How to increase the RF footprint and bandwidth of a wireless network

How to increase the RF footprint and bandwidth of a wireless network

How to increase the RF footprint and bandwidth of a wireless network

Date: Nov 12, 2008

An acceptable business class wireless network requires aggressive management of an organization's radio frequency (RF) footprint and bandwidth. The employees in your office -- wherever they're located in the building -- will need to have network services readily available to them.

After revealing the two most important qualities of an enterprise network service, Joel Snyder of Opus One reviews how to provide sufficient bandwith for users' needs.


Read the full text transcript from this video below. Please note the full transcript is for reference only and may include limited inaccuracies. To suggest a transcript correction, contact editor@searchsecurity.com.     

How to increase the RF footprint and bandwidth of a wireless network

Joel Snyder: Another issue of security in wireless networks is management of
the RF footprint and the RF bandwidth. This you have to be very aggressive on
to provide an acceptable business class service. Now I’m defining availability
and usability as part of building a secure wireless network, in order for a
network to be a business class secure network it has to have sufficient
bandwidth for the user's needs. What that means is that the user has to be
able to connect from wherever they want to connect and have all the
bandwidth that they need. That does not mean that you walk around the
building with your laptop, associate with the SSID and try to ping and say,
'Yes, I can ping, so I guess everything is OK.' True bandwidth means true
bandwidth, all the way out of the edges. In addition, the network has to be
where the users are and where the users want to use it. That does not mean,
again, that you walk around with your laptop and you say, "Yes, I see the
SSID. I guess this is OK,' it means that you can actually connect up and
get that bandwidth. When you build a good wireless service, that makes it a
good secure wireless service, it is secure from the point of view of the
enterprise not from the techy geek that might be thinking only about WPA2.
It has to be up, because wireless will become critical in most enterprises.
If you have not come to that realization yet, you will over the short term,
trust me. Opinions about wireless will change like that, as soon as people
really see good business cases for it and they are changing as quickly as
these presentations are going through.

This requires you to have a new paradigm, which is looking at the RF and
looking at the bandwidth. This can be difficult because most of us are not
electrical or RF engineers, we might have a little bit of engineering
background, we might be from CS, might have a business degree, or maybe
none of that. In any case, very few people in the IT business are true RF
engineers, which means you are going to have to learn about RF. Things that
you have to understand are that it is very difficult to predict how a
wireless network is going to change over time. You cannot just set it up
and say, 'OK. I am done. I am never going to look at it again,' because
people, enormous bags of water that really affect the RF, are moving around
your system, your building, you got file cabinets and other surfaces that
are going to start bouncing stuff around. You have interference with other
sources, that microwave in the break room, they change out the microwave,
now you suddenly might have a wireless problem every time someone heats up
a cup of coffee. You have to be efficient in your use of limited bandwidth
and you have to be careful about thinking about wireless. It is very easy
to plug in an access point but it is very difficult to build an enterprise
class wireless network.

I got a simple story about a team that had to do a data center move. They
worked for six months, 40 hours a week working hard, hard, hard all the
time, maybe 60 hours a week, whatever it was. After 6 months they shut the
machines down on Friday at 5:00, on Saturday at 8:00 a.m. the machines were
back up, and on Monday morning, no one said anything. Same team, a week
later went down to Best Buy and bought a $10.00 access blunt plugged it in,
in the break room, and all of a sudden people are walking up to the IT
people saying, 'Thank you for wireless. We love you. You did a great job.'
Plugging in an access point does not necessarily mean that you are going to
have a secure wireless network, but on the other hand, giving people
wireless will make them love you a lot more then moving their data center
without any interruptions.

Let us talk about total bandwidth. I do not know how many of you that are
watching this are old timers, as you can see, I have a certain amount of
grey myself, but wireless is like the bad old days of 10 megabit hubs. We
have shared bandwidth, we have the potential for meltdowns, and we have a
half duplex communications channel. If you take a look this picture here,
you see I got a couple of laptops hanging around an access point, and that
is OK. As I add more users, now I am worried about this half duplex thing,
each one can only send or receive. There can only be one person talking at
a time; you do not get full duplex like you have for the switch channel,
things that we are so used to doing. Your total throughput is going to be
in the 20 to 40 megabit range if you got 80211g or a, that is assuming that
everything works great. If adding users to the network is important, you
are going to find that everyone gets less bandwidth because we are sharing
this channel.

