802.11
Wireless Networking
Although wireless networking was used extensively by Management Support Teams (MST) under the DHHS during deployment, CAT5 hardwire is strongly urged on future deployments for security reasons. See Security Issues below.
Principally wireless networking is used for two
functions.
First, to provide access by laptops to printers connected to other
laptops.
Second, to provide WAN, internet, and email capability. In
addition,
other government networks can also be tapped by a network connection.
The Office of Emergency Preparedness had
been using systems that are compatible with IEEE 802.11b
standards. These will work with other manufacture's
equipment as long as they
are 802.11b compliant. A partial list of some of the manufactures
making
802.11b wireless systems is:
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IEEE 802.11b stations operate in the 2.4 GHz band with a throughput of up to 11 Mb/s, and are usually limited to about 150 feet indoors for full bandwidth communications. Slower data rates may be supported up to 450 feet indoors. However, real use show these distances are ideal in nature as we experienced problems in as little distance as 50 feet depending on structures that the signal had to propagate through.
IEEE 802.11g uses the 2.4 GHz band and has a potential higher throughput of up to 54 Mb/s.
IEEE 802.11a uses the 5 GHz band and also has
a
potential throughput of up to 54 Mb/s. However, the "a" and "g"
protocol
usually has a minimum baud rate of 6 Mb/s which will not transmit as
far
as the "b" protocal's 1 Mb/s rate. Using NETGEAR as an example,
the
maximum distance, outdoors that 802.11a is rated for is 1200 feet,
while
802.11b can go a maximum of 1650 feet in the same conditions. 
Thus
we would suggest using the slower 802.11b version for field
applications
where conditions can not be controled as it may actually transfer data
in conditions when the 802.11a version can not. Note!
Engenius makes 802.11b hardware that is double the power output, thus
have
an increased coverage area.
IEEE 802.11b has two basic operational modes
demonstrated
below. These modes are Ad-Hoc
or Access Point, Infrastucture, Managed, etc.
Ad-Hoc allows laptops to operate in a peer-to-peer mode and depending
on
the system can handle 10 or more laptops in a Basic Service Set (BSS).
A Basic Service Set or BSS is all
the
stations that can talk with each other excluding any hardwired networks.
Access Point systems use a special
additional
station that is usually connected to a hardwired network and acts like
a repeater. Access Points may be connected to other Access Points
on the network to provide Cells of coverage.
In an Ad-Hoc mode, stations must be within the Basic
Service
Set (BSS) to work with another station. A station may be members
of either BSS cell if it is in the footprint of two BSS networks by
manually
switching channels. 
This is where the Access Point
system
comes in. Access Points can be used to connect many BSS groups
together
to a wired network thus allowing all to communicate together and to an
outside network if desired. Switching between cells with an
Access
Point system is automatic.
An Access Point system allows laptop stations
to roam or move between BSS groups. In the above example we can
see
Station 4 is served by both Access Points and can move at will between
service areas. Service will be continuous as long as the
each
cells Access Point signals overlap. Each BSS/Access group operate on
seperate
wireless channels. A station that roams will search for available
channels as it goes from one BSS cell to another. Data is not
lost
although there is an interuption, lasting less than a second, in
the flow of data as a station searches for a good signal from the next
BSS cell.
By using an Access Point, stations can be connected
to
the internet as in the above example.
Although a BSS group can be connected to
the internet without a router, if the DSL internet system allows
multiple
connections, members in the group may not see each other if the ISP has
firewalls between its network users. Such is usually the case in
hotels, etc. If this is the case, you will not be able to share
resources
such as a printer. This is because the DSL internet server
usually assigns Dynamic IP address when a station connects.
Stations connected have no way of knowing what each other's IP
addresses
are and thus can not connect to each other to share resources.
By adding a router, one can separate the
DSL server from the stations. The DSL will assign one IP to the
router,
and the router will accept the manually or automatically assigned IP
address
from each station in your network. This gives the best of two
worlds,
peer-to-peer and internet.
WPA Security Issues
Standard WEP encryption and key protection is not approved for use by
US government agencies. Newer WPA (WiFi Protected Access) is an
improvement on WEP technology. WPA changes the encryption key every
10,000 bytes using the IEEE 802.11i Temporal Key Integrity Protocol
(TKIP), so is very difficult to break by those trying to listen
in. WPA2 is yet an improvement over WPA allowing for hardened
encryption protocols. Most wireless router manufacturers have moved
into the new WPA2 protocol. WPA2 using Advanced Encryption
Standard (AES) has support from most agencies and complies with
esblished
government security standards. These standards
include the NIST FIPS 140-2 standard.
Installation and Setup
Setup of Wireless Network card involves settings
in several different areas. Below is a list of basic items that
needs
to be done to set up a PCMCIA card.