Current network technology has grown rapidly. Various technologies have been in
developed to assist humans in communicating. If the era of the 80s
computer network technologies rely on cable-based networking technologies, today
The technology started many left because of some limitations, such as the size
costs that must be issued by the organization when using this technology (wired network),
besides that this technology is also not flexible because it is very dependent on the cable. Currently, if we
note as companies begin implementing wireless technology (wireless) or
commonly called the Wireless Fidelity (WiFi). This we can see many companies
which offers a Hotspot Area (the area contained a WiFi-based Internet network) that can be
access by all people either for free or by way of registration to the service provider
them.
Seeing the rampant trend of companies offering HotSpot Area in public areas such as place
shopping (mall), libraries, restaurants, kaffe, and even almost all educational institutions
such as universities already provide HotSpot acres for their students as part
of facilities supporting their teaching and learning programs. So we know we should bear
about this technology (WiFi), how it works, type-type, and how the network security
This is an issue that really needs to be considered when we want to switch
using this technology.
2. Type Configuration Wireless LAN (WLAN)
In general there are 2 types of configuration for WLAN-based networks, :
Based Ad-hoc
In this network, the communication between a computer device with another one done
spontaneously / directly without going through a specific configurations for a signal from the Access Point can
be received well by computer devices in this network.
Based Infrastructure
In this network, one ata more Access Points (APS) connecting via a WLAN network
cable-based network. So in this tissue type, to serve the computer equipment in
network, the Access Point requires a connection to the first cable-based network.
Because many types of WLAN networks on the market, the IEEE 802.11 standard
set interface (interface) between the client WLAN (wireless client) with the Access Network
Point him (network APS). To distinguish the difference between a WLAN network with
other WLAN networks, the 802.11 using the Service Set Identifier (SSID). With
These markers can then differentiate between a WLAN network with each other because the network
WLAN with one another definitely has a number of different SSID marker. Access
Point (AP) use the SSID to determine the traffic data packets which are in designated
for the Access Point.
802.11 standard also specifies the frequency that can be used by the WLAN network. For example
for industrial, scientific, and medical (ISM) radio frequency operating at 2.4 GHz. 802.11
also define three types of transmission at the physical layer to the Open Systems Interconnection model
(OSI), namely: direct-sequence spread spectrum (DSSS), frequency-hopping spread spectrum
(FHSS), and infrared.
In addition to the frequency distribution of the above, the 802.11 standard also divides its type frame into 3 (three)
categories, namely: control, data, and management.
802.11 standard allows devices (devices) that follow the 802.11 standard for
communicate with each other at a speed of 1 Mbps and 2 Mbps in the range of about 100
meters. Another type of 802.11 standard will be developed to provide speed
faster data transfer with a better level of functionality than that available today.
We have several types of variants of the 802.11 standard, namely: 802.11a, 802.11b, 802.11g.
802.11a Standard
802.11a standard is used to define a wireless network that uses a frequency of 5
GHz unlicensed National Information Infrastrusture (UNII). Network speed is faster
from standard 802.11 and 802.11b standards on transfer speeds up to 54 Mbps. This speed
can be even faster if you use the right technology.
To use the 802.11a standard, computer devices (devices) requires only
support the communication speed of 6 Mbps, 12 Mbps and 24 Mbps. 802.11a standard also
operate the channel / channel 4 (four) times more than what can be done by
802.11 and 802.11b standards. Although the 802.11a standard is similar to standard
802.11b in the lining of the Media Access Control (MAC), was still not compatible with
standard 802.11 or 802.11b as the 802.11a standard uses 5 GHz radio frequency
while the 802.11b standard uses the 2.4 GHz frequency.
The advantages of 802.11a standard is because it operates at a frequency of 5 GHz radio so
do not have to compete with wireless communication devices (cordless) phones, such as
cordless (cordless phones), which generally use a frequency of 2.4 GHz. Another major difference between 802.11a standard with 802.11 and 802.11b standards are
that the 802.11a standard uses additional modulation called Orthogonal
Frequency Division Multiplexing (OFDM) in physical layer in the OSI model.
Although the 802.11a standard is not compatible with 802.11b standard, several vendors / companies
Access Point device maker trying to get around this by creating a kind of bridge
(Bridge) that connects between the standard 802.11a and 802.11b access devices
made their point. Access points are made in such a way that can be used
in 2 (two) types of standards that is the standard 802.11a and 802.11b standards without each other
affect one another.
802.11a standard is a very expensive option when implemented. This
because these standards need more access points to reach speeds
highest communication. The reason is because of the fact that the wave
5 GHz frequency has a weakness on the coverage.
802.11b standard
802.11b standard is the most widely used standard in the 802.11 standard class. Standard
This is a development of the 802.11 standard for high-speed physical layer.
802.11b wireless network is used to define the direct-sequence spread spectrum
(DSSS), which uses frequency bands indusrial, scientific, medicine (ISM) 2.4 GHz
and communicate at speeds up to 11 Mbps. It’s faster than the speed of 1 Mbos
or 2 Mbps offered by 802.11a standard. Also compatible with 802.11b standard
DSSS all devices that operate on the 802.11 standard.
802.11b standard only concentrate only on the physical layer and Media Access Control (MAC).
This standard uses only one type of frame that has a maximum width of 2346 bytes.
However, it can be further divided into 1518 byte jik at connecting cross (cross) with
access point device that can also communicate with Ethernet-based network
(Cable-based).
802.11b standard only focuses on the operation of DSSS devices only. Standard
This provides a method for those devices to find (discover), associations,
and authenticate each other. Standari It also provides a method to handle collisions
(Collision), and fragmentation and possible methods of encryption through WEP protocols (wired
equivalent protocol).
802.11g Standard
802.11g standard is basically similar to the 802.11a standard which provides a channel of communication
High speed up to 54 Mbps. However, the frequency used in this standard together with
frequency used 802.11b standard is the wave frequency of 2.4 GHz and can also
compatible with 802.11b standard. It is not owned by the 802.11a standard.
As 802.11.a standard, the devices on the 802.11g standard using a modulation
OFDM to obtain high-speed data transfer rates. Unlike device-
devices on the 802.11a standard, the devices on the 802.11g standard can be automatically
switch to quadrature phase shift keying (QPSK) to communicate with the device-
device in a wireless network using 802.11b standard.
Compared with 802.11a, 802.11g turns out to have advantages in terms of compatibility
with standard 802.11b network. But the problems that may arise when the device-
802.11g standard devices that try to switch to the 802.11b network, or even vice versa
is that the causes interference problems by using a frequency of 2.4 GHz. Because such
described earlier that the frequency of 2.4 GHz is the frequency of the most widely used
by the other wireless-based devices.
The use of wireless-based network technology is the right choice today. This
due to start shifting behavior of firms in their business. With
portability and compatibility offered by wireless technology is certainly
a very attractive option. But behind it must also consider wireless technology
what is appropriate to apply at a company that can really help business
company. This can be seen from the differences of each wireless standard
available today (802.11, 802.11a, 802.11b, 802.11g). Viewed from the side of safety, of course 802.11b
slightly better because it can implement an encryption method using the WEP protocol
in the network. When viewed from the side of no interference / noise of course technology
802.11a standard is superior because it only uses 5 GHz frequency band in which this frequency
not widely used by devices other wirelees based. So for
overcome the problems mentioned above, it appears to bridge the 802.11g standard
weakness in 802.11a and 802.11b standards.
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