Take a look at this case here. I got some user at the very bottom of the
screen, he, or she, is connected up to this access point from a far
distance. What does that mean? That is going to mean that their packets are
going to be transmitting at 1 or 2 megabits per second. A packet that is
transmitted at 11 megabits a second is so long, a packet that is
transmitted at 2 megabytes a second is 5 times as long, which means that
this user is talking very slowly. When they are talking, no one else can
talk, which means that that user is the equivalent to adding 5 users to the
inside of the network. You have to worry about how far away people are and
when they are using their wireless, someone on the edge can hog the whole
network and basically make life bad for everyone and that someone could be
some device that is a wireless device on a person's desk that is just
pinging every once in awhile or doing some email downloads, like a cell
phone or something like that.

I drew this picture using 80211b, because I only have so much of my life's
time devoted to doing PowerPoint and with G, I would have another 8
circles. I just drew 4 circles, but the picture is exactly the same for
80211g, it is the same for 80211a. The picture says that at the point that
is closest to the access point you get the best bandwidth as you
throughput, as you get further away, you connect up at slower and slower
speeds. What does this mean? Take a look at this picture here; this is what
I call the naive layout. This is someone who says, 'I can connect up and
ping everywhere within all of the boundaries of the blue, purple, green,
and light blue circles, everywhere that you see here. We got no coverage
holes, everyone can get on the wireless network.' This is what we get in
hotels, really, really bad coverage mask. The problem is that everyone who
is outside of those core areas, everyone that is in the red, is in this
ghetto poor neighborhood of bad throughput, they are not getting a good
signal. What does that mean? That means that if I overlay a standard
building floor plan on top of this picture, you will see, I am trying to
point somehow, but I cannot really do that, you will see that most of the
offices in this picture, if you start looking at it yourself, are in the
red. They are not in these wonderful core areas where we are giving them
good throughput; they are in the bad parts of the wireless network which
means they are not getting good service. They are second class citizens in
your wireless network.

You want to build a secure network where secure means available. Take a
look at this, this picture here shows you 4 radios laid out on this
network, 4 is not good enough because most people are going to be in that
red area. Instead, you would actually need to lay out a minimum of 12
radios just to get the good coverage to cover that rectangle that I have
shown you as part of the building plan. In addition to the 12, you are
going to have to spare radios, as well. Just a simple wireless survey that
says, 'Yes, I can see the SSID and associate.' If you are not getting it at
high speeds, you are not giving people a business class network; therefore,
the network is not a secure network. You can also go to 80211a. 80211a is
great technology, you get more channels, which is nice, so you can pack
things a little tighter, but it is actually less resilient then a BNG
because the higher frequency falls off more quickly with distance. 80211a
is nice because not everyone has a so you can run both radios at the same
time to get even more throughput, but you have to be careful to engineer
for 80211a's tighter distance limitations compared to 80211b/g on the 2.4
range.

This graph is another one that I would like focus on for just a couple of
seconds. Turning up the power on your access points does not help, in fact,
it actually hurts. In this graph, you can see there is a peak where the
power is at a mid-level, and we actually get the best signal strength or
best throughput. Why does this peak occur at the middle and not at the
edge? The reason is that with wireless, we want to have just enough power
to get from the access point to the user and no more. If I am shouting and
I got lots and lots of power, what happens is the user sees the signal, in
addition, it bounces off the wall and it goes out the window and it bounces
off another building, and it bounces off in the other direction because it
is on the directional. All of a sudden the user is seeing multiple copies
of the same information, but of course, offset in time because of that
whole speed of light thing that we have not been able to do anything about,
this is called multipath interference. Suddenly, the user is getting a poor
signal, because they are seeing too many copies, because you have too much
power. You actually want to get the power turned down so that it is just
enough to reach the user and not anymore, and that is actually where you
are going to get the best throughput.

More on Wireless LAN Design and Setup

There are Comments. Add yours.

 
TIP: Want to include a code block in your comment? Use <pre> or <code> tags around the desired text. Ex: <code>insert code</code>

REGISTER or login:

Forgot Password?
By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy
Sort by: OldestNewest

Forgot Password?

No problem! Submit your e-mail address below. We'll send you an email containing your password.

Your password has been sent to: