What is Bluetooth? Bluetooth technology is a peripheral that connects to a variety of products in order to provide wireless connections.

Why is it called “Bluetooth”? Harald Bluetooth was king of Denmark in the late 900s. He managed to unite Denmark and part of Norway into a single kingdom then introduced Christianity into Denmark. He was killed in 986 during a battle with his son, Svend Forkbeard.

Choosing this name for the standard indicates how important companies from the Baltic region (nations including Denmark, Sweden, Norway and Finland) are to the communications industry, even if it says little about the way the technology works.

History of Bluetooth Technology was born in Swedish town of Lund in 1994 Research facility was tied to the local university The research that developed Bluetooth came about by accident

History continued… In Feb. 1998, 5 companies got together to and formed a SIG further the university’s research on Bluetooth and May 20, 1998 it was publicly announced as a marketable product

Bluetooth continued to thrive, although it didn’t evolve into it’s current form until 4 companies joined the original 5, these include: Motorola, Microsoft, Lucent and 3-Com

How Bluetooth Works Bluetooth communicates on a frequency of 2.45 gigahertz This frequency was allocated for industrial, scientific and medical devices (ISM) This band also works for baby monitors, garage-door openers, and the newer cordless phones

Bluetooth and interference To prevent interference with other devices, Bluetooth sends out minute signals of 1 milliwatt This only allows units to send out signals for a distance of 10 meters, however this is strong enough to go through a normal wall

Spread-spectrum frequency hopping In order to avoid crossing signals between devices, Bluetooth utilizes frequency hopping. Using 79 individual, random frequencies in an area, the device hops from one to another regularly.

How Bluetooth interacts When 2 Bluetooth devices come within the range of each other, they electronically speak to each other to determine whether they have data to share or if one will control the other

Piconet The devices then set up a personal-area network (PAN) or piconet. In a piconet network, one device is assigned the master role, and up to seven other devices are assigned to be slaves. The master transmits in the even time slots, slaves transfer in the odd time slots.

Piconet data channels Devices in a piconet connect through a common data channel, which has a capacity of 1 Mbps A channel is divided into time slots of 625 microseconds long Each data channel hops randomly 1,600 per second.

Channel Control There are two major states in channel control; Standby and Connection Standby – the default low power state, only the native clock runs, and there is no interaction with the device Connection – master and slave exchange packets using the master’s access code and native clock

Inquiry Phase Page Procedure Inquiry Phase IF CONNECTION STATE IS ACTIVE… Inquiry Phase Page Procedure Inquiry – enables a device to find other devices within range. Page – procedure where an actual connection is made . Inquiry Phase 1. Unit sends out inquiry packets and receives replies if anything is present 2. Receiving unit is hopefully in scan state to receive packets 3. Receiving unit then switches to response states and replies to sending source

Paging Procedure 1. Source device pages destination device(s) 2. Destination receives the page 3. Destination replies to source 4. Source sends an FHS packet to destination 5. Destination sends its second reply to source 6. Destination and source then switch to source channel parameters

Piconet modes Active Mode – Bluetooth actively participates Sniff Mode – slave listens to the piconet at reduced rates, reducing its duty cycle Hold Mode – master unit can put a slave unit into hold mode where only the internal timer is running Park Mode – a device is still synched but not actively participating in traffic

Piconet Packets Packets can be up to five time slots wide Data in the packets can be up to 2,754 bits in length Data is transferred in two types in Bluetooth Devices: Sychnronous connection oriented (SCO) or asynchronous connectionless (ACL)

SCO link SCO link is a symmetric point-to-point link between a master and slave Master maintains the link by using reserved slots at regular intervals (circuit switch) Master can support up to 3 links, while slaves can maintain 2-3 SCO is mainly used for voice info transferred at 64/Kb

ACL link ACL is a point-to-multipoint link between master and all the slaves in the network In the slots unused by the SCO, the master can create a ACL link on a per-slot basis to any slave (packet switch) Only a single ACL link can exist in a piconet

Bluetooth Devices