Fig: Header format for bluetooth packets:

The header format for all Bluetooth packets is shown in above figure. It consists ofsix fields:

• AM_ADDR: The 3-bit AM_Addr contains the "active mode" address (temporary address assigned to this slave in this piconet) of one of the slaves. A transmission from the master to a slave contains that slave's address; a transmlssion from a slave contains its address. The 0 value is reserved for a broadcast from the master to all slaves in the piconet.

• Type: Identifies the type of packet. Four type codes are reserved for control packets common to both SCQ and ACL links. The remaining packet types are used to convey user information. For SeQ links, the HVl, HV2, HV3 packets each carry 64-kbps voice. The difference is the amount of error protection provided, which dictates how frequently a packet must be sent to maintain the 64-kbps data rate. The DV packet carries both voice and data. For ACL links, 6 different packets are defined. These, together with the DMI packet, carry user data with different amounts of error protection and different data rates.There is another packet type common to both physical links, it consists of only the access code, with a fixed length of 68 bits. This is referred to as the ID packet and is used in the inquiry and access procedures.

• Flow: Provides a 1-bit flow control mechanism for ACL traffic only. When a packet with Flow = 0 is received, the station receiving the packet must tem- porarily halt the transmission of ACL packets on this link. When a packet with Flow = 1 is received, transmission may resume.

• ARQN: Provides a 1-bit acknowledgment mechanism for ACL traffic protected by a CRC. If the reception was successful, an ACK (ARQN = 1) is returned; otherwise a NAK (ARQN = 0) is returned. When no return message regarding acknowledge is received, a NAK is assumed implicitly. If a NAK is received, the relevant packet is retransmitted.

• SEQN: Provides a I-bit sequential numbering schemes. Transmitted packets are alternately labeled with a 1 or O. This is required to filter out retransmissions at the destination, if a retransmission occurs due to Cl failing ACK, the destination receives the same packet twice.

• Header error control (HEC): An 8-bit error detection code used to protect the packet header.