Wireless Local Area Network, 1



Wireless Advantages versus Disadvantages





Wireless Local Area Network (WLAN)

Advantages vs. Disadvantages





Mike M. Khayat









INNS 690, Professional Seminar

Mr. John Meinke

March 12, 2002












Wireless Local Area Network. 2







Table of Contents



Abstract ……………………………………………………….
Page 3
Research statement …………………………………………..
Page 4
Introduction ………………….…………………………….. ..
Page 4
Figure 1 WLAN topology
……………………………….
Page 4
Mobility ………………………………………………………
Page 5
Figure 2 handling off the WLAN connection between AP…..
Page 5
Range ………………………………………………………..
Page 6
Figure 3 WLAN range………………………………………..
Page 6
Frequency …………………………………………………….
Page 8
Figure 4 WLAN frequency …………………………………..
Page 8
Figure 5 WLAN frequency and range ……………………….
Page 9
Equipment cost ……………………………………………….
Page 9
Table 1 Equipment cost, range and performance…………….
Page 10
Table 2 leased line rates ……………………………………..
Page 10
Table 3 switched line rates ………………………………… .
Page 10
Table 4 leased line rates in GE………………………………
Page 10
Table 5 types of LANs comparison ………………………….
Page 11
Equipment bandwidth and performance …………………….
Page 11
Table 6 types of media ……………………………………. .
Page 12
Figure 6 WLAN performance ….……………………………
Page 12
Table 7 LANs comparison …………………………………..
Page 12
Table 8 IEEE series comparison …………………………….
Page 12
Equipment procurement and configuration………………..
Page 13
Figure 7 WLAN vendors …………………………………….
Page 13
Figure 8 WLAN configuration ………………………………
Page 14
Table 9 criteria selection ……………………………………
Page 14
Security ……………………………………………………….
Page 15
Figure 9 MAC layer …..………………………………………
Page 15
Analysis – Advantages ……………….…………….……….
Page 17
Disadvantages ………………………………………………
Page 17
Conclusion ……………………………………………………
Page 18
Figure 10 WLAN architecture………. ……………………….
Page 19

Bibliography …………………………………………………..
Page 21
Glossary ………………………………………………………
Page 23

Wireless Local Area Network. 3



Abstract

This paper addresses the Wireless Local Area Network (WLAN) for companies in European
countries. The wireless system for Local Area Network (LAN) is an important landmark in the
history of the Internet and electronic applications. It opens up existing systems, databases and
intranets to mobile equipment such as telephones and hand-held terminals through a graphical
customer interface. The most important benefit of WLAN is that it is independent of different
mobile technologies that are used in different parts of the world.

The recent increase in mobile computing technologies and projects in the enterprise
environment has resulted in extensive use of numerous point-to-point products that cover only a
small part of the total mobile and wireless infrastructure that is required.

This paper is intended to be used as a recommendation for any company involved in building
more effective use of commercial WLAN in European countries. Much of what is required to
build an enterprise WLAN standard has been already defined years ago. It is critical that this be
synthesized and summarized so that network managers and managements can have a better
understanding of how to manage this great WLAN technology in the commercial environment.
This paper attempts to fill in that space and concludes with an opinion of the WLAN technology
based on the research.










Wireless Local Area Network. 4


Research statement

Challenges exit which will prevent wireless networking from becoming feasible in Europe in
the short-term.

Introduction

Wireless LAN is a networking technology that allows the connection of computers without
any wires and cables, mostly using radio and infrared frequency (RF) technology. It's called
LAN because the range targets within an office, a building, a store, a small campus, or just a
house.

The description of a WLAN is a mobile data communication connectivity system installed
and configured as an alternative in some cases for traditional LAN. The WLAN equipment is
capable of receiving and sending data over an adequate range. In the United States, the WLAN
business is increasing in areas like the airports, health-care, warehousing and manufactures.
Several research companies are predicting a healthy increase in WLAN business market in the
coming years. The WLAN provides advantages over traditional LAN technology such as buried
cables in the ground, hidden cables behind walls, and long cable runs measured in feet or miles.
Without restrictions, the new technology infrastructure can easily be installed and ready to be
used.

Current growth concerning network communication technology in the enterprise
communication environment has resulted in widespread deployment of numerous products that
cover only a small part of the total mobile and WLAN infrastructure required. The WLAN
industry has experienced phenomenal increase over the past ten years. The U.S. wireless
industry posted revenue of $40 billion in 1999, according to the Cellular Telecommunications
Industry Association, and employed 156,000 workers (Palazzo, 2002). Most manufacturer
companies offer WLAN equipment to improve field productivity, increase customer approval
and reduce operational costs by shifting the way field workers and dispatchers perform their
jobs.
S e r v e r
U s e r s
U s e r s

Figure 1. WLAN Topology, source WLANA, 2000

Using the WLAN technology has already increased the speed from 1 to 11 Mbps with the
introduction of the IEEE 802.11b (Frank, 2002). Office and field workers can now send and
receive data wirelessly over the intranet, using state-of-art leading edge equipment. With the
latest product and service, there is no need to invest in costly computer services and products or
Wireless Local Area Network. 5



suffer through a lengthy installation and implementation project. The objective is to rapidly
provide customers with data network solutions and mobile equipment for enhanced connectivity,
mobility, and flexibility, while at same time, maintain acceptable security. Customer influence
was measured with WLAN systems that can be provided at anytime, anywhere and cost less, see
figure 1 for WLAN topology.

