VISHAL H GOHEL
LECTURER OF COMPUTER DEPT
GOVERNMENT POLYTECHNIC BHUJ
It is desired to get rid of the spaghetti of wires connecting the various
devices used daily and so Bluetooth technology provides a low cost, low
power and low complexity solution for ad-hoc wireless connectivity.
Bluetooth is a short range wireless technology that forms the basis of
communication platform which needs to be flexible, self organizing, highly
scalable and energy efficient.
The Bluetooth technology is capable of connecting a wide variety of devices
like Personal Digital Assistants (PDA), mobile and cordless phones,
headsets, desktops and notebook PCs, digital cameras, home appliances etc.
The applications include eliminating cables/wires between devices like PCs,
printers, modems, projectors, self synchronization between PDAs and PCs,
wirelessly connecting to local area networks (LANs) through access points
and internet through mobile phones, providing home networking solutions
In this paper, the author presents an overview of Bluetooth technology and
its applications. The Bluetooth system is introduced and its various modes of
operation are also discussed. A description of functionalities of Bluetooth
layers and the protocol specifications is presented. The various links for
communication among Bluetooth devices are also illustrated. The author has
made an attempt to enlighten various important issues related to error
correction, security and personalization of Bluetooth devices. The literature
is enriched by discussion of other wireless technology, WiFi working
together with Bluetooth. Thus the paper will provide helpful evaluation of
Bluetooth technology, for the budding engineers.
Definition of Bluetooth .
Why Bluetooth ?
How need arise of Bluetooth?
What is SIG ?
What is Bluetooth?
What is it - a technology, a standard, an initiative, or a product?
Bluetooth wireless technology is a de facto standard, as well as a
specification for small form factor, low-cost, short range radio links between
mobile PCs, mobile phones and other portable devices. The Bluetooth
Special Interest Group is an industry group consisting of leaders in the
telecommunications, computing, and networking industries that are driving
development of the technology and bringing it to market.
How did the need arise?
In phase with the IT boom, the mobility among people
has constantly grown and wireless technologies for voice and
data have evolved rapidly during the past years. Countless
electronic devices for home, personal and business use have
been presented to the market during recent years but no
widespread technology to address the needs of connecting
personal devices in Personal Area Networks (PANs). The
demand for a system that could easily connect devices for
transfer of data and voice over short distances without
cables grew stronger.
Bluetooth wireless technology fills this important
communication need, with its ability to communicate both
voice and data wirelessly, using a standard low-power, lowcost technology which can be integrated in all devices to
enable total mobility. The price will be low and result in
mass production. The more units around, the more benefits
for the customer.
Why Bluetooth ?
What will Bluetooth wireless technology deliver to end users?
It will enable users to connect a wide range of computing and
telecommunications devices easily and simply, without the need to buy,
carry, or connect cables. It delivers opportunities for rapid ad hoc
connections, and the possibility of automatic, unconscious, connections
between devices. It will virtually eliminate the need to purchase additional
or proprietary cabling to connect individual devices. Because Bluetooth
wireless technology can be used for a variety of purposes, it will also
potentially replace multiple cable connections via a single radio link. It
creates the possibility of using mobile data in a different way, for different
applications such as "Surfing on the sofa", "The instant postcard", "Three in
one phone" and many others. It will allow them to think about what they are
working on, rather than how to make their technology work. The solution
eliminates the annoying cable and its limitations regarding flexibility (often
specific for a brand or pair of devices) and range. But, Bluetooth implies
more than that. The technique provides the means for connecting several
units to each other such as setting up small radio LANs between any types of
Bluetooth devices. A number of user scenarios are described. They highlight
more possibilities that reach far beyond just an elimination of the point-topoint cable.
By the way if, you're wondering where the Bluetooth name originally
came from , it is named after a Danish Viking and King of Denmark
between 940 and 981 AD, Harald Blåtand (Bluetooth in English),
who lived in the latter part of the 10TH century. Harald Blåtand united and
controlled Denmark and Norway (hence the inspiration on the name : uniting
devices through Bluetooth
The idea that resulted in the Bluetooth wireless
technology was born in 1994 when Ericsson Mobile
Communications decided to investigate the feasibility of a
low-power, low-cost radio interface between mobile phones
and their accessories. The idea was that a small radio built
into both the cellular telephone and the laptop would replace
the cumbersome cable used today to connect the two
A year later the engineering work began and the true
potential of the technology began to crystallize. But beyond
unleashing devices by replacing cables, the radio technology
showed possibilities to become a universal bridge to existing
data networks, a peripheral interface, and a mechanism to
form small private ad hoc groupings of connected devices
away from fixed network infrastructures.
The requirements regarding price, capacity and size were set so that
the new technique would have the potential to outdo all cable solutions
between mobile devices. Initially a suitable radio interface with a
corresponding frequency range had to be specified. A number of criteria for
the concept were defined regarding size, capacity and global uniformity. The
radio unit should be so small and consume such low power that it could be
fitted into portable devices with their limitations. The concept had to handle
both speech and data and finally the technique had to work all around the
world. The study soon showed that a short-range radio link solution was
When designers at Ericsson had started to work on a transceiver chip,
Ericsson soon realized that they needed companions to develop the
technique. The associates strove not only to improve the technical solutions
but also to get a solid and broad market support in the business areas of PC
hardware, portable computers and mobile phones. Fear for a market situation
with a multitude of non-standard cable solutions, where one cable is
designed specifically for one pair of devices, was one of the motives that
made competing companies join the project. Ericsson Mobile
Communications, Intel, IBM, Toshiba and Nokia Mobile Phones formed a
Special Interest Group (SIG) in 1998.
What is SIG?
In February 1998 the Special Interest Group (SIG) was
formed. Today the Bluetooth SIG includes promoter
companies 3Com, Ericsson, IBM, Intel, Lucent, Microsoft,
Adopter/Associate member companies. By signing a zero cost
agreement, companies can join the SIG and qualify for a royalty-free license
to build products based on the Bluetooth technology.
This group represented the diverse market support that was needed to
generate good support for the new Bluetooth technology. In May of the same
year, the Bluetooth consortium announced itself globally. The
assignment of the SIG originally was to monitor the
technical development of short-range radio and to create an
open global standard, thus preventing the technology from
becoming the property of a single company. This work
resulted in the release of the first Bluetooth Specification in
The intention of the Bluetooth SIG is to form a de facto standard for
the air interface and the software that controls it.
development of the Specification still is one of the main
tasks for the SIG, other important ones being
interoperability requirements, frequency band harmonization
and promotion of the technology. The Bluetooth wireless
technology was developed by the Bluetooth Special Interest Group, to define
an industry-wide specification for connecting personal and business mobile
devices. More than 1,4000 companies are now members of the Special
Interest Group, signifying the industry‟s unprecedented acceptance of the
Bluetooth wireless technology.
