WLAN solution is an attractive alternative, especially
in places where it's difficult to install a wired LAN
infrastructure. WLANs provide mobility, are easy and
fast to deploy; secure, reliable, and invisible. A look
at the way WLANs work and how it can benefit you. by
Soutiman Das Gupta
year saw a steady trickle of WLAN solutions into enterprises
in India. Companies across verticals like manufacturing,
software solution providers, and hospitality deployed
WLANs in their organizations and gained substantial
value from it.
Mobility has been the biggest advantage that companies
have derived from the deployments. It's after all, a
great utility to allow a user to carry a portable computer
anywhere within the campus and access the available
applications and databases. The other benefits are less
time to deploy, no hassles of digging the ground to
lay cables, and no getting caught in red tape in order
to get a permit to dig. Moreover, WLANs are standards-based,
reliable, secure, and easy to deploy. All these factors
have spurred worldwide acceptance of the technology.
Although the initial investment for a WLAN solution
can be higher than that for a wired LAN solution, the
overall installation expenses and lifecycle costs can
be significantly lower.
Gartner Dataquest estimates that the market for WLAN
products is likely to expand from USD 1.5 billion in
2001 to almost USD 3.4 billion by 2005. The CAGR will
be 22 percent. Unit shipments of 802.11-based wireless
access points (devices for transmitting and receiving
signals) totaled 1.8 million in 2001 and will rise to
4.5 million units in 2005.
802.11e - This draft specification from IEEE
creates the industry's first true universal
wireless standard. It offers seamless interoperability
between business, home and public environments
like airports and hotels. It adds QoS (Quality
of Service) features and multimedia support
to the existing 802.11b and 802.11a wireless
standards, while maintaining full backward compatibility
with these standards.
802.11i - This specification is currently under
consideration. It features security and mobility
enhancements to the existing standards.
802.11f - This specification is also under consideration.
It involves the IAPP (Inter Access Point Protocol)
In a typical WLAN configuration, a transceiver (device
that can both transmit and receive) connects to the
wired network from a fixed location using standard cabling.
This transceiver is usually called an 'Access Point'.
The access point receives, buffers, and transmits data
between the WLAN and the wired network infrastructure.
A single access point can support a small group of users
and can function within a range of a few hundred feet,
depending on vendor offerings. An antenna attached to
the access point is usually mounted at an elevated place.
However, it may be mounted practically anywhere as long
as the desired radio coverage is obtained.
End users access the LAN through WLAN adapters (wireless
versions of Network Interface Cards) that are installed
as PCMCIA cards in notebook or palmtop computers, and
PCI cards in desktop PCs. It can also be integrated
with handheld computers. WLAN adapters provide an interface
between the client NOS (Network Operating System) and
the airwaves via an antenna. The nature of the wireless
connection is transparent to the NOS.
There were a couple of WLAN standards in the beginning:
802.11b and HiperLAN2. 802.11b emerged as the most preferred
choice of vendors and users due to its flexibility and
features. Within a few months, just as the market warmed
up to the possibilities of WLAN using 802.11b, a new
standard called 802.11a arrived. And now, 802.11g, a
new standard has just been introduced.
802.11b is an IEEE (Institute of Electrical and Electronics
Engineers) standard, which provides a full Ethernet-like
data rate of 11 Mbps. It focuses on the bottom two levels
of the OSI model which are the physical layer and the
data link layer. Any LAN application, NOS, or protocol,
including TCP/IP, will run on 802.11 compliant WLANs
as easily as they run over Ethernet.
Since its release, the 802.11b high-rate standard has
been adopted by almost all of today's wireless vendors.
wireless network adapter card prices dropped an average
of 200 percent in the past 12 months.
The IEEE has also developed 802.11a, which represents
the next generation of enterprise-class WLANs. It provides
greater scalability, better interference immunity, and
higher speed than the current technologies. It also
allows higher bandwidth applications to be run simultaneously
and supports more users.
Devices utilizing 802.11a are required to support speeds
of 6, 12, and 24 Mbps. Optional speeds go up to 54 Mbps,
but will also typically include 48, 36, 18, and 9 Mbps.
In cases of both 802.11b and 802.11a, when the client
device travels farther from its access point, the connection
will remain intact but speed decreases. However, 802.11a
has a significantly higher signaling rate than 802.11b.
802.11g is a unique technology that promises backward
compatibility with 802.11b. It can transmit data via
the 2.4 GHz frequency at 54 Mbps and standardize technologies
among the 2.4 GHz and 5 GHz bands. It supports three
modulation schemes simultaneously. Both new and existing
users can connect to the network from a single access
point at higher speeds.
802.11g can serve as a major upgrade to 802.11b, but
the full 54 Mbps speed cannot be achieved unless 802.11g
NICs are matched with 802.11g access points. It offers
support for only three communication channels making
it unattractive in dense areas.
