Polytechnic UniversityElectrical and Computer Engineering Department
EE-3414
Multimedia Communication
Wireless LAN Bluetooth vs IEEE802.11b
By
Kettly Joseph
And
Stephan Dubissette
Introduction
In the last few years, many wireless connectivity standards/technologies have
emerged. These technologies deliver opportunities for rapid ad-hoc connections, and
the possibility of automatic connections between devices. The objective of this project is
to compare and contrast two of these technologies namely the IEEE802.11 and
Bluetooth. Bluetooth is an emerging technology that is used for short range indoor
wireless networks based on Frequency Hopping - Code Division Multiple Access/Time
Division Duplexing (FH-CDMA/TDD). IEEE 802.11 is the standard set by the IEEE
(Institute of Electrical and Electronics Engineers) for wireless network connections. Over
the past seven years most of the articles written on these two technologies have tended
to make believe that they were used for the same purpose. However, from our research,
we discovered that they were two different technologies which unfortunately were using
the same frequency band. The main difference being that IEEE802.11 will usually be
used for long periods of network connectivity where as Bluetooth will usually be used
when there is a need for a few devices to be connected for short period of time. Below
is an outline of the points that we focused on for the successful realization of this project
and also the result of our research. Since Wireless Network is a new field most of the
observations made is subject to improvement and can even become obsolete. One of
the big issues today is the attempt to used Bluetooth and IEEE802.11 on the same
network. But this is still an area of research.
Project Plan
1. OSI Model Kettly Joseph (03|14|03|) Definition
OSI Model Architecture
Placement of IEEE802.11 and Bluetooth in the OSI Reference Model
2. Overview of Spread Spectrum Technology Kettly Joseph 3. What is Wireless LAN Kettly Joseph ( 03|20|03)
Definition and Configuration
4. IEEE802.11 Kettly Joseph(04/ 15/03) Origin
Description
Data layer
Physical layer
Network layer
5. Bluetooth
Origin Stephan Dubissette (03/20/03) Description
Physical layer
Data Layer
Network layer
6. Differences and Similarities Kettly Joseph7. Discussion and Conclusion Kettly Joseph 8. References
1. OSI Model Definition
The OSI Model is a standardized network scheme developed by ISO in 1984 to
create a common and unified platform that will allow interoperability among all the
network technologies in the world. To reduce the complexity of the process, the OSI
model is divided into seven layers. Each layer corresponds to a network function,
provides service to the above layer in the protocol and communicates with the same
layer located at the other end of the other communicating device.
OSI Model ArchitectureThe seven layers mentioned above are described as follow:
Application: Provides different services to the applications
Presentation: Converts the information
Session: Handles problems which are not communication issues
Transport: Provides end to end communication control
Network: Routes the information in the network
Data Link: Provides error control between adjacent nodes
Physical: Connects the entity to the transmission media
In table1 the lower four layers are concerned with the flow of data from end to end
communication. The upper three are aimed to serve the applications.
Application Layer
Application LayerPresentation Layer
Presentation Layer
Session Layer Session Layer
Transport Layer Transport LayerNetwork Layer Network LayerData Layer Data Layer Physical Layer Physical Layer
Table 1
Placement of IEEE802.11 and Bluetooth in the OSI Reference Model
The main interest in OSI model is to better understand the use of IEEE802.11
and Bluetooth. As stated in table1 above the lower four layers in the OSI model are
responsible for the flow of data. Mainly, Figure4 shows that these two technologies are
situated in the data link layer and Physical layer which are the body of data processing
in a network.
Figure 1
2. Overview of Spread Spectrum Technology In 1985, the FCC (Federal Communications Commission) allocated three
frequency bands for radio transmission techniques know as spread spectrum
communications, originally developed by the military. Spread spectrum technology was
mainly used by military because it resists jamming and is hard for an enemy to
intercept. Today it is the fundamental building blocks in current and next-generation
wireless system. The reason is that they are unlikely to interfere with other signals
Bluetooth
Use to allowed interoperability among networks (1984)
intended for business and consumer users even the ones transmitted on the same
frequencies. Common spread spectrum systems are of the "direct sequence" or
"frequency hopping" type, or else some combination of these two types (called a
"hybrid") as shown in figure2 and figure 3.
