1. Networking over Bluetooth: overview and issuesm
Networking over Bluetooth: overview and issues s s s
Pravin Bhagwat
Mobile Networking Group
IBM T. J. Watson Research
IAB Wireless Workshop
Feb 29 - March 2, 2000
Sunnyvale, CA

2. Bluetooth A cable replacement technology 1 Mb/s symbol rate
IBM Research
Bluetooth
A cable replacement technology
1 Mb/s symbol rate
Range 10+ meters
Single chip radio + baseband
at low power & low price point
Why not use Wireless LANs?
- power
- cost
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P. Bhagwat (IBM Research)
P. Bhgwat

3. Value proposition of Bluetooth
Cordless
headset
Cell phone
mouse
Data access
point
Internet access
Cable replacement
Ad hoc networking
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P. Bhagwat (IBM Research)

4. 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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P. Bhagwat (IBM Research)

5. P. Bhagwat (IBM Research)
New Applications
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6. P. Bhagwat (IBM Research)
Synchronization
User benefits
Automatic synchronization of calendars, address books, business cards
Push button synchronization
Proximity operation
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7. P. Bhagwat (IBM Research)
Cordless Headset
Cordless
headset
User benefits
Multiple device access
Cordless phone benefits
Hand’s free operation
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P. Bhagwat (IBM Research)

8. Usage scenarios examples
Data Access Points
Synchronization
Headset
Conference Table
Cordless Computer
Business Card Exchange
Instant Postcard
Computer Speakerphone
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9. P. Bhagwat (IBM Research)
Bluetooth
Specifications
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10. P. Bhagwat (IBM Research)
Bluetooth Stack
Applications
Control IP
SDP
RFCOMM
Data
Audio
L2CAP
Single chip with RS-232,
USB, or PC card interface
Link Manager
Baseband RF
A hardware/software/protocol description
An application framework
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11. 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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12. P. Bhagwat (IBM Research)
Technical
Overview
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13. Bluetooth Radio Specification
Applications
Control IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband RF
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14. P. Bhagwat (IBM Research)
Radio
Low Cost
Single chip radio (minimize external components)
Today’s technology
Time divison duplex
Low Power
Standby modes Sniff, Hold, Park
Low voltage RF
Robust Operation
Fast frequency hopping hops/sec
Strong interference protection
Fast ARQ
Robust access code
Forward header correction
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15. P. Bhagwat (IBM Research)
Radio
0 dBm
Tx power
-20
Rx 10 cm
Allow low cost low IF
Trade sensitivity for integration
One chip radio is possible
-70
Rx 10m
C/I = 21 dB
-91
Noise floor
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16. P. Bhagwat (IBM Research)
Baseband
Applications
Control IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband RF
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17. P. Bhagwat (IBM Research)
Connection Setup
Inquiry - scan protocol
to lean about the clock offset and device address of other nodes in proximity
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18. P. Bhagwat (IBM Research)
Piconet formation
Page - scan protocol
to establish links with nodes in proximity
Master
Active Slave
Parked Slave
Standby
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19. P. Bhagwat (IBM Research)
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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20. P. Bhagwat (IBM Research)
Piconet channel
FH/TDD f1 f2 f3 f4 f5 f6 m s1 s2
625 sec
1600 hops/sec
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21. P. Bhagwat (IBM Research)
Multi slot packets
FH/TDD f1 f4 f5 f6 m s1 s2
625 sec
Data rate depends on type of packet
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22. P. Bhagwat (IBM Research)
Packet Format
72 bits
54 bits
bits
Access
code
Header
Payload
Synchronization
identification
Filtering
Error correction
1/3 rate FEC
2/3 rate FEC
ARQ scheme for
the data
Address
Packet Type
Flow control
ARQ
SEQN
HEC
Smaller than an ATM cell !
Notice that there is no protocol type field
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23. P. Bhagwat (IBM Research)
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 Kbps
Asymmetric data rate up to 723 Kbps
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24. P. Bhagwat (IBM Research)
Mixed Link Example
SCO
ACL
ACL
SCO
SCO m s1 s2
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25. Inter piconet communication
IBM Research
Inter piconet communication
Cordless
headset
Cell phone
mouse
Cordless
headset
Cell phone
Cell phone
Cordless
headset
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P. Bhgwat