To avoid different interpretations of the Bluetooth standard regarding
how a specific type of application should be mapped to Bluetooth, the SIG
number of user models and protocol profiles. These are described in more
detail in the section entitled Bluetooth Usage Models and Profiles.The SIG
also works with a Qualification Process. This process defines criteria for
bluetooth product qualification that ensures that products that pass this
process meet the Bluetooth specification.
OVERVIEW OF BLUETOOTH SYSTEM.
The technology is an open specification for wireless communication
of data and voice. It is low cost short range radio link, built into a 9X9 mm
microchip, facilitating protected ad hoc connections for stationary and
mobile communication environment. Bluetooth technology allows for the
replacement of the many proprietary cables that connect one device to
another device with one universal short range radio link. For instance
Bluetooth radio technology built in both the cellular telephone and the laptop
would replace the cumbersome cables used today to connect the laptop to a
Printers, PDA‟S, desktops, fax machines, keyboard, joysticks and
virtually any other device can be part of the Bluetooth system. But beyond
untethering devices by replacing the cables, Bluetooth radio technology
provides a universal bridge to existing data networks, a peripheral interface,
and a mechanism to form small private ad hoc grouping of connected
devices away from fixed network infrastructures. Designed to operate in
noisy radio frequency environment, the Bluetooth radio uses a fast
acknowledgement and frequency hopping scheme to make the link robust.
The Bluetooth radio modules avoid interference from other signals by
hopping to a new frequency after transmitting or receiving a packet.
Compared with other systems operating in the same frequency band, the
Bluetooth radio typically hops faster and uses shorter packets. This makes
the Bluetooth radio robust than the other system. Short packages and fast
hopping also limit the impact of random noise and long distance links. The
encoding is optimized for uncoordinated environment. Bluetooth radios
operate in the unlicensed ISM band at 2.4GHz. a frequency hop transceiver
is applied to combat interference and fading. A shaped binary FM
modulation is applied to minimize transceiver complexity. The gross data
rate is 1mbps. A Time Division Duplex scheme is used for full duplex
transmission. The Bluetooth base band protocol is a combination of circuit
and packet switching. Slots can be reserved for synchronous packet. Each
packet is transmitted in a different hop frequency. A packet nominally
covers a single slot, but can be extended to cover up to 5 slots. Bluetooth can
support an asynchronous data channel, up to 3 simultaneous synchronous
voice channels, or a channel that simultaneously supports asynchronous data
synchronous voice. Each voice channel supports 64 kbps synchronous
The asynchronous channel can support an asymmetric link of
maximally 721 kbps in either direction while permitting 57.6 kbps in the
return direction, or a 432.6 kbps symmetric link.
The Bluetooth technology answers the need for short range wireless
connectivity within three areas :
Data and voice access points .
Ad hoc networking
The Bluetooth technology specification specifies a system solution
comprising hardware, software and interoperability requirements. The
Bluetooth radio operates in a globally available 2.4GHz ISM band,
ensuring communication compatibility worldwide.
Data and voice access point :
The Bluetooth technology facilitates real time voice and data
transmission. The technology makes it possible to connect any portable and
stationary communication device as easily as switching on the light. You
can, for instance, surf the Internet & send e-mail on your potable PC or
notebook regardless of whether you are wirelessly connected through a
mobile phone or
Voice channel use the Continuous Variable Slope Delta Modulation
(CVSD) coding scheme, and never retransmit voice packets. The CVSD was
chosen for its robustness in handling dropped and damaged samples. Rising
interference levels are experienced as increased background noise; even at
bit error rate up to 4% the CVSD coded voice is quite audible.
The Bluetooth technology eliminates the use for numerous often
proprietary cable attachments for connection of practically any kind of
device. Connections are instant and they are maintained even when devices
are not within line of sight. The range of each radio is approximately 10
meters but it can be extended around 100 meters with an optional amplifier.
A device equipped with Bluetooth radio establishes instant connection
to another Bluetooth radio as soon as it comes into range. Since Bluetooth
technology supports both point to point and point to multi point connection,
several piconets can be established and linked together ad hoc. The
Bluetooth technology is best described as multiple piconet structure.
Piconet is a connection of devices connected via Bluetooth
technology in an ad hoc fashion . A piconet starts with two connected
devices ,such as portable PC and cellular phone and may grow into eight
connected devices. All Bluetooth devices are peer units and have identical
implementation. However, when establishing a piconet, one unit will act as a
master and the other as a slave for the duration of piconet connection.
Scatternet, ad-hoc combinations in a point-to-multipoint and
Bluetooth units that come within range of each other
can set up ad hoc point-to-point and/or point-to-multipoint
connections. Units can dynamically be added or
disconnected to the network. Two or more Bluetooth
units that share a channel form a piconet.
Several piconets can be established and linked together
in ad hoc scatternets to allow communication and data
exchange in flexible configurations. If several other piconets
are within range they each work independently and each
have access to full bandwidth. Each piconet is established by
a different frequency-hopping channel. All users participating
on the same piconet are synchronized to this channel.
Unlike infrared devices, Bluetooth units are not
limited to line-of-sight communication. To regulate
traffic on the channel, one of the participating units becomes
a master of the piconet, while all other units become slaves.
With the current Bluetooth Specification up to seven slaves
can actively communicate with one master. However, there
can be almost an unlimited number of units virtually
attached to a master being able to start communication
BLUETOOTH PROTOCOL STACK.
Bluetooth protocol stack & network architecture.
The Bluetooth architecture strategy.
THE BLUETOOTH PROTOCOL STACK
IT’S NETWORK ARCHITECTURE
Host Controller Interface
Figure 1 The Bluetooth Protocol Stack
OBEX OBject Exchange Protocol
Web Application Protocol
User Datagram Protocol
Point to Point Protocol
RFCO Serial Cable emulation protocol based on
ETSI TS 07.10 Interface
LLCA Logical Link Control and Adaptation
Protocol Discovery Protocol
Telephony Control Protocol
Link Manager Protocol
This section describes the Bluetooth architecture. The complete
protocol stack comprises, as seen in Figure 1, of both Bluetooth specific
protocols and non-Bluetooth specific protocols. In the figure, nonBluetooth specific protocols are shaded.
The Baseband and Link Control layer enables the physical RF link
between Bluetooth units forming a piconet. This layer controls the Bluetooth
unit's synchronization and transmission frequency hopping sequence. The
two different link types defined in Bluetooth, Synchronous Connection
Oriented, SCO, and Asynchronous Connectionless, ACL, described in the
section Link types, are also managed by this layer.