Mobility

The most important benefits of WLAN are flexibility, mobility and portability, but no
industry standard currently addresses the tracking or management of mobile equipment in its
Management Information Base (MIB). This omission would reject customers from roaming
between WLAN APs that cover a common work area, such as a complete floor of a building.
The manufacture has engineered this problem, offering its own solutions of flexibility algorithms
that facilitate roaming within an IP domain such as a floor with an eye towards optimizing
roaming across IP domains.

The WLAN equipment can provide customers with connectivity to real-time information
anywhere in their work areas. This flexibility supports productivity and service opportunities not
possible with traditional wired networks. Installation of WLAN equipment can be fast, easy and
can eliminate the need to pull cable through walls and ceilings.



Figure 2. Handing off the WLAN Connection Between APs. (Source WLANA, 2000)

This new equipment enables technology, through a gateway infrastructure deployed in mobile
operator's network, this will bridge the gap between the mobile world and the intranet, bringing
sophisticated solutions to WLAN customers, independent of the bearer and network. When a
customer sends data using WLAN equipment, it sends low energy radio waves to a local antenna
site, which connects the customer with the landline or wireless location from where the customer
is dialing. That same antenna also sends signals back to the customer wireless equipment. The
WLAN equipment has the ability to move from one area to another within an adequate range.
This technology allows services to derive the function and added value of the WLAN network.
There is a key set of general functions and basis services that must be supported to have a viable
service offering. This key set of functions and services includes the ability for the customer’s
Wireless Local Area Network. 6



computer to register, transmit which is to send, receive, and maintain data via one or more
different media types. These features can be provided to the customer within a reasonable time
if a tactical mission is on the horizon. The RF result is low power, and works with an AP that
sends the radio waves to several customers. High expand antennas and multiple APs are
required to send the signals over thousands of feet, see figure 2. Handing off the WLAN
Connection Between APs.

Range

In the analysis of WLAN range, there is marginal theoretical difference in the range
capabilities of Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread
Spectrum (DSSS) systems. The largest range difference will be caused by two sources; the type
and location of the antenna system not the spread spectrum modulation used and the environment
that the equipment is operating in. The antenna diversity is one of the most important influences
on the range and performance of equipment, particularly near the edge of the range profile, the
marginal area. The antenna diversity is the use of multiple antennas that are physically
separated. This is done because the radio waves will reflect off all objects, walls, buildings,
bridges, cars, hills, trees, etc and cause nulls and peaks arbitrarily distributed in the air (OCBN,
2001).

It is significant for a good path to have a high height for the antenna. Basically, a better
antenna elevation means better connectivity range, with all other things being equal. An
appropriate antenna height would be required to “shoot over” path obstructions like hills or trees
and also to reach suitable “Fresnel” zone permission, see figure 5 on WLAN frequency & range.
This is much the same as the peaks and troughs that are seen on the surface of water when
separate waves encounter each other and are called "Multipath" in the radio environment. With
two antennas separated by a quarter of a wavelength, a few inches for 2.4 GHz band, it is
statistically very unlikely that both antennas will be in a null or wave trough at the same time,
whereas a single antenna will be realistically possible to be in a null in a highly reflective
environment, such as an office building (Proxim,1998).

Figure 3, WLAN range between client and AP. (Source Proxim, 2000).

For a better performance, large antennas placed high above the ground will always provide
better range than small antennas that extend marginally from a Personal Computer (PC) card and
are low down on the side of a notebook computer. The range of the different equipment
Wireless Local Area Network. 7



components is therefore different. Single PC cards have the shortest range, 100-500 feet
depending on the environment, see figure 3. An AP with elevated, efficient antennas will
achieve up to 3000 feet. Fortunately in most communication equipment the client card will
communicate with an AP and the overall link will benefit from the better antenna on the AP,
though it will still have a shorter range than two APs communicating with each other.

The environment that the equipment is used in has a very significant influence on the range
and performance. This should be of a little surprise to everyone that has used a cordless phone,
as they suffer from similar range and performance problems as WLAN. When the environment
is outside, in line of sight (LOS), with little to reflect off and cause multi-path, the range is at its
best. When the environment is in a solid walled building, such as an old stone house or in the
building basement, the range is greatly reduced. This is the same for WLAN, however the multi-
path problem can significantly degrade megabit communications where it will not significantly
affect connectivity quality.

Every WLAN configuration is different, when engineering an in-building solution, varying
facility sizes, construction materials, and interior divisions raise a host of transmission and multi-
path considerations. When implementing a building-to-building solution, range, physical
obstructions between facilities, and number of transmission points involved must be accounted
for. Several factors come into evaluation when measuring radio transmission range like,
transmitter power, receiver sensitivity, antenna gain, antenna height, RF cable attenuation (RF
connection from transmitter to antenna), and terrain. Since WLAN equipment operates in the 2.4
GHz band they need a LOS transmission path. The link range will be severely degraded if trees,
hills, walls, heavy fog, or other obstructions are in the radio transmission path. It is very difficult
to predict link range achievement for non-LOS paths.

