1. Wireless and Mobile Networks
CMPE Spring 2006 Bluetooth

2. Announcements Access to QualNet. Two options:
Get a CD from the helpdesk (BE 240).
Contains license and necessary instructions.
Or, remote access via ssh.

3. Today
Bluetooth.

4. Bluetooth

5. Overview Cable replacement technology. Industry standard.
Connect devices such as phone handsets, headsets, computer peripherals, etc.
Industry standard.
Allows wireless communication between devices.

6. Applications: Cable Replacement
1 Mb/s.
Range ~10 meters.
PANs
Single chip radio.
Low power & low cost.
Why not use Wireless LANs?
- power
- cost

7. Applications: Synchronization
Automatic synchronization of calendars, address books, business cards.

8. Applications: Cordless Headset
Multiple device access.
Hands-free operation.

9. More applications… Conference table. Cordless computer.
Instant photo transmission.
Cordless phone.

10. 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.

11. 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.

12. 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.

13. More History…
Recently, IEEE standard for Wireless PANs (WPANs)
Only MAC and PHY.

14. Goals Open spec. Low cost. Power efficiency.
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.

15. 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.

16. Bluetooth Protocol Stack
Application
Applications
RFCOMM/SDP
Presentation Layer
L2CAP
Session Layer
Host Controller Interface
Transport Layer
Link Manager
Network Layer
Link Controller
Data Link Layer
Baseband
PHY RF
OSI/ISO

17. 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.

18. The Bluetooth PHY

19. 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.

20. Unlicensed Radio Spectrum
33cm
12cm
5cm
26 Mhz
83.5 Mhz
125 Mhz
902 Mhz
2.4 Ghz
5.725 Ghz
928 Mhz
Ghz
5.785 Ghz
cordless phones
baby monitors
Wireless LANs
802.11
Bluetooth
Microwave oven
unused

21. Bluetooth Radio Link MA scheme: Frequency hopping spread spectrum.
1Mhz
. . . 1 2 3 79
83.5 Mhz
MA scheme: Frequency hopping spread spectrum.
2.402 GHz + k MHz, k=0, …, 78
1,600 hops per second.
1 Mb/s data rate.

22. 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.

23. 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.

24. Host Controller Interface
Baseband
Control end of baseband
+link controller=
Data link layer
Applications
RFCOMM/SDP
L2CAP
Host Controller Interface
Link Manager
Carries out MAC
functions.
Link Controller
Baseband RF

25. 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.

26. 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.

27. More on Piconets
On a piconet, slaves only have direct links to master.
Point-to-point or point-to-multipoint connections.

28. 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.

29. 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.

30. BT States Standby . Initially, all nodes in standby.
. Node (master) can begin
inquiry to find nearby
devices.
. Piconet is then formed.
. Devices join by paging.
Unconnected
Inquiry
Page
Connecting
Transmit
Connected
Active
Sniff
Park
Hold
Low power

31. Inquiry
Device discovery
Listeners respond with
their address.

32. Paging Device enters paging to invite others to join its piconet.
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.

33. 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.

34. Bluetooth Link Formation
Point-to-point link:
Master-slave relationship. m s s m
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.

35. 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.

36. 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.

37. Packet Format 72 bits 54 bits 0 - 2744 bits Access code Header Payload
No CRC
No retries
Voice
header
Data
CRC
FEC (optional)
Mention that over SCO link you cannot carry any other real-time traffic. There is no protocol-id field in the SCO header/payload. Is this really true?
ARQ
FEC (optional)
625 µs
master
slave

38. Access Code 72 bits Access Payload code Header
Address of piconet master.

39. Packet Header m s Purpose Max 7 active slaves
54 bits
Access
code
Header
Payload
Purpose
Addressing (3)
Packet type (4)
Flow control (1)
1-bit ARQ (1)
Sequencing (1)
HEC (8)
Max 7 active slaves
16 packet types (some unused)
How useful is header protection when payload is unprotected
Broadcast packets are not ACKed
For filtering retransmitted packets
Verify header integrity
total
18 bits

40. 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”.

41. Scatternets
Interconnection of multiple piconets.
Slave
Master

42. 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.

43. Link Controller and Link Manager
Applications
RFCOMM/SDP
L2CAP
Attaching/detaching slaves from
piconet; power management; security.
Host Controller Interface
Link Manager
Link Controller
Carries out inquiry and paging
operations; manages multiple
links and different piconets.
Baseband RF

44. Power Management Low-power modes: prolong battery life.
Devices can be turned-off when idle.
Devices wake up periodically to send/receive data.

45. 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.

46. Security Authentication and encryption.
LMP provides mechanisms for negotiation of encryption modes, keys, etc.

47. Host Controller Interface
Applications
Optional interface layer
between higher and lower
layers of the BT stack.
RFCOMM/SDP
L2CAP
Host Controller Interface
Link Manager
E.g., when lower- and higher
BT layers run on different
Devices: PCMCIA card and
PC’s processor.
Link Controller
Baseband RF

48. Logical Link Control and Host Controller Interface
L2CAP
Applications
RFCOMM/SDP
Logical Link Control and
Adaptation Protocol=
Session Layer.
L2CAP
Host Controller Interface
Link Manager
Link Controller
L2CAP provides
Protocol multiplexing
Quality of service negotiation
Baseband RF

49. Host Controller Interface
RFCOMM/SDP
Applications
RFCOMM/SDP
L2CAP
Service discovery, serial port
interface.
Host Controller Interface
Link Manager
Link Controller
Baseband RF

50. References: Bluetooth papers in reading list.
Johansson and Gerla’s Bluetooth Tutorial at Mobicom 2001.
Bluetooth 1.1: Connect Without Cables, Bray and Sturman.

51. Bluetooth on the market:
PC cards, Cell phones, Head sets, Chip sets,…
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)
Company
Toshiba,
Motorola,
Digianswer
IBM, TDK
3COM
10 m user-user;
100 m user-Base Station
SW- & FW-upgradeable
LAN access, Fax,
Unconscious connection
149 $
Nokia
Point-to-point
Connectivity Battery
for the cell phone
Ericsson,
Sigma
Point-to-point;
ARM processor;
USB; RFCOMM ports
Basic BT Radio stack
Embedded or Host stack
Programmable
500 $
1500$