The ACL links, for data, and the SCO links, mainly for audio, can be
multiplexed to use the same RF link .
Audio transmissions can be performed between one or more
Bluetooth units, using many different usage models. Audio data do not go
through the L2CAP layer (described below) but go directly, after opening a
Bluetooth link and a straightforward set-up, between two Bluetooth units.
Host Controller Interface, HCI
The Host Controller Interface, HCI, provides a uniform interface
method for accessing the Bluetooth hardware capabilities. It contains a
command interface to the Baseband controller and link manager and access
to hardware status. Finally, it contains control and event registers .
Link Manager Protocol, LMP
The Link Manager Protocol, LMP, is responsible for link set-up
between Bluetooth units. It handles the control and negotiation of packet
sizes used when transmitting data. The Link Manager Protocol also handles
management of power modes, power consumption, and state of a Bluetooth
unit in a piconet. Finally, this layer handles generation, exchange and control
of link and encryption keys for authentication and encryption .
Logical Link Control and Adaptation Protocol, L2CAP
The Bluetooth logical link control and adaptation protocol, L2CAP, is
situated over the Baseband layer and beside the Link Manager Protocol in
the Bluetooth protocol stack. The L2CAP layer provides connection-oriented
and connectionless data services to upper layers.
The four main tasks for L2CAP are:
Multiplexing – L2CAP must support protocol multiplexing since a
number of protocols (e.g. SDP, RFCOMM and TCS Binary) can
operate over L2CAP.
Segmentation and Reassembly – Data packets exceeding the
Transmission Unit, MTU, must be segmented before being
This and the reverse functionality, reassemble, is performed by
Quality of Service – The establishment of an L2CAP connection
allows the exchange of information regarding current Quality of
Service for the
connection between the two Bluetooth units.
Groups – The L2CAP specification supports a group abstraction that
permits implementations for mapping groups on to a piconet.
An L2CAP implementation must be uncomplicated and implying low
overhead since it must be compatible with the limited computational
resources in a small Bluetooth unit .
Service Discovery Protocol, SDP
The Service Discovery Protocol, SDP, defines how a Bluetooth
client's application shall act to discover available Bluetooth servers' services
and their. Bluetooth characteristics. The protocol defines how a client can
search for a service based on specific attributes without the client knowing
anything of the available services. The SDP provides means for the
discovery of new services becoming available when the client enters an area
where a Bluetooth server is operating. The SDP also provides functionality
for detecting when a service is no longer available .
Cable replacement protocol
The RFCOMM protocol is a serial port emulation protocol. The
protocol covers applications that make use of the serial ports of the unit.
RFCOMM emulates RS-232 control and data signals over the Bluetooth
baseband. It provides transport capabilities for upper level services, e.g.
OBEX that use a serial line as the transport mechanism.
Telephony control protocol
Telephony Control – Binary
The Telephony Control protocol – Binary, TCS Binary or TCS BIN,
is a bit-oriented protocol, which defines the call control signalling for the
establishment of speech and data calls between Bluetooth units. The protocol
defines the signalling for establishment and release of calls between
Bluetooth units. As well as signalling to ease the handling of groups of
Bluetooth units. Furthermore, TCS Binary provides functionality to
exchange signalling information unrelated to ongoing calls. Establishment of
a voice or data call in a point-to-point configuration as well as in a point-tomultipoint configuration is covered in this protocol (note, after
establishment, the transmission is from point to point). The TCS Binary is
based on the ITU-T Recommendation.
Telephony Control – AT Commands
A number of AT-commands are supported for transmitting control
signals for telephony control. These use the serial port emulation,
RFCOMM, for transmission.
This section describes a number of protocols that are defined to be
adopted to the Bluetooth protocol stack. Note some of these adaptations are
at the moment incomplete.
The IETF Point-to-Point Protocol (PPP) in the Bluetooth technology
is designed to run over RFCOMM to accomplish point-to-point connections.
PPP is a packet-oriented protocol and must therefore use its serial
mechanisms to convert the packet data stream into a serial data streams.
The TCP/UDP/IP standards are defined to operate in
Bluetooth units allowing them to communicate with other units
connected, for instance, to the Internet. Hence, the Bluetooth
unit can act as a bridge to the Internet. The TCP/IP/PPP
protocol configuration is used for all Internet Bridge usage
scenarios in Bluetooth 1.0 and for OBEX in future versions. The
UDP/IP/PPP configuration is available as transport for WAP.
IrOBEX, shortly OBEX, is an optional application layer protocol
designed to enable units supporting infrared communication to exchange a
wide variety of data and commands in a resource-sensitive standardized
fashion. OBEX uses a client-server model and is independent of the
transport mechanism and transport API. The OBEX protocol also defines a
folder-listing object, which is used to browse the contents of folders on
remote device. RFCOMM is used as the main transport layer for OBEX.
The formats for transmitting vCard and vCalendar information are
also defined in the Bluetooth specification. The formats do not define
transport mechanisms but the format in which electronic business cards and
personal calendar entries and scheduling information are transported. vCard
and vCalendar is transferred by OBEX.
Wireless Application Protocol, WAP
The Wireless Application Protocol (WAP) is a wireless protocol
specification that works across a variety of wide-area wireless network
technologies bringing the Internet to mobile devices. Bluetooth can be used
like other wireless networks with regard to WAP, it can be used to provide a
bearer for transporting data between the WAP Client and its adjacent WAP
Server. Furthermore, Bluetooth‟s ad hoc networking capability gives a WAP
client unique possibilities regarding mobility compared with other WAP
The traditional form of WAP communications involves a client device
that communicates with a Server/Proxy device using the WAP protocols.
Bluetooth is expected to provide a bearer service as specified by the WAP
architecture. The WAP technology supports server push. If this is used over
Bluetooth, it opens new possibilities for distributing information to handheld
devices on location basis. For example, shops can push special price offers
to a WAP client when it comes within Bluetooth range.he Bluetooth air
This section describes the Bluetooth air interface. It is a continuation
of the introduction to the air interface and is based on .
The Bluetooth architecture strategy
A number of profiles have been defined by the Bluetooth
standardization organization. These profiles have been developed in order to
describe how implementations of user models are to be accomplished. The
user models describe a number of user scenarios where Bluetooth performs
the radio transmission. These profiles specify how applications and devices
shall be mapped onto the Bluetooth concept.
A profile defines a selection of messages and procedures from the
Bluetooth specifications and gives an unambiguous description of the air
interface for specified services and use cases. A profile can be described as a
vertical slice through the protocol stack. It defines options in each protocol
that are mandatory for the profile. It also defines parameter ranges for each
protocol. The profile concept is used to decrease the risk of interoperability
problems between different manufacturers' products.
The profile defined for exchanging of vCard information is illustrated
in Figure 2, where an application, vCard, is defined to operate over a certain
subset (OBEX, RFCOMM and so on) of the Bluetooth protocol stack. Some
of the user models and their profiles are described in section Bluetooth
Usage Models and Profiles.
Figure 2: The Object Push Profile
There are four general profiles defined, on which some of the highest
prioritized user models and their profiles are directly based on. These four
models are; the Generic Access Profile (GAP), the Serial Port Profile, the
Service Discovery Application Profile (SDAP) and the Generic Object
Exchange Profile (GOEP). Protocols such as OBEX and UDP have been
included in the protocol architecture to facilitate the adaptation of
applications using such existing protocols. This gives for instance a number
of existing applications supporting UDP an interface to the Bluetooth
DIVISION AS FUNCTIONAL UNIT
Authentication, Privacy & Security.
DIVISION AS FUNCTIONAL UNITS
The different functional units in the Bluetooth system are:
A radio unit
A link control unit
As already mentioned, the Bluetooth system support both point to
point and point to multi point connections. In this, each piconet is identified
by a different hopping signal. All users participating on the same piconet are
synchronized to this hopping sequence.
The full duplex data rate within a multiple piconet structure with 10
fully loaded, independent piconets is more than 6 mbps. This is due to a
data throughput reduction rate of less then 10% according to system
simulation based on 0 dbm transmitting power (at the antenna).
The Bluetooth air interface is based on a nominal antenna at 0 dBm.
The air interface compiles with the FCC rules for the ISM band at power
levels up to 0 dBm. Spectrum spreading has been added to facilitate optional
operation at power levels up to 100 mw worldwide. Spectrum spreading is
accomplished by frequency hopping in 79 hops displaced by 1 MHz, starting
at 2.402 MHz and stopping at 2.480GHz. Due to local conditions the
bandwidth has been reduced in Spain, France and Japan.
The baseband describes the digital signal processing hardware-the
Bluetooth link controller, which carries out the baseband protocols and other
low level link routines. Before establishing any network connections in a
piconet structure, all devices are in the stand-by mode. In this mode an
unconnected unit periodically „listens‟ for messages every 1.28 seconds.
Each time a device wakes up, it listens on a set of 32 hop frequencies
defined for that unit. The number of frequencies varies in different
geographical regions ; 32 is a number for most countries ( except Spain,
France and Japan).
The connection procedures are initiated by any of the devices which
then become master. A connection is made by a page message if the address
is already known, or by an enquiry message followed by a subsequent page
message if the address is already known. The master unit is the device in the
piconet structure whose clock and hopping frequencies are used to
synchronize all other units in the piconet. The devices other than master are
called the slave units. In the initial page state, the master unit will send a
train of 16 identical page messages on 16 different hop frequencies defined
for the device to be paged(slave unit ). If no response, the master transmits a
train on the remaining 16 hop frequencies in the wake up sequence. The
maximum sequence before the master reaches the slave is twice the wake up
period (2.56 sec.), while the average delay is the wake up period (0.64 sec.).
The enquiry typically used for finding Bluetooth devices, including public
printers, fax machines and similar devices with an unknown messages, but
may require 1 additional train period to collect all the responses. A power
saving mode can be used for connected units in a piconet if no data need to
be transmitted. This power saving mode is the sniff and hold mode in which
the device activity is lower. The master unit can put the slave units into the
hold mode, Data transfer restarts instantly when units transits out of the hold
mode. The hold is used when connecting several piconet or managing a low
power device such as temperature sensor. Two more low power modes are
available, the sniff and the park mode. In the sniff mode, the slave devices
listens to the piconet reduced rate thus reducing its duty cycle. The sniff
interval is programmable and depends on the application. In the park mode a
device is still synchronized to the piconet but dose not participate in the
traffic. Such a device is the parked device and does not have a MAC
address. The MAC address is a three bit address to distinguish the units
participating in the piconet structure. Parked device have given up their
MAC addresses and occasionally listen to the traffic of the master to
resynchronize and check on broadcast messages. If we list modes in
increasing order of power efficiency, the sniff mode has the higher duty
cycled followed by the hold mode with a lower duty cycle .
The link manager software entity carries out link set up,
authentication, link configuration and other protocols. The Link Manager
discovers other remote Link Managers and communication with them via the
Link Manager protocol. To perform its service provider role, the Link
Manager uses the service of the under lying controller. Services provided are
1. Sending and receiving of data.
2. The link manager has an efficient means to inquire and report a name or
device ID up to 16 characters in length.
3. Link address inquiries.
4. Connection set up.
6. Link Mode negotiation and set up, e.g. data or data/voice. This may be
changed during a connection.
7. The Link Manager decides the actual frame type on a packet to packet
8. Setting a device in sniff mode ; In sniff mode, the duty cycle of the slaves
reduces. It listen only every M slots, where M is negotiated at the Link
Manager. The master can start transmission in specified time slots spaced
at regular intervals.
9. Setting a link device on hold ; In hold mode, turning off the receiver for
long periods saves power. Any device can wake up the link again, with
an average latency of 4 seconds. This is defined by the link Manager and
handled by the Link Controller.
10.Setting a device in park mode ; It wakes up at regular intervals to listen to
the channel in order to resynchronize with the rest of the piconet, and to
cheek page messages.
Bluetooth devices will be required to support baseline interoperability
feature requirements to create a positive consumer experience. For some
devices, these requirements will extend from radio module compliance and
air protocols and object exchange formats. For other devices, such as
headset, the feature‟s requirements will be significantly less. Ensuring that
any device displaying the Bluetooth „logo‟ interpolates with other Bluetooth
devices is the goal of the Bluetooth program. Software interoperability
begins with the Bluetooth link level protocol responsible for multiplexing ,
device and service discovery, segmentation and reassemble, Bluetooth
devices must be able to recognize each other and load the appropriate
software to discover the higher level abilities each device supports.
Interoperability at the application level requires identical protocol stacks.
Different classes of Bluetooth devices(PC‟s, handheld, headsets,
cellular telephones) have different compliance requirements. For example, a
Bluetooth headset is not expected to contain an address book. Headsets
compliance implies Bluetooth radio compliance, audio capability and device
discovery protocols. More functionality would be expected from cellular
phones, handheld and notebook computer. To obtain this functionality, the
Bluetooth software framework will reuse existing specifications such as
OBEX, Vcard/Vcalender, Human Interface Device and TCP/IP rather than
inventing yet another set of new specifications. Device compliance will
require conformation to both, the Bluetooth specification and existing
protocols. The software framework is contemplating the following functions:
1.Configuration and diagnosis utility
2. Device discovery
5.Audio communication and call control
6.Object exchange for business cards and phone books Networking
LINK TYPES AND PACKET TYPES:
The link defines “what” of packets can be used on a particular link.
