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