Upload
hemant-singh-chauhan
View
222
Download
0
Embed Size (px)
Citation preview
8/4/2019 Bluetooth and BlueZ
1/26
BLUETOOTH
Hemant Singh Chauhan
8/4/2019 Bluetooth and BlueZ
2/26
About Bluetooth
Open wireless Technology
Uses Short Wavelength Radio Technology (SWRT)
Create PANs
Managed by BSIG
Uses ISM band at 2.4 GHz
8/4/2019 Bluetooth and BlueZ
3/26
How It Works
Uses Radio Technology FHSS
FHSS chops data and transmit it :
Up to 79 channels
1600 hops per sec
Data and Voice Transmission :
ACL Data Connection
SCO Voice Channels
Piconet and Scatternet Topology
Packet Based protocol and Master-Slave Structure
8/4/2019 Bluetooth and BlueZ
4/26
Piconet
active slave
master parked slave
standby
Star Topology
Master:
determines hopping
scheme and timing
Administers piconet
(polling)
Logical Channels
Asynchronous, packetoriented
Synchronous Connection-
Oriented
8/4/2019 Bluetooth and BlueZ
5/26
Operational States
Master
P
SB
SB
SB
Operational States
Slave
Parked*
Standby*
* Low power states
A piconet
M
S
S
S
S
8/4/2019 Bluetooth and BlueZ
6/26
Forming a Piconet - I
Initially, devices know only about themselves
No synchronization
Everyone monitors in standby mode
All devices have the capability of serving as master or
slave
D AE
B
CF
KJ
H
G
I
M
NL
P
O
Q
8/4/2019 Bluetooth and BlueZ
7/26
Forming a Piconet - II
Unit establishing the piconet automatically becomes themaster
It sends an inquiry to discover what other devices are out
there
Addressing
Active devices are assigned a 3-bit active member address(AMA)
Parked devices are assigned an 8-bit parked member address(PMA)
Standby devices do not need an address
8/4/2019 Bluetooth and BlueZ
8/26
Connection Establishment
INQUIRY PAGE CONNECTION
8/4/2019 Bluetooth and BlueZ
9/26
States
disconnected
connecting
active
detach
standby
inquiry page
TransmitAMA
ConnectedAMA
ParkPMA
HoldAMA
SniffAMA
low power
Typical = 2s
Typical = 0.6s
AMA = Active Member Address
PMA = Parked Member Address
Typical = 2ms
8/4/2019 Bluetooth and BlueZ
10/26
Connecting to a Piconet
Device in standby listensperiodically
If a device wants to establish apiconet, it sends an inquiry,
broadcast over all wake-up carriers It will become the master of
the piconet
If inquiry was successful, device
enters page mode Devices in standby may respond to
the inquiry with its device address
It will become a slave to thatmaster
standby
inquiry page
TransmitAMA
ConnectedAMA
ParkPMA
HoldAMA
SniffAMA
8/4/2019 Bluetooth and BlueZ
11/26
Page and Connect States
After receiving a response from
devices, the master can connect to
each device individually
An AMA is assigned Slaves synchronize to the
hopping sequence established
by the master
In active state, master and slaveslisten, transmit and receive
A disconnect procedure allows
devices to return to standby
mode
standby
inquiry page
TransmitAMA
ConnectedAMA
ParkPMA
HoldAMA
SniffAMA
8/4/2019 Bluetooth and BlueZ
12/26
Low Power States
Sniff state Slaves listen to the piconet at a
reduced rate
Master designates certain slotsto transmit to slaves in sniff state
Hold state
Slave stops ACL transmission, butcan exchange SCO packets
Park state
Slave releases its AMA
Still FH synchronized and wakesup periodically to listen tobeacon
standby
inquiry page
TransmitAMA
ConnectedAMA
ParkPMA
HoldAMA
SniffAMA
8/4/2019 Bluetooth and BlueZ
13/26
Scatternet
8/4/2019 Bluetooth and BlueZ
14/26
Features
Piconets with overlapping coverage use differenthopping sequences
Collisions may occur when multiple piconets use the same
carrier frequency at the same time Devices can participate in multiple piconets
simultaneously, creating a scatternet
A device can only be the master of one piconet at a time
A device may serve as master in one piconet and slave inanother
A device may serve as slave in multiple piconets
8/4/2019 Bluetooth and BlueZ
15/26
Bluetooth Architecture
Hardware layer
Radio, Baseband and Link Manager
Access through the Host Controller Interface
Standards for USB and UART
Host protocols
L2CAP, RFCOMM, BNEP, AVDTP etc.
Application profiles
Serial Port Profile, Dialup, PAN, A2DP, HID etc.
8/4/2019 Bluetooth and BlueZ
16/26
Bluetooth Stack
8/4/2019 Bluetooth and BlueZ
17/26
Complex View
8/4/2019 Bluetooth and BlueZ
18/26
Baseband
Responsible for channel coding/decoding, timing
and managing a Bluetooth link.
Master/slave
Devices in a connection are either master or slave.
Communication is only possible between a master
and its slaves. A master and the slaves are named piconets.
Scatternet; multiple piconets connected together.
8/4/2019 Bluetooth and BlueZ
19/26
The Link Manager
Responsible for establishing, supervising and tear down
connections and logical links.
Link controller states introduced to carry out thesetasks.
States:
Standby
Inquiry / Inquiry Scan
Page / Page Scan
Connection
8/4/2019 Bluetooth and BlueZ
20/26
The Link Manager (cont.)
Inquiry
Used to detect all devcies in an unknown environment.
Page / Page Scan Describes how connection is established.
Have to know the address of the other devices. Is usually
achieved through inquiry.
Connection Master and slaves are synchronized.
Connection is established.
8/4/2019 Bluetooth and BlueZ
21/26
Bluetooth and linux
Many Implementations
Embedded and non-free Protocol Stack
Four major known Bluetooth Stacks : OpenBT, BlueDrekar, BlueZ and Affix
Official Protocol stack is BlueZ
Released May, 3rd 2001 Integrated to Linux kernel 2.4.6
8/4/2019 Bluetooth and BlueZ
22/26
BlueZ
Core Layers Real hardware abstraction over HCI
Generic interface for drivers
Support of multiple devices
8/4/2019 Bluetooth and BlueZ
23/26
BlueZ Protocols
Kernel modules for core protocols
Use of the BSD socket interface
Management sockets
Stream or sequential packet sockets
8/4/2019 Bluetooth and BlueZ
24/26
Bluetooth Network
Dialup and LAN access
RFCOMM terminal emulation
Using of PPP and AT commands
LAN access using PPP
Personal Area Networks (PAN)
Linux TCP/IP with BNEP
Use bridging, netfilter, NAT etc.
Access to ISDN
CAPI integration with CMTP
8/4/2019 Bluetooth and BlueZ
25/26
Summary Of BlueZ
BlueZ is qualified by the Bluetooth SIG
Full access to all Bluetooth host layers
Native integration into many projects
Active development
8/4/2019 Bluetooth and BlueZ
26/26
THANK YOU