wireless Local area network AND Worldwide Interoperability for Microwave Access
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wireless Local area network AND Worldwide Interoperability for Microwave Access



WLAN (Wire less Local Network) is commonly used to connect the nodes, which are also
called wireless terminals. This is used to connect the terminals in a building or an enterprise.
There are many types of WLAN architectures. In the traditional WLAN architecture there are
many flaws. In the switching WLAN architecture the switch acts as a problem. So it is expensive
to connect this architecture. The next one is routed WLAN architecture, which is an advanced
one than past WLAN architectures. WIMAX (Worldwide Interoperability for Microwave
Access) this an advanced one compared to WLAN. WLAN uses narrow bandwidth compared to
WIMAX. This is because the WIMAX uses more number of sub carriers than WLAN. Also
more number of duplexing techniques is used in WIMAX. Generally every node (computer) in a
network of an enterprise wants to communicate with other node. To arrange the communication
local area network is designed such that every node can communicate with another. The
disadvantages of LAN lead to invent WAN (Wide Area Network). The disadvantages may be
coverage, complexity in the network components and so on. Again there are some disadvantages
in the WAN. The WAN is used to connect only the far distances. To connect all the nodes inside
a building LAN with complex circuitry or a WAN whose components occupy more space are
required. Thus Wireless-LAN (WLAN) came into existence. This study covers the theory of
Wireless Local Area Networks (WLAN), their practical solutions in education and a course to
teach WLANs. Also covered is planning of a WLAN in an enterprise environment. Besides the
technological view also a pedagogical aspect is evaluated in the course and the environment. The
usage of laptop computers is enormously. This paper involves the topology of the WLAN. The
properties of the cells. The architectures of the Wireless LAN is discussed .The construction of
the WLAN topology. WLAN usage of the bandwidth. The advanced technology next to WLAN
is WIMAX. Further the advantages of WIMAX over WLAN are discussed.


Wireless Local Area Network, Wireless LAN (WLAN) is a data transmission media that uses
radio waves instead of the traditional copper wires in connecting the computers to the network.
The wireless LAN is used at the last link between the LAN and users. So there will be a network
connection to all users in a building or campus. The backbone network is wire line. WLAN is
expected to be an important connection form in many business areas. Market is expected to grow
as the benefits of WLAN are recognized. Frost and Sullivan estimates the WLAN market to have
been 1998 0,3 billion US dollars and 2005 1,6 billion dollars. So far WLANs have been installed
primarily to ware houses and resellers, but having new installations in different kinds of schools.
The future large markets are estimated to be in health care, educational institutes and corporate
offices. In business environment meeting and public areas and side offices would be ideal for
WLAN is an option to wire line LAN in places where cabling is hard or even impossible. Such
places could be old protected buildings or classrooms with circumstances not suitable for LAN
installation. The WLAN installations are also cheap because the installations consist only of the
access points and backbone network installations and for the last part of the network is in the air.


Wireless LANs allow workstations to communicate and to access the network using radio
propagation as the transmission medium. The wireless LAN can be connected to an existing
wired LAN as an extension, or can form the basis of a new network. While adaptable to both
indoor and outdoor environments, wireless LANs are especially suited to indoors locations such
as office buildings, manufacturing floors, hospitals and universities.
The basic building block of the wireless LAN is the Cell. This is the area in which the wireless
communication takes place. The coverage area of a cell depends upon the strength of the
propagated radio signal and the type and construction of walls, partitions and other physical
characteristics of the indoor environment. In general, a cell covers a more-or- less circular area.
PC-based workstations, notebook and pen-based computers can move around freely in the cell.
All radio communication in the cell is coordinated by a traffic management function. In the
Breeze NET PRO.11 system, a unit called an Access Point performs the radio traffic
management function.
The Access Point connects the cells of the wireless LAN with one another and connects wireless
LAN cells to a wired Ethernet LAN via a cable connection to an Ethernet LAN outlet. An
example of Breeze NET PRO.11 LAN topology is shown in the figure below.
Wire less LAN configuration
The basic building blocks of WLAN are cells. The cell covers an area with radio propagations.
Such that any wireless terminal such as laptop, pen based computer can move freely in the cell.
The coverage of the cell depends on the type of the walls, the strength of the signals. There will
be more traffic of the radio signals in the cell. This traffic is produced due to more transmitters
and receivers in the cell. The access points control this traffic. Thus the cell is formed The
Access Point connects the cells of the wireless LAN with one another and connects wireless
LAN cells to a wired Ethernet LAN via a cable connection to an Ethernet LAN outlet. An
example of Breeze NET PRO.11 LAN topology is shown above. The figure of the stand-alone
cell in the breeze net system is shown below. Thus a cell is comprised of an access point and a
number of wireless work stations.
Stand alone cell configuration
In a busy environment cell comprises of 50 work stations .In a relaxed environment up to 200
workstations are covered.
These cells are connected Ethernet or any wireless network. Some of the properties of the cells
are discussed here. When the area in the building is within the coverage area of the two access
points the cells are said to be overlapped.
Cells overlapped, roaming
The figure shows the overlapping of cell. When a user moving from one cell the when the two
are overlapped he doesnâ„¢t observe any difference at the intersection of the two cells.
The interesting point is the multi cell. When two or more access points converge to a cell then
the cell is called multi cell. The multi cell can use the best access point, which covers it more.
This application is best used in a heavy traffic area. This provides constant system back up
facility. This keeps the cell in the fail-safe region.
Multi cell configuration