Figure 2 (Direct sequence SP) Figure 3 (Frequency Hoping SP)
Direct sequence spread spectrum systems use a high speed code sequence,
along with the basic information being sent, to modulate their RF carrier. Since the
system makes use of the Code Division Multiple Access the signal can easily be spread
out over a large frequency range and make all other users look like noise to the
destination. This allows for higher data rates and more users. IEEE802.11 uses this
system and there no specific limit set on the number of user of an 802.11 network.
In Frequency hopping systems the carrier frequencies changes (hops) rapidly
with time on the frequency band, and enables many users to utilize the same frequency
band with less interference. Frequency hopping could cause delays in the transmission
and the only way to prevent this is to slow down the information exchange. Therefore
only 1 packet is sent on 1 hop frequency. But, in the case of a larger packet, it could be
spread out over a maximum of 5 time slots (or the equivalent of missing 5 hop
frequencies). Bluetooth uses this system.
3. Wireless LANDefinition
A wireless LAN is a flexible data communication network that is used to transmit
and receive data over the air by using electromagnetic waves. One of the main
advantages of the Wireless LAN is that it minimizes the need of wired connection.
Today it is widely recognized and is very helpful within several markets, including
health-care, retail, manufacturing, warehousing, and academic arenas. The U.S.
wireless LAN market is rapidly approaching $1 billion in revenues. It can be set up in
four different ways which are: Independent WLANs, Microcells and Roaming,
Infrastructure WLANs and Ad-hoc. In this project we will elaborate on the last two later
on since IEEE802.11 and Bluetooth use Infrastructure them.
4 . IEEE 802.11 Origin
IEEE 802.11 is the standard set by the IEEE (Institute of Electrical and
Electronics Engineers) used for wireless network connections.
Description
The Target areas for IEEE 802.11 are inside buildings and also outdoor uses.
Like Bluetooth there is an accommodation of transmission rates of 1 Mbps as well as 2
Mbps. There is support for most market applications and for asynchronous and time-
bounded delivery service continuity of service within extended areas via a system such
as Ethernet
Data Layer
IEEE proposes two different ways to configure a network in Wireless LAN mainly
802.1. They included Ad-hoc and infrastructure. In the ad-hoc network there is no
structure, the devices are connected to any points and each of them is able to
communicate with each other as shown in figure4. Contrary to what others might think,
order is maintain in this type of network by using algorithm like the spokesman election
algorithm (SEA) which elect a device as master and the others as slave.
On the other hand is the Infrastructure network which uses fixed network access
points with which mobile nodes can communicate as shown in figure5. To widen the
wireless LAN the access points are sometimes connected from one node to the other
one by connecting them to landlines.
Figure 4 (Ad-Hoc network)
Figure 5 (Infrastructure network)
Physical layer
The physical layer handles the transmission of data between nodes and can use
either direct sequence spread spectrum, frequency-hopping spread spectrum which can
operate in the 2.4 - 2.4835 GHz, or infrared (IR) pulse position modulation which uses
300 - 428,000 GHz for IR transmission. It can operate at the data rate of 1Mbps or
2Mbps. One of the most important function of the physical layer is to maintain order in
the network in the use of shared medium. It does so by using the Medium Access
Carrier protocol or MAC layer.
The 802.11 standard specifies a carrier sense multiple access with collision
avoidance (CSMA/CA) protocol. This mean when a node receives a packet before
transmitting it the node assure that there is no traffic. If the channel is busy it chooses a
random "backoff factor" which determines the amount of time the node must wait until it
is allowed to transmit its packet. However this method has a great probability of leading
two channels to collide if they have the same amount of waiting time. The other method
use is the Virtual Carrier Sense Mechanism (VCSM).
In this method a short ready-to-send (RTS) packet containing information on the
length of the packet is sent to the other node. Once the receiving node responds with a
short clear-to-send (CTS) packet the node could then be safely transmitted. When the
packet is received successfully, as determined by a cyclic redundancy check (CRC), the
receiving node transmits an acknowledgment (ACK) packet. This method is more
efficient and avoids hidden node and collisions between nodes by used of the 4 way
hand shake as shown in figure6.
