Tachyon 100G PCB Performance Attributes and Applications
Bluetooth.ppt
1. CMPE 257 - Wireless and Mobile Networking
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Bluetooth
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Overview
• Cable replacement technology.
– Connect devices such as phone handsets,
headsets, computer peripherals, etc.
• Industry standard.
– Allows wireless communication between
devices.
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Applications: Cable Replacement
1 Mb/s.
• Range ~10 meters.
• PANs
• Single chip radio.
– Low power & low cost.
Why not use Wireless LANs?
- power
- cost
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Applications: Synchronization
• Automatic synchronization of
calendars, address books,
business cards.
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More applications…
• Conference table.
• Cordless computer.
• Instant photo transmission.
• Cordless phone.
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Bluetooth Origins
• Study by Ericsson Mobile Communications in
1994.
– Alternatives to cables connecting mobile
phones to accessories.
– Use of radio links instead of infrared.
• Why?
– Transmission of data and voice.
• Result: Bluetooth spec.
– Named after Harald Blatand (Danish for
Bluetooth).
– 10th century Viking king who united Denmark
and Norway.
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Bluetooth SIG History
• Early 1998: Bluetooth SIG is formed.
– Promoter company group: Ericsson, IBM,
Intel, Nokia, Toshiba.
– Goal: develop license-free technology for
universal wireless connectivity.
– Target: handheld market.
– Bluetooth spec: defines RF wireless
communication interface and protocols.
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Bluetooth SIG History
• May 1998: Public announcement of Bluetooth SIG.
• July 1999: 1.0A spec (>1,500 pages) published.
• December 1999: version 1.0B released.
• December 1999: promoters increases to 9.
– 3Com, Lucent, Microsoft, Motorola
• February 2000: 1,800+ adopters.
• February 2001: version 1.1 out.
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More History…
• Recently, IEEE 803.15.1 standard for
Wireless PANs (WPANs)
– Only MAC and PHY.
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Goals
• Open spec.
• Low cost.
– In order to replace cables, should have similar cost.
– Cell phone cable is ~ $10.
• Power efficiency.
• Lightweight and small form factor.
• Easy to use.
• Reliable and resilient to failures.
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The Bluetooth Standard
• Defines a protocol stack to enable
heterogeneous devices to communicate.
• The Bluetooth stack includes protocols for
the radio layer all the way up to device
discovery, service discovery, etc.
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Bluetooth Protocol Stack
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
PHY
Data Link Layer
Network Layer
Transport Layer
Session Layer
Presentation Layer
Application
OSI/ISO
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Bluetooth Layers
• Radio: physically transmits/receives data.
• Baseband/Link Controller: controls PHY.
• Link Manager: controls links to other devices.
• Host Controller:e2e communication.
• Logical Link Control:
multiplexes/demultiplexes data from higher
layers.
• RFCOMM: RS323-like serial interface.
• SDP: allows service discovery among
Bluetooth devices.
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The Bluetooth PHY
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Radio Band
• 2.4 GHz license-free ISM band.
• Available worldwide.
• Industrial, Scientific, Medical (ISM) band.
– Unlicensed, globally available.
– Centered around 2.4 GHz.
• Resilient to interference.
• Frequency hopping.
• Range: 10, 20, and 100m.
• 1MB/s.
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Bluetooth Radio Link
• MA scheme: Frequency hopping spread spectrum.
– 2.402 GHz + k MHz, k=0, …, 78
– 1,600 hops per second.
– 1 Mb/s data rate.
. . .
1Mhz
1 2 3 79
83.5 Mhz
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BT Radio Link (Cont’d)
• Time-division duplex (TDD)
– Separation of Xmission and reception in time.
– Units alternate transmits and receives.
• Gaussian Frequency Shift Keying (G-FSK)
modulation.
– ‘1’s as positive frequency deviations from
carrier frequency; ‘0’s as negative deviations.
