Bluetooth Stack

• L2CAP – Logical Link Control and Adaptation Protocol.

• LMP – Link Manager Protocol.

• HID – Human Interface Device.

• RFCOMM – serial cable emulation (ETSI).

Bluetooth includes:

• A HW description.

• An environment for applications.

Bluetooth Protocol

Radio layer.

Defines requirements for a Bluetooth radio transceiver.

• Handles conformity to 2.4GHz band.

• Establishes specifications for using Spread-Spectrum Frequency Hopping.

• Classifies device into one of three power classes:

  • long range; (Class 1 - 100mW, 100m)

  • normal/standard range; (Class 2 - 2.5mW, 10m)

  • short range; (Class 3 - 1 mW, 1m)

RF: international 2.4Ghz band

2.4GHz issues.

• Channel BW limited to 1MHz.

• Spread spectrum must be used.

• Multiple independent networks can interfere.

• Microwave ovens also use these frequencies.

• ICs at 2.4 GHz need huge current levels.

Bluetooth remedies.

• 1 Mb/s baud taxes exploit BW at maximum.

• Voice coding (CVSDM) allow high speed operation.

• Fast “frequency hoping” and small packets to avoid interference.

• Interface with the channel minimizes power consumption.

• Interface specifications are relaxed enough to allow its integration in low power chipsets.

Radio Layer

Radio: FH SS.

• 79/23 channels of 1 Mb/s.

• Hoping: per slot.

  • Packets have 1, 3, or 5 slots of 625 μs.

  • Hoping (nominal) 1600 times per second.

• Frame includes two packets.

  • Transmission followed by reception.

• Radio designed to low cost and universal usage.

  • (noise, synchronous action technology 2.4GHz, etc...).