Wireless Control-
Access Points manage connections to several Clients
at a time (for example, multiple laptop users controlling
or monitoring the same network), giving the Clients
access to each other and to the wired LAN.
In simplest form an Access Point has a Wi-Fi ra-
dio and one Ethernet port; however, many products
combine other functions with an Access Point. Wire-
less switches (an Access Point and Ethernet switch in
the same box), and wireless routers (an Access Point
and Ethernet router in the same box) are examples.
(See Figure 4.) Be careful with terminology though; a
“router” is not an Access Point unless it is wireless.
For reference, a leading Access Point product is the
Linksys WAP54G; a leading wireless router is the Link-
sys WRT54GS (note that these are “g” devices match-
ing the earlier “g” card). In addition to providing the
hub for the wireless devices, these convert wireless to
wire to connect to RPMs.
Ad Hoc (Peer-to-Peer) vs. Infrastructure
Networks
References to ad hoc or peer-to-peer (unmanaged)
mode versus infrastructure (managed or hosted) mode
appear in documentation for Clients and Access Points.
A wireless ad hoc mode network is a network with
no Access Point (i.e., no infrastructure). The ad hoc
advantage is that the wireless devices can talk directly
to each other.
RPM units do not support ad hoc networks.
This means that you cannot control RPMs directly
from a Wi-Fi laptop without adding an Access Point.
Therefore after installing your Wi-Fi card configure
it for an infrastructure network. (Gateway is an inter-
changeable term.)
SSID
The service set identifier (SSID) is similar to a user
name without a password. It is the name of the WLAN.
This user name or SSID is transmitted by the Access
Point for anyone to receive and connect to the network.
In search mode, a PC listens for all the SSIDs in the
immediate area, and lets you pick the one you want.
Connecting to any wireless network requires the SSID
so you must assign one to your WLAN.
Building a Simple WLAN for Drag Net
To setup a simple WLAN you need a computer with a
Wi-Fi card (Client), and an Access Point that connects
to the RPMs with CAT 5 cable.
Begin by configuring the Access Point while the
computer is connected to it with a cable. This is done
using the configuration program provided by the
manufacturer. Most equipment allows you to also
change settings through a Web interface. Using an
Internet browser of your choice (e.g., Internet Explorer,
Netscape, etc.) you type in the IP address of the Access
Point and up pops a web page that lets you set the Ac-
cess Point’s parameters.
Recommended is to setup your small LAN with
static IP addresses so you can locate the Access Point
by its IP address. RPMs only support static addresses so
they are ready to go.
The Access Point may allow you to use DHCP (i.e.,
automatic IP address assignment), but if you do that,
you will have trouble locating the Access Point by IP
address and it will be difficult to use the Web pages to
set and adjust it, so we advise against it.
You should set the SSID to something that makes
sense to you. This will let you properly locate and
connect to this Access Point when other WLANs are
within range of your Client card.
You will have a choice to set passwords and security
settings for your Access Point (and later on, your Client
card). We recommend that you set the password (
and
write it down where you can find it a year from now
).
Initially leave the security turned off -- but only
while you are setting up the system. After it’s working,
always set the security to exclude other Clients from
the network. It is easy to do and will stop strangers
from messing with or inadvertently damaging/dis-
abling your WLAN.
Once your Access Point is configured, disconnect
your computer and attach the Access Point to the
RPMs to form a LAN. With a single RPM, this would
be a minimal LAN with a single cable connecting it to
the Access Point. With more than one RPM, you need
an Ethernet switch to connect them together as shown
in Figure 4.
After installing the Wi-Fi card, open up the adapter’s
control panel software and you should see the Access
Point in the available wireless networks list. Go ahead
and connect to it. This is usually a matter of double
clicking on its entry in the WLAN list.