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Bluetooth Connection: Packets, Errors, Flow, Modes, Study notes of Mobile Computing

An overview of bluetooth packets, their formats, error correction and flow control mechanisms, and connection modes. It covers the use of access codes, packet headers, and the role of the master device in controlling traffic on the piconet. The document also discusses various power saving modes and applications of bluetooth technology.

Typology: Study notes

2010/2011

Uploaded on 09/04/2011

amit-mohta
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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, (0-2745 bits) Payload.
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff

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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)
      • VoiceData packets (ACL) packets (SCO)
  • (^) 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, (0-2745 bits) Payload.

Packet Format

Access code Header Payload

Voice^ 1/3/5 Unprotected/ 2/3 FEC ARQ scheme – retran-^ slot packets Single-slot Unprotected/ Never retransmitted packets 1/3 or (^64) 2/3 kbps FEC smit lost data pkts Robust CVSD encoding used

72 bits 54 bits 0 - 2745 bits

header data CRC

SCO

ACL

mble^ prea^ syn c trail er addres^ AM^ s type flow^ ARQ^ N^ SEQ^ N HEC

Access Code

  • (^) Access code is used for timing synchronization, inquiry and paging. There are 3 types of access codes
  • (^) Channel unique piconet. Derived from the device address of Access Code (CAC) : Used to identify a

the master of the piconet. All “normal” (non inquiry and paging) packets on the piconet will use the CAC.

  • (^) Device procedure (initial synchronization). Derived from the Access Code (DAC) : Used for paging
  • device address of the slave. Inquiry Access Code : Used for inquiry procedure (to

get device addresses). 2 types : Generic and Device IACs

Header

  AddressingPacket type (3) : Max 7 slaves per piconet(4) : 13 packet types (some

 unused)Flow control (1)

 1-bit ARQ Acked (1) : Broadcast packets are not

 Sequencing packets (1) : for filtering retransmitted

 HEC Total = 18 (8) : Verify Header Integrity bits

Encode with 1/3 FEC to get 54 bits

Bluetooth Connection Establishment

  • (^) Two step process : Inquiry – to get device address Paging – for Synchronization
  • (^) Inquiry the IAC (DIAC or GIAC) : Uses the Inquiry hop sequence and
  • (^) Paging the DAC of the device to be paged : Uses the Paging hop sequence and

Connection Establishment -

Inquiry

Inquiry Inquiry Scan Inquiry Response

Inquiry pkt FHS pkt

No master and slaves at this point

Device A (^) Device B

Connection Establishment

times

Inquiry Paging^ Connected

Typical Max

5.12 s 15.36 s

0.64 s 7.38 s

Connection Modes

  • (^) Active piconet (^) Mode channel : Device actively participates on the
  • (^) Sniff ModePower Saving modes^ Power Saving modes : 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 inquiry, paging, participation in another piconet. links are still supported. Frees capacity for

  • (^) Park Mode address. But remains synchronized (beacon channel). : The slave gives up its active member

Listens to broadcasts. Most power efficient.

Major Baseband states of a Bluetooth device standby

Hold AMA Sniff AMA

Transmit AMA

Park AMA

inquiry Connected AMA

page

Low Power

active

connecting

unconnected Detach

Device Addressing

• Bluetooth Device Address unique 48 bit address (BD_ADDR)

• Active Member Address - 3 bit address to identify (AM_ADDR) active

slave in a piconet - MAC address of Bluetooth device

address^ - all 0 is broadcast

• Parked Member Address - 8 bit parked (PM_ADDR)slave address

Bluetooth – Applications (2)

  • (^) In meetings and conferences you can transfer selected documents instantly with selected participants cards automatically, without any wired connections., and exchange electronic business
  • (^) Connect your wireless headset to your mobile phone, mobile computer or any wired connection to keep your hands free for more important tasks when you're at the office or in your car
  • (^) If your digital cameras in Bluetooth enabled, you can send still or video images from any location connecting your camera to the mobile phone on the to any location without the hassle of
  • wireline phone. Upon arriving at your home, the door automatically lights come on, unlocks and thefor heatyou, isthe adjusted entry way to your pre-set preferences.

• Bluetooth – Applications (3) Have automatic synchronization of your desktop, mobile

computer, notebook (PC-PDA and PC-HPC) and your mobile phone. list and calendar in your notebook will automatically be updated to For instance, as soon as you enter your office the address agree with the one in your desktop, or vice versa.

  • (^) Automatic portable PC while you're on an airplane. As soon as you've landed and switched on your mobile phone, all messages are immediately Message Delivery: Compose e-mails on your sent.
  • (^) IBM researchers are working on a number of personal devices like a Bluetooth. WatchPad The Watch Pad is very thin and contains 8MB of RAM. that could be connected with other devices through They CyberPhone CyberPhone are also - can thatworking show can asprojecton mucha versiondata information onto of CyberPhone a smallas a mirror.small called PDAThe because of high resolution VGA screen.