Bluetooth Flashcards
What is Bluetooth?
- Wireless Personal Area Network (WPAN)
- Universal short-range wireless capability
- Uses 2.4 GHz
- IEEE 802.15
What is Frequency Hopping Spread Spectrum (FHSS):
- Signal hops from frequency to frequency at fixed intervals
- Hopping sequence dictated by spreading code
- Receiver, hopping between frequencies in synchronization with transmitter, picks up message
How does FHSS Transmitter work?
User data -> modulator -> narrowband signal -> modulator - frequency synthesizer- hopping sequence -> spread transmit signal
How does FHSS Receiver work?
received signal narrowband signal -> demodulator-frequency synthesizer - hopping sequence -> data
What is in Access Code?
- Timing synchronization
- Frequency offset compensation
- Paging, and inquiry
- Address of Piconet primary
What is in a packet header?
- Addressing (Max of 7 active secondary devices)
- Packet type (16 packet types)
What is in the payload?
- Voice
- Header | DATA | CRC
What is a piconet?
- BT communication takes place over Piconets
- Piconet formation initiated by primary
- All other participants are secondary devices
How many participants are allowed to 1 primary?
7 secondary
- Each assigned a locally unique address.
How long do primary/secondary roles last?
For the duration of the piconet
What is the initial state of nodes when unconnected?
Standby
What is inquiry?
When primary node find nearby devices during connection
What is paging?
When the primary invite others to join its piconet and send paging message to selected receiver
How does a secondary respond to a paging message by a primary?
Sending an ACK
What happens in active state?
- Transmit
- Connected
What are the three states of Low-Power?
- Hold
- Sniff
- Park
What is hold?
Node sleeps for specified interval
- Primary can put secondary in hold while searching for new members, attending another piconet, etc
What is sniff?
Secondary low-duty cycle mode
- Secondary wakes up periodically to talk to primary
- fixed sniff intervals
What is park?
Very low power state
- Used to admit more than 7 secondary devices in Piconet - gives up its active member address and receives parked member address
- Wakes up periodically listening for broadcasts which can be used to “unpack” node
What makes multiple piconets?
- When piconet overlap in space and time due to nodes participating in more than 1 piconet
- “Time sharing”
What is scatternet?
- Interconnection of multiple piconets
- Interconnection by bridge nodes
What are the roles of bridge nodes?
- “Stay” in a piconet for some time, then switch to another Piconet by changing hop sequence
- Send and receive in each Piconet
- Forward from one Piconet to another
What is A2DP: Advanced Audio Distribution Profile
Stereo Audio from smartphone to headphone
What is aptX?
- Wireless real-time streaming of high quality audio
- Proprietary audio compression algorithms
What is Enhanced Data Rate (EDR)?
- Faster data transfer
- Lower power consumption using reduced duty cycle
What is High Speed?
- Data is carried over Wi-Fi Link
- Used for control channel
What is Bluetooth Beacons?
- Bluetooth Low Energy (BLE) based
- Bluetooth beacon devices transmit a unique user ID (UUID) number that can be read by a Bluetooth receiver
What are Bluetooth Beacons for?
Proximity, not localization
What are the programmable parameters of Beacons?
- Transmit power
- Frequency
What are applications of Bluetooth Beacons?
- Advertisement and Coupon distribution
- Home automation systems
- Transportation systems
- Sport stadiums
