Wireless Network Components - Basics of Any Wireless Network
By Shaun Hummel
Client Software and Adapter
Any client computer, laptop or wireless device with a compatible wireless client
adapter allows connectivity with an access point. The client adapter is a radio
transmitter with firmware that supports any of 802.11a⁄b⁄g signaling.
That is needed before the device can associate and authenticate with the access
point. Some access points have a no client mode that doesn't allow any association
from clients extending network distance.
Client wireless software included with the adapter must be implemented with specific
Windows platforms. The client adapter will be integrated with the laptop, PCMCIA slot or
desktop PCI bus slot. They will support specific wireless standards, antenna
characteristics, WiFi certification, WDS, network range and security. The wireless
manufacturer software must be implemented for all available features. The following
is a list of some client adapter configured settings.
Access Point (AP)
As the name suggests an AP (access point) allows connectivity between the wireless
client or wireless device and the wired network. The AP takes wireless data packets from a
client and translates them to standard Ethernet data frames before transmitting across the
wired network. Standard category 5 twisted pair cabling will connect the AP point Ethernet
port with a catalyst switch Ethernet port. The maximum distance between access point and
network switch is 100 meters standard with Ethernet design.
WLAN Controllers
Wireless designs with hundreds of root APs on an enterprise network will sometimes
deploy wireless LAN controllers. The design specifies lightweight APs connecting to a
network switch. The 4404 WLAN controller device acts as a hub connecting 4 network
switches supporting 100 access points. Cisco wireless control system (WCS) wireless
network management software is sometimes deployed with WLAN controller design for
planning, configuring and optimizing the network.
Power Injector
Cisco access points have a variety of power options such as AC adapters, power over
Ethernet and power injectors. The placement of APs is such that in some situations an AC
power outlet isn't available. Should your Ethernet switch not support power over Ethernet,
an option such as power injectors extends the distance from an AC outlet. Distances of
1.24 miles are available with a fiber optic media converter.
Power over Ethernet
Cisco access points can be deployed with power over Ethernet (PoE) should the network
switch modules support that feature. The distance of 300 feet is the same with Cisco
prestandard and 802.3af. The Cisco prestandard use Cat 5 cabling pins 1, 2, 3, 6 for
powering devices while 802.3af uses 1, 2, 3, 6 with 10⁄100⁄1000BaseT
signaling and 4, 5, 7, 8 with 10⁄100BaseT. Select a network switch module with
the power over Ethernet standard your AP has implemented and has a power wattage rating
per port for your specific devices.
The network switch power supply should be upgraded to support additional power draw
from multiple devices. Deploying power over Ethernet will decrease implementation costs
with deployment of IPT, wireless and Gigabit. See network switch documents at Cisco web
site for information on what network switching modules support PoE and wattage ratings.
802.3af defines powered device class 2 at 3.84W - 6.49W and class 3 at 6.49W - 12.95W.
Power Patch Panel
Cisco inline power patch panels can be deployed where Ethernet switches don't support
power over Ethernet and power injectors aren't an option. The patch panel does no
switching. It powers the devices through a Cat 5 cable that is a maximum 300 feet at a
specific rated wattage per port. The patch panel connects the access point to the wired
switch with a patch cable.
Shaun Hummel is the author of
Cisco Wireless Network Design Guide
and has a web site focused on information technology solutions, online technical
interviews and certifications.
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