Figure 6 (Virtual Carrier Sense’s Mechanism)
Network Layer
The network layer handles the security of the wireless networking. A suggested
protocol is Mobile IP which unfortunately only use version 4 of the IP protocol. It is work
as followed:
Before moving to a foreign network the mobile agents informs a home agent to
which foreign agent their packets should be forwarded to. Then the mobile agent
registers itself with that foreign agent on the foreign network. Therefore all packets
intended for the mobile agent are forwarded by the home agent to the foreign agent who
sends them to the mobile agent on the foreign network. When the mobile agent returns
to its original network, it informs both agents (home and foreign) that the original
configuration has been restored. No one on the outside networks need to know that the
mobile agent moved. However this configuration is not efficient. Depending on the
distance the mobile agent travel through there may need to be some store and
forwarding of packets while the mobile agent is on neither the home nor the foreign
network. Research is being conducting now from the improvement of this feature.
3 . BLUETOOTH Origin:
The name “Bluetooth” came from a Viking whose name was King-Harald Blatand
(“Bluetooth”). It was claimed that the king (Blatand) had reportedly united Denmark and
Norway a long time ago and hence so as wireless technology is uniting people today.
It was founded in 1994 by a group of companies called the Bluetooth Special Interest
Group(SIG) and comprised of Ericcsson, Intel, Nokia, IBM, and Toshiba who companies
wanted to set up a technology for short range radio frequency wireless technology.
Description:
Bluetooth is a standard developed for short range wireless transfer of data
between Personal Area Networks using low power radio as shown in figure7 below. The
major principal is to insert chipset into each device so that they could easily
communicate with each other. In this technology data transfer occurs at the frequency
of 2.4 GHz which is compatible to the unlicensed ISM (Industrial, Scientific, and
Medical) band. The devices are connected to each other forming a scatternet which
provides a transfer range up to 10 meters. Since there is no central transmitter station,
the devices communicate with each other in an Ad-Hoc fashion. Bluetooth also
transmits on the basis of Frequency Hopping-Code Division Multiple Access/Time
division Duplexing which makes it immune to interruption by electromagnetic waves.
Similarly to IEEE802.11 it has a transfer bit rate of 1Mbs.
Figure 7: Use of Bluetooth in a personal area network.
Data Layer:
Bluetooth devices form overlapping networks called piconets. Each piconet can
carry a maximum of eight devices as shown in Figure8 below and can also overlap to
form a scatternet. In this setting one device is called the master in the remaining seven
are called slaves. These piconets are constantly being formed and reformed as the
different devices move around the network area in the same fashion as people walk
around a room and communicate with each other.
Bluetooth transmit data into packets at a gross rate of 1 Mbps. The packets are
each divided in three parts. This included the Access Code, the Header and the
payload. The Access Code is a means of identifying the devices on a piconet. All
packets sent to a particular piconet would have the same access code. The Header is
broken into six fields, but the two main fields are AM_ADDR which is used to identify the
different devices in a piconet by the master and ARQN which is used to acknowledge a
successful transmission. There are also two types of packet transfer, Asynchronous
Connectionless(ACL) links for data transmission and Synchronous Connection oriented
(SCO) for audio/ voice transmission.
Figure 8
Physical Layer:
Bluetooth utilizes Gaussian Frequency Shift Keying (GFSK) for the modulation of
data stream. This modulation involves the representation of a positive frequency shift by
a “1” and a negative frequency shift by a “0”. Another characteristic element of the
modulation scheme is the normalized filter bandwidth (BT). It is the bandwidth of the low
pass filter that filters out higher frequency components which causes a compression in
the frequency domain and an expansion in the time domain that raises the intersymbol
interference (ISI). However, the BT cannot be too small because the ISI would
overpower the signal and cause the bit error rate to rise inconsiderably.
Bluetooth also transmits data among devices at 1mW using Frequency Hopped
Spread Spectrum (FHSS) and low power Radio Frequency (RF) waves. This has an
advantage over the Infra-red radiation use by 802.11 which require line of sight
connections because the rays travel in a straight line.
