Editing Wireless network (section)

== Properties ==

=== General ===
In a general sense, wireless networks offer a vast variety of uses by both business and home users.<ref name="dean">{{cite book |author= Dean Tamara |title= Network+ Guide to Networks |year=2010 |publisher=Cengage Learning |location=Boston |edition= 5th |isbn= 978-1-4239-0245-4 }}</ref>
<blockquote>"Now, the industry accepts a handful of different wireless technologies. Each wireless technology is defined by a standard that describes unique functions at both the Physical and the Data Link layers of the [[OSI model]]. These standards differ in their specified signaling methods, geographic ranges, and frequency usages, among other things. Such differences can make certain technologies better suited to home networks and others better suited to network larger organizations."<ref name="dean" /></blockquote>

=== Performance ===
Each standard varies in geographical range, thus making one standard more ideal than the next depending on what it is one is trying to accomplish with a wireless network.<ref name="dean" />
The performance of wireless networks satisfies a variety of applications such as voice and video. The use of this technology also gives room for expansions, such as from [[2G]] to [[3G]] and, [[4G]] and [[5G]] technologies, which stand for the fourth and fifth generation of cell phone mobile communications standards. As wireless networking has become commonplace, sophistication increases through configuration of network hardware and software, and greater capacity to send and receive larger amounts of data, faster, is achieved. Now the wireless network has been running on LTE, which is a 4G mobile communication standard. Users of an LTE network should have data speeds that are 10x faster than a 3G network.<ref name="daddy">{{cite web |title= Wireless LAN Technologies |work= Source Daddy website |url=http://sourcedaddy.com/networking/wireless-lan-applications.html |access-date= 29 August 2011 }}</ref>

=== Space ===
Space is another characteristic of wireless networking. Wireless networks offer many advantages when it comes to difficult-to-wire areas trying to communicate such as across a street or river, a warehouse on the other side of the premises or buildings that are physically separated but operate as one.<ref name="daddy" /> Wireless networks allow for users to designate a certain space which the network will be able to communicate with other devices through that network.

Space is also created in homes as a result of eliminating clutters of wiring.<ref name="center">{{cite web |title= WLAN Benefits |work= Wireless Center commercial web site |url= http://www.wireless-center.net/Cisco-Wireless-Networking/726.html |access-date= 29 August 2011 |archive-date= 2 September 2011 |archive-url= https://web.archive.org/web/20110902135346/http://www.wireless-center.net/Cisco-Wireless-Networking/726.html |url-status= dead }}</ref> This technology allows for an alternative to installing physical network mediums such as [[Twisted pair|TPs]], [[Coaxial cable|coaxes]], or [[fiber-optics]], which can also be expensive.

=== Home ===
For homeowners, wireless technology is an effective option compared to [[Ethernet]] for sharing printers, scanners, and high-speed Internet connections. WLANs help save the cost of installation of cable mediums, save time from physical installation, and also creates mobility for devices connected to the network.<ref name="center" />
Wireless networks are simple and require as few as one single [[wireless access point]] connected directly to the Internet via a [[Router (computing)|router]].<ref name="dean" />

=== Wireless network elements ===
The telecommunications network at the physical layer also consists of many interconnected wireline [[network element]]s (NEs). These NEs can be stand-alone systems or products that are either supplied by a single manufacturer or are assembled by the service provider (user) or system integrator with parts from several different manufacturers.

Wireless NEs are the products and devices used by a wireless carrier to provide support for the [[Backhaul (telecommunications)|backhaul]] network as well as a [[mobile switching center]] (MSC).

Reliable wireless service depends on the network elements at the physical layer to be protected against all operational environments and applications (see GR-3171, ''Generic Requirements for Network Elements Used in Wireless Networks – Physical Layer Criteria'').<ref name="wireless">{{cite web|url=https://telecom-info.njdepot.ericsson.net/site-cgi/ido/docs.cgi?ID=SEARCH&DOCUMENT=GR-3171&|title=Generic Requirements for Network Elements Used in Wireless Networks – Physical Layer Criteria|website=Ericsson}}</ref>

What are especially important are the NEs that are located on the cell tower to the [[base station]] (BS) cabinet. The attachment hardware and the positioning of the antenna and associated closures and cables are required to have adequate strength, robustness, corrosion resistance, and resistance against wind, storms, icing, and other weather conditions. Requirements for individual components, such as hardware, cables, connectors, and closures, shall take into consideration the structure to which they are attached.

