Abstract—Bluetooth which takes a narrowband signal and

Abstract—Bluetooth is a short range, low power, low
cost wireless communication technology designed to connect phones, laptops and
PDAs. The greater availability of portable devices with Bluetooth connectivity
imposes wireless connection between enabled devices. This paper considers the
problems of Bluetooth communication and also proposes a new expanded network to
overcome the basic limitation of Bluetooth devices that is the range
constraint. This creates a network of devices that will include laptops, set
top devices and also mobile phones. The main purpose of this proposal is to
establish a network will enable the users to communicate outside the range
without any range constraint.


Index Terms— Bluetooth, Pico Net, Scatter Net, Frequency Hopping, ISM

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obility originated from the desire to move either toward resources
or away from scarcity. Mobile computing is concerned about the movement of
physical devices, user applications and mobile agents. Bluetooth technology
developed by Ericsson Mobile Communications and it replace the cables used to
connect devices, with one universal short-range radio link. These radio waves
are operating in the unlicensed ISM band and also having 2.45 GHz frequency.
Bluetooth uses a spread-spectrum frequency-hopping technique which takes a
narrowband signal and spreads it over a broader portion of the available radio
frequency band. . This prevents the interference with other devices. Since only
the intended receiver is aware of the transmitter’s hopping pattern, only that
receiver can make sense of the data being transmitted. This technique ensures
Bluetooth’s security and limits interference.

The Bluetooth technology eliminates the need for cables  and connectors. So the expenses for cables and
connectors are reduced, which gives large economic benefit 1. The effective
range of Bluetooth devices is 32 feet (10 meters). A major challenge lies in
Bluetooth communication is this range constraint. This paper studies the basic
limitation of Bluetooth communication and also presents a possible solution for
this. The paper tries to explore the basic routing algorithm and it can be used
for expanding the range of Bluetooth devices.


Bluetooth Architecture –

Bluetooth is the term used to describe the protocol of a short range
(10 meter) communication. It places an important role in wireless
communication. The goal of Bluetooth specification is the uniform structure for
a wide range of devices to connect and communicate with each other. These specifications
are developed and licensed by the Bluetooth Special Interest Group (SIG). The Bluetooth
SIG consists of companies in the areas of telecommunication, computing,
networking, and consumer electronics. The data transfer rate of Bluetooth is
1Mbps. The Bluetooth specification can support three synchronous voice channels
at 64 Kbps each. Bluetooth devices typically require 1mW of power to operate.


Bluetooth devices are organized as a network of two to eight devices
called Pico nets. A Bluetooth pico-net consists of a single master device and
one or more slave devices. Each node in the Pico net uses the same frequency
hopping technique. A slave or master in one Pico net can communicate with the
master or slave in other Pico net. This bridging structure is termed as scatter
net (Figure 1). In addition to seven slave nodes in the Pico net, there can be
up to 255 nodes in the network. The Bluetooth model is working under the
concept of Bluetooth protocol stack. Bluetooth network is divided into
different layers as shown in (Figure 2). It has many protocols groups loosely
into layers. This layering structure is different from any other reference model.
The radio layer is somewhat similar to the physical layer of internet model. By
using frequency hopping technique reduce the interferences. Base band layer is
roughly equivalent to Mac sub layer in internet.  In this TDMA is used as the access method.
Single slave and multiple slave communication is possible in this layer. There
are two links used for communication. Synchronous connection oriented and
asynchronous connection less. Next layer is the L2CAP layer. Multiplexing,
Segmentation and Reassembly, QOS and group management are the main duties of
the L2CAP layer.

networking transmits data via low-power radio waves. It communicates on an International
agreed frequency (ISM) of 2.45 gigahertz. A Time Division Multiplexing (TDD)

technique is used in this communication. This divides the channel
into 625p slots and, with a 1MBPS symbol rate, a slot can carry up to 625 bits.
Transmission occurs in packets and each packet is transmitted on a different
hop frequency with a maximum frequency hopping rate of 1600 hops/s. Based on
output power rating Bluetooth devices are divided into three


Figure 1 : Scatter-Net


classes. Most powerful devices are in class 1 category. These can
have up to 100 mW of power, and a range of about 40 m – 100 m (130 – 330 ft).
Class 2 devices are lower power, with up to 2.5 mW of power and a range of
about 15 m – 30 m (50 – 100 ft). Third category is class 3. This uses less
power up to 1 mW and a range of about 5 m – 10 m (16 – 33 ft). Most of the
Bluetooth devices will fall under class 2 or class 3.


Figure 2 : Bluetooth


Challenges in Bluetooth

The present scenario using Bluetooth has many drawbacks. Data can be
transmitted only over short distances, network overloading may occur, if one
path is busy then we have to wait till the path is cleared, data transmission
rate will be slow if network is busy etc are some of the obscurity in Bluetooth
network. The devices in the network have low power. So this low power limits
the range of a Bluetooth device to about 10 meters (32 feet paper). Even with
the low power, Bluetooth doesn’t require line of sight between communicating
devices. The nodes in Pico net are classified into four categories according to
their states. These are active, idle, parked and sniffing. Data exchange takes
place only between active nodes but the nodes periodically change its states.
This imposes a greater challenge in Bluetooth design. Which node is selected as
a master, and how many nodes that can be used to connect to other Pico net are
the challenging areas.

Bluetooth is primarily intended to facilitate short
range data transfer using low power. The main disadvantage of this technology
is the nodes involve in the data transfer have to be very near each other.
Because of this range constraint most of the time the greater number of
Bluetooth enabled devices are inactive. So the communication throughput is
decreased. In this paper we are concentrating on the range limitation of
Bluetooth communication and we are trying to expand the range by using the
enabled intermediate devices.


Proposed Network Solution

The main goal of this paper is to overcome the basic limitation of
Bluetooth devices. The range of Bluetooth devices are usually of 10 meters.
This range restriction is overcome by allowing a device to another device outside
its range through an intermediary device, which has access to both the devices
(figure 3).

First step of expansion is to establish a network. To
set up the network each device broadcast a list of accessible devices within
its range. Each device updates their table of accessible devices according to
this list. Each device prepared a list of other devices that can be accessed
directly or indirectly. If a device wishes to send a message to another device
in this list, a path is found through intermediary device through which the
destination can be reached and forwards the message to the first device in the
path. But the intermediate devices dynamically choose the path through which
the message is forwarded depending upon the traffic and availability of devices.


Figure 3 : Expanding Range Using Intermediate



Model for Proposed Solution

This paper tries to expand the range of Bluetooth data transfer by
involving intermediate devices between the sender and receiver. A message from
the source goes to one or more intermediate device finally ends up at
destination. This is typically considers as a client server architecture. The
device which sends the data is the client and receives the data is the server.
The client node expands its network by searching for the Bluetooth enabled
device in its range. All devices continue this searching for devices within the
range until the destination is reached. A model of the proposed system is in
the figure 4.


Figure 4 : Model for Proposed Solution


This network consists of devices of smaller speed and relatively
smaller network. The routing algorithm I have chosen is distance vector routing
algorithm. The operation of the algorithm is as follows. When a node starts it
can directly access its immediate neighbors. Each node creates a list of nodes
that can be accessible. Each node, on a regular basis, sends to each neighbor
its own current idea of the total cost to get to all the destinations it knows
of. Cost is determined by the number of nodes in the path. The neighboring
nodes examine this information and update their routing table accordingly. Over
time, all the nodes in the network will discover the best next hop for all
destinations, and the best total cost.

A node wants to send message to another node in
the network first it check whether this node is in the range of the sender. If
so then it can directly send message. Otherwise it 


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