Most office environments are constructed of materials that are relatively "translucent" to radio
waves at 2.4 GHz so the range will not be greatly limited, however they do tend to present very
reflective and refractive environments and the ultimate limitation will probably be caused by
severe multi-path problems. Range up to 80 meters was achieved in point to multipoint tent
configurations. Indoor range is considerably less and depends on the physical layout. Equipment
based on the “Bluetooth” WLAN technology interferes with IEEE 802.11b WLAN. For most
cases, Germany and European cities in general, support 2.4 Gbps transmissions to 100 mw:

100mw = 1mw transmitter * 20 dbi Dish Antenna
100mw = 5mw transmitter * 14 or 15dbi Yagi Antenna
100mw = 50mw transmitter * 2dbi monopole antenna

The standard IEEE 802.11b data is encoded using DSSS technology. The DSSS works by
taking a data stream of zeros and ones and modulating it with a second pattern, the chipping
sequence. The standard IEEE 802.11, that sequence is known as the Barker code, which is an
11-bit sequence (10110111000) that has certain mathematical properties making it ideal for
modulating radio waves. The basic data stream is exclusive OR'd with the Barker code to
generate a series of data objects called chips. Each bit is "encoded" by the 11-bit Barker code,
and each group of 11 chips encodes one bit of data (Conover, 2000).

Communication network managers often find that WLAN fall short of expected range. Even
though a vendor's specifications may say that the equipment has a range of 300 feet, obstacles
such as walls, desks and filing cabinets can significantly reduce the range in some directions.
Wireless Local Area Network. 8



This results in an irregular propagation pattern of the radio signal. To provide adequate radio
coverage throughout work areas, communication network manager needs to perform a RF site
survey that determines the number and location of APs, as well as uncover potential RF
interference (Geier, 2001).

Frequency

The FHSS uses a slim band carrier that changes frequency in a pattern known to both
transmitter and receiver. Properly synchronized, the net effect is to maintain a single logical
channel. To an unintended receiver, FHSS appears to be short duration impulse noise (NDC
Communications, 1999).
Radio Frequency
Waves
RF Signal
Paths
Transmitting
Antenna
Receiving
Antenna
Hard, Flat Surface
(Reflects RF W aves)



Figure 4, WLAN RF, source (Burd, 998)

There are two main technologies that are used for WLAN communications today, RF and
infra red (IR). In general they are good for different applications and have been designed into
products that optimize the particular features of advantage. The RF is very capable of being used
for applications where communications are not LOS and over longer range. The RF signals will
travel through walls and communicate where there is no direct path between the equipment. In
order to operate in the license free portion of the spectrum called the industrial, Scientific and
Medical (ISM) band, the radio system must use a modulation technique called Spread Spectrum
(SS). In this mode a radio is required to distribute the signal across the entire spectrum and
cannot remain stable on a single frequency. This is done so that no single customer can dominate
the band and collectively all users look like noise (NDC Comm.,1999).

The SS communications were developed during World War II by the military for secure
communications links. The fact that such signals appear to be noise in the band means that they
are difficult to find and to jam. This technique lends itself well to the expected conditions of
operation of a real WLAN application in this band and is by its very nature difficult to intercept,
thus increasing security against unauthorized listeners, see figure 5 for WLAN frequency and
range.

Wireless Local Area Network. 9



The WLAN uses RF or IR instead of copper or fiber optic cable to connect customers
together into a LAN. The WLAN is appealing because it allows customer mobility, flexibility
can easily be reconfigured, and requires no cable infrastructure. The WLAN is particularly
useful when mobile access to data is necessary, such as in health care environments and
warehouses. It is also appropriate in situations where a temporary LAN is needed but no
communication infrastructure is available, such as when hosting conferences at hotels or
community clubs, or when providing computer based training in ad-hoc classrooms, exercises,
and emergency missions. Frequency hopping addresses a significant problem with RF
“transmission-Multipath” distortion, which occurs when an RF signal bounces off the stationary
objects.
11 MBS up to 5KM
Router or Hub
Router or Hub
RF Receiver
RF Receiver
2.4 – 2.48 Ghz
Radio Frequency
At less than 100 Mw
Output power
NES REDSIDE
Connection
CASIS INSERTION
POINT


Figure 5. WLAN frequency and range

A receiving antenna can receive multiple copies of the same signal at slightly different
times, figure 4, WLAN RF, which blurs or smears the signal content causing bit detection errors.
The problem is especially severe in-door where there are numerous hard, flat surfaces to
“bounce” RF signals (Burd,1998).

