Introduction to Wireless Networks - Chipps

Introduction to Wireless Networks - Chipps

Introduction to Wireless Networks Last Update 2013.01.07 1.3.0 Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 1 Purpose of a Network What is a data network for A network is used to share things

If there is nothing to share, there is no need for a network Wireless networks are used to share the same things that wired networks do, such as Applications Printers Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 2 Network Types

For our purposes the types of networks are by geographic size When classified by the size there are four types of networks LAN Local Area Network CAN Campus Area Network MAN Metropolitan Area Network WAN Wide Area Network Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 3

LAN The LAN covers a small area This is usually just a single building or a few floors in a single building The LAN contains devices such as workstations, servers, and printers It is used to share these things among the users of the LAN Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 4

LAN This is the Environmental Education, Science, and Technology Building as shown in the virtual tour of the campus A single LAN could cover this entire building Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 5 CAN A CAN typically connects LANs that are

located in separate buildings that are near to each other By near I mean you can walk to each building and back without much trouble A CAN may also connect LANs on several floors in a tall building Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 6 CAN

This distance is 1.3 kilometers or .8 miles This distance is 1.8 kilometers or 1.1 miles Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 7

MAN In a MAN size network you cannot easily walk there But you can drive there and back in a short while If we blowup the top corner of the map, we can see that UNT has a research facility 7.5 km or 4.5 miles from the main campus Now this is too far to walk, but you could drive there and back without any trouble Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com

8 MAN Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 9 WAN A WAN covers a very large area or connects sites together that are far apart You could drive there, but it would be hard

to do so and return in the same day For example, as a news release from the University of North Texas says Dr. Timothy Montler, has been working for over two decades to preserve the languages of Pacific Northwest Native American tribes Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 10 WAN Washington

This distance is 2500 kilometers 1500 miles Texas Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 11 Network Types

The point to this discussion of network types is that different frequencies and techniques are used depending on the size of the network Besides the distances used to define the different types of networks the terrain makes a difference Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 12

Network Types For example the UNT campus map does not show that the middle of the campus when going east to west is on quite a rise You cannot see the stadium on the west side from the buildings on the east side Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 13 Network Types

Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 14 Network Types The map also does not show that the campus is covered in trees None of these definitions are set in stone They are just offered as guidelines to use when judging the size of a network

Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 15 Network Types Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 16 What About a Wireless Network

Wireless networks can be used in any of these four types of networks One note here, many wireless networks that are used to connect end users to a central site as in a last mile solution are called wide area networks by some This is not the case Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 17

What About a Wireless Network Any network of that type is clearly a CAN or a MAN The only case where a wireless network is truly used as part of a WAN, are the long range point-to-point microwave connections used to span long distances Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 18

Nature of Wireless Networks It must be kept in mind that wireless networks are fundamentally different from those that use wires Wireless signals are unbounded and dynamic A wireless signals environment is quite similar to a microclimate as used when discussing the weather Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 19

Nature of Wireless Networks In fact, the weather and wireless networks are very similar They both suffer from the same problem For the weather we know about the behavior of large weather systems and climate in general We can then predict that in the summer the weather will be hot Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com

20 Nature of Wireless Networks During the monsoon, it will rain often What we do not know is exactly where it will rain and exactly how much Even if rain can be predicted for an area, will it rain on my house This is the microclimate problem There are simply too many variables, engaging in too many interactions Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com

21 Nature of Wireless Networks Lets look at an example of this problem related to forecasting exactly where it will rain The forecast was for a 100 percent chance of rain for the DFW area But where exactly did it actually rain and how much at each location Copyright 2005-2013 Kenneth M. Chipps Ph.D.

www.chipps.com 22 Nature of Wireless Networks Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 23 Nature of Wireless Networks As the map shows it poured in some

places and did not rain at all in others We have the same problem with radio frequency networks as we have with the weather network Much is known, in general, about how radio frequency signals traverse the environment Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 24 Nature of Wireless Networks

But we cannot accurately predict what they will do or not do from a base station antenna to an end users location The usual way of handling this problem for both the weather and radio frequency networks is a fudge factor or fade margin Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 25 Capacity of Wireless Networks

In addition to the variability of wireless signals just discussed there is also the issue of the load a wireless network can handle For example Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 26 Capacity of Wireless Networks

Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 27 Capacity of Wireless Networks What happened The introduction of the device was marred by a glitch with Mr. Jobs initially having difficulty getting web pages to load and causing the largely enthusiastic crowd to go silent "I'm afraid we have a problem and I'm not going to be able to show you much today," said Mr. Jobs, who

tried switching devices and also asked the audience to disconnect from the Wi-Fi network, before managing to connect Copyright 2005-2013 Kenneth M. Chipps Ph.D. www.chipps.com 28 Capacity of Wireless Networks In the unlicensed environment wireless cannot replace wired Copyright 2005-2013 Kenneth M. Chipps Ph.D.

www.chipps.com 29

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