2. Low power : peak tx power <= 20 dBm
What is Bluetooth
Bluetooth is a universal radio interface in the 2.4 GHz frequency band that enables electronic devices to connect and communicate wirelessly via short-range ( m), ad-hoc networks.
Key Features :
Peak data rate : 1 Mbps
Low power : peak tx power <= 20 dBm
Low cost : target is $5-10 per piece
Ability to simultaneously handle both voice and data

3. Bluetooth History Invented in 1994 by L. M. Ericsson, Sweden
Named after Harald Blaatand “Bluetooth”, king of Denmark A.D.
Bluetooth SIG founded by Ericsson, IBM, Intel, Nokia and Toshiba in Feb 1998
More than 1900 members today
Bluetooth version 1.0 and 1.1 have been released
Ericsson realized that for the system to succeed and the required synergy between devices, a critical mass of portable devices must use the short range radio.

4. Intended Application for Bluetooth
Cordless
headset
Cell phone
mouse
Ubiquitous Computing environment of intelligent networked devices
Mobile access to LANs/Internet
Home Networking
Automatic Synchronization of data
Voice applications - hands-free headset
Started as a Cable replacement technology

5. System Challenges
Work across a diverse set of devices with varying computing power and memory
Dynamic environment - the number, location and variety of devices changing - connection establishment, routing and service discovery protocols have to take this into consideration
Unconscious connection establishment
Size of the implementation should be small. The power consumption should not be more than a fraction of the host device .

6. Bluetooth Protocol Stack
System Architecture
Applications
Control
The Radio, Baseband and
Link Manager are on firmware.
The higher layers could be in soft-
ware.
The interface is then
through the Host Controller
(firmware and driver)
The HCI interfaces defined for
Bluetooth are UART, RS232 and
USB. IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband RF
Bluetooth Protocol Stack

7. Bluetooth Air Interface
Piconet channel definition
Physical link definition
Packet definition

8. Choices made ISM Band Frequency Hopping
Global Availability
License Free
2,400-2,483.5 MHz in Europe and US
2,471-2,497 MHz in Japan
Frequency Hopping
Interference from baby monitors, garage door openers, cordless phones and microwave ovens.
Spread-Spectrum for interference suppression
FH supports low power, low cost radio implementations
In the US radios operating in the ISM band are required to apply spread spectrum spreading if their transmitted power levels exceed 0 dBm

9. Frequency Hopping
1Mhz
83.5 Mhz 79 1
Divide Frequency band into 1 MHz spaced 79 hop channels
Radio hops from one channel to another in a pseudo
-random manner as dictated by a hop sequence
1600 hops per second hop-rate--> provides good immunity
from other interfering sources
Dwell time 625 micro second
The instantaneous (hop) bandwidth remains small
Narrow band interference rejection
Low cost narrowband transceivers
Hop sequence – long period –23hrs, short term equal prob for each of the 79 hop channels

10. Piconets, Masters and Slaves
In principle each unit is a peer with the
same hardware capabilities
Two or more Bluetooth units that share
a channel form a piconet
One of the participating units is becomes
the master (by defn the unit that
establishes the piconet).
Participants may change roles if a slave
unit wants to take over as master
Only one master in a piconet.
Upto 7 slaves m s

12. Piconet Channel
The piconet channel is represented by a pseudo-random hopping sequence (through 79/23 RF frequencies)
The hopping sequence is unique for the piconet and is determined by the device address of the master of the piconet. The phase is determined by the master clock.
Channel is divided into time slots microsecs each .
Each slot corresponds to a different hop frequency.
Time Division Duplex - master and slave alternately transmit/listen.
Packet start aligned with slot start
Nominal hop frequency of 1600 hops/sec

13. Piconet Channel m s1
625 sec f1 f2 f3 f4

14. Physical Link
Synchronous Connection Oriented (SC0) Link : - symmetric point-to-point link between m and s - reserved 2 consecutive slots at regular intervals - master can support upto 3 simultaneous SCO links - mainly for audio/voice never retransmitted
Asynchronous Connection-less (ACL) Link :
- symmetric/asymmetric point-to-multipoint between master and all slaves - on a per-slot basis (polling scheme for control) - only one ACL link per piconet - packets retransmitted (ARQ)

15. Packets
All data on the piconet channel is conveyed in packets
13 packet types are defined for the Baseband layer - Control packets (ID, NULL, FHS, POLL) - Voice packets (SCO) Data packets (ACL)
Multi-slot packets (1/3/5) : To support high data rates. Packets always sent on a single-hop carrier – that for the first slot. After multi-slot packet revert to original hop sequence.
Packet format - (68/72 bits) Access Code, (54 bits) Header, ( bits) Payload.