The Bluetooth baseband technology supports two link types:
Synchronous connection oriented (SCO) type (used primarily for
Asynchronous connectionless (ACL) type (used primarily for packet
Different master slave pairs of the same piconet structure can use
different link types and the link type may change arbitrarily during a session.
Each link “supports up to 16 different packet types. Four of these are control
packets and are common for both SCO and ACL links. Both link types use a
Time Division Duplex (TDD) scheme for full duplex transmission.
SYNCHRONOUS CONNECTONS ORIENTED TYPE:
The SCO link is symmetric and typically supports time bound voice
traffic. SCO packets are transmitted over reserved intervals. Once the
connection is established, both master and slave units may send SCO
packets without being polled. One SCO packet type allows both voice and
data transmission ; with only the data portion being retransmitted when
ASYNCHRONOUS CONNECTIONLESS LINK TYPE:
The ACL link is packet oriented and supports both, symmetric and
asymmetric traffic. The master unit controls the link bandwidth and decides
how much piconet bandwidth is given to each slave, and the symmetry of
the traffic. Slaves must be polled before they can transmit data. The ACL
link also supports broadcast messages from the master to all slaves in the
In order to make different hardware implementations
compatible, Bluetooth devices use the HCI as a common
interface between the Bluetooth host (e.g. a portable PC)
and the Bluetooth core.
Higher-level protocols like the SDP, RFCOMM
(emulating a serial port connection) and the TCP are
interfaced to baseband services via the LLCAP. Among the
issues LLCAP takes care of, is segmentation and reassemble
to allow larger data packets to be carried over a Bluetooth
baseband connection. The service discovery protocol allows
applications to find out about available services and their
characteristics when e.g. devices are moved or switched off.
HARDWARE ARCHITECTURE :
The Bluetooth hardware consists of an analog radio
part and a digital part - the Host Controller. The Host
Controller has a hardware digital signal processing part
called the Link Controller (LC), a CPU core and interfaces to
the host environment
The Link Controller consists of hardware that performs
baseband processing and physical layer protocols such as
ARQ (Automatic Repeat reQuest) protocol and FEC (Forward
Error Correction) coding. The function of the Link Controller
includes Asynchronous transfers, Synchronous transfers,
Audio coding and Encryption.
The CPU core allows the Bluetooth module to handle
Inquiries and filter Page requests without involving the host
device. The Host Controller can be programmed to answer
certain Page messages and authenticate remote links.
The Link Manager (LM) software runs on the CPU core. The
LM discovers other LMs and communicates with them via the
Link Manager Protocol (LMP) to perform its service provider
role and to use the services of the underlying Link
There are three error correction schemes defined by the Bluetooth
1/3 rate Forward Error Correction code (FEC)
2/3 rate Forward Error Correction code
automatic repeat request (ARQ) scheme for data
FORWARD ERROR CORRECTION:
The purpose of the FEC on the data payload is to reduce the number
of retransmission. However, in a reasonably error free environment, FEC
creates unnecessary overhead that reduces the throughput. Therefore, the
packet definitions have been kept flexible as to whether or not to use the
FEC in the payload. The packet header is always protected by a 1/3 rate
FEC; it contains valuable link information and should survive bit errors.
AUTOMATIC REPEAT REQUEST:
An unnumbered ARQ scheme is applied in which the data transmitted
in one slot is directly acknowledged by the recipient in the next slot. For a
data transmission to be acknowledged, both the header error check and the
cyclic redundancy check must be maintained otherwise a negative
acknowledge is returned.
AUTHENTICATION, PRIVACY & SECURITY:
The Bluetooth baseband provides user protection and information
privacy mechanism at the physical layer. Authentication and privacy is
implemented in the same way in each Bluetooth device, appropriate for the
ad-hoc nature of the network. Connections may require a one way, two ways
or no authentication. Authentication is based on a challenge-response
algorithm. Authentication is a key component of any Bluetooth system,
allowing the user to develop a domain of trust between a personal Bluetooth
device, such as allowing only the owners notebook computer to
communicate through the owners cellular phone.
Encryption is used to protect privacy of the connection. Bluetooth
uses a string cipher well-suited for a silicon implementation with secret key
lengths of 0, 40 or 64 bits. Key management is left to higher layer software.
The goal of Bluetooth‟s security mechanism is to provide an appropriate
level of protection for Bluetooth short-range nature and use in a global
environment. Users requiring stalwart protection are encouraged to use
stronger security mechanisms available in network transport protocols and
Introducing the Bluetooth technology as a cable replacement
technique exposes the need for security functionality in the wireless solution.
By replacing the cable and introducing radio signals there is a need for the
Bluetooth device to have built-in security to prevent eavesdropping and
falsifying the message originator. Therefore, functionality for authentication
and encryption has been added to the Bluetooth technology. Authentication
is used to prevent unwanted access to data and to prevent falsifying of the
message originator. Encryption is used to prevent eavesdropping. These two
techniques combined with the frequency hopping technique and the limited
transmission range for a Bluetooth unit, usually 10 m, give the technology
higher protection against eavesdropping.. Since the need for security is
dependent on what kind of application is executed, three levels of security
are defined in the Bluetooth concept.
1. Non-secure: This mode bypasses functionality for authentication &
2. Service-level security; Security procedures are not initiated until L2CAP
3. Link-level security; Security procedures are initiated before the link set-up
the LMP level is completed.
In the Service-level security mode, it is suggested to introduce a
Security Manager that controls the access to services and units. This security
mode provides the possibility to define trust levels for the services and units
used respectively. The access is restricted according to the defined trust
The Link-level security mode is based on the concept of link keys.
These keys are secret 128 bit random numbers stored individually for each
pair of devices in a Bluetooth connection. Each time two Bluetooth units
communicate, the link key is used for authentication and encryption.
COMMUNICATION – FREQUENCY HOPPING.
The frequency hopping technique.
The Frequency Hopping Technique
Interference is avoided by using a frequency-hop, FH, spread
spectrum technology. This technology is well suited for low-power, low-cost
radio implementations and is used in some wireless LAN products. The
main advantage with Bluetooth's choice of parameters is the high hop rate,
1600 hops per second, instead of just a few hops per second. The shorter
packet length in the Bluetooth technology is another benefit. The frequency
band in FH systems is divided into a number of hop channels. Every hop
channel is just a fraction of the total frequency band. In Bluetooth one
channel is used in (one slot) followed by a hop in a pseudo-random order to
another channel for another transmission, repeated constantly. In this way
the hopping spreads the Bluetooth traffic over the entire ISM band and a
system with good interference protection is achieved. If one of the
transmissions is jammed by, for instance, a microwave oven, the probability
of interference on the next hop channel is very low. Error correction
algorithms are used to correct the fault caused by jammed transmissions.
