What is Frequency-Hopping
Spread Spectrum (FHSS)?
Frequency-Hopping Spread-Spectrum (FHSS) is a spread spectrum modulation scheme
that uses a narrowband carrier that changes frequency in a pattern known to both
transmitter and receiver. Properly synchronized, they maintain a single logical
channel. To an unintended receiver, FHSS appears as short-duration impulse
noise. More simply, the data is broken down into packets and transmitted to the
receiver of other devices over numerous “hop frequencies” (79 total) in a pseudo
random pattern. Only transmitters and receivers that are synchronized on the
same hop frequency pattern will have access to the transmitted data. The
transmitter switches hop frequencies 1,600 times per second to assure a high
degree of data security
How secure is a Bluetooth
Bluetooth is extremely secure in that it employs several layers of data
encryption and user authentication measures. Bluetooth devices use a combination
of the Personal Identification Number (PIN) and a Bluetooth address to identify
other Bluetooth devices. Data encryption (i.e., 128-bit) can be used to further
enhance the degree of Bluetooth security. The transmission scheme (FHSS)
provides another level of security in itself. Instead of transmitting over one
frequency within the 2.4 GHz band, Bluetooth radios use a fast frequency-hopping
spread spectrum (FHSS) technique, allowing only synchronized receivers to access
the transmitted data
What is the future direction
of the Bluetooth standard?
At this time, we anticipate the Bluetooth SIG to evolve the Bluetooth technology
to provide greater bandwidth and distances, thus increasing the potential
platforms and applications used in the emerging personal area networking
How is Bluetooth used?
Bluetooth can be used to wirelessly synchronize and transfer data among devices.
Bluetooth can be thought of as a cable replacement technology. Typical uses
include automatically synchronizing contact and calendar information among
desktop, notebook and palmtop computers without connecting cables. Bluetooth can
also be used to access a network or the Internet with a notebook computer by
connecting wirelessly to a cellular phone.
Do you Know about OBEX
IrOBEX (shortly OBEX) is a session protocol developed by the Infrared Data
Association (IrDA) to exchange objects in a simple and spontaneous manner. OBEX,
which provides the same basic functionality as HTTP but in a much lighter
fashion, uses a client-server model and is independent of the transport
mechanism and transport API, provided it realizes a reliable transport base.
Along with the protocol itself, the “grammar” for OBEX conversations between
devices, OBEX also provides a model for representing objects and operations. In
addition, the OBEX protocol defines a folder-listing object, which is used to
browse the contents of folders on remote device. In the first phase, RFCOMM is
used as sole transport layer for OBEX.
What is Service Discovery
Discovery services are crucial part of the Bluetooth framework. These services
provide the basis for all the usage models. Using SDP, device information,
services and the characteristics of the services can be queried and after that,
a connection between two or more Bluetooth devices can be established. SDP is
defined in the Service Discovery Protocol specification.
What is Link Manager
The link manager protocol is responsible for link set-up between Bluetooth
devices. This includes setting up of security functions like authentication and
encryption by generating, exchanging and checking of link and encryption keys
and the control and negotiation of baseband packet sizes. Furthermore it
controls the power modes and duty cycles of the Bluetooth radio device, and the
connection states of a Bluetooth unit in a piconet.
Is it possible to connect
multiple Bluetooth hubs?
No, only one hub can be used at a time with a computer. USB or Serial devices
can be added.
List some Technology
characteristic of Bluetooth?
Adaptive output power to minimize interference,
Support Synchronous & asynchronous services,
Fast Frequency Hopping to avoid interference,
Short data packets to maximize capacity during interface.
What is the total number of
masters and slaves in a piconet?
1 Master and 7 Slaves.
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