26. P. Bhagwat (IBM Research)
Scatternet
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27. P. Bhagwat (IBM Research)
Scatternet, scenario 2
How to schedule presence in two piconets?
Forwarding delay ?
Missed traffic?
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28. P. Bhagwat (IBM Research)
Link Manager Protocol
Setup and Management
of Baseband connections
Piconet Management
Link Configuration
Security
Applications
Control IP
SDP
RFCOMM
Data
Audio
L2CAP
LMP
Link Manager
Baseband RF
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29. P. Bhagwat (IBM Research)
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
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30. Logical Link Control and
L2CAP
Logical Link Control and
Adaptation Protocol RF
Baseband
Audio
Link Manager
L2CAP
Data
RFCOMM
SDP IP
Applications
L2CAP provides
Protocol multiplexing
Segmentation and Re-assembly
Quality of service negotiation
Group abstraction
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31. L2CAP Packet Format (CO)
15 bits
16 bits
0 - 64K bytes
Length
DCID
Payload
Minimum MTU is 48 bytes !
default is 672 bytes !
Baseband packets
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32. L2CAP Packet Format (CL)
15 bits
16 bits
0 - 64K bytes
Length
DCID
PSM
Payload
Baseband packets
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33. Serial Port Emulation using RFCOMM
Applications IP
SDP
RFCOMM
Data
Serial Port emulation on top of a packet oriented link
Similar to HDLC
For supporting legacy apps
Audio
L2CAP
Link Manager
Baseband RF
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34. Bluetooth Service Discovery Protocol
Applications IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband RF
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35. P. Bhagwat (IBM Research)
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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36. P. Bhagwat (IBM Research)
IP over Bluetooth V 1.0
Applications IP
SDP
RFCOMM
GOALS
Data
Internet access using cell phones
Connect PDA devices & laptop computers to the Internet via LAN access points
Audio
L2CAP
Link Manager
Baseband RF
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37. LAN access point profileIP
Access Point
PPP
Security
Authentication
Access control
Efficiency
header and data compression
Auto-configuration
Lower barrier for deployment
Why use PPP?
RFCOMM
L2CAP
LMP
Baseband
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38. Inefficiency of layering
Palmtop
LAN access point IP IP
packet oriented
PPP
PPP
rfc 1662
byte oriented
rfc 1662
RFCOMM
RFCOMM
packet oriented
Bluetooth
Bluetooth
Emulation of RS-232 over the Bluetooth radio link could be eliminated
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P. Bhagwat (IBM Research)

39. Terminate PPP at LAN access point
Palmtop
Access Point IP IP
PPP
PPP
ethernet
RFCOMM
RFCOMM
Bluetooth
Bluetooth
PPP server function at each access point
management of user name/password is an issue
roaming is not seamless
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P. Bhagwat (IBM Research)

40. P. Bhagwat (IBM Research)
L2TP style tunneling
Palmtop
Access Point
PPP server IP IP
PPP
PPP
ethernet IP
UDP
ethernet IP
UDP
RFCOMM
RFCOMM
radio link
radio link
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
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41. P. Bhagwat (IBM Research)
IP over Bluetooth
Next steps
IP based network
connectivity
peer-to-peer
connectivity
Internet connectivity
for non-PC devices
IP over
wireless media
Decentralized techniques
for link formulation, naming, addressing, and routing
Investigation of the right
design point for
running IP over
toasters, light switches,
& fire alarms
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42. P. Bhagwat (IBM Research)
Research challenges
Internet
Plug-n-play applications
cell phone
Palmpilot
cable modem PC
keyboard
mouse
head set
Cordless base
cell phone
Palmpilot
cable modem PC
keyboard
mouse
head set
Cordless base
Resource Discovery s m s m
Routing over scatternets
Techniques for link formation
Will the current solutions for each layer
work in this environment?
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43. What is different in this scenario ?
cell phone
Palmpilot
cable modem PC
keyboard
mouse
head set
cordless
base s m
Connection oriented, low-power link technology
Small, multi-hop networks
Simple devices
Isolated network
Dynamic network
Applications ---> services ----> routing ----> link creation
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44. P. Bhagwat (IBM Research)
Link Formation
The problem does not exist
in most wired/wireless networks x7 x8 x6 x4 x3 x5 y2 x2 x1 y1
Proximity 
Link
Low power modes require
careful use of broadcast
Maintaining connectivity in absence of application traffic seems wasteful
Hints from higher layer are needed
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45. Routing over Scatternets
Nodes must co-operate to forward
packets (MANET style protocols) x5 x1 y1 y2
Forwarding at Layer 2 or Layer 3? x2 x4 x6 x8
Bridging or routing ? x3 x7
What interface should be exported to the above layer?
Better coupling with the service discovery layer is needed
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46. P. Bhagwat (IBM Research)
Service discovery
Need solutions for address allocation,
name resolution, service discovery
cell phone
Palmpilot
cable modem PC
keyboard
mouse
head set
cordless
base s m
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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47. P. Bhagwat (IBM Research)
Point to ponder
Zero-conf
Will Zero-conf on top of MANET
on top of scatternet construction
algorithm solve our problem? s m r
MANET
Layered and simple, but potential
inefficiencies
Cross-layer optimizations are
worth considering
Scatternet formation
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48. P. Bhagwat (IBM Research)
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 re-evaluate our assumptions about network layering. Should IRTF start looking into those issues?
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P. Bhagwat (IBM Research)