Modulation/Transmission and packet definition
A Gaussian shaped binary FSK modulation is used to reduce the
transceiver complexity in Bluetooth units. Full duplex transmission
capability is achieved by using time division duplex, subsequent slots are
used for transmitting and receiving. The Bluetooth baseband protocol is a
combination of circuit and packet switching. Reservation of slots can be
done for synchronous packets. One packet typically uses one slot, but a
multi-slot method is also defined in the Bluetooth specifications. Multi-slot
packets can cover three or five slots. Packets are always sent on one single
hop channel. That means that when multi-slot packets are transmitted the
hopping frequency is reduced and there is no hop until the whole packet is
sent. This is illustrated in Figure 5. The channel using the white packet.
starts the illustrated sequence with a multi-slot packet covering three slots.
Note that the hopping channel after the multi-slot packet is the same
(compare with Figure 4) as if there had not been a multi-slot packet.
When Bluetooth units are communicating, one unit is master and the
rest of the units act as slaves. The master unit's system clock and the master
identity are the central parts in the frequency hop technology. The hop
channel is determined by the hop sequence and by the phase in this
sequence. The identity of the master determines the sequence and the master
unit's system clock determines the phase. In the slave unit, an offset may be
added to its system clock to create a copy of the master's clock. In this way
every unit in the Bluetooth connection holds synchronized clocks and the
master identity, that uniquely identifies the connection. Hops synchronized
with the master can therefore be achieved as described in Figure 6. 79 hop
carriers have been defined for the Bluetooth
Technology except for France and Spain where 23 hop carriers have
been defined, because the ISM-band is narrower there. Slave
The hop selection
The Bluetooth packets have a fixed format. A 72-bit access code
comes first in the packet. The access code is based on the master's identity
and the master's system clock, i.e. it provides the means for the
synchronization. This code is unique for the channel and used by all packets
transmitting on a specific channel. A 54-bit header follows the access code.
This header contains error correction, retransmission and flow control
information. The error correction information can. be used for correcting
faults in the payload and in the header itself. Finally
Comes he payload field with anything between zero and 2,745 bits, i.e. up to
Figure 7 The Bluetooth packet format
Bluetooth units operate on the ISM band, at 2.45 GHz. The
transmitting power is between 1 and 100 mW. The radio-frequency
transmitters are very small. Ericsson's 1 mW Bluetooth radio module is only
10.2x14x1.6 mm. The low power consumption implies that a Bluetooth unit
can operate on the power from a small battery for a long time (months).
These hardware characteristics make it possible to fit a Bluetooth unit in
many electrical devices. The maximum Bluetooth range is 10 m, with a
possibility to extend it to 100 m. The maximum bit rate is 1 Mbit/s.
Maximum effective payload is lower because the different protocol layers
require data payload for signalling to their
Corresponding layers in the unit with which the device is
communicating. Estimates have indicated data transfer rates up to 721 kbit/s.
Data packets are protected by an Automatic Retransmission Query,
ARQ, and scheme. This scheme implies that at every packet reception an
error check is done. If an error is detected, the receiving unit indicates this in
the return packet; thus lost or faulty packets only cause a one-slot delay. In
this way, retransmission is in this way selective, only faulty packets are
retransmitted. Since retransmission is not optimal for voice transmissions
due to its vulnerability for delays, a voice-encoding scheme is used. This
scheme is highly resistant to bit errors. The errors that cannot be corrected
result in an increasing background noise.
Piconet and Scatternet
Any two Bluetooth devices that come within range of each other can set up a
so-called ad hoc connection. When such a connection is established a
piconet is formed. There is always a master unit in a piconet and the rest of
the units act as slaves. Up to eight active units can form a piconet, which is
defined by the channel these units share. The number of devices in a piconet
is actually unlimited even though you can have only eight active devices at
any given moment. There is no difference in hardware or software between a
master and a slave, hence any unit can be master. The unit that establishes
the piconet becomes the master unit.
The roles in a piconet can change but there can never be more than
one master. The master unit controls all traffic in the piconet. It allocates
capacity for SCO links and handles a polling scheme for ACL links. Slave
units may only send in the slave-to-master slot after being addressed in the
preceding master-to-slave slot. If the master does not have any information
to send in the master-to-slave slot, a packet with access code and header
only is sent. That is, every slave unit is addressed in a specific order, and
polling scheme, and may only send upon being addressed. In this way,
packet collisions between sending slave units are eliminated.
Establishing network connections
Before a unit has joined a piconet it is in standby mode. In this mode,
an unconnected unit periodically wakes up and listens for messages every
1.28 seconds. Paging messages are transmitted on 32 of the 79 (16 of 23 for
Spain and France) hop carriers which are defined as wake-up carriers (the
unit's identity determines which of the hop carriers it is). A connection is
made by a page message if the address is already known, or by an inquiry
message followed by a subsequent page message if the address is unknown.
The wake-up sequence is transmitted by the master over the 32 (or 16
for Spain and France, below is the 32 hop carrier system described) wake up
carriers. Initially, the 16 first hop carriers are used, if there is no response,
the rest of the carriers are used. The slave's system clock determines the
phase in the wake-up sequence. The slave listens for 18 slots on the wake-up
carrier and compares the incoming signal with the access code derived from
its own identity. If there is a match, the unit invokes a connection-set-up
procedure and enters Connected mode. The master unit must know the
slave's identity and its system clock. This is required to calculate the proper
access code and the wake-up sequence and to predict the wake-up sequence
phase. To keep track of the slaves' system clocks, a paging procedure is
defined for the master unit. It defines how identities are. transmitted between
master and slave units and how the slaves' current system clocks are
distributed to the master. To connect units with an unknown address an
inquiry signal is transmitted initially. This signal is used to inform the
master unit of the slave's identity within transmission range. The paging unit
on the inquiry wake-up carriers sends an inquiry access code. Units
receiving this message respond with their identity and system clock. The
inquiry message is typically used for finding Bluetooth devices, including
public printers, fax machines and similar devices with an unknown address.
Power saving modes
Three different power saving modes have been defined, Hold, Sniff
and Park. They can be used if there is no data transmission ongoing in the
piconet. A slave can either demand to be put in Hold mode or be put in Hold
by the master unit. In Hold mode only an internal timer is running. Data
transfer restarts instantly when units make the transition out of Hold mode.
