networks are becoming viable solutions for office and home computing by
offering easy ways to link two or more computers together. The main advantage
concerns not having to run cabling between the computers. The next advantage
is that the computer does not have to remain at one location. Cabling for
the network can be a real problem in that the network may have to run between
rooms or floors and would carry an installation cost that makes the network
prohibitive. Or, the cabling, if left uncovered, would be in the way, or
would be unsightly. And, the convenience of being able to move that new
laptop computer from room to room is really nice. The IEEE 802.11 series
of standards are becoming known as the “wireless Ethernet”.
And, as noted in my October 2002 column, wireless networking is main
stream. One account noted that the wireless LAN market is slated to grow
from $771 million dollars in 1999 to over $2.2 billion in 2004. (Wireless
LAN Market Analysis, 2000). Wireless broadband routers and other components
are now shelf purchase items. Belkin, Linksys, Intel, Buffalo, Cisco, Netgear,
U.S. Robotics, Multitech, Grandtec, OriNOCO, D-Link, SMC, and 3Com all
have wireless systems and components that meet the IEEE 802.11 series standards.
All of the computer catalogs that I use, Data Comm Warehouse, Micro
warehouse, Zones, and PC Connection, carry multiple vendors.
The local sellers, Best Buy, CompUSA, and Altex all have components on
the shelf. Whether all of the vendors meet all of the IEEE 802.11 series
standards is another question. The standard is such that components from
different vendors is suppose to work together.
IEEE 802.11 Series Standards
This IEEE standard is fairly new. It was approved in 1997. In its original
form, the standard proposed three techniques, mutually incompatible, for
the physical layer, i.e., the media.IR (InfraRed)
pulse position modulation, RF (Radio
in the 2.4 GHz band using FHSS (Frequency
noted in the October 2002 column. The IR method never worked commercially.
The RF methods worked, but had low transmission speeds (2Mbit/s). IEEE
then set up two task groups to find alternative methods of 802.11. Task
Group A would look at the 5 - GHz band to attempt to achieve throughput
speed of up to 54 Mbit/s. Task Group B would continue to explore the 2.4
- GHz throughput speed band.
The Task Group A exploration was to publish its 802.11a standard by
2002 or 2003. It is not completely out yet, though there are some components
becoming available. The Task Group B standard published in 1999. Most wireless
systems being sold today follow the 802.11b standard at the 11 Mbit/s speed
The transmission medium is the most striking difference between wired
Ethernet and wireless LANs. This medium is the RF method of sending the
data from node to node in the LAN. Radio waves broadcast on a given band
can be received by any receiver within the range tuned to that same frequency.
Wireless NIC (Network
are equipped with antennae, radio transceiver, and circuitry to convert
between the analog radio signal and the digital pulse used by computers.
The range is governed by the signal power, distance, and interference from
intervening objects (trees, walls, etc.), and other radio signals. The
802.11b range is approximately 300 feet unobstructed. Radio signals are
governed by groups in the United States and other bodies internationally.
The FCC (Federal
the U. S. governing body. The 802.11b standard delivers its maximum performance
within the FCC limits, current radio technology, and the laws of physics.
Unobstructed, the standard delivers up to 11 Mbit/s. It is also designed
to step down to a slower transmission rate when the signal is obstructed,
i.e., walls, leaves, etc., get in the way. The step-down speed rates are
11, 5.5, 2, and 1 Mbit/s. My Lucent/OriNOCO equipped laptop shows this
speed step-down when I move it down stairs to watch television as I surf
the Net. My network connection, however, is fully compatible with all the
functions that I need to do any work, i.e., search other computers, print,
or save data files at these slower speeds.
