METROPOLITAN AREA NETWORKS
communication channels for telephony-grade voice communication and asynchronous
communication channels for data communications. These facilities enable a rich set of
devices and applications to participate in the Bluetooth WPAN. For example, a cellular
phone may use the circuit-switched channels to carry audio to and from headset while
concurrently using a packet-switched channel to exchange data with a notebook computer.
The Bluetooth WPAN operates in the unlicensed 2.4-GHz ISM band. A fast frequency-
hop (1600 hops/sec) transceiver is used to combat interference and fading in this band
(i.e., reduce the probability that all transmission is destroyed by interference). A Gaussian-
shaped binary frequency shift keying (FSK) with a symbol rate of 1 Msymbols/sec
minimizes transceiver complexity. A slotted channel is used, which has a slot duration
µsec. A fast time division duplex (TDD) scheme is used that enables full duplex
communications at higher layers. On the channel, information is exchanged through pack-
ets. Each packet is transmitted on a different frequency in the hopping sequence. A packet
nominally covers a single slot, but can be extended up to either three or five slots. For
data traffic, a unidirectional (i.e., symmetric) maximum of 723.2 kbps is possible between
two devices. A bidirectional 64-kbps channel supports voice traffic between two devices.
Figure 13.3 shows the general format for a single-slot, payload-bearing packet trans-
mitted over the air in a Bluetooth WPAN. The packet comprises a fixed-size access code,
which is used, among other things, to distinguish one Bluetooth WPAN from another;
a fixed-size packet header, which is used for managing transmission of the packet in a
Bluetooth WPAN; and a variable-size payload, which carries upper layer data. Due to
the small size of these packets, large upper-layer packets need to be segmented prior to
transmission over the air.
Bluetooth WPAN Connectivity Topologies
The Bluetooth WPAN Piconet
. A piconet is a WPAN formed by a Bluetooth device
serving as a master in the piconet and one or more Bluetooth devices serving as slaves.
A frequency-hopping channel based on the address of the master defines each piconet.
All devices participating in communications in a given piconet are synchronized to the
The payload can be fragmented to fit into one, three, or five 625 microsecond slots.
68 - 72 bits
0 - 2745 bits
1 0 1 0
0 1 0 1
1 0 1 0
0 1 0 1
The 18 bit heater is encoded with a rate
1/3 FEC resulting in a 54 bit header.
Sync Word is
derived from a
Format for an over-the-air payload bearing Bluetooth WPAN packet. (From Figure 3, page
24, IEEE 802.15.1. Reprinted with permission, Ref. 6.)