Bluetooth

Comparison Between Wireless Technologies

Personal Networks

When ?

• Access mostly to “transported devices”.

• No dominant need for Information Technologies.

• No physical access to cabled networks.

• No need for large communication rates.

• Very low cost system required.

• Consumer electronics integration is mandatory.

Target deployment environment: communication of personal devices working together.

• Short-range.

• Low Power.

• Low Cost.

• Small numbers of devices.

• Sometimes have more “bus-like” characteristics.

PAN Standards

• Bluetooth – Industry consortia.

• IEEE 802.15.1 – ”Bluetooth” based.

• IEEE 802.15.2 – Interoperability and coexistence.

• IEEE 802.15.3 – High data rate WPAN (UWB).

• IEEE 802.15.4 – Low data rate WPAN (Zigbee,...).

• IEEE 802.15.5 – Mesh Networks.

• IEEE 802.15.6 – Body Area Network.

Bluetooth

Originally for replacing “USB”, not “Ethernet”.

• Cable replacement technology.

• Later also used as Internet connection, phone, or headset.

Created by Ericsson.

PAN - Personal Area Network.

• Up to 1 Mbps connections.

• Includes synchronous, asynchronous, voice connections.

• Piconet routing.

Small, low-power, short-range, cheap, versatile radios.

Master/slave configuration and scheduling.

Versions

Higher speeds

Enhanced Data Rate (EDR)

Introduced in Bluetooth v2.0 to support faster data transfer.

Supports a data rate up to 3 Mbps.

Using reduced duty cycle control (time radio is ON), EDR can provide lower power consumption.

High Speed (HS)

BT HS was released in April 2009 (in Bluetooth version 3.0+HS).

Bluetooth 3.0+HS provides data transfer speeds of up to 24 Mbps, though not over the Bluetooth link itself:

• BT link is used for negotiation and establishment, and the high data rate traffic is carried over a collocated 802.11 link.

• HS part of the specification is not mandatory in BT 3.0.

• Only devices that display the "+HS" logo actually support Bluetooth over 802.11 high-speed data transfer.

Features

Radio network, on the 2.4 GHz, world-wide!

Airplane friendly!

FH (Frequency Hopping) spread spectrum:

• 79 (23 - .jp .es .fr) channels (de 2.402GHz - 2.480GHz).

Defines a master that synchronizes everyone to his hop-pattern.

Defines two types of networks:

• piconets.

• scaternets.

Maximum 8 devices per piconet (1 master + 7 slaves).

Transmission rate: 720 Kb/s (max), assymetrical variable.

Frequency Hopping Spread Spectrum (FHSS)

Signal broadcast over a seemingly random series of frequencies.

Receiver hops between frequencies in sync with the transmitter.

• Each frequency has the bandwidth of the original signal.

• Dwell time is the time spent using one frequency.

Spreading code determines the hopping sequence.

• Must be shared by the sender and receiver (e.g. standardized).

Eavesdroppers hear unintelligible blips.

Jamming on one frequency affects only a few bits.

• Typically a large number of frequencies are used.

  • Improved resistance to jamming.

Bluetooth classic vs. cable

Low power

Global architecture for low power.

• Hold and Park mode: 60 μA current.

  • Connected device, but not operating.

  • Device operates after a 2 ms wait process.

  • In Hold: keeps its AMA (Active Member Address); in Park has to free AMA, and later has to claim it back.

Transmission power ~1mW.

• 100mW classes also exist.

Standby Current < 0.3 mA.

• 3 months.

Voice mode: 8-30 mA.

• 75 hours.

Data mode (medium): 5 mA (0.3-30mA, 20 kbit/s, 25%).

• 120 hours.