Network Layer
As for 802.11 the network layer is used for security purposes. However
Bluetooth developed specific routines to enable secure connections among each other.
One of the routine is the E1 algorithm which is based on a challenge/ response system
and is performed in the BD_ADDR(Bluetooth device address) bits of the Header
together with these following three procedures:128 bit authentication bits, 8-128 bits of
encryption algorithm and Random key generator of128 bits.
The other routine is called the E0 algorithm which encrypts the data sent to
other devices. The header and the access code are not encrypted so devices are able
to communicate with each other but nothing is known about the data in each packet.
Authentication bits are created at the “setup” of the two devices, and only
changes when the device gives up its AM_ADDR. The encryption bits are regenerated
whenever the encryption changes. This means that the lifetime of a particular set of
encryption bits is less than that of the authentication bits. The combination of these
routines is used to determine if a device is authentic and if information about the piconet
should be sent to it.
4. DIFFERENCES AND SIMILARITIES: The major similarities of Bluetooth and IEEE802.11 is that they are both wireless
‘network’ technologies and they operates in the same 2.4 GHz unlicensed ISM band.
Also they provide flexibility for user, inexpensive and are both connected electronic
devices without any wires.
Nonetheless, they are mainly different. The major difference is the data rates of
the two technologies. Bluetooth uses GFSK (Gaussian frequency Shift Keying) as
opposed to the CCK (Complementary Code Keying) used by 802.11. Also Bluetooth
uses Frequency Hopping which creates delay in the transmission of data and 802.11b
uses DSSS (Direct Sequence Spread Spectrum) which by the use of CDMA allows the
signal to be spread out over a large frequency range and make all other users look like
noise to the destination. This allows for higher data rates and more users with no limit
on the number of user in the system. More over IEEE 802.11 has a much large outdoor
range of 300m compare to the 10 meters used by Bluetooth. All the addressing in
Bluetooth is handled by the master of the piconets. IEEE802.11 address and access on
the other hand is taken from the Ethernet standard. And finally Bluetooth is a low power
device which is used for device to device data transfer whereas IEEE802.11 uses
different access points which sends the data to the other computers on the network.
5. Discussion and Conclusion The objective of this project was to compare two wireless LAN technologies
namely IEEE802.11 and Bluetooth. From our research we can conclude that these two
technologies are more different than similar. It is true that they are both wireless LAN
technologies, they provide flexibility for users and share the same 2.4GHz ISM.
However they are both oriented in different direction mainly due to there different data
rate which are affected by the different entities which we elaborates in part 4 (Difference
and Similarities above).
Nonetheless, there is an attempt today to reunite these technologies on the same
network. The idea is tempting but there are problems. Due to the fact that Bluetooth is
using FHSS from transmission of data and that IEEE802.11 is using DSSS form
transmission of data that will create interference of the signal and the data of
IEEE802.11 will be jammed. The alternative will be to make 802.11 use FHSS for
transmission of data. However this is still an area of study and noting is yet to be
decided.
Note that this project is base on current information from both Bluetooth and
IEEE802.11 they can be different in the near future since wireless in a new area of
study.
References
Standards and protocol - IEEE802.11b - by Al petrick [Online]. Available:
http://www.csdmag.com/main/2000/06/0006stand.htm
Bluetooth and IEEE802.11 - by Brent Miller ( October 2001)- [Online]. Available :
http://www-106.ibm.com/developerworks/wireless/library/wi-phone/?
t=gr,p=WirelessBuds
10meters.com (2000-2001) Bluetooth and 802.11: A
Tale of Two Technologies. 10Meters.com, San Francisco, CA.
[Online]. Available:
http://www.10meters.com/blue_802.htmlhttp://www.amigocom.com/News/news1-
2-03.pdf
http://www.amigocom.com/News/news1-2-03.pdf
http://www.dcs.napier.ac.uk/~bill/cisco_presentation/osi31.pdf
http://www.sss-mag.com/ss.html
http://www.intersil.com/data/wp/WP0548.pdf
http://www.kmj.com/proxim/pxhist.html
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