WLAN: Smoothening Wireless Expansion

Anywhere, anytime connectivity-that's the new business rule.
Organizations are conducting business on the go. Companies need fast responses
and want immediate results. Business environment is fast transforming with
instant messaging, text paging, voice services, network access while traveling,
and real-time network access in the office.

WLANs are now business-critical. This year the wireless
networks, both WLANs and cellular data networks, are poised to get a lot more
effective. Draft 2 of the IEEE 802.11n WLAN standard is expected to become final
this year. Products based on the draft standard are expected to start appearing
by mid 2007 and could have a major impact on enterprise backbone networks. These
products, with throughput of 100 to 300Mbps, will be aimed first at the
residential, home office and small-business markets, which already have been
snapping up so-called pre-11n gear that began shipping in 2006.

At the enterprise level, however, the installation and
management of WLAN services has proven to be very time consuming and expensive.
As a result, engineers have been developing more efficient 'managed access'
mobile solutions that are making WLAN more practical for use in enterprise
applications. In addition, many of these technology advances are also in the
process of migrating back into improvements for new-generation 'public access'
hot spots and evolving unified SMB switching platforms.

Identifying the Challenges

Wireless LAN deployment is inherently somewhat complicated though easier to
deploy compared to wired network deployment because of RF nature of the links
involved. Each building has different characteristics, and unexpected radio
interferences need to be overcome. However, WLAN deployment is not a major
challenge once the placements of the Access Points (APs) are freezed on.

CIOs or IT managers often find price points of access points and
WLAN controllers on the high side. Vendors have been trying to impress upon them
the fact that there is much more to determine actual costs than these initial
capital expenses.

Before deploying WLAN, enterprise should consider the variable
costs that go beyond simple equipment list prices to ensure that the technology
they are investing in maximizes productivity while minimizing cost.

Following are six key issues faced during a typical
enterprise-wide wireless LAN deployment:

Technology Selection: Currently,
802.11 a, b, and g are widely used by enterprises. Different technologies can
support different data rates. 802.11b can only support a maximum link layer data
rate of 11Mbps. On the other hand, 802.11a and 802.11g can go up to a
theoretical maximum of 54Mbps. These high rates do not come free, as the range
at which 802.11a/g support higher rates is much lower, therefore requiring a
larger number of access points to provide similar coverage.

802.11n, which has yet to be fully ratified, is designed to
deliver a five-fold increase in data transfer rates compared to current 802.11g
equipment and to double the range.

AP Placement and Cell Sizing:
The two key objectives of WLAN is to provide connectivity (or coverage) at all
desired locations and to provide reasonable capacity to cater to the bandwidth
needs of client applications. Depending on the type of WLAN equipment deployed
and the intended applications, companies may be forced to overlay two sets of
access points-upgrade client devices, add extra access points because of weak
technology that limits capacity-and to spend additional money on
pre-deployment studies as well as ongoing configuration.

Locations with high user density, or with users running
communication-intensive or interactive applications require better capacity than
other locations. Bandwidth aggregation through multiple overlapping cells, or
use of densely packed small-sized cells are two ways to provide higher capacity
at desired locations.

Accounting the Cost: To
determine the cost of the deployment and how technology can help, it's
important to understand the elements that comprise the total cost of deployment.
Every access point (AP) requires an associated Power over Ethernet (PoE) port, a
cable run to the place where the AP will reside, and the time associated with
deploying all of these. An access point, for instance, that costs $150 can climb
up in the $400-550 range when the planning, labor, and PoE are taken into
account.

Knowing the limitations of 802.11 and how advanced systems are
designed to help can save on equipment as well as labor costs. Costs can be
lowered by implementing thin wireless access points (APs), particularly in
larger networks. Traditional wireless deployments utilise thick APs, each
configured individually.

Limited Channels:
Because of limited number of available channels in 802.11 wireless LAN
technologies, channels need to be re-used beyond certain re-use distance.
Without proper assignment of channels and power calibration of access points,
co-channel interference can degrade the performance of wireless LAN. The 802.11b
and 802.11g wireless LAN standards operate in the 2.4 GHz band. This band only
offers three non-overlapping channels. Each channel is a separate 'pipe' of
bandwidth. All clients attached to the access point share that same bandwidth.

The task of the channel assignment process is two-fold-reduce
the interference among neighboring cells, and provision enough capacity.

Supporting Mobility and
Automation: The obvious aspect where a wireless network excels above
wired is mobility. Having the ability to connect anywhere, anytime is a powerful
motivator for wireless. However, the biggest downside to having the wrong
pervasive WLAN design is the ongoing tuning and reconfiguration of the network.

If the WLAN system requires RF planning tools to deploy, this
will be an ongoing task. Adding new desktops, moving an employee, or even
renovating a part of the office building in a way that was not originally
predicted, will change the RF environment and, therefore, require changes to the
network. If those changes are not handled by the system automatically, the IT
manager must manually intervene with software tools. This process is commonly
referred to as RF spectrum management and is the bane of IT staffers' lives.

Mobility needs to be supported at two different levels-link-layer
and IP-layer. 802.11 specifications support link-layer mobility by providing a
mechanism for a client to detect new access points and switch across access
points based on signal strength measurements.

Handoff Between APs:
When a client roams from one access point to another, the time between
disconnecting from the first access point and reconnecting to the second access
point is non-zero. For some clients, this process can take up to several
seconds. If a micro-cell configuration is deployed to increase throughput, then
this handoff problem is exponentially worse.

One should bear in mind that there are inherent limitations to
the number of connections to an access point. A good rule of thumb for designing
is that each access point can support 20-30 simultaneous users. Applications
that don't demand high bandwidth and/or low latency will suffer performance
when the number of simultaneous access point users is too great. How the access
points connect to the backbone is important as well.