Traditional wireless LAN

Traditional architecture uses bridges or access points to interconnect wireless clients with a
wired backbone, thus providing access to other network elements and resources. As a user roams
out of the radio coverage range of one access point and into the range of another, the connection
is automatically handed off by a dialogue between the access points themselves. Higher levels of
protocol stack are completely unaware of this hand off, and the arbitrarily extended by adding
more access points. Note that each point is independent of the others, must be configured and
managed individually.
This architecture has many drawbacks. It is fundamentally flawed for large enterprise
installations. Despite falling prices, enterprise-class access points remain expensive, and not just
to acquire-the costs associated with maintaining and managing a large number of access points
can be significant operational expense.

Switched wireless LAN

The new switched WLAN architecture is based on a central controller that interconnects
lightweight or thin access points. These access points are much simpler than traditional access
points. The brains of the installation resides centrally in the wireless switch, so the acquisition
and management costs are lower in installation and the operations staff deals with a single unit
via a single IP address rather than a large number of individual access points. A much more
reasonable approach especially is large-scale deployment. But the switches have there
fundamental architectural flaws. First the light weight APâ„¢s are proprietary, with similarly
proprietary protocols between them and the switch. The switches themselves designed to be
isolated layer 2 subnets. Mobility across the subnets can range from very difficult to essentially
impossible, depending upon the implementation. Thus the switches became complex and

Routed WLAN architecture

A router is core element of almost every network configuration. It provides a broad range of
services from internetworking to essential network monitoring, management and control. The
power of the router lies in its ability to deal with network issues and opportunities at layer-3 of
the open system interconnection model, which is, after all the network layer. The routed
architecture keeps both the 802.11 MAC and the physical layer functionality in the access point
and moves all the higher level functionality, such as authentication and IP address management
to the wireless controller as this architecture leverages the routed IP network, the wireless
controller can be located essentially any where in a network, across multiple switch or router
hops or even across WAN links.
Routed WLAN

WIMAX-Worldwide Interoperability for Microwave Access

WIMAX is proving useful in delivering broadband services to rural areas where it's cost-
prohibitive to install landline infrastructure. WIMAX supports subchannelisation, meaning that
instead of transmitting on all 192 data sub carriers, you can transmit on just a subset. In this
scenario, by using the same amount of power over fewer carriers, the system achieves greater
range. WIMAX also uses a variable-length guard interval to improve performance in multi-path
environments. The guard interval is a time delay at the beginning of the packet to compensate for
multi-path interference .the overall spectral efficiency of the WIMAX systems is increased from
15 to 40% higher than that of WLAN systems by using more number of sub carriers.


This figure shows some of the different types of uses that WIMAX networks can
provide. This diagram shows that WIMAX systems can be used for point-to-point
high-speed business connections. This example
shows that the point to point (PTP) connection may be independent from all other
systems or networks. The point to multipoint (PMP) system allows a radio system to provide
services to multiple users. WiMax systems can also be setup as mesh networks allowing the
WiMax system to forward packets between base stations and subscribers without having to
install communication lines between base stations.
WIMAX system


Thus the WLAN are used in the schools, offices, hospitals and the places where network is
required. The main requirement of day - day life is the mobility of information. Using laptop
does this. The laptops with WLAN cards are easy to use if the whole area where the laptop is
used is covered. Electricity is more easily accessible than LAN. The special application of
WLAN is video streaming that adapts to a variable transmission rate. The prices of WLAN
equipment are coming down. WLAN supports only TDD (time division duplexing). Where as
WIMAX supports TDD, FDD (frequency division duplexing), H-FDD (half duplex-FDD). H-
FDD transmits data on different frequencies at different times. WIMAX has a lower error rate
than WLAN. The noise figure of WLAN is 10dB.where as noise figure of WIMAX is 7dB.
WIMAX supports transmit ranges of several kilometers, and transmitting at maximum power
near the base station would be disastrous.


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