The mode is used when connecting several piconets or managing a low
power device such as a temperature sensor. In the Sniff mode, a slave device
listens to the piconet at reduced rate, thereby reducing its duty cycle. In the
Park mode a unit remains synchronized in the piconet but does not
participate in the traffic .
To optimize the use of the available spectrum, several piconets can
exist in the same area. This is called Scatternet. Within one Scatternet all
units share the same frequency range but each piconet uses different hop
sequences and transmits on different 1 MHz hop channels. Thus, a way to
optimize the data transmission capability is to keep the piconets small (i.e.
few units). All piconets share the 80 MHz band, where each piconet uses 1
MHz, thus, as long as the piconets pick different hop frequencies, no sharing
of 1 MHz hop channels occurs.
BLUETOOTH USAGE MODELS.
Bluetooth usage models.
Bluetooth Usage Models
In this section a number of Bluetooth usage models are described. For
each usage model there is one or more corresponding profiles defining
protocol layers and functions to be used. The profiles are not described in
detail in this document, for more information refer to the Bluetooth
The File Transfer usage model offers the capability to transfer data
objects from one Bluetooth device to another. Files, entire folders,
directories and streaming media formats are supported in this usage model.
The model also offers the possibility of browsing the contents of the folders
on a remote device. Furthermore, push and exchange operations are covered
in this usage model, e.g. business card exchange using the vCard format.
The File Transfer model is based on GOEP.
The Internet Bridge usage model describes how a mobile phone or
cordless modem provides a PC with dial-up networking capabilities without
the need for physical connection to the PC. This networking scenario
requires a two-piece protocol stack, one for AT-commands to control the
mobile phone and another stack to transfer payload data..
The LAN Access usage model is similar to the Internet Bridge user
model. The difference is that the LAN Access usage model does not use the
protocols for AT-commands. The usage model describes how data terminals
use a LAN access point as a wireless connection to a Local Area Network.
When connected, the data terminals operate as if it they were connected to
the LAN via dial-up networking.
The synchronization usage model provides the means for automatic
synchronization between for instance a desktop PC, a portable PC, a mobile
phone and a notebook. The synchronization requires business card, calendar
and task information to be transferred and processed by computers, cellular
phones and PDAs utilizing a common protocol and format.
The Three-in-One Phone usage model describes how a telephone
handset may connect to three different service providers. The telephone may
act as a cordless telephone connecting to the public switched telephone
network at home, charged at a fixed line charge. This scenario includes
making calls via a voice base station, and making direct calls between two
terminals via the base station. The telephone can also connect directly to
other telephones acting as a “walkie-talkie” or handset extension i.e. no
charging needed. Finally, the telephone may act as a cellular telephone
connecting to the cellular infrastructure. The cordless and intercom scenarios
use the same protocol stack.
The Ultimate Headset usage model defines how a Bluetooth equipped
wireless headset can be connected, to act as a remote unit‟s audio input and
output interface. The unit is probably a mobile phone or a PC for audio input
and output. As for the Internet Bridge user model, this model requires a twopiece protocol stack; one for AT-commands to control the mobile phone and
another stack to transfer payload data, i.e. speech. The AT-commands
control the telephone regarding for instance answering and terminating calls.
There are a number of competitors to the Bluetooth technology.
However, there is no obvious single competitor in all the market segments in
which the Bluetooth technology can operate.
The main competitor in the cable replacement market segment is
IrDA. IrDA is an infrared interface standard providing wireless solutions
between, for instance, mobile phones and PDAs. The technique is well
known in the market but has had problems because some IrDA
manufacturers have made implementations incompatible with standard
implementations. The maximum payload in the IrDA technology exceeds
the maximum Bluetooth payload. The two main disadvantages with IrDA
are that it is limited to point-to-point connections (only two parties in a
connection) and its need for line of sight (since it is based on infrared light).
Implementations based on IEEE 802.11
The main competitors in the market segment for wireless LAN are the
implementations based on the IEEE 802.11 standard. Some of these
implementations also use the frequency hopping technology. The main
differences between Bluetooth and these implementations are:
* The number of simultaneous users is higher for IEEE 802.11-based
* The Bluetooth hardware size is considerably smaller
* The five Euro unit is 10 to 20 times cheaper than an IEEE 802.11 unit
* The number of frequency hops is considerably higher for Bluetooth than
an IEEE 802.11 implementation.
Ultra-Wideband Radio, UWB
Ultra-Wideband Radio, UWB, is a new radio technology. The concept
is similar to radar. Short pulses are transmitted in a broad frequency range.
The information is modulated by the pulses' time and frequency. The
technique is not fully developed but might be a threat to the Bluetooth
concept since its superiority in capacity and power consumption. UWB
prototypes indicate payloads up to 1.25 Mbit/s with 70 meters range at just
0.5 mW power consumption.
Home RF is a technique developed by a consortium with, among
others, Microsoft, Intel, HP, Motorola and Compaq. The technique is
developed from the. DECT concept and operates in the 2.4 GHz frequency
band (the same as Bluetooth). The intention has been to develop a technique
for the home market. There are many similarities with Bluetooth, price per
unit, range, transmitting power etc. The major differences are that Home RF
can handle up to 127 units per net and it uses just 50 frequency hops per
second. The figures for Bluetooth are 8 and 1600 respectively.
1 mbps(gross rate)
Packet oriented for data applications,max
full duplex data rate is 432 kbps,
arranged as 64 kbps channels for speech
Primarily designed as noice service, not
packet, expensive (typically $100 for a
handset and home base station)
Very cheap (now ariund $1 to $2 per
installation) low range (~1m) and line of
The Bluetooth concept offers several benefits compared with other
The main advantages of Bluetooth are:
* The minimal hardware dimensions
* The low price on Bluetooth components
* The low power consumption for Bluetooth connections.
The advantages make it possible to introduce support for Bluetooth in
many types of devices at a low price. The diversity in product offerings
(mobile phones, PDAs, computers, computer hardware, notebooks etc) from
companies in the Bluetooth SIG and their broad support for the technique
creates a unique market position. Both hardware and device manufacturers
will work for the introduction of Bluetooth in many different devices.
The capabilities provided by Bluetooth, approximately 720 kbit/s, can
be used for cable replacement and several other applications such as speech,
LAN and so on, as described in the use cases, described in the section
entitled Bluetooth Usage Models. Figure 8 indicates in what areas the
Bluetooth concept can be used. Defining of specific user models and
corresponding profiles combined with the four general profiles will most
likely lead to a market situation where applications covered by the user
models will use the defined user models and their profiles. Furthermore, it is
likely that new applications will use the standard profiles and thereby avoid
interoperability problems between different manufacturers.