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Multiple Access
• BT targets large number of independent
communications active in the same area at the same
time.
• Single FH channel: 1 Mb/s.
• Each 1Mb/s channel shared by limited number of
participants.
– In target user scenarios, it’s unlikely that all units in-
range will share data among all of them.
– 1 MB/s is reasonable. (is it?)
• Theoretically, total bandwidth is 79 Mb/s.
– In practice, < 79 Mb/s since codes are non-orthogonal.
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Baseband
Carries out MAC
functions.
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
Control end of baseband
+link controller=
Data link layer
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Master and Slaves
• Communicating devices must agree on
hopping sequence.
• BT devices can operate as masters or slaves.
• Master node defines sequence to be used.
• Slave units use master id to pick sequence.
• Master also controls when devices are
allowed to transmit.
– Master allocates slots to slaves.
– Allocates total available bandwidth among
slaves.
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Piconets
• BT communication takes place over piconets.
• Piconet formation initiated by master.
• All other participants are slaves.
• Number of participants limited to 8 (1 master and 7
slaves).
– Channel capacity and addressing overhead.
– Each slave assigned a locally unique ID.
• Master/slave roles last for the duration of the piconet.
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More on Piconets
• On a piconet, slaves only have direct links to
master.
• Point-to-point or point-to-multipoint
connections.
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Piconets: Considerations
• Most target applications involve local
communication among small group of
devices.
• Piconets with up to 8 nodes match well.
• If many groups of devices active
simultaneously, each group as separate
piconet.
• Overlapping piconets can coexist.
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Contention-Free MA
• Master and slaves.
• Master performs medium access control.
– Schedules traffic through polling.
• Time slots alternate between master and slave
transmission.
– Master-slave: master includes slave address.
– Slave-master: only slave chosen by master in previous
master-slave slot allowed to transmit.
– If master has data to send to a slave, slave polled
implicitly; otherwise, explicit poll.
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BT States
Standby
Inquiry Page
Transmit Connected
Park Hold Sniff
Unconnected
Connecting
Active
Low power
. Initially, all nodes in
standby.
. Node (master) can begin
inquiry to find nearby
devices.
. Piconet is then formed.
. Devices join by paging.
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Inquiry
• Device discovery
• Listeners respond with
their address.
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Paging
Master
Active Slave
Parked Slave
Standby
• Device enters paging to
invite others to join its
piconet.
• Establishes links with nodes
in proximity.
• Paging message unicast to
selected receiver.
• Receiver sends ACK.
• Sender becomes master,
receiver slave.
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Piconet New Node Admission
• Master can actively try to discover new nodes
or wait (in scan/listen mode) to be discovered.
• Communication in the current piconet
suspended.
• Admission latency versus piconet capacity
tradeoff.
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Bluetooth Link Formation
• Point-to-point link:
– Master-slave relationship.
m s
s
s
m
s
• Piconet:
– 8 units: channel capacity.
– Master (establishes piconet) can
connect to up to 7 slaves.
– Master/slave relationship lasts while
link/piconet lasts.
– No slave-to-slave communication.
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Link Types
• 2 types of links:
– Synchronous (SCO) links:
• Point-to-point between master and slave.
• Link established by reserving slots in either direction
periodically.
• Used to carry real-time traffic (voice).
– Asynchronous (ACL) links:
• Point-to-multipoint between master and slaves.
• Use remaining slots on channel.
• Traffic scheduled by master.
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Error Control
• Supports both FEC and retransmission.
• FEC for SCO packets.
• ARQ for ACL traffic.
– If no ACKs, retransmit.
– Stop-and-wait ARQ.
• Fast-ARQ: ACK included in RX slot
immediately following the TX slot in which
packet was sent.
– CRC to check for errors.
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Packet Format
72 bits 54 bits 0 - 2744 bits
Access
code
Header Payload
Data
Voice CRC
No CRC
No retries
625 µs
master
slave
ARQ
FEC (optional)
FEC (optional)
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Access Code
• Address of piconet master.