=== Difficulties ===

==== Interference ====
Compared to wired systems, wireless networks are frequently subject to [[electromagnetic interference]]. This can be caused by other networks or other types of equipment that generate radio waves that are within, or close, to the radio bands used for communication. Interference can degrade the signal or cause the system to fail.<ref name="Zander" />

==== Absorption and reflection ====
Some materials cause [[Absorption (electromagnetic radiation)|absorption]] of electromagnetic waves, preventing it from reaching the receiver, in other cases, particularly with metallic or conductive materials reflection occurs. This can cause dead zones where no reception is available. Aluminium foiled thermal isolation in modern homes can easily reduce indoor mobile signals by 10&nbsp;dB frequently leading to complaints about the bad reception of long-distance rural cell signals.

==== Multipath fading ====
In [[multipath fading]] two or more different routes taken by the signal, due to reflections, can cause the signal to cancel out each other at certain locations, and to be stronger in other places ([[upfade]]).

==== Hidden node problem ====
[[Image:Wifi hidden station problem.svg|right|thumb|200px|In a hidden node problem Station A can communicate with Station B. Station C can also communicate with Station B. However, Stations A and C cannot communicate with each other, but their signals can interfere at B.]]
The [[hidden node problem]] occurs in some types of network when a [[Node (networking)|node]] is visible from a [[wireless access point]] (AP), but not from other nodes communicating with that AP. This leads to difficulties in [[medium access control]] (collisions).

==== Exposed terminal node problem ====
[[Image:Exposed terminal problem.svg|thumb|left|200px]]
The [[exposed terminal problem]] is when a node on one network is unable to send because of [[co-channel interference]] from a node that is on a different network.

==== Shared resource problem ====
The wireless spectrum is a limited resource and shared by all nodes in the range of its transmitters. [[Bandwidth allocation]] becomes complex with multiple participating users. Often users are not aware that advertised numbers (e.g., for [[IEEE 802.11]] equipment or [[LTE (telecommunication)|LTE]] networks) are not their capacity, but shared with all other users and thus the individual user rate is far lower. With increasing demand, the [[Bandwidth allocation#Data crunch|capacity crunch]] is more and more likely to happen. [[User-in-the-loop]] (UIL) may be an alternative solution to ever upgrading to newer technologies for [[over-provisioning]].

=== Capacity ===

==== Channel ====
{{Main article|Channel capacity#Channel capacity in wireless communications|l1=Channel capacity in wireless communications}}
[[File:MIMO SIMO MISO SISO explanation without confusion.svg|thumb|upright=0.9|Understanding of SISO, SIMO, MISO and [[MIMO]]. Using multiple antennas and transmitting in different frequency channels can reduce fading, and can greatly increase the system capacity.]]

[[Shannon's theorem]] can describe the maximum data rate of any single wireless link, which relates to the bandwidth in hertz and to the noise on the channel.

One can greatly increase channel capacity by using [[MIMO]] techniques, where multiple aerials or multiple frequencies can exploit multiple paths to the receiver to achieve much higher throughput – by a factor of the product of the frequency and aerial diversity at each end.

Under Linux, the Central Regulatory Domain Agent (CRDA) controls the setting of channels.<ref>{{cite conference
| url = https://books.google.com/books?id=yLOWkHIhr6UC
| title = Towards Maximising Wireless Testbed Utilization Using Spectrum Slicing
| author = Anadiotis, Angelos-Christos| year = 2010
| conference = 6th International ICST Conference, TridentCom 2010, Berlin, Germany, May 18–20, 2010
|editor1=Thomas Magedanz |editor2=Athanasius Gavras |editor3=Huu Thanh Nguyen |editor4=Jeffrey S. Chase | volume = 46
| book-title = Testbeds and Research Infrastructures, Development of Networks and Communities: 6th International ICST Conference, TridentCom 2010, Berlin, Germany, May 18–20, 2010, Revised Selected Papers
| publisher = Springer Science & Business Media
| access-date = 2015-07-19
| quote = […] Central Regulatory Domain Agent (CRDA) […] controls the channels to be set on the system, based on the regulations of each country.
| page = 302
| isbn = 9783642178504
|display-authors=etal}}</ref>

==== Network ====
The total network bandwidth depends on how dispersive the medium is (more dispersive medium generally has better total bandwidth because it minimises interference), how many frequencies are available, how noisy those frequencies are, how many aerials are used and whether a directional antenna is in use, whether nodes employ power control and so on.

Cellular wireless networks generally have good capacity, due to their use of directional aerials, and their ability to reuse radio channels in non-adjacent cells. Additionally, cells can be made very small using low power transmitters this is used in cities to give network capacity that scales linearly with population density.<ref name="Zander" />