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Mobile Computing - Bluetooth - System Architecture, Study notes of Mobile Computing

In this document topics covered which are System Architecture, Link manager Protocol, Baseband, Logical Link Control and adaptation protocol , Service Discovery Protocol, Frequency Hopping.

Typology: Study notes

2010/2011

Uploaded on 09/04/2011

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System Architecture
RF
Baseband
Link Manager
Audio L2CAP
Control
Data
RFCOMM
SDP IP
Applications
Bluetooth Protocol Stack
The Radio, Baseband and Link
Manager are on firmware. The
higher layers could be in software.
The interface is then through the
Host Controller (firmware and
driver). The HCI (Host Controller
Interface) interfaces between the
baseband and L2CAP provides a
command interface to the baseband
controller and link manager and
access to the hardware status and
control registers. The HCI
Interface defined for Bluetooth are
UART, RS232 and USB. Audio
Applications may directly use the
basband layer after encoding the
audio signals.
pf3
pf4
pf5

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1

System Architecture

RF

Baseband

Link Manager Audio L2CAP

Data Control

RFCOMM SDP IP

Applications

Bluetooth Protocol Stack

The Radio, Baseband and Link Manager are on firmware. The higher layers could be in software. The interface is then through the Host Controller (firmware and driver). The HCI (Host Controller Interface) interfaces between the baseband and L2CAP provides a command interface to the baseband controller and link manager and access to the hardware status and control registers. The HCI Interface defined for Bluetooth are UART, RS232 and USB. Audio Applications may directly use the basband layer after encoding the audio signals.

System Architecture The core protocols of Bluetooth comprise the following elements:

  • (^) Radio: Specification of the air interface, i.e. frequencies, modulation and transmit power.
  • (^) Baseband: Description of basic connection establishment, packet formats, timing and basic Qos parameters.
  • (^) Link manager Protocol: Link set-up and management between devices including security functions and parameter negotiation. Link Manager handles
    • Piconet managementPiconet management (attach/detach slaves, master- slave switch)
    • Link ConfigurationLink Configuration (low power modes, QoS, packet type selection)
      • Authentication,Authentication,^ pairing,pairing, encryption,encryption, synchronization,synchronization,^ capabilitycapability negitiation, QoS negotiation, Power controlnegitiation, QoS negotiation, Power control
  • (^) Logical Link Control and adaptation protocol (L2CAP): Adaptation of higher layers to the baseband (connection & connection-oriented services). Its functions include
  1. Protocol multiplexing
  2. Segmentation and reassembly
  3. QoS specifications
  4. Signalling channel for connection request, config etc
  • (^) Service Discovery Protocol: Devices discovery in close proximity plus querying of service characteristics.

Bluetooth Air Interface Choices Made ISM Band  (^) 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

Frequency Hopping

1Mhz 83.5 Mhz 1 79

Divide Frequency band into 1 MHz hop channels

Radio hops from one channel to another in a pseudo

-random manner as dictated by a hop sequence

The instantaneous (hop) bandwidth remains small

 Narrow band interference rejection

Physical Link  (^) Synchronous Connection Oriented (SC0) Link : - classical Telephone (voice))  (^) - 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 : (Typical data application (web traffic))
  • 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)