Equipment Cost

An analysis reveals savings can be measured in terms of equipment cost for WLAN compared
to what customarily is in used for wired LAN connection. In order for two customers to
communicate over the wired network, the following are required for installation, network cable
installation with, data drop ($500), PC LAN card ($50), a hub ($100), small router ($2,500), a
network T1 modem ($1,300), and cable conduit between customer buildings, bringing the total to
$9,000. For the WLAN, connecting two customers to a LAN, the total cost is not more than
$7,000 that to include the bridge 100Mw output ($1,400), ceiling antenna ($82.00), 11Mbps
DSSS AP ($990) and cable ($120). The big savings is that there is no need to open a trench to
bury network cable
Wireless Local Area Network. 10



beneath the ground, quick installation, and can easily to be removed, see table 1 on equipment
cost, range and performance for three types of WLAN equipment. The relatively high cost of
transmission equipment and licenses makes short wave radio a rare method for a signal user or
company; instead, companies are formed to purchase and maintain the required licenses and
infrastructure (Burd,1998).


Feature

Type 1

Type 2


Type 3
distance (feet):
500


1000



1000
(meters):
150


300



300
speed/protocol:
full duplex 10
from 4/16 Mbps

from 45Mpbe
T3 to 100 Mbps
Token Ring to full



Ethernet


FDDI & Fast
Ethernet to 155



Duplex 10 Mbps
Mbps ATM



Ethernet
Remote management: no


yes



yes
List price ($US):
$6,995

$8,995


$16,995



Table 1, Equipment cost, range and performance

For usual wired LAN connectivity, the immediate cost is high, the installation site requires
extra money compared to the WLAN connectivity, this is not to include the wired cable is a lease
line, and switched line rates, the actual rates for dedicated leased lines may vary from one
country to another. In the U.S. the rates are based on range, see table 2 for leased line rates and
table 3 for switched line rates in the U.S (Stamper,1999).

Range




Rate
First 100 miles



$2.52 per mile
Next 900 mike (101-1000)


$0.94 per mile
Each mile over 1000


$0.58 per mile



Table 2 leased line rates in U.S. Source (O’Brien,1999)

Type of charge



Rate
Fist minute of connect time


$0.60
Each additional minute


$0.40


Table 3 switched line rates

Line type




Rate (year)

One time cost
E1 Speed




$87,732

$5,000
T1 Speed




$84,264

$5,000
Fiber 2 strands distance 40KM

$252,000



Table 4 leased line rates in Germany

Wireless Local Area Network. 11



Factor in the price of a mobile device plus application software, wireless service,
maintenance and support, each users’ tally can reach $3000 annually (Bednarz, 2001). Table 5
shows the immediate and recurring requirements comparison for two LANs, the traditional wired
LAN and WLAN. The difference between these two LANs is small.

Immediate Requirements



Wired LAN


WLAN
equipment upgrades:



X



X

documentation:




X



X
site preparation (AC, raised floor, etc..):

X



---
hardware installation:



X



X
installation applications:



X



X

testing:





X



X
training (users, operators, administrators):

X



X

installation of cabling:



X



---
equipment software installation:


X



X
creating user environments:



X



X
space required for new equipment:


X



---
supplies and spares:




X



X
backup:





X



X


Recurring Requirements:
LAN management, personnel costs:

X



X
consumable supplies:



X



X
hardware and software maintenance:

X



X
training (new users, administrators):

X



X




Table 5, two types of LANs comparison

A WLAN implementation includes both infrastructure costs for the Wireless APs and user
costs for the wireless LAN adapters. Infrastructure costs depend mainly on the number of APs
deployed, APs range in price from $800.00 to $2,000.00. The number of APs typically depends
on the required coverage region and/or the number and types of customers to be supported. The
supported area is proportional to the square of the product range (WLANA, 2000).

Equipment bandwidth and performance

The WLAN protocol is engineered to reduce the demanded bandwidth and maximize the
number of wireless network types that can deliver. Multiple WLAN networks within an area can
be achieved, with the additional aim of multiple networks. In other words, an IP-networked
world will enable the multimedia evolution to optimize the bandwidth required to support the
multimedia applications demanded by the marketplace. This will reduce the cost to own or lease
a dedicated LAN circuit. The WLAN equipment can go point-to-point (PPP), speed up to
100MB at range of a 3000 meters. The WLAN equipment speed is adequate among customers
to send and receive e-mail messages, upload and download documents (PowerPoint briefing
slides, spreadsheet, etc.) and small data files, see table 1 equipment cost, range and
performance for WLAN performance.

Wireless Local Area Network. 12



The ISM spread spectrum bands do not offer a great deal of bandwidth, keeping data rates
lower than desired for some applications. The IEEE 802.11 working group, however, dealt with
methods to compress transmission data, making the best use of available bandwidth. Efforts are
also underway to increase the data rate of 802.11 to accommodate the growing need for
exchanging larger and larger bandwidths (Geier, 1999).