The Bluetooth baseband protocol is a combination of circuit and
packet switching. Slots can be reserved for synchronous packet. Each packet
is transmitted in a different hop frequency. A packet nominally covers a
single slot, but can be extended to cover up to 5 slots. Bluetooth can support
an asynchronous data channel, up to 3 simultaneous synchronous voice
channels, or a channel that simultaneously supports asynchronous data
synchronous voice. Each voice channel supports 64 kbps synchronous
(voice) link. The asynchronous channel can support an asymmetric link of
maximally 721 kbps in either direction while permitting 57.6 kbps in the
return direction, or a 432.6 kbps symmetric link.
APPLICATION ON 3-G WORLD.
Possible 3-G support application.
MAJOR APPLICATIONS IN THE 3-G WORLD
Possible 3G Support Applications
The following examples demonstrate how 3G and Bluetooth
together, providing local intercommunication as well as wide area
connectivity in a wide range of applications. These are not definitive and by
no means exhaustive, but aim to show how complementary standards can
work together to provide a greater level of service than either could achieve
Vending machines in shopping mall
All the automatic vending machines within a confined area can,
through a Bluetooth access system, be connected to a central vending
machine administration unit, that in turn uses a 3G access system to call for
maintenance or supplies. Minor problems can be relayed to the Mall
technician directly through his Bluetooth communicator. Pricing changes
can be sent from central administration and locally “broadcast” to all
Bluetooth vending machines.
E-mail delivery to the PC
3G terminals will be able to handle several channels simultaneously
(e.g. voice, fax and data each requiring different channel characteristics and
speeds). With predictions of terminal penetration being very high (every
member of the population above the age of 12 in a few years), the PC itself
does not have to be a 3G terminal in order to receive e-mails on the move. A
Bluetooth/3G terminal can receive e-mail as a data transmission and forward
it, via Bluetooth to the PC (assuming it is within close proximity). When the
reception is complete, the PC can notify the user via Bluetooth and a short
message to his mobile terminal that he has e-mail, and if an item is urgent,
this fact can be forwarded too. This concept allows the 3G terminal to be the
local “headend” for a variety of applications that are locally interconnected
via Bluetooth. If for example, such an e-mail was received while waiting for
a train or plane, the user could approach a Bluetooth services booth
(example new commercial enterprise for business travelers). Here, for a fee
chargeable to his charge/credit card or e-Wallet, he can instruct his PC to
print the e-mails of interest (using his 3G/Bluetooth terminal to control it,
leaving the PC in the briefcase).
Many people believe that the mobile phone can become the portal of
first choice to the e-commerce world. At present however a separate Smart
Card is required to hold electronic cash - no-one wants to remove their SIM
from the phone in order have it read by a Point of Sale terminal. Bluetooth
of course will allow the SIM (which now becomes a multi-function Smart
Card) to be read while it remains in the phone. With 100 Kbytes Smart
Cards on the horizon we can foresee our mobile phones becoming the main
repository for our cash, health info, personal preferences, season tickets, etc.
etc. The wide area cellular world will be one of the main routes for updating
The Underground Train
Underground facilities suffer from “poor” coverage on cellular
Many underground rail operators are overcoming this by installing systems
designed to provide driver and station staff with a reliable communication
network. Systems such as TETRA (TErrestrial Trunked Radio) provide
sufficient capacity that there is spare to carry some passenger traffic too.
Carriages equipped with Bluetooth transceivers would provide a gateway
between the train TETRA system and the user‟s 3G/Bluetooth terminal, and
the TETRA system would provide the gateway to the surface public
networks. For the convenience of other passengers, not all carriages would
be enabled for support of voice over Bluetooth (though the use of Bluetooth
for broadcasting timetable information, advertising etc. could be available in
The Bluetooth Headset
The 3G/Bluetooth terminal mentioned in the above example does not
in fact need to be in the user‟s hand or pocket during most of the noted
transactions. The user will have a Bluetooth headset (a product already
announced by Ericsson) allowing him to leave the terminal in his briefcase
too. This may provide voice control/recognition functionality, removing
most of the need for a keyboard or display on the 3G terminal. These
suggestions may raise the question as to where the terminal (3G) in fact
should reside. Much of the functionality delivered by 3G systems will be
directed towards a data terminal device such as a PC or palm top computer
and it may be logical to build the 3G terminal into it. With an external
(Bluetooth) headset, there would be nothing to hold, though a simple MMI
(Man Machine Interface) device to allow dialing and displaying of short
messages (connected to the main terminal by Bluetooth of course) may be
required. If this could be made credit card sized it becomes a small version
of the bpad discussed above and may well replace the handset/terminal as
we know it. Alternatively, as has been suggested previously in this paper, the
PC and 3G terminal may be physically separate devices while being
functionally connected when in close proximity to each other. This perhaps
offers greater flexibility (it wouldn‟t be necessary to carry a PC everywhere
simply to make and receive calls), while losing none of the functionality of
the combined device. In some cases it may even be possible to leave the PC
at home connected to the Home Base Station (via Bluetooth), and retrieve
data from it directly to the bpad using Bluetooth and 3G together.
THE SPECIFICATION IS AS FOLLOWS:
Frequency band :2.4 GHz (unlicensed ISM band)
Transmitting power: 1 milliwatt(0dBm)
Technology : spread spectrum ; hybrid direct sequence and frequency
Maximum voice channels : 3 per piconet
Data speed : 721 kbps per piconet
Expected system range : 10 meters (40 feet)
Number of devices supported : 8 per piconet, 10 piconets in coverage area.
Security : Yes, link layer.
Power requirements :2.7 volts.
Power consumption : 30 uA sleep, 50 uA hold, 300uA stand by, 830mAtransmitting.
Module size : 0.5 square inches.
Interference : Bluetooth minimize potential interference by employing fast
frequency hopping –1600 times a second.
TECHNICAL DEFINITIONS :
PICONET : A collection of devices connected via Bluetooth technology in
an ad hoc fashion. A piconet starts with grow to eight connected devices. All
Bluetooth devices are peer unit and have identical implementations.
However, when establishing a piconet connection. The Bluetooth system
supports both point-to-point and point-to-multi point connections.
SCATTERNET : Multiple independent and non-synchronized piconets
form a Scatternet.
MASTER UNIT : The devices in the piconet whose clock and hopping
sequence are used to synchronize all other devices in the piconet.
SLAVE UNITS : All devices in the piconet that are not the master.
MAC ADDRESS : 3-bit address to distinguish between units participating in
PARKED UNITS : Devices in a piconet, which are synchronized but do not
have a MAC address.
SNIFF AND HOLD MODE : Devices synchronized to a piconet can enter
power saving modes in which device activity is lowered.