The Right Tools

Wireless LAN applications continue to mature in features and usability.
Higher speeds, increased security, quality of service (QoS) and centralized
management are just a few of the wireless developments in the past few years,
and more advances are coming. On the operational side also the configurations
and the security settings are quite simpler compared to other managed
technologies.

What enterprises need are WLAN systems that are designed
specifically for pervasive Wi-Fi access in enterprises. These systems are cost
effective as they handle the issues of pervasive WLAN deployment automatically,
require no RF planning, do away with quality-killing handoffs, can eliminate
interference problems and enable greater scalability.

Centralized AP management has become a popular method of
wireless installation that moves all intelligence from the APs to an appliance.
A centralized wireless deployment allows for the Virtual LAN (VLAN) to be
extended over the existing wired network. Configuration changes are applied at
the management switch instead of at each AP. Since the APs are communicating
with a central device, advanced capabilities, such as automatic channel and
power configuration and rogue detection, are possible. In addition, each thin AP
generally costs significantly less than its more feature-rich cousin.

The downside to a centralized model is the up-front costs. The
central management switch is usually expensive. However, if the deployment
involves many APs, or wireless expansion is anticipated in the future, the
up-front costs of a centrally managed application are often eclipsed by the
benefits.

Don't Throw Away the Wires

Determining whether a network should be wired, wireless or a mixture of both
should be part of every new network design process. It's best advised that in
network design, wireless connectivity should augment but not replace wired
connections. Often a decision on how to proceed is based on what worked well the
year before for a similar project. However, since the available offerings change
rapidly, the question of wired vs wireless should be explored in-depth as part
of every network design process, regardless of what worked for a previous
project of similar scope.

By integrating their wired and wireless networks, businesses
simplify the network, resulting in a decrease in TCO and, more importantly, they
become able to find new and better ways of doing business. As businesses are
becoming mobile, Unified WLAN Architecture is being accepted by enterprises
looking for business transformation.

A non-unified wireless network is typically a controller-based
WLAN solution that has little or no unification with the wired network.
Non-unified wireless solutions might or might not come from the incumbent data
networking provider. Deploying a WLAN from a supplier other than the incumbent
data networking provider usually results in different code, management, and user
interfaces across the wired and wireless networks, resulting in a lack of
benefits when compared to a unified solution (See Non-unified WLAN
Architecture).

A unified wired and wireless architecture typically requires the
wired and wireless infrastructures to be delivered from the same technology
provider. With this architecture, many of the services offered as standard
features on the wired network can be extended to the wireless network because of
the unification of user and management interfaces (See Unified WLAN
Architecture).

Complete wired and wireless integration allows the control and
management of access points and controllers to be centralized into the core of
the network. This centralized control significantly decreases the overhead
and time required to manage the wireless system. Instead of touching individual
controllers or access points, IT administrators can have a single management
point that spans the breadth of individual wireless components.

Deployment Trends

According to IDC, the global market intelligence and advisory firm, the
worldwide WLAN will continue to grow and surge to about 487 mn units by 2009,
due to new end-market opportunities in consumer and mobile devices as well as
technology advancements such as MIMO, which extend bandwidth and range.

Chip suppliers will play an important role in accelerating the
adoption of WLAN features, particularly in high volume consumer device segments
such as gaming consoles, set-top boxes, digital TVs and future mobile phones
designs. Support of QoS features on the chip will also serve as a critical
aspect of future designs, especially for audio and video streaming applications
requiring advanced traffic management and prioritization.

WLAN at home is fast becoming the medium of choice, but it does
not overshadow Ethernet in all countries. Successful implementations of wireless
technologies in numerous healthcare applications may result in further uptake of
wireless technologies. End users are embracing the freedom and flexibility of
wireless connectivity, and business executives are recognizing the competitive
advantage of business-critical mobile applications. Organizations are deploying
WLANs to increase employee productivity, enhance collaboration, and improve
responsiveness to customers.

The 802.11n Effect

The 802.11n standard is expected to offer transfer speeds that are up to
eight times faster than existing WLAN networks, without performance degradation.
Due to the high level of throughput it will deliver, 802.11n is likely to be
used beyond traditional enterprise and home environments. This will encompass
areas such as cellular telephony, mobile radio and VoIP. But with this dramatic
increase in performance also comes an increase in complexity.

Integration of wired and wireless networks in unified WLAN architecture reduce capital and operational expenditures

Vendors are cautious about 802.11n as it is still early days for
the standard. Existing standard 802.11b has proven to be the workhorse of WLAN
connectivity, with 802.11a and 802.11g providing higher speeds for that freedom.

It's critical that system vendors have the ability to perform
the functional and performance testing of 802.11n devices in a precise,
repeatable, and automated fashion. Despite the important impact IEEE 802.11n
will have on wireless networks, it is yet to be finalized as a standard, making
flexible testing and evaluation products a critical part of the development
process.

Efforts in Force

Two years ago, security was the number one wireless network concern for the
enterprises. Currently, many enterprises affirm that they are equally or more
concerned about manageability. A moderately-sized WLAN of today has grown beyond
a handful of wireless access points to over 1000s of APs. Increasing number of
business networks extend upwards to 10,000 access points distributed across
hundreds or thousands of facilities.

As the number and diversity of devices connecting to WLANs
increase, there's a growing demand on IT managers to develop a plan to support
multiple security policies simultaneously, and to understand new mobility
patterns within the enterprise.

More IT organizations are likely to face the challenge of how to
support multiple wireless architectures and topologies in addition to
multi-vendor networks. Moreover, without sufficient budget available to replace
their old hardware, as they integrate different technologies into their
networks, most enterprises both expect and need their wireless infrastructure to
last three years or more.

Malovika Rao


malovikar@cybermedia.co.in