Type of Media



Maximum BPS (kilobits per sec)
Twisted pair – unshielded/shielded

2M-100M (million)
Coaxial cable – baseband/broadband
264M-550M (million)
Satellite/terrestrial microwave

100M (million)
Wireless LAN



3.3M (million)
Infrared LAN



4M (million)
Fiber optic cable



40G (Billion)

Table 6, types of media. Source (O’Brien,1999)

5
0
10
15
20
25
30
35
Normal
Turbo Mode
Read
Writes
Megabits per secondWLAN gains
eWEEK Lab’s performance tests
show that 802.11a-based devices are
five times faster than 802.11b-based
gear, whose through averages about
5M bps.
Fig 6 WLAN performance, source (Taschek, 2002)

The standard for WLAN networks is IEEE 802.11b. The 802.11b standard specifies the use of
DSSS in the 2.4 GHz band. Most European countries have a maximum of 100mw power output.
The data communications rate for this standard is at 1 and 2 Mbps. The 802.11b high-rate (HR)
Wi-Fi version of the standard increases the throughput to 11 Mbps but the same power maximum
applies in Europe. The WLAN equipment can theoretically support up to 200 customers. Table
7 compares the conventional wired LAN and WLAN. The evaluation performance rates criteria
on a scale of 1 to 5, with 1 being Best.


Criteria




Wired LAN
WLAN
Number of workstations:



1

4
initial cost:





4

2
personnel costs:




5

1
operations/maintenance costs:


5

2
Wireless Local Area Network. 13



expandability:




1

4
microcomputer workstation support:

4

3
user transparency:




3

1
accommodation for multiple users:


1

1
ease of use:





3

1
ease of management:



3

1
interface to other networks:



1

5




Table 7, LANs comparison

The “Multipath” Fading problem is caused by a signal bouncing off the walls and other
surfaces, as the signal arrives at the receiver, a reflection of the signal will arrive shortly
afterwards. This causes interference as old signals arrive at the same time as the new data.
Frequency hopping equipment is protected from this problem since a reflected signal arrives
after the receiver has hopped to a new frequency and any signal on the old frequency is ignored.
Direct sequence systems do not have this advantage, however a technique identified as antenna
diversity allows them to show some improvement. Antenna diversity involves having two
antennas built into the hardware. Two antennas allow the equipment to determine which signal
is stronger (Canterbury Campus, 2001). Table 8 displays the IEEE series topologies and
protocols:

Criteria

IEEE 802.3


IEEE802.5


IEEE 802.11
Speed:

10, 100, 1000Mpbs

4, 16, 100 Mpbs

vary
Medium:

twisted-pair wires

twisted-pair wires

wireless



Coaxial cable, fiber optic

Range:

500 m for thick table
366 m for the main ring





up to 1000 m



185 m for thin-net cable
750 w/repeaters



up to 2500 m

400o m fiber optic



w/repeaters

number

802.3-100 per thick

260



200
of stations:



cost for

$30 per thin-net
NIC and

$50 per station

$225 per station

N/A
connectors
only:




Table 8, IEEE series comparison

Equipment procurement and installation

In view of wireless technology, cost reductions of network components will be possible
compared to alternative technologies like traditional wired LAN. Cards that plug into PC or
laptop are promptly available, and operate either Peer-to-Peer or Peer-to-AP Mode. The WLAN
equipment can be configured in a matter of hours while customarily used equipment (hard wire)
can take a week to a month if cable between customers is not available. For scalability, WLAN
can be installed and configured in a variety of topologies to meet the needs of specific
Wireless Local Area Network. 14



applications and installations, see figure 7 on vendor equipment.
A iro n et
P C 35 00
F H
U p to 2
M b ps
10 0 m W
15 0 m
6 00 m
PC M C IA
Typ e II
U
-
IEEE
80 2.1 1
75 m (2
M b p s)
30 0 m (2
M b p s)
U
10 0 m (1
M b p s)
50 0 m (1
M b p s)
Lu cent
W aveL A N
PC -A T
W ire less
Ad ap te r
D S
2 M bps
8 8 m W
2 4 0 m
-
IS A ca rd
U
54 5 -
Lu cent
W aveL A N
PC M C IA
W ire less
Ad ap te r
D S
2 M b p s
88 m W
24 0 m
-
PCM C IA
Typ e II
U
4 9 5 -
Pro x im R angeL A N 2
71 00 IS A
FH
1 .6 M b p s
10 0 m W
15 0 m
3 00 m
IS A ca rd
U
5 9 5
1 5 channels.
O E M
versio n
availab le.
IEEE
80 2.1 1
co m p lian t
P rice ($ U S )
A iro n et
P C 45 00
D S
1 o r 2 M b p s 5 0 /1 00 m W
PC M C IA
Typ e II
-
M iscella n eo
us
V end or
P rod u ct
T yp e
D ata R a te
H o st
N a tio n ?
10 0 m W
15 0 m
3 00 m
Po w er
M a xim u m R a n g e
In d o o r /O utdo or
C o n fig u ra t
io n
Pro x im
R angeL A N 2
74 01 /0 2 P C
Card
F H
1.6 M b ps
1 5 channels.
Severa l
antennas
PC M C IA
T yp e II
69 5
U

Figure 7, WLAN vendors

The WLAN configurations are easily changed and range from peer-to-peer networks suitable
for a small number of customers to full infrastructure networks of thousands of customers that
enable roaming over a broad area, as used in several U.S airports and hospitals. Micro cells (the
physical areas covered by each of the LAN AP) are established to provide coverage to all
customers, figure 8 shows a notional WLAN configuration.


