Wireless Networks

1. Wireless Networks http://www.youtube.com/watch?v=B7yayA6mJe8 John Vogt 11/14/12

2. Overview • Wireless networks are used almost everywhere: At home, in industry, for entertainment…. • Anywhere there is communication required, WLAN’s are used • We will discuss how wireless networks work: Routers Mesh and Ad Hoc • Supporting Technology and Limitations • Standards

3. A Few Facts • Bandwidth- net bit rate or channel capacity (8 lane freeway vs 2 lane) • Speeds range from a few bps to 2.5 Tbps (Researchers at USC have achieved this at a distance of 1 meter) A new 802.11 standard will allow 7 Gbps in 2014. • Distance of a wireless connection depends on the hardware. Using satellites, connections over 100 miles from source to node have been made. A common household router can range from 20 to 300 ft depending on bandwidth and physical obstructions. • The different frequencies (Bandwidth) that a device operates at can determine range and quality.

4. Different kinds of Wireless • A TV remote controller sends control command information to your TV, commanding it to go to the sports channel, or turn the sound up. • A wireless network-connected laptop computer sends and receives packets of complex data, allowing it to talk to other computers on the network. • A cellular phone system routes packets of telecommunications information simultaneously on many channels in vast quantities. • Information can travel in both directions. Without cables, the information still needs something to carry it: Radio waves, Microwaves, Infra-red Light, Lasers (Electromagnetic Energy) • A wireless network consists of multiple stations communicating with radios that broadcast with a certain bandwidth.

5. Routers • Routers receive data from the internet through a wired connection • The router then translates the data into a radio signal that is sent to the wireless card on a device (or a wireless USB adapter). • Long wavelengths of radio waves allow data to be transferred longer distances and through barriers.

6. Cellular Networks • Use microwave to transmit data. Microwaves are more easily focused into narrow beams than radio waves while still having high frequency which allows a broad bandwidth • Each cell tower covers a region and is assigned multiple frequencies that correspond to radio stations. Similar to how walkie-talkies work. • Towers can use the same radio stations if there is at least a one tower gap in between the reuse of frequencies. • Example: Calculating Reuse Distance • R = Cell Radius • N = Number of cells per cluster

7. http://www.youtube.com/watch?v=VROSqrP2L9w

8. Class Application Chemical facility in Texas needed to test for pipe corrosion in an extrmemly hazardous area. Before sensors were hooked to a network, sections of the plant had to be shut down to allow operators access to take readings. Cost of a wired solutions limited corrosion monitoring locations. With a wireless solution, data can be checked anytime in more locations. • Now, if one AP goes down at a crucial time, how do you continue to transfer data so that the plant does not have to be immediately shut down?

9. Mesh and Ad Hoc Network • A mesh network is where each node must not only receive and send its own data, but also serve as a relay for other nodes. • “Floods” every part of the network with data. This is how a program would solve a maze. • A mesh network can be self healing because there is usually more than one path between a source and a destination. • Ad Hoc doesn’t rely on a preexisting infrastructure. Each node can be mobile and still forward data. • Used in military and government to pass along emergency notifications.

10. Cloud Computing • Instead of having necessary hardware, software and personnel on sight to upgrade a system, companies rent the goods and services they need. Data centers provide services when needed. • Saves time!

11. Technical Paper:Network awareness and dynamic routing: The ad hoc network casehttp://www.sciencedirect.com.erl.lib.byu.edu/science/article/pii/S1389128611001034 • Networks have to be aware of the constantly changing topologies in a mobile ad hoc network. • Problems arise because you have to anticipate every situation in which a device might connect • Dynamic systems must be used that can adapt and change on their own to achieve the best connectivity. Constant restructuring. • Nodes talk to each other and if one access point goes down, the others reconfigure themselves to pick up the slack. With this system there’s no single point of failure. Forms a system that doesn’t need controllers.

12. Cost • Routers: $20 ~ $500 • Price of a school network with 500 users with 2 devices each Budget of $13000: Wireless- Accommodates 750 devices Wired- 13 users on the network at a time • AT&T is currently spending $14 Billion to upgrade and expand their 4G LTE coverage across the nation over the next two years.

13. Vendors Vecima Networks WiNetworksWiMAX Trango Broadband Wireless DigitalPathTechnology Aperto Networks Sputnik Wi-Fi Hotspots Value Point Mesh Routers and Gateways Airpath

14. Supporting Technology and Limitations • When using routers, all communication must pass through the router. Can congest bandwidth. • Ad Hoc networks are generally not as fast as a network with a common access point. • Hardware determines your bandwidth and transmission speeds (Routers, Wireless Cards) • Software used can limit applications • COST! Not every network can be mesh or Ad Hoc and not every network needs to operate at large frequencies. • There can be interference from similar radio frequencies (Bigger bandwidth minimizes interference) • Sometimes there is a choice between range or quality (Depending on frequency of the receiver)

15. Standards Most wireless networks are based on the IEEE 802.11standards. 802.11b – 11 Mbps 802.11a and g – 54Mbps 802.11n – 300 Mbps http://www.merunetworks.com/products/80211ac/index.html (45)

16. PanOulu A city in Finland uses a mesh network to provide wireless internet connection for the entire city. Nodes throughout the city communicate with each other are able to fix the network if any connection fails. The city utilizes the wireless connections in their traffic cameras, parking meters and public transportation systems. Allows the public to know exactly when a bus will arrive at its destination!!

17. References • http://www.youtube.com/watch?v=0GW4NecZJrg • http://www.wireless-technology-advisor.com/how-does-wireless-technology-work.html • http://en.wikipedia.org/wiki/Cellular_network • http://news.cnet.com/8301-1035_3-57546244-94/at-t-will-spend-$14b-to-pump-up-wireless-wireline-networks/ • http://en.wikipedia.org/wiki/Mesh_network • http://www.youtube.com/watch?v=uYGQcmZUTaw&NR=1&feature=endscreen • http://en.wikipedia.org/wiki/Mesh_network • http://freewimaxinfo.com/wireless-networks-limitations.html • http://en.wikipedia.org/wiki/IEEE_802.11 • http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/network-wireless.html • http://resources.metapress.com/pdf-preview.axd?code=n154p165n1172h76&size=largest • http://www.sciencedirect.com.erl.lib.byu.edu/science/article/pii/S1389128611001034