WLAN transmits data over the air using radio waves
and it can be received by any WLAN client in the
area served by the data transmitter. Since radio
waves travel through ceilings, floors, and walls,
transmitted data may reach unintended recipients
on different floors and even outside the building
of the transmitter. Installing a wireless LAN
may seem like putting Ethernet ports everywhere,
including in your parking lot. Data privacy is
a genuine concern with wireless LANs because there
is no way to direct a wireless LAN transmission
to only one recipient.
The protocols and standards that define security
are quite mature now. They are WEP (Wired Equivalent
Privacy), 802.11x, and wireless VPN. However the
use of a VPN is independent of any native WLAN
WEP is an IEEE standard which uses a symmetric
scheme where the same key and algorithm are used
for both encryption and decryption of data. WEP
can carry out access control and ensure privacy.
It performs access control by preventing unauthorized
users, who lack a correct WEP key, from gaining
access to the network. It ensures privacy because
it protects WLAN data streams by encrypting them
and allowing decryption only by users with the
correct WEP keys.
Support for WEP with 40-bit encryption keys is
a requirement for Wi-Fi (Wireless Fidelity) certification
by WECA (Wireless Ethernet Compatibility Alliance).
Some vendors implement the computationally intense
activities of encryption and decryption in software,
while others use hardware accelerators to minimize
the performance degradation of encrypting and
decrypting data streams.
802.11x is a standard of defining port-based authentication
and key distribution for wired and wireless networks.
It's based on a protocol called EAP (Extensible
Authentication Protocol) which facilitates the
authentication process between the authenticator
(access point) and the suppliant (NIC of the user
Once the server approves access an additional
authentication process like LEAP (Lightweight
Extensible Authentication Protocol) verifies the
user based on a digital certificate and then dynamically
generates WEP keys. 802.11x enhances WEP by changing
the shared keys as often as the network manager
desires but the drawback is that it is still based
on the 40-bit encryption level of WEP.
Wireless VPN - VPNs have provided security for
many wired LANs and may eventually provide the
same protection for WLANs as well. A VPN secures
a connection by acting as a boundary between the
enterprise LAN and the Internet. Through integration
with firewall software VPNs can offer authentication,
privacy, access control, and traffic shaping capabilities
to control bandwidth consumption. Companies can
now implement a VPN through a VPN gateway to enhance
security over WEP, but do not allow for much customization.
New software products are being developed that
involve unique policy-based controls to meet the
different needs of each company.
to consider before implementation
Now that you plan to implement a WLAN solution
in your enterprise, here are some aspects to consider
before making the buying decision.
Range and coverage: The distance over which the
transmission can travel depends on the transmission
power and receiving capabilities of the transceiver.
It also depends on the path to be taken for the
data. Interactions with typical building objects
like walls, metal, and even people, can affect
how energy propagates. This limits the range and
coverage of a particular system.
Throughput: Throughput is affected by the number
of users, range, the type of WLAN system used,
latency and bottlenecks on the wired portions
of the LAN. You may recall that state-of-the-art
V.90 modems transmit and receive at optimal data
rates of 56.6 Kbps. In terms of throughput, a
WLAN operating at 1.6 Mbps is almost thirty times
Compatibility with the existing network: Most
WLANs provide industry-standard interconnection
with wired networks that use Ethernet or Token
Ring. WLAN nodes are supported by NOSs with the
help of appropriate drivers just like any other
LAN node. Once installed, the network treats wireless
nodes like any other network component.
Interoperability of Wireless Devices: WLAN systems
from different vendors may not interoperate for
use different frequency bands, different vendors
have different implementation procedures, and
different products may use different standards.
You can look for Wi-Fi certified products. WECA
is an organization behind Wi-Fi that certifies
products meeting the 802.11b specification through
Licensing Issues: WLANs are typically designed
to operate in portions of the radio spectrum where
government regulatory bodies do not require the
end-user to purchase a license to use the airwaves.
Look for a WLAN manufacturer who is certified
by the appropriate agency.
Security: Since your data travels in the air,
security provisions are typically built into WLANs.
This makes WLANs more secure than many wired LANs.
It is extremely difficult for unintended receivers
to listen in on WLAN traffic. Complex encryption
techniques make it impossible for all but the
most sophisticated to gain unauthorized access
to network traffic.
Cost: A WLAN implementation includes infrastructure
costs for the wireless access points and user
costs for WLAN adapters. The cost of installing
and maintaining a WLAN is generally lower than
the cost of installing and maintaining a traditional
wired LAN. A WLAN eliminates the direct costs
of cabling and the labor associated with installing
and repairing it.
Safety: The output power of WLAN systems is much
less than that of a handheld cellular phone. Even
then, WLANs must meet stringent government and
industry regulations for safety from radiation.
However, no adverse health affects have been attributed
to WLANs, so far.
Das Gupta can be reached at firstname.lastname@example.org