Router or Hub
LAN Access Point B
LAN Access Point A
users
users
Server
Uplink to
Installation
Network




Figure 8. WLAN Configuration

The range a WLAN can be from a LAN AP depends on many factors including the types and
numbers of obstructions (such as walls, hills, trees, etc.), the data rate, and the equipment used.
Wireless Local Area Network. 15



The LAN AP serves as the LAN hub for the WLAN customers and as connection points into
normal building LANs. Each LAN AP typically supports large number of customers, depending
upon their network use.

A variety of factors must be considered when selecting type equipment for LAN connectivity.
The company should decide whether a wired LAN is required or an alternative like WLAN will
be sufficient. Factors, which must be considered, include cost- effectiveness, hardware,
application software, security, training, etc. The weight associated with each selection criterion
may differ among companies. In making the right selection, company management and IT
analysts need to evaluate the alternatives from the perspective of their companies’ immediate
short-term and long-term communication objectives, see evaluation criteria below.

Criteria





WLAN


others
cost:
number of concurrent users:
medium:
short-term and long term objectives:
expandability:
software and hardware:
vendor support (just-in-time):
number of workstations:
type of use:
mobility and flexibility:
environment
maintenance:
life cycle:
speed:
equipment connectivity:
vendor on site:
manageability:
type of workstations:
number of printers:
applications:
connectivity with other networks:
type of mission, location, country:
adherence to established standards:
security:
host nation approval:
range:
frequency:




Table 9, criteria selection


Security

The WLAN service cannot be perfectly secured, but the wireless industry has made
significant investments to prevent intruders and hackers. The WLAN equipment can support
session layer protocols that establish the connection between applications, enforces rules for
Wireless Local Area Network. 16



carrying on the dialogue, and tries to re-establish the connection if a failure occurs. The WLAN
manufacturing companies claim that the current IEEE 802.11b standard contains an optional 40-
bit encryption algorithm to ensure data sent over the air is scrambled and remains private.

A small research group at the University of California at Berkeley in recent times put out a
statement stating that they found flaws in the IEEE 802.11 standard (and IEEE 802.11b
standard). Their statement says that they were able to intercept transmissions over the wireless
network. These transmissions were encrypted, but the encryption was broken (Dunne, 2001).

Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data-Link Layer
Physical Layer
Logical Link Control (LLC)
Media Access Control (MAC)


Figure 9, MAC layer

A company may implement WLAN for the customer’s specific requirement, however,
WLAN security is the most serious issue that a customer must consider. Most WLAN circuits
enter European controlled areas; non-secure encryption device is a requirement. Throughput is
the next most critical WLAN issue. WLAN should not be used for critical data transfer without
a study on the maximum throughput requirement. The WLAN technology is considered an
emerging technology, and therefore should be approached with caution. The technology is
largely untested for the secure environment, and it introduces a potential for operational data-loss
and yet-unknown security risks.

As with wired networks, the first line of security defense is the customer IDs and passwords
in the operating system of client computers and servers. Additional security varies from one AP
to another.

Many AP manufacturers allow network administrators to limit AP connections by creating a
table of wireless client hardware media access control (MAC) addresses, see figure 9 above on
MAC layer. There is no WLAN solution exists for sensitive data processing. Also, before any
wireless equipment is procured or operated in Europe, the customer must verify that the specific
wireless equipment used has host-nation approval to be used in the country where the LAN is to
be set up. Although WLAN is a part of the Information Systems Architecture (ISA), there are
numerous procedural guidelines processes that must be completed before they can be
implemented, host-nation approval is required for any wireless application. Host-nation vendor
equipment that is used out-of-the-box by anyone must be approved before use for company
applications.

The WLAN is still considered an emerging technology. Several technologies (Fast
Ethernet-Gig E, Cell Telecommunications) are in competition with this new technology and it is
not determined that this technology wins out in any particular situation. It has promise and with
faster data rates and longer reliable operating distance. This new technology may become a more
Wireless Local Area Network. 17



important player as these characteristics improve. All new implementations must meet minimum
current standards of 3DES for security and 100mw at 2.4 GHz frequency requirements.

The WLAN can’t send or receive signals over much larger areas than that of traditional wired
media such as twisted-pair, coaxial cable, and optical fiber optic (FO). In terms of privacy,
therefore, the WLAN have a much larger area to protect. To utilize security, the IEEE
802.11group have to organize their work with the IEEE 802.10 standards committee accountable
for developing security mechanisms for all IEEE 802 LAN series (Geier, 1999).

Security mechanisms in IEEE 802.11b networks should be equivalent to existing mechanisms
in wire-based networks. Traditional wired network jacks are located in buildings already
protected from unauthorized access through the use of keys, badge access, facial recognition,
finger printing and so forth. A customer must gain physical access to the network building in
order to plug a client computer into a network jack. In contrast, a WLAN AP that is configured
incorrectly may be accessed from off the grounds (for instance, from a parking lot next to the
building). Properly designed WLAN secure access to the APs and isolate the APs from the
internal private network prior to user authentication into the company network domain (Vector,
2000).