16. Packet Format SCO ACL 72 bits 54 bits 0 - 2745 bits Access code Header
Payload
SCO
ACL
Voice
data
header
CRC
Single-slot packets
64 kbps
Unprotected/ 1/3 or
2/3 FEC
Never retransmitted
Robust CVSD encoding
used
1/3/5 slot packets
Unprotected/ 2/3 FEC
ARQ scheme – retran-
smit lost data pkts

17. Data Rates on ACL TYPE SYMMETRIC (Kbps) ASYMMETRIC (Kbps)
DM1 (2/3 FEC)
108.8
DH1 (unprotected)
172.8
DM3
256.0
384.0
54.4
DH3
576.0
86.4
DM5
286.7
477.8
36.3
DH5
432.6
721.0
57.6.
DM – 2/3 FEC DH – unprotected
DHx, DMx – x slot

18. Access Code
Access code is used for timing synchronization, inquiry and paging. There are 3 types of access codes
Channel Access Code (CAC) : Used to identify a unique piconet. Derived from the device address of the master of the piconet. All “normal” (non inquiry and paging) packets on the piconet will use the CAC.
Device Access Code (DAC) : Used for paging procedure (initial synchronization). Derived from the device address of the slave.
Inquiry Access Code : Used for inquiry procedure (to get device addresses). 2 types : Generic and Device IACs

19. Header
Addressing (3) : Max 7 slaves per piconet
Packet type (4) : 13 packet types (some unused)
Flow control (1)
1-bit ARQ (1) : Broadcast packets are not Acked
Sequencing (1) : for filtering retransmitted packets
HEC (8) : Verify Header Integrity
Total = 18 bits Encode with 1/3 FEC to get 54 bits

20. NETWORKING Connection Establishment Piconet Communication
Scatternet Communication

21. Piconet Channel

22. Channel Complete contention free mac, controlled by master
A channel is associated with a piconet, a temporary state
Channel is determined by identity (providing hop-sequence) and clock (providing hop phase) of the master unit, different channel have different master and so different hop sequence.
The unit that established the piconet becomes the master

23. Packet communication Master also controls the packetized traffic
A packet is not greater than 625 microsecond, the dwell time
Master controls, only communication between master and more than one slave is possible.
Time slots are alternately used for transmitting and receiving.
For each slave-to-master slot, the master decide which slave to transmits.
So it send a short POLL packet from master to slave slot ( along with data for that slave if it has.

24. Multi slot packet
1, 3 or 5 slot packet. Indicated to destination in packet header

25. Connection Establishment
Problem how to communicate hop sequence of master and hop phase?
Inquiry – to get device addr
Inquiry Scan: The master uses the Universal Inquiry hop sequence and the (Inquiry Access Code) IAC
Inquiry Response: The recipient sends back FHS packet in universal inquiry response hop sequence ( providing for clock and identity)
Paging – for Synchronization

26. Connection Establishment Contd..
Inquiry Scan
A device which needs to be discovered will chose out of the 16 frequencies in the inquiry hop sequence depending on its device address. It will stay in that state long enough for an enquiring device to cover 16 different frequencies.
Inquiry Response
not sent in the immediately following slot after the slot in which inquiry is received as that might cause many devices listening at a given frequency to respond simultaneously, resulting in a collision.
So the responding device waits somewhere between microseconds and then sends its FHS packet to the inquirer. The FHS packet contains the device address, its clock and information about when the device enters its page scan states. After responding to an inquiry, the device continues its inquiry scan at another frequency.

27. Connection Establishment Contd..
With inquire process the master device collects the device id s and an idea about device clocks
Page Scan State:
In page scan state, the slave listens to page packets addressed to its DAC for a time window at a frequency it chooses out of the page scan sequence. This window is long enough to cover 16 frequency hops of a paging device.

