Bluetooth

Question 1

Which is the intention of using BT?

Answer 1

Replace cables connecting portable and/or fixed electronic devices.

Question 2

Which is the bandwidth used in BT?

Answer 2

Unlicensed 2.4GHz radio band (Industrial Scientific, Medical - ISM)

Question 3

Which are the data rates, range and usage of BT

Answer 3

1Mbit/s up to 3Mbit/s (enhanced).
10m up to 100m(with amps)
PAN network used as data/voice access point

Question 4

Explain Frequency hopping and Adaptatice Freq Hopping and why it is used.

Answer 4

Used to combat interference and fading by providing many FHSS (Freq. hopping spread spectrum).
Uses 79 frequencies (from 2402 to 2480 MHz )
1600 or 3200 hops/s
Connected devices use a specific freq. hopping pattern which is algorithmically determined. Basic pattern is pseudo random ordering of the 79 freq. Hopping pattern may be adapted to exclude a portion of the freq that are used by interfering devices. This improves coexistence with static ISM systems when these are co-located.

Question 5

Which are the BT power classes?

Answer 5

Class1: max pow 100mW (20dBm)
            min pow 1mW (0dBm)
Class2: max pow 2.5mW (4dBm)
            min pow 0.25mW (-6dBm)
Class1: max pow 1mW (0dBm)
received signal strength indicator (RSSI) based power control

Question 6

Explain the BT Radio Channel

Answer 6

During Operation, a physical radio channel is shared by a group of devices that are synch to a common clock and hopping pattern.

Question 7

What is the Piconet?

Answer 7

One device provides synch and reference and its known as master. All other devices are known as slaves. A group of devices synch in this fashion form a Piconet.

Question 8

Frames and Packets

Answer 8

BT uses TDD (channel devided into time units known as slots)
1,3 or 5 consecutive slots may be allocated to a single packet.
One frame consists of 2 packets(transmitted followed by receive)

Question 9

Piconet structure.

Answer 9

Only one master (dynamically selected; roles may change)
Up to 7 active slaves
Up to parked slaves
No central network structure (Ad-hoc)
Piconet is characterized by the master (hopping scheme; access code ; Timing synchronization)

Question 10

Bluetooth connection setup

Answer 10

Inquire:
Paging radio issues page packet with inq ID.
Any radio doing an inquire scan responds with an FHS packet (information is Dev ID and clock.)
If there is a collision, radios wait a random time before responding to inquire.
After proccess is done, inquiting radio has dev id and radios of all devs in range.