Empowering the customer with the ability to access a large quantity of information and
services from WLAN equipment will create a new battleground. The WLAN industry will fight
to provide their customers with sophisticated and value added services. As WLAN technology
becomes a more secure and trusted channel by which customers may conduct their financial
affairs, the market for WLAN will become even more lucrative.










Analysis

Advantages

• The WLAN Internet connectivity is great for any company whose site is not conducive to
LAN wiring because of building or budget limitations, such as older buildings, leased space,
or temporary sites.
• While the initial investment required for WLAN hardware can be higher than the cost of
traditional wired LAN hardware, overall installation expenses and life-cycle costs can be
significantly lower. Long-term cost benefits are greatest in dynamic environments requiring
frequent moves and changes.
• The WLAN concept ensures the Internet customer, web-served mobile communication
and field service productivity, the benefits of wireless communications sooner, and hard-
dollar savings quicker than from any other commercial equipment available today. WLAN
can provide network hardware for in-building and building-to-building data networks, as well
as mobile communication equipment for information capture and display.
• WLAN mobility, i.e., a student attending class on a campus accesses the Internet,
accesses information, information exchanges, and learning.
• Senior executive officers, managers can present their briefings using WLAN without
carrying the data files, charts, and any storage equipment.
• Trade show and branch office workers minimize setup requirements with central
database thereby increasing productivity.
Wireless Local Area Network. 18



• Most WLAN equipment is plug-and-play. This will help to reduce the total cost to
include vendor technical installation, equipment maintenance and to eliminate equipment
redundancy in case of system crash.
• WLAN technology allows the network to go where regular wire cannot go.
• The WLAN was clearly better then wired in setup/teardown time and effort.





Disadvantages

• Due to the limited bandwidth, the WLAN technology cannot support Video
Teleconference (VTC). However, experts believe that WLAN will support VTC
within the next five years.
• Due to the security reason, using the WLAN equipment as a contingency model
is not recommended.
• The WLAN operated within typical wired LAN parameters provides less downtime and
an increased invisibility to the customer.
• The WLAN technology also have obvious potentials in customer mobility and
configuration changes significantly worse then wired in the risk of jamming, in the
potential for interference, and in the detection of customer location.
• The WLAN is not capable to download and upload large data files.
• The WLAN is significantly worse then wired in the risk of jamming, potential for
inference, and in the detection of RF signal.
• Products from different WLAN manufacturers are often incompatible with each other.
•
Interference from friendly network will likely effect WLAN operation as the popularity
of this industry increases.
• The WLAN equipment is not capable of sending and receiving data successfully during
field exercises in case of heavy fog or dust storm.
• The WLAN equipment have difficulties at time in sending and receiving data when a
flying object passes over a WLAN field exercise.
•
If too many people or businesses in the same area have WLAN, then the band of air that
they transmit signals on can become overloaded. Problems with signal interference are
already happening and there are no doubts that the airwaves will become overloaded (Dunne,
2001).
• Most office environment and modern homes are constructed of materials that are
relatively “translucent” to radio waves at 2.4 GHz so the range will not be greatly limited,
however they do tend to present very reflective and refractive environments and the ultimate
limitations will probably be caused by severe “multipath” problems.
• The problem has been the lack of interoperability among WLAN products from different
manufacturers. The classic Ethernet 802.11 standard was ignored in developing current
WLAN products (Seymour 2000).
• The WLAN weakness is susceptibility to many forms of external interface and the cost of
transmitting stations. In addition, United States, international authorities and treaties strictly
regulate most of the bands that can support high-speed communication. Use of these bands
requires an expensive license (Burd, 1998).


Conclusion

Wireless Local Area Network. 19



The architecture provides customers with a logical migration path to IP-based networking for
achieving peer-to-peer and non-hierarchical communication while maintaining interpretability
with the existing infrastructure. This architecture permits the partition of customer and the LAN
network, enabling network managers the flexibility for deploying end-customer services and
applications independent of wireless switch manufacturers. The Wireless architecture will
provide the framework for innovative technology enhancements. It’s important to look at the
interoperability between different wireless technologies and the interfaces with one another.

Wireless manufacturers are adopting standards and conflicts could result from the use of
different standards in equipment in the same area. The current use of cell phones is different
from that of a WLAN; phones have higher power and lower bandwidth equipment than a
WLAN. The WLAN has a limited range, but it can be used as an extension of a wired LAN.
Those two can co-exist on the same network. As far as multiple standards go, there is IEEE
802.11a, which specifies 25mb/s at 5ghz and IEEE 802.11b, which specifies 11mb at 2.4ghz, and
Home RF, which is at 1mb/s and could be raised to10mb/s. It is not clear which standard will be
adopted in the WLAN market, but once one is developed, prices will fall as chipmakers develop
specific ICs around the standards, and the FCC may open a spectrum bandwidth and faster
equipment, for WLAN manufactures per cost, see figure 7.

