推荐使用Chrome浏览器查看

Overview

  • operates in the unlicensed ISM band at 2.4 GHz
  • employs a frequency hopping transceiver to combat interference and fading and provides many FHSS carriers.
  • uses a shaped, binary frequency modulation to minimize transceiver complexity.
  • Basic Rate: supporting 1 Mb/s bit rate.
  • Enhanced Data Rate: supporting a gross air bit rate of 2 or 3Mb/s.

Overview

  • physical radio channel is shared by a group of devices.
  • those devices are synchronized by a common clock and frequency hopping pattern.
  • the device provide the synchronization reference is called as master, others are called as slaves.
  • a group of devices formed a piconet.

Frequency Hopping Pattern

  • a specific frequency hopping pattern is algorithmically determined by certain fields in the Bluetooth address and the clock of the master.
  • The basic hopping pattern is a pseudo-random ordering of the 79 frequencies, separated by 1 MHz, in the ISM band.
  • The Hopping pattern can be adapted on per-salve device basis to exclude some frequencies.
## Physical Channel * The physical channel is sub-divided into time units known as slots. * Data in the packets are transmitted in those slots. * Using TDD, bluetooth technology allow the effect of full duplex transmission.

Hierachy of Channels and Links

  • above the physical channel are the layering of links , channels and associated control protocols.
  • From physical channel upward are:
    • physical channel
    • physical link
    • logical transport
    • logical link
    • L2CAP channel

Physical link

  • Typically, a physical link is formed between a master device and slave devices.
  • Inquiry scan & Page scan don't need an associated physical link.
  • Physical link is generally bi-directional transmition except in the case of a Connectionless Slave Broadcast physical link.
  • There is a physical link between each slave and master.
  • NO direct physical links are formed between slaves.
## Physical Link * used as a transport for one or more logical links. * Logical links support unicast synchronous, asynchronous and isochronous traffic, and broadcast traffic. * Traffic on logical links is multiplexed onto the physical link by ocuppying slots.

Link Manager Protocol(LMP)

  • carried over logical links.
  • ACL logical transport are the default asynchronous connection-oriented logical transport used to transport LMP protocol signaling.
  • whenever a device joins a piconet, a primary ACL logical transport is created.
  • Connectionless Slave Broadcast devices are exceptional, they are purely listening to Connectionless Slave Broadcast packets. a Connectionless Slave Broadcast logical transport is created.
  • For all devices, additional logical transports may be created to transport synchronous data streams when required.
## Link Manager * The Link Manager function uses LMP to control the operation of devices in the piconet. * provide services to manage the lower architectural layers(radio layer and baseband layer).

L2CAP

  • provides a channel-based abstraction to applications and services.
  • applicaiton segmentation and reassembly of application data.
  • multiplexing and de-multiplexing of multiple channels over a shared logical link.
  • has a protocol control channel carried over the default ACL logical transport.
  • any logical link supporting L2CAP protocol can carry L2CAP encapsulated data.

谢谢收看


返回主页

回到顶部