooth: overview and issues

s Pravin Bhagwat Mobile Networking Group IBM T. J. Watson Research http://www.research.ibm.com/people/p/pravin [email protected] IAB Wireless Workshop Feb 29 - March 2, 2000 Sunnyvale, CA

Bluetooth

 A cable replacement technology  1 Mb/s symbol rate  Range 10+ meters  Single chip radio + baseband

Why not use Wireless LANs? - power - cost

 at low power & low price point 02/29/00

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Value proposition of Bluetooth Cordless headset mouse Cell phone

Data access point

Internet access

Cable replacement

Ad hoc networking 02/29/00

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Bluetooth working group history  February 1998: The Bluetooth SIG is formed  promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba  May 1998: The Bluetooth SIG goes “public”  July 1999: 1.0A spec (>1,500 pages) is published  December 1999: ver. 1.0B is released  December 1999: The promoter group increases to 9  3Com, Lucent, Microsoft, Motorola  February 2000: There are 1,500+ adopters  adopters "enjoy" royalty free use of the Bluetooth technology  products must pass Bluetooth certification

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New Applications

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Synchronization

User benefits  Automatic synchronization of

calendars, address books, business cards  Push button synchronization  Proximity operation 02/29/00

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Cordless Headset Cordless headset

User benefits  Multiple device access  Cordless phone benefits  Hand’s free operation

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Usage scenarios examples  Data Access Points  Synchronization  Headset  Conference Table  Cordless Computer  Business Card Exchange  Instant Postcard  Computer Speakerphone

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Bluetooth Specifications

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Bluetooth Stack Applications

Co

Data Audio

ol ntr

SDP

IP RFCOMM

L2CAP Link Manager

Baseband RF

Single chip with RS-232, USB, or PC card interface

 A hardware/software/protocol description  An application framework 02/29/00

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Interoperability & Profiles

 A profile represents a default solution for a usage

model  Vertical slice through the protocol stack  Basis for interoperability and logo requirements  Each Bluetooth device supports one or more profiles

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Technical Overview

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Bluetooth Radio Specification Applications

Co

Data Audio

ol ntr

SDP

IP RFCOMM

L2CAP Link Manager

Baseband RF

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Radio  Low Cost  Single chip radio (minimize external components)  Today’s technology  Time divison duplex  Low Power  Standby modes  Low voltage RF

Sniff, Hold, Park

 Robust Operation  Fast frequency hopping  Strong interference protection

1600 hops/sec

 Fast ARQ  Robust access code  Forward header correction

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Radio 0 dBm -20

Tx power Rx power @ 10 cm  Allow low cost low IF  Trade sensitivity for integration  One chip radio is possible

-70 -91

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Rx power @ 10m Noise floor

C/I = 21 dB

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Baseband Applications

Co

Data Audio

ol ntr

SDP

IP RFCOMM

L2CAP Link Manager

Baseband RF

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Connection Setup  Inquiry - scan protocol  to lean about the clock offset and device address of other nodes in proximity

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Piconet formation  Page - scan protocol  to establish links with nodes in proximity

Master Active Slave Parked Slave Standby

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Addressing  Bluetooth device address (BD_ADDR)  48 bit IEEE MAC address  Active Member address (AM_ADDR)  3 bits active slave address  all zero broadcast address  Parked Member address (PM_ADDR)  8 bit parked slave address

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Piconet channel FH/TDD f1

f2

f3

f4

f5

f6

m

s1 s2 625

sec

1600 hops/sec 02/29/00

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Multi slot packets FH/TDD f1

f4

f5

f6

m

s1 s2 625

sec

Data rate depends on type of packet 02/29/00

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Packet Format 72 bits 54 bits

Access code

Header

Synchronization identification Filtering

0 - 2745 bits

Payload

Address Packet Type Flow control ARQ SEQN HEC

Error correction 1/3 rate FEC 2/3 rate FEC ARQ scheme for the data

Smaller than an ATM cell ! Notice that there is no protocol type field 02/29/00

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Physical Link Types  Synchronous Connection Oriented (SCO) Link  slot reservation at fixed intervals  No ARQ, No CRC  FEC (optional)  64 Kbps

 Asynchronous Connection-less (ACL) Link  Polling access method  ARQ, CRC  FEC (optional)  Symmetric data rate 108 - 433 Kbps  Asymmetric data rate up to 723 Kbps

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Mixed Link Example

m

SCO

ACL

ACL

SCO

ACL

ACL

SCO

ACL

ACL

s1 s2

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Inter piconet communication Cordless headset

mouse

Cordles s headset

Cell phone

Cell phone

Cell phone

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Cordless headset

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Scatternet

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Scatternet, scenario 2 How to schedule presence in two piconets? Forwarding delay ? Missed traffic?

