Transcript Ad Hoc Nets
Ad Hoc Nets - MAC layer
Part II – TDMA and Polling -
Bluetooth
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Bluetooth Bluetooth Piconet : a polling/TDMA scheme Bluetooth working group history
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February 1998 : The Bluetooth SIG is formed
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promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba
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+ 3Com, Lucent, Microsoft, Motorola Where does the name come from?
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To honor a 10th century king Bluetooth in Denmark who united that country and established Christianity
What does Bluetooth do for you?
Landline Data/Voice Access Points …and combinations!
Personal Ad-hoc Networks Cable Replacement - Synchronization - Cordless Headset
Example...
Bluetooth Physical link
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Point to point link
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master - slave relationship radios can function as masters or slaves m
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Piconet
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Master can connect to 7 slaves
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Each piconet has max capacity = 1 Mbps s
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~ 10 100 Meter hopping pattern is determined by the master m s s s
Connection Setup
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Inquiry scan protocol
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to learn about the address clock offset and device of other nodes in proximity
Piconet formation
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Page scan protocol
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to establish links with nodes in proximity Master Active Slave Parked Slave
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Connected
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Not in Pico Standby
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Addressing Bluetooth device address
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48 bit IEEE MAC address (BD_ADDR)
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Active Member address (AM_ADDR)
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3 bits active slave address
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all zero broadcast address
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Parked Member address (PM_ADDR)
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8 bit parked slave address
m Piconet MAC protocol : Polling FH/TDD f1 f2 f3 f4 f5 f6 s 1 s 2 625 µ sec 1600 hops/sec
FH/TDD m Multi slot packets f1 f4 f5 f6 s 1 s 2 625 µsec Data rate depends on type of packet
Physical Link Types
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Synchronous Connection Oriented ( SCO ) Link
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slot reservation at fixed intervals Asynchronous Connection-less ( ACL ) Link
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Polling access method ACL
m
ACL ACL ACL ACL ACL
s 1 s 2
Packet Types ID* Null Poll FHS DM1 Control packets Voice HV1 HV2 HV3 DV Data/voice packets DM1 DM3 DM5 data FHS – Frequency Hop Synchronization DM – Data Medium rate HV – High quality Voice DV – Data Voice DH – Data High rate DH1 DH3 DH5
Packet Format 72 bits 54 bits Access code Header 0 - 2744 bits Payload master Voice No CRC No retries FEC (optional) 625 µs slave Data CRC ARQ FEC (optional)
54 bits Packet Header Access code Header Payload s m s s Purpose
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Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8) total 18 bits Max 7 active slaves 16 packet types (some unused) Broadcast packets are not ACKed For filtering retransmitted packets Verify header integrity Encode with 1/3 FEC to get 54 bits
Inter piconet communication Cordless headset mouse Cordless headset Cell phone Cell phone Cell phone Cordless headset
Scatternet Gateway node participates in more than one piconet on a time-division basis
Scatternet, scenario 2 How to schedule presence in two piconets?
Forwarding delay ?
Missed traffic?
Baseband: Summary Device 1 Device 2 L2CAP LMP Baseband Data link L2CAP LMP Baseband Physical
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TDD , frequency hopping physical layer Device inquiry and paging Two types of links: SCO and ACL links Multiple packet types ( multiple data rates with and without FEC)
L
ink
M
anager
P
rotocol SDP Applications IP RFCOMM Data L2CAP Audio Link Manager Baseband RF LMP Setup and management of Baseband connections
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Piconet Management Link Configuration Security
Piconet Management
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Attach and detach slaves Master-slave switch Establishing SCO links Handling of low power modes ( Sniff, Hold, Park ) Paging m s s s req response
L2CAP SDP Applications IP RFCOMM Data L2CAP Audio Link Manager Baseband RF L2CAP L ogical L ink C ontrol and A daptation P rotocol L2CAP provides
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Protocol multiplexing
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Segmentation and Re-assembly
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Quality of service negotiation
RFCOMM
( R adio F requency Comm unication) --
Serial Port Emulation using RFCOMM SDP Applications IP RFCOMM Data L2CAP Audio Link Manager Baseband RF
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Serial Port Serial Port emulation
top of a packet oriented link
Similar to HDLC
on
(High level
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Data Link Control protocol)
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RS232 For supporting legacy apps
IP over Bluetooth V 1.0
SDP Applications IP RFCOMM Data L2CAP Audio Link Manager Baseband RF GOALS
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Internet access cell phones using
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Connect PDA devices & laptop computers to the Internet via points LAN access
Palmtop Inefficiency of layering LAN access point IP PPP rfc 1662 packet oriented IP PPP rfc 1662 byte oriented RFCOMM RFCOMM packet oriented L2CAP L2CAP
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Emulation of RS-232 over the Bluetooth radio link could be eliminated
Bluetooth Networking: A Layer 2 Support IP Ethernet-like broadcast segment Bluetooth slave 1 slave 2 master slave 3 slave 4 master slave 5
Where is BNEP in the Bluetooth Stack?
Bluetooth Network Encapsulation Protocol
Host Controller Interface BNEP IP IP PPP RFCOMM L2CAP Baseband Bluetooth Radio SDP LMP
The Bluetooth Network Encapsulation Protocol (BNEP) Purpose?
Create a Ethernet-like broadcast environment for IP in a Bluetooth Scatternet, hiding Bluetooth specifics (e.g. notion of piconet/scatternet forming and maintenance) from IP and above
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Features: Clear division between Bluetooth spec and IP IP and IP networking applications will work as usual (DHCP, ARP) Easy to apply zeroconf protocols across
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scatternets Ad-hoc L2 routing, handle loop-free broadcast
0 4 BNEP Type = 0x02 E 8
BNEP Overhead
12 16 20 Networking Protocol Type 24 28 Extension Header or BNEP Payload ...
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Type: 7 bit Bluetooth value identifies the type of BNEP header contained in this packet 1 bit extension flag that indicates if one or more extension headers follow the BNEP Header before the data payload. 1M of Data transfer
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Additional ~0.2% Overhead
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Additional Bluetooth Transmission time: 11 mSec
Bluetooth Personal Area Networks - Ad Hoc and extend to Mesh
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PANs extend the Internet to the user personal domain 3G (2.5G) networks will give Internet access to PANs PANs will generate more traffic than a single device Utilize an aggregate of access networks ( WLAN , 3G, DSL)
IP Bluetooth Networking - Conclusions
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Bluetooth IP networking opens up new possibilities --- Mesh networks Enables
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spontaneous Ad Hoc Between people, Between machines, networking Mainly
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small , short range ad-hoc networks Solves your “ personal problems ” ...
Limited complexity and security risks The enabler for
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PANs ! Gives a natural extension of Internet into the PAN
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via 3G Enables stepwise upgrading of devices -- not tied to one multimedia terminal!
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Makes use of the 3G bandwidth immediately QoS ~ Bluetooth ?