Wireless Network

Wireless network Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecommunications network whose interconnections between nodes is implemented without the use of wires.[1] Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses electromagnetic waves, such as radio waves, for the carrier and this implementation usually takes place at the physical level or "layer" of the network.[2] Contents [hide] •

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1 Types o 1.1 Wireless LAN o 1.2 Wireless MAN o 1.3 Mobile devices networks 2 Uses 3 Environmental concerns and health hazard 4 See also 5 References

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6 External links

[edit] Types [edit] Wireless LAN Wireless Local Area Network (WLAN) is similar to other wireless devices and uses radio instead of wires to transmit data back and forth between computers on the same network. Wireless LANs are standardized under the IEEE 802.11 series.

Screenshots of Wi-Fi Network connections in Microsoft Windows. Figure 1, left, shows that not all networks are encrypted (locked unless you have the code, or key), which means anyone in range can access them. Figures 2 and 3, middle and right, however, show that many networks are encrypted. •

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Wi-Fi: Wi-Fi is a commonly used wireless network in computer systems to enable connection to the internet or other machines that have Wi-Fi functionalities. Wi-Fi networks broadcast radio waves that can be picked up by Wi-Fi receivers attached to different computers or mobile phones. Fixed Wireless Data: Fixed wireless data is a type of wireless data network that can be used to connect two or more buildings together to extend or share the network bandwidth without physically wiring the buildings together.

[edit] Wireless MAN

Wireless Metropolitan area networks are a type of wireless network that connects several Wireless LANs. •

WiMAX is the term used to refer to wireless MANs and is covered in IEEE 802.16d/802.16e.

[edit] Mobile devices networks •

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Global System for Mobile Communications (GSM): The GSM network is divided into three major systems which are: the switching system, the base station system, and the operation and support system (Global System for Mobile Communication (GSM)). The cell phone connects to the base system station which then connects to the operation and support station; it then connects to the switching station where the call is transferred to where it needs to go (Global System for Mobile Communication (GSM)). This is used for cellular phones, is the most common standard and is used for a majority of cellular providers.[3] Personal Communications Service (PCS): PCS is a radio band that can be used by mobile phones in North America. Sprint happened to be the first service to set up a PCS. D-AMPS: D-AMPS, which stands for Digital Advanced Mobile Phone Service, is an upgraded version of AMPS but it is being phased out due to advancement in technology. The newer GSM networks are replacing the older system.

[edit] Uses

An embedded RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI WiFi card widely used by wireless Internet service providers (WISPs) in the Czech Republic. Wireless networks have had a significant impact on the world as far back as World War II. Through the use of wireless networks, information could be sent overseas or behind enemy lines easily, efficiently and more reliably. Since then, wireless networks have continued to develop and their uses have grown significantly. Cellular phones are part of huge wireless network systems. People use these phones daily to communicate with one another. Sending information overseas is possible through wireless network systems using satellites and other signals to communicate across the world. Emergency services such as the police department utilize wireless networks to communicate important information quickly. People and businesses use wireless networks to send and share data quickly whether it be in a small office building or across the world.[4] Another important use for wireless networks is as an inexpensive and rapid way to be connected to the Internet in countries and regions where the telecom

infrastructure is poor or there is a lack of resources, as in most developing countries. Compatibility issues also arise when dealing with wireless networks. Different components not made by the same company may not work together, or might require extra work to fix these issues. Wireless networks are typically slower than those that are directly connected through an Ethernet cable. A wireless network is more vulnerable, because anyone can try to break into a network broadcasting a signal. Many networks offer WEP - Wired Equivalent Privacy - security systems which have been found to be vulnerable to intrusion. Though WEP does block some intruders, the security problems have caused some businesses to stick with wired networks until security can be improved. Another type of security for wireless networks is WPA - Wi-Fi Protected Access. WPA provides more security to wireless networks than a WEP security set up. The use of firewalls will help with security breaches which can help to fix security problems in some wireless networks that are more vulnerable. [edit] Environmental concerns and health hazard In recent times, there have been increased concerns and research linking usage of wireless communications with poor concentration, memory loss, nausea, premature senility and even cancer.[5] Questions of safety have been raised, citing that long term exposure to electromagnetic radiation of the sort emitted by wireless networks may someday prove to be dangerous.[6]

History of wireless mesh networking From Wikipedia, the free encyclopedia Jump to: navigation, search This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. (July 2008)

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Fig 1:Self-Healing Mesh

Fig 2:Three generations of Mesh

Fig 3: Single Radio Mesh Cycle

Fig 4:Third Generation Cycle The core advantage of wireless mesh networks is their inherent ability to form a network on power up. Watch what happens in Fig 1, when the mesh nodes power up (green LED on box turns on). The nodes hear each other's broadcast and a network is self-formed. Also watch what happens when a node fails and how the nodes re-discover an alternate routing path. Network connectivity is thus preserved automatically. Over the years, wireless mesh networking has seen three unique deployments based on radio technology, each incorporating iterative improvements allowing for greater scalability and higher network performance - both throughput and latency. This early stage of technological development or innovation in wireless mesh is pre IEEE standard and is known a first Generation of Wireless Mesh. The following deployments are briefly described of various configuration of first generation Wireless Mesh Networking: 1.First Configuration: 1-Radio Mesh. As shown in Fig 2, this configuration uses one radio channel both to service clients and to provide the mesh backhaul. The single mesh radio, provides both services - client access and backhaul. Comparative performance analysis indicates this architecture provides the worst services of all the options , as expected- both backhaul and service compete for bandwidth. Also all single radio mesh architectures suffer from the send-receive-wait cycle shown in Fig 3. Since there is only radio, the mesh node has to listen, then send, then listen again. This intermittent stop-and-go behavior

adversely affects network performance especially if the destination is far away and the traffic has to be re-transmitted ("hop") across many intermediate nodes first. 2. Second Configuration: Dual-Radio with a 1-Radio backhaul mesh. This configuration can also be referred to as a "1+1" network, since each node contains two radios, one to provide service to the clients, and one to create the mesh network for backhaul. The "1+1" appellation indicates that these radios are separate from each other - the radio providing service does not participate in the backhaul, and the radio participating in the backhaul does not provide service to the clients. These two radios can operate in different bands. For example, a 2.4 GHz 802.11 b/g radio can be used for service and an 802.11a (5 GHz) radio can be used exclusively for backhaul. Most mesh products available today fall into this category. Separating the service from the backhaul improves performance when compared with conventional ad hoc mesh networks. But since a single radio mesh is still servicing the backhaul, packets traveling toward the Internet share bandwidth at each hop along the backhaul path with other interfering mesh backhaul nodes - all-operating on the same channel. This leads to throughput degradations as shown in Fig 3, which are not as severe as for the single radio mesh, but which are sizeable nevertheless. Second generation mesh products are best employed in 1 or 2 hop configurations. 3. Third Configuration: 2 radio backhauls. The last architecture shown (far right in Fig 2) is one that provides separate backhaul and service functionality and dynamically manages channels of all of the radios so that all radios are on non-interfering channels. Performance analysis indicates that this provides the best performance of any of the methods considered here. Note that the two backhaul radios for the 3-radio configuration shown in Fig 2 right are of the same type - not to be confused with 1+1 so-called dual radio meshes where one radio is typically of type 802.11 A (backhaul) and the other of type 802.11 B/G (service). In the 3-radio configuration, 2 radios provide up link and down link backhaul functionality, and the other radio provides service to clients. Fig 4 shows how the two radios of the backhaul transmit traffic, with both radios operating independently and on separate channels