BT overview

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Networking over Bluetooth: overview and issues : 

Networking over Bluetooth: overview and issues Pravin Bhagwat Mobile Networking Group IBM T. J. Watson Research s s m s http://www.research.ibm.com/people/p/pravin pravinb@us.ibm.com IAB Wireless Workshop Feb 29 - March 2, 2000 Sunnyvale, CA

Bluetooth: 

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

Value proposition of Bluetooth: 

Value proposition of Bluetooth Cable replacement Ad hoc networking Data access point Internet access

Bluetooth working group history: 

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

Slide5: 

New Applications

Synchronization: 

Synchronization User benefits Automatic synchronization of calendars, address books, business cards Push button synchronization Proximity operation

Cordless Headset: 

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

Usage scenarios examples: 

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

Slide9: 

Bluetooth Specifications

Bluetooth Stack: 

Bluetooth Stack A hardware/software/protocol description An application framework

Interoperability & Profiles: 

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

Slide12: 

Technical Overview

Bluetooth Radio Specification: 

Bluetooth Radio Specification

Radio: 

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 1600 hops/sec Strong interference protection Fast ARQ Robust access code Forward header correction

Radio: 

Radio Allow low cost low IF Trade sensitivity for integration One chip radio is possible 0 dBm -20 -70 -91 Tx power Rx power @ 10 cm Rx power @ 10m Noise floor C/I = 21 dB

Baseband: 

Baseband

Connection Setup: 

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

Piconet formation: 

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

Addressing: 

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

Piconet channel: 

Piconet channel m s1 s2 625 sec f1 f2 f3 f4 1600 hops/sec f5 f6 FH/TDD

Multi slot packets: 

Multi slot packets m s1 s2 625 sec f1 f4 f5 f6 FH/TDD Data rate depends on type of packet

Packet Format: 

Packet Format Access code Header Payload 72 bits 54 bits 0 - 2745 bits Synchronization identification Filtering 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

Physical Link Types: 

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

Mixed Link Example: 

Mixed Link Example m s1 s2 SCO SCO SCO

Inter piconet communication: 

Inter piconet communication Cell phone Cordless headset Cordless headset Cell phone

Scatternet: 

Scatternet

Scatternet, scenario 2: 

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

Link Manager Protocol: 

Link Manager Protocol Setup and Management of Baseband connections Piconet Management Link Configuration Security

Link Manager Protocol: 

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

L2CAP: 

L2CAP Logical Link Control and Adaptation Protocol L2CAP provides Protocol multiplexing Segmentation and Re-assembly Quality of service negotiation Group abstraction

L2CAP Packet Format (CO): 

L2CAP Packet Format (CO) Length DCID Payload 15 bits 16 bits 0 - 64K bytes Baseband packets Minimum MTU is 48 bytes ! default is 672 bytes !

L2CAP Packet Format (CL): 

L2CAP Packet Format (CL) Length DCID Payload 15 bits 16 bits 0 - 64K bytes Baseband packets PSM

Serial Port Emulation using RFCOMM: 

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

Bluetooth Service Discovery Protocol: 

Bluetooth Service Discovery Protocol

Example usage of SDP: 

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

IP over Bluetooth V 1.0: 

GOALS IP over Bluetooth V 1.0 Internet access using cell phones Connect PDA devices & laptop computers to the Internet via LAN access points

LAN access point profile: 

LAN access point profile Access Point

Inefficiency of layering: 

Inefficiency of layering Emulation of RS-232 over the Bluetooth radio link could be eliminated Bluetooth RFCOMM rfc 1662 PPP IP Bluetooth RFCOMM rfc 1662 PPP IP Palmtop LAN access point packet oriented packet oriented byte oriented

Terminate PPP at LAN access point: 

Terminate PPP at LAN access point PPP server function at each access point management of user name/password is an issue roaming is not seamless Bluetooth RFCOMM PPP IP Bluetooth RFCOMM PPP IP ethernet Palmtop Access Point

L2TP style tunneling: 

L2TP style tunneling 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 radio link RFCOMM PPP IP Palmtop Access Point radio link RFCOMM PPP IP PPP server

IP over Bluetooth: 

IP over Bluetooth 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 Next steps

Research challenges: 

Research challenges Techniques for link formation Routing over scatternets Resource Discovery Plug-n-play applications Internet Will the current solutions for each layer work in this environment?

What is different in this scenario ?: 

What is different in this scenario ? Dynamic network Isolated network Simple devices Small, multi-hop networks Connection oriented, low-power link technology Applications ---> services ----> routing ----> link creation

Link Formation: 

Link Formation Low power modes require careful use of broadcast The problem does not exist in most wired/wireless networks Maintaining connectivity in absence of application traffic seems wasteful Hints from higher layer are needed

Routing over Scatternets: 

Routing over Scatternets x7 x8 x6 x4 x3 x5 y2 x2 x1 y1 Nodes must co-operate to forward packets (MANET style protocols) Forwarding at Layer 2 or Layer 3? Bridging or routing ? What interface should be exported to the above layer? Better coupling with the service discovery layer is needed

Service discovery: 

Service discovery 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

Point to ponder : 

Point to ponder Will Zero-conf on top of MANET on top of scatternet construction algorithm solve our problem? Layered and simple, but potential inefficiencies Cross-layer optimizations are worth considering

Final Remarks: 

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? http://www.research.ibm.com/people/p/pravin