28. Paging by master:
Similar to Inquiry with the exception that now it is unicast with listeners device id and on paging hop sequence
Masters tries to estimate the phase which may be wrong. Hence it pages in all page sequence hops ( determined by listener’s device id) with device id.
On receiving Page, the listener transmits in the next slot.
On receiving response the master send the FHS at appropriate frequency hop
The listener joins the piconet as slave

29. Connection Establishment - Inquiry
No master and slaves at this point
Inquiry pkt
Inquiry Scan
Inquiry
FHS pkt
Inquiry Response
Device A
Device B

30. Connection Establishment - Paging
Master
Slave
Page pkt
Page
Page Scan
ID pkt
Slave Page
Response
Master Page
Response
FHS pkt
Uses FHS to get
CAC and clk info
ID pkt
Assigns active
addr
POLL
NULL
Connected
Connected

31. Connection Establishment times
Connected
Inquiry
Paging
Typical
5.12 s
0.64 s
Max
15.36 s
7.38 s

32. Connection Modes
Active Mode : Device actively participates on the piconet channel Power Saving modes
Sniff Mode : Slave device listens to the piconet at a reduced rate . Least power efficient.
Hold Mode : The ACL link to the slave is put on hold. SCO links are still supported. Frees capacity for inquiry, paging, participation in another piconet.
Park Mode : The slave gives up its active member address. But remains synchronized (beacon channel). Listens to broadcasts. Most power efficient.

34. Intra-piconet communication
The master controls all traffic on the piconet
SCO link - reservation
The master allocates capacity for SCO links by reserving slots in pairs.
ACL link – polling scheme
The slave transmits in the slave-to-master slot only when it has been addressed by its MAC address in the previous master-to-slave slot. Therefore no collisions.

35. Device Addressing
Bluetooth Device Address (BD_ADDR) unique 48 bit address
Active Member Address (AM_ADDR) bit address to identify active slave in a piconet - MAC address of Bluetooth device - all 0 is broadcast address
Parked Member Address (PM_ADDR) bit parked slave address

36. A group of overlapping piconets is called a scatternet
Why Scatternets
A group of overlapping piconets is called a scatternet
Users in a piconet share a 1 Mbps channel – individual throughput decreases drastically as more units are added
The aggregate and individual throughput of users in a scatternet is much greater than when each user participates on the same piconet
Collisions do occur when 2 piconets use the same 1 MHz hop channel simultaneously. As the number of piconets increases, the performance degrades gracefully

37. Inter-piconet communication
A unit may particpate in more than one piconet on a TDM basis.
To participate on a piconet it needs the master’s identity and the clock offset.
While leaving the piconet it informs the master
The master can also multiplex as slave on another piconet. But all traffic in its piconet will suspended in its absence.

38. Architecture Overview
Link Manager
L2CAP
SDP and RFCOMM

39. Bluetooth Protocol Stack
System Architecture
The Radio, Baseband and Link
Manager are on firmware. The
higher layers could be in soft-
ware. The interface is then
through the Host Controller
(firmware and driver)
The HCI interfaces defined for
Bluetooth are UART, RS232 and
USB.
Applications
Control IP
SDP
RFCOMM
Data
Audio
L2CAP
Link Manager
Baseband RF
Bluetooth Protocol Stack

40. Link Manager
LMP (Link Manager Protocol) basically consists of a number of PDUs sent in the baseband payload.
LMP packets can be recognised by the L_CH field in the baseband header.
Link Manager handles Piconet management (attach/detach slaves, master- slave switch) Link Configuration (low power modes, QoS, packet type selection) Security

41. Logical link and adaptation protocol
L2CAP
Logical link and adaptation protocol
Only ACL links
Concept of L2CAP channels and Channel ids – analogous to sockets in TCP/IP
Functions
Protocol multiplexing
Segmentation and reassembly
QoS specifications
Signalling channel for connection request, config etc

42. Transport protocol providing serial data transfer
Higher layers
SDP
Service Discovery Protocol – runs on a client server model. Each device runs only one SDP server and one client may be run for each application.
RFCOMM
Transport protocol providing serial data transfer

43. References

44. References
Jaap Haarsten, Bluetooth – The universal radio interface for ad-hoc wireless connectivity, Ericsson Review, no. 3,
Palowireless
Aman Kansal, Connection Establishment in Bluetooth
The official bluetooth site -