Another difference between Ethernet and wireless LANs is the way that
each controls access to the medium, the determination who may talk and
when. Ethernet uses CSMA/CD (Carrier
Access with Collusion
Ethernet devices can send and listen to the cabling at the same time, detecting
the pattern that shows a collision is taking place. A radio can not transmit
and listen on the same channel at the same time as its own transmission
drowns out all other signals. 802.11b LANs use CSMA/CA (Carrier
Access with Collision
a four-way handshake to gain access to the airwaves. A originating node
sends a short RTS (Request
packet on the air addressed to the destination. If that destination hears
the transmission and is able to receive, it replies with a short CTS
The originating node then sends the data and the destination acknowledges
all transmitted packets by returning a short ACK (Acknowledgment)
packet for every transmitted packet received.
Wireless LAN topologies are also slightly different from the Ethernet
Star configuration. The simplest topology is referred to as an ad hoc group
of independent wireless nodes communicating as a peer-to-peer network.
The 802.11b standard refers to this arrangement as an IBSS (Independent
Set). The standard
provides a measure of coordination by electing one node as the proxy for
controlling the LAN. Ad hoc networks are great for lone machine or hard
to wire locations. Ad hoc networks also work for temporary networks such
as a group of laptops in a conference room.
Complex topologies or infrastructure topologies include Access Points
or base stations as part of the network. Access Points provide synchronization
and coordination to the network. Access Points have a connection into the
wired portion of the network and are able to receive and send to multiple
wireless nodes. The 802.11b standard refers to a topology with a single
Access Point as a BSS (Basic
Additional Access Points are installed in the network expands. Multiple
Access Point networks are called ESS (Extended
Each Access Point is assigned a different channel to minimize RF interference.
Each mobile device will find the clearest signal and least amount of network
traffic to allow seamless roaming from one Access Point to another.
The wireless network needs some tolerance of connections being dropped
and reestablished to ensure minimum disruption of data delivery, including
forwarding of distributed nodes. Higher level networking protocols such
as TCP/IP may not be tolerant of this network jumping. The TCP/IP DHCP
assignment of IP addresses may chase a node to lose its connection when
it moves across cell boundaries in an ESS. This area of the standard is
under review to make improvements.
Authentication and privacy issues restrict the ability to transmit in
the wireless network. If authentication is open, i.e., no restrictions,
then any 802.11b compliant device can be authenticated. When authentication
is exercised, then each device logging onto the network must prove it belongs
there via a shared authentication key by acknowledging that it knows that
shared key. Privacy is the second half of the security formula and is supported
in 802.11b as WAP (Wired
WAP uses shared keys and a pseudorandom number (PN) as a technique to encrypt
data packets that are transmitted. 802.11b WAP supports both 64-key and
I have been using a wireless network node in my home LAN for over two
years. I have a Lucent/OriNOCO wireless PC Card NIC mounted in one of the
PCMCIA slots of my Toshiba laptop. It is 802.11b 11 Mbit/s compatible and
works through an OriNOCO 2000 Access Point. The Access point connects into
the ethernet wired network through a 10/100 100baseT HUB. As noted above,
this node performs all network functions without problems. I have file
and printer service at the 11 Mbit/s speed any time I am near the Access
point. The speed falls off when I move the laptop downstairs and to the
back of the house. The Access Point NIC has an antenna installed. The antenna
connects to the PC Card NIC via a three (3) foot cable, giving me the flexibility
to move the antenna for best reception. Downstairs and at the back of the
house, I get 2 Mbit/s throughput speeds. This might be better if I had
an antenna on the laptop NIC.
I have network access controlled by my NT 4.0 server. To access my
network, the NT authentication and privacy codes must be known by outside
wireless users. I do not have the privacy encryption mode turned on at
this time, as the throughput speed is lower when the WAP encryption is
I am well satisfied with the long term performance of the OriNOCO components.
I plan on installing a Multitech wireless router in the near future to
test this unit against the current equipment. Wireless networks take away
some of the installation problems of routing wiring and fixing the locations
of computers. The components are available from multiple vendors and has
become a shelf item in cost. The IEEE 802.11b standard has proven to be
good and works. I am looking forward to the IEEE 802.11a standard of 54