Today, the WLAN has redefined what it means to be connected. It has stretched the limits of
the LAN. It makes an infrastructure as dynamic as it needs to be. It's only just beginning, the
IEEE standard is less than three years old, with the high speed IEEE 802.11b yet to reach its first
birthday. With standard and interoperable WLAN products, LAN can reach scales unimaginable
with a wired infrastructure. They can make high-speed interconnections for a fraction of the cost
of traditional wide area technologies. In a WLAN world, customers should be able to roam not
just within a campus but within a city, while maintaining a high speed link to extranets, intranets,
and the Internet itself. The future of WLAN is imminent (OCBN 2001).


Figure 10, WLAN Architecture, source Smart Home Forum (2001)

Wireless Local Area Network. 20



The WLAN is “plug and play” equipment, open architecture built around a customary
expensive wired LAN to eliminate interoperability problems. The WLAN architecture will serve
as a reference to facilitate the efficient and effective coordination of common business process,
technology, information flow, systems and investments among companies.

A proper WLAN architecture framework provides a structure to develop, maintain and
implement an excellent operation environment and supports implementation of automated
information systems, see figure 10 on WLAN architecture. The Intel personal Internet client
architecture has been designed to keep pace with the arrival of next generation WLAN
equipment and with the notion that hardware and software must be allowed to develop in
parallel. The WLAN architecture will allow applications to be written to re-programmable
microprocessors.

Data-rich applications and Internet content, including streaming audio and video (VTC), put
intense demands on the data processing capabilities of handheld equipment, making re-
programmable microprocessors more appropriate for the job. A preliminary requirement
detailing the architecture has been distributed to key WLAN manufacturing companies, and a
final specification and software developer kit will be accessible to the industry in the very near
future (Johnson, 2000).

Today important emphasis on WLAN end-user satisfaction continues to encourage a
departmental shortsightedness, creating vertical systems with their own proprietary data,
software, and technology components (Cook, 1996).

In my opinion, WLAN technology is offering great opportunities for remote connectivity for
in-door small businesses and for families connecting their PCs at home. However, the WLAN
technology is not ready yet to offer to the big companies building-to-building or out in the field
solutions due to numerous reasons that I stated earlier in my paper, these reasons are; range
limitation, frequency availability, cost effective, bandwidth size, and security access. Once all of
those challenges are resolved and meet the standard, the WLAN business will be ready to operate
for any company size and for any mission anywhere in Europe. Today communication business
requires VTC sessions, as well ability to upload and download large briefing slides and data.
The WLAN technology can’t support the requirements. The WLAN manufacturers need to look
at these features while trying to keep their product cost under control. Also, security is the most
important element in communication networks today, and companies in Europe would not
hesitate to spend the extra money to use the traditional wired LAN if the WLAN technology
can’t support it. True, the traditional wired LAN costs more money to install hard wires inside
the building and to lease a dedicated line from building-to-building. Doing that gives customers
guarantee that their data will not be compromised. I predict that until the WLAN industry must
work harder to get end-user satisfaction by resolving disadvantages, technical issues and the
challenges.





Wireless Local Area Network. 21


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Wireless Local Area Network. 23



Glossary


Access Point : A hardware equipment that transports data between a wireless network and a
wired network

HR: High-rate

IEEE 802.X: A set of specifications for Local Area Networks from The Institute of
Electrical and Electronic Engineers (IEEE). Most wired networks conform to 802.3, the
specification for CSMA/CD based Ethernet networks. The 802.11 committee completed
a standard for 1 and 2 Mbps WLAN in 1997 that has a single MAC layer for the
following physical-layer technologies: Frequency Hopping Spread Spectrum (FHSS),
Direct Sequence Spread Spectrum (DSSS), and Infrared. IEEE 802.11 HR, an 11 Mbps
version of the standard is expected to be completed by the end of 1999.

Independent network: A network that provides (usually temporarily) peer-to-peer
connectivity without relying on a complete network infrastructure.

Infrastructure network: A wireless network centered about an AP. In this environment,
the AP not only provides communication with the wired network but also mediates
wireless network traffic in the immediate neighborhood.

IR: Infra Red

ISA: Information Systems Architecture

IR: infrared radiation

ISM: industrial, scientific and medical

LOS: line-of-sight

MAC: access control

MIB: Management Information Base

Microcell: A bounded physical space in which a number of wireless equipment can
communicate. Because it is possible to have overlapping cells as well as isolated cells,
the boundaries of the cell are established by some rule or convention.

Multipath: The signal variation caused when radio signals take multiple paths from
transmitter to receiver.

PPP: point-to-point

Radio Frequency (RF) Terms: GHz, MHz, Hz: The international unit for measuring
frequency is Hertz (Hz), which is equivalent to the older unit of cycles per second. One
Mega-Hertz (MHz) is one million Hertz. One Giga-Hertz (GHz) is one billion Hertz. For
Wireless Local Area Network. 24



reference: the standard US electrical power frequency is 60 Hz, the AM broadcast radio
frequency band is 0.55 -1.6 MHz, the FM broadcast RF band is 88-108 MHz, and
microwave ovens typically operate at 2.45 GHz.

RF: Radio Frequency

Roaming: Movement of a wireless node between two microcells. Roaming usually
occurs in infrastructure networks built around multiple APs.

SS : Spread Spectrum

VTC: Video Teleconference