This
list of Frequently Asked Questions has been designed to be read
from top to bottom with each question and answer increasing in
complexity and assumes the previous answers have been read.
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| Q1 |
What does WiFi
mean? |
| A1 |
WiFi is the popular term for a high-frequency wireless local
area network (WLAN). It is also is a set of standards for
wireless local area networks (WLAN) currently based on the IEEE
802.11 specifications to ensure interoperability of wireless
networking products. |
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|
| Q2 |
What is a WLAN? |
| A2 |
WLAN stands for Wireless Local Area Network. Wireless
networks are made up of network adapters that transmit high
frequency radio signals instead of using wires or cables to send
information to other computers or devices on a network. |
|
|
| Q3 |
What equipment do
I need to make a wireless network? |
| A3 |
In its most basic form a wireless network can be created by
adding a wireless network adapter to 2 computers and setting
them up in "Adhoc" mode.
More commonly used however, is a wireless router or access point
which controls the flow or "routs" the information being sent
around the network with wireless network adapters being added to
each computer on the network, these computers connecting to the
access point are called clients. |
|
|
| Q4 |
How far can a
WLAN reach? |
| A4 |
Manufacturers of domestic grade products typically rate
their equipment to reach approximately 40m indoors and around
100m outdoors. These ratings however are based upon "average"
conditions and as such may not be a reliable indication for
individual network coverage.
The best way to guess how far your wireless
network will reach is by imagining the network in a similar
perspective as your mobile and cordless telephones. The distance
and quality of connection will vary according to both physical
and electromagnetic interference. |
|
|
| Q5 |
What constitutes
Physical and Electromagnetic interference? |
| A5 |
Physical interference is anything
you can physically touch - walls, people, computers etc, even clear substances such as water and glass greatly affect the
strength and quality of the signal used for wireless networks.
Electromagnetic interference is any electrical signal on or near
the same frequency that wireless networks operate. Interference
can also be caused by signals not on or near the same frequency
but strong enough to drown out the signals from your wireless
network. |
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|
| Q6 |
What can I do
about interference? |
| A6 |
There are 2 things you can do to overcome interference,
eliminate and overpower- i) Eliminate interference by moving
your access point to a central location within your network thus
reducing the amount of interference between each point.
ii) Overpower the interference by increasing each transmitters'
signal transmit and power and receive sensitivity.
Imagine you are trying to have a conversation
with another person 2 bedrooms away. You are the access point
and they are another computer (client). You are having trouble
hearing each other and there is a lot of "what did you say?"
going on so your conversation is slowed down to communicating at
about 1 complete sentence a minute. In network terms lets say
1mb/s. At this point your dog starts barking (cordless phone
radio interference) and you cant achieve 1mb/s - windows at this
point will probably inform your friend 2 rooms away that they
are unable to connect to the network - your conversation has
been terminated.
You can move into the next room adjacent to your friend and that
may be enough to reconnect to the network.
Changing rooms may not be an option because you also need to
communicate with someone else in the opposite direction and
changing rooms may result in not being able to establish
communication with them. In this case you need to talk louder
and listen harder by increasing your signal strength (loudness)
and listening harder. |
|
|
| Q7 |
Am I able to
increase a transmitters signal strength and receive sensitivity? |
| A7 |
You cannot increase a transmitters signal strength or
sensitivity unless it is an option the manufacturer offers in
the equipments settings. This option however is extremely
uncommon so the realistic option is to modify or focus the
signal after it has left the unit, this is done through the use
of antennas. All wireless networking equipment uses an antenna
to transmit and receive signals in one form or another. Some
antennas are internal whilst others are external. When the
antenna is internal there is nothing you can do to modify the
signal short of physically pulling the unit apart.
For units with external antennas some are detachable, in these
cases you are able to remove the original antenna and attach
another antenna in its place. The replacement antenna used could
be one that concentrates a signal or focuses the direction in
which it transmits and receives, would effectively improve the
units transmit and receive ability in those directions. |
|
|
| Q8 |
How do antennas
increase signal strength? |
| A8 |
Antennas work in both directions, transmit (TX) and receive
(RX). When a signal is pushed into the base of the antenna from
the transmitting unit, the signal is converted into radio waves
or (RF). An antenna in its simplest form can be as simple as a
straight length of bare metal in which case the RF signal
leaving it would be uncontrolled and unfocused. The radio waves
emitted from the antenna if you could see them would form a
shape like a sphere in all directions, this shape is called the
radiation pattern. RF engineers design antennas to take the
available signal being pushed into the antenna and focusing its
energy into given directions thus providing gain measured in dB.
As the antenna is used for both transmit and receive the gain
works in both directions, signals already in the air coming from
the directions the antenna has been designed to concentrate on
be louder when going back into the receiver and signals coming
from outside of the concentration areas will be quieter. The
higher the gain in the antenna the more focused will be its
transmit radiation pattern and also its receive sensitivity. |
|
|
| Q9 |
How do I pick an
antenna that is right for me? |
| A9 |
When choosing an antenna it is vitally important to know the
physical layout of the network and the potential interference
that will cause connectivity issues. The location of the central
access point, the clients and interference points will be the
determining factor for the antenna requirements. You should
always conduct a site survey of the proposed WLAN using test
equipment that measures signal strengths and interference levels
at all access point and client locations before purchasing
products. |
| Q10 |
I have
a wireless router with a removable antenna.
I can’t seem to pick up the signal with my laptop when I
go outside.
Will the WTR-2407 do the job. The D-link WDL-50AT is a 5db and
it says it can do up to 500 meters? |
| A10 |
The reason for the laptop not connecting to the
router is interference. The WTR-2407 will increase the signal
power and receive sensitivity of the wireless router by 7db.
Without conducting a site survey of the WLAN it is impossible
for us to tell you the degree of improvement to the laptop's
range to the router. For best results you should also attach a
WTR-2407 antenna to the laptop and move the router away from
other transmitting devices. |
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