Access
code
Header Payload
72 bits
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Packet Header
• Addressing (3)
• Packet type (4)
• Flow control (1)
• 1-bit ARQ (1)
• Sequencing (1)
• HEC (8)
Access
code
Header Payload
54 bits
Purpose
Broadcast packets are not ACKed
For filtering retransmitted packets
18 bits
total
s
s
m
s
16 packet types (some unused)
Max 7 active slaves
Verify header integrity
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Multiple Piconets
• Piconets may overlap in space and time.
• They can work independently.
– Each with its own hopping sequence.
– Packets with different access codes.
• Or they can overlap, i.e., nodes can
participate in more than 1 piconet.
– “Time sharing”.
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Scatternets
• Interconnection of multiple piconets.
Master
Slave
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Scatternets (cont’d…)
• Interconnection by bridge nodes.
– Bridge nodes are members of piconets they
interconnect.
– Bridge node “stay” in a piconet for some time,
then switch to another piconet by changing
hop sequence.
– Do this for all member piconets.
– Send and receive in each piconet.
– Forward from one piconet to another.
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Link Controller and Link
Manager
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
Carries out inquiry and paging
operations; manages multiple
links and different piconets.
Attaching/detaching slaves from
piconet; power management; security.
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Power Management
• Low-power modes: prolong battery life.
– Devices can be turned-off when idle.
– Devices wake up periodically to send/receive
data.
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Low-Power Operation
• 3 modes:
– Hold: node sleeps for specified interval.
• Master can put slaves in hold while searching for new
members, attending another piconet, etc.
• No ACL packets.
– Sniff: slave low-duty cycle mode.
• Slave wakes up periodically to talk to master.
• Fixed “sniff” intervals.
– Park:
• Very low power state.
• Used to admit more than 7 slaves in piconet.
– Slave gives up its active member address.
– Receives “parked” member address.
• Wakes up periodically listening for broadcasts which can be
used to “unpark” node.
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Security
• Authentication and encryption.
• LMP provides mechanisms for negotiation of
encryption modes, keys, etc.
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Host Controller Interface
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
Optional interface layer
between higher and lower
layers of the BT stack.
E.g., when lower- and higher
BT layers run on different
Devices: PCMCIA card and
PC’s processor.
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L2CAP
Logical Link Control and
Adaptation Protocol=
Session Layer.
L2CAP provides
• Protocol multiplexing
• Quality of service negotiation
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
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RFCOMM/SDP
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
Service discovery, serial port
interface.
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References:
• Bluetooth papers in reading list.
• Johansson and Gerla’s Bluetooth Tutorial at
Mobicom 2001.
• Bluetooth 1.1: Connect Without Cables, Bray
and Sturman.
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Features Cost
20 dBm (~100 m)
Point-to-multipoint
No Scatternet
Applications
File Transfer,
Dial-Up Networking
LAN access, Fax, …
169 $
---
200 $
0 dBm (~10 m)
Point-to-multipoint
No Scatternet
File Transfer,
Dial-Up Networking
LAN access, Fax, …
169 $
---
Company
Toshiba,
Motorola,
Digianswer
IBM, TDK
3COM
10 m user-user;
100 m user-Base Station
Point-to-multipoint
SW- & FW-upgradeable
File Transfer,
Dial-Up Networking
LAN access, Fax, E-mail
Unconscious connection
149 $
Nokia
10 m user-user;
Point-to-point
Connectivity Battery
for the cell phone
File Transfer,
Dial-Up Networking
LAN access, Fax, E-mail
Unconscious connection
149 $
Ericsson,
Sigma
10 m user-user;
Point-to-point;
ARM processor;
USB; RFCOMM ports
Basic BT Radio stack
Embedded or Host stack
Programmable
500 $
1500$
Bluetooth on the market:
PC cards, Cell phones, Head sets, Chip sets,…