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Link Manager Protocol Setup and Management of Baseband connections

Applications

Audio

ntr

Data

• Piconet Management • Link Configuration • Security

Co

SDP

ol

IP RFCOMM

L2CAP Link Manager

LMP

Baseband RF

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Link Manager Protocol  Piconet Management  Attach and detach slaves  Master-slave switch  Establishing SCO and ACL links  Handling of low power modes ( Sniff, Hold, Park)

 Link Configuration  packet type negotiation  power control

 Security functions  Authentication  Encryption 02/29/00

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L2CAP Applications SDP

IP RFCOMM

Logical Link Control and Adaptation Protocol

Data Audio

L2CAP Link Manager

Baseband RF

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• L2CAP provides • Protocol multiplexing • Segmentation and Re-assembly • Quality of service negotiation • Group abstraction

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L2CAP Packet Format (CO) 15 bits 16 bits Length

DCID

Baseband packets 02/29/00

0 - 64K bytes Payload

Minimum MTU is 48 bytes ! default is 672 bytes ! P. Bhagwat (IBM Research)

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L2CAP Packet Format (CL) 15 bits 16 bits Length

DCID

0 - 64K bytes PSM

Payload

Baseband packets 02/29/00

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Serial Port Emulation using RFCOMM Applications IP RFCOMM

SDP

Data Audio

L2CAP Link Manager

Baseband RF

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Serial Port emulation on top of a packet oriented link • Similar to HDLC • For supporting legacy apps

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Bluetooth Service Discovery Protocol Applications SDP

IP RFCOMM

Data Audio

L2CAP Link Manager

Baseband RF

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Example usage of SDP  Establish L2CAP connection to remote device  Query for services  search for specific class of service, or  browse for services  Retrieve attributes that detail how to connect to the

service  Establish a separate (non-SDP) connection to user the service

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IP over Bluetooth V 1.0 Applications SDP

IP RFCOMM

Data Audio

L2CAP Link Manager

Baseband RF

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GOALS  Internet access using cell phones  Connect PDA devices & laptop

computers to the Internet via LAN access points

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LAN access point profile IP Access Point

PPP Why use PPP? Security Authentication Access control Efficiency header and data compression Auto-configuration Lower barrier for deployment

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RFCOMM L2CAP LMP Baseband 37

Inefficiency of layering

Palmtop IP PPP rfc 1662

LAN access point

packet oriented byte oriented

PPP rfc 1662 RFCOMM

RFCOMM

Bluetooth

IP

packet oriented

Bluetooth

 Emulation of RS-232 over the Bluetooth radio link could be

eliminated

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Terminate PPP at LAN access point

Palmtop

Access Point

IP

IP

PPP

PPP

RFCOMM

RFCOMM

Bluetooth

ethernet

Bluetooth

 PPP server function at each access point

 management of user name/password is an issue  roaming is not seamless

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L2TP style tunneling

Palmtop

Access Point

PPP server

IP

IP

PPP

PPP UDP

UDP

RFCOMM

RFCOMM

IP

IP

radio link

radio link

ethernet

ethernet

 Tunneling PPP traffic from access points to the PPP server

 1) centralized management of user name/password  2) reduction of processing and state maintenance at each access point  3) seamless roaming 02/29/00

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IP over Bluetooth Next steps

IP based network connectivity IP over wireless media

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peer-to-peer connectivity Decentralized techniques for link formulation, naming, addressing, and routing

P. Bhagwat (IBM Research)

Internet connectivity for non-PC devices Investigation of the right design point for running IP over toasters, light switches, & fire alarms

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Research challenges Internet Plug-n-play applications cable modem head set

m

s

keyboard mouse

s m

PC

s

s

Cordless base

cell phone

s

Palmpilot

sm

Resource Discovery Routing over scatternets Techniques for link formation

Will the current solutions for each layer work in this environment?

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What is different in this scenario ? cable modem

m

head set

s

s

keyboard mouse

s m

PC

cordless s base s cell phone Palmpilot

sm

Connection oriented, lowpower link technology Small, multi-hop networks Simple devices Isolated network Dynamic network

Applications ---> services ----> routing ----> link creation

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Link Formation The problem does not exist in most wired/wireless networks

x1

x5

y1 x2

x4 x3

Proximity

y2 x6

x8 x7

Link

Low power modes require careful use of broadcast Maintaining connectivity in absence of application traffic seems wasteful

Hints from higher layer are needed 02/29/00

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Routing over Scatternets

x1

x5

y1 x2

x4 x3

Nodes must co-operate to forward packets (MANET style protocols)

y2 x6

Forwarding at Layer 2 or Layer 3?

x8

Bridging or routing ?

x7

What interface should be exported to the above layer? Better coupling with the service discovery layer is needed

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Service discovery cable modem

m

head set

s

s

keyboard mouse

s m

PC

cordless s base s cell phone Palmpilot

sm

Need solutions for address allocation, name resolution, service discovery Existing solutions in the Internet depend on infrastructure Judicious use of Multicast/broadcast is needed

These goals are similar to what Zero-conf WG is already working on

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Point to ponder

Zero-conf

rm rs

rs sr

rs

Layered and simple, but potential inefficiencies

rm rs

Will Zero-conf on top of MANET on top of scatternet construction algorithm solve our problem?

MANET

Cross-layer optimizations are worth considering

Scatternet formation 02/29/00

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Final Remarks •

Zero-conf and Bluetooth can benefit from each other

• Similarly,

MANET and Bluetooth can also benefit from

each other • A new working group in IETF for IP over Bluetooth ? • Multi-hop

wireless networks will force us to reevaluate our assumptions about network layering. Should IRTF start looking into those issues? http://www.research.ibm.com/people/p/pravin 02/29/00

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