Cell phone (telefone celular) is a wireless, portable, long-range, electronic telephone, which during travel can seamlessly change antenna connections, from one radio reception cell to another radio reception cell, without dropping or losing the ongoing call.
Besides the standard voice function of a telephone, latest cell phones (telefone celular) have features such as SMS for text messages, MMS for multimedia messages, radio, games, internet connectivity for email, browsing, blogging, music (MP3) playback, memo recording, built-in cameras and camcorders, ringtones, personal organizers, Push-to-Talk (PTT), Bluetooth and infrared connectivity, call registers, streaming video, downloading video, video call, and also serve as wireless modems for PCs that can be connected to the Internet.
The power in a cell phone (telefone celular) is obtained from rechargeable batteries, which can be recharged from the mains, a USB port or a cigarette lighter port in an automobile. Nickel Metal Hydride were the most common types of batteries, which due to the “memory effect” (the user can recharge only when the entire battery is drained off) were replaced by Lithium-Ion batteries, which did not suffer from any memory effect.
Cell phones (telefone celular) came into existence because of the invention of hexagonal cells in 1947, for the base stations by Bell Labs engineers at AT&T. This was further developed during the 1960s by Bell Labs. During a call, the channel frequency could not be changed automatically from one cell (base station coverage area) to another cell (base station coverage area) as the person traveled from the area of one cell to the area of another cell. Amos Joel of Bell Labs invented a breakthrough invention and called it as the `call handoff` by which the channel frequency could be changed automatically from one cell to another cell, during the same call, as the mobile user traveled from one cell to another cell. Due to their heavy construction, these phones were used mainly in automobiles.
The first practical cell phone in a non-vehicle setting, and which could be handheld, was invented by Martin Cooper, the General Manager (Communications Division) of Motorola, who made the world`s first handheld cell phone (telefone celular) call on April 3, 1973.
The technology by which the cell phone (telefone celular) works depends on the mobile phone operator; however, all of them use electromagnetic radio waves, which are in touch with a cell site (base station). The base station is composed of several antennas which are mounted on a pole, tower, or building. Cell sites are spread at a distance of 5 to 8 miles (approx. 8 to 13 km) from each other. The low power transceiver from the cell phone transmits the voice and data to the nearest cell site. During movement, the cell phone will “handoff” the information to other cell site. Mobile phone operators use many technologies to maintain the smooth stream of digitized data from the cell phone to the cell site and vice versa.
The wireless telephone technologies are grouped under heads known as generations, starting from zero generation or 0G. The current generation going on is 4G; however, there are old cell phones (telefone celular) that still operate on 1G, 2G, and 3G technologies. The wireless telephone technologies used in each generation are as given below:
The impact of cell phone (telefone celular) usage on human health has been of considerable worldwide concern. Research studies in Copenhagen, from the Danish Institute of Cancer Epidemiology, the National Cancer Institute, and the Institute of Cancer Research, do not establish any link between cancer and cell phone usage. However, an intergovernmental agency IARC (International Agency for Research on Cancer) forming part of the World Health Organization of the United Nations, undertook a study of 4,500 users and found a statistically significant link between cell phone usage and tumor frequency. Further research is going on.
Cell phone (telefone celular) usage and driving is a common worldwide phenomenon. Some jurisdictions have banned usage of hand-held phones during driving, but allowed the hands-free fashion of cell phone usage while driving. However, studies have found out that the distraction is caused by the conversation itself; hence, both hand-held and hands-free cell phones contribute towards road traffic accidents. Further studies on cell phone usage and driving are going on.
Nokia Corporation is currently the world`s largest manufacturer of cell phones (telefone celular). Other notable cell phone manufacturers, in alphabetical order, are 3G, Audiovox (now UT Starcom), Benefon, BenQ-Siemens, Fujitsu, High Tech Computer Corporation (HTC), Kyocera, LG Mobile, Motorola, NEC, Panasonic (Matsushita Electric), Pantech Curitel, Philips, Research In Motion, Sagem, Samsung, Sanyo, Sharp, Siemens, Sierra Wireless, SK Teletech, Sony Ericsson, T&A Alcatel, Toshiba, and Verizon.
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WiMAX is designed as a wireless alternative to DSL and cable for last mile broadband access and as way to interconnect Wi-Fi hotspots into a Metropolitan Area Network. Although, the actual uses for WiMAX overlaps those for Wireless Local Area Network up until the mobile Wide Area Network level. Telephone and cable companies are closely probing the potential of WiMAX as a “last mile” connectivity option. This will result to a better-priced service for both home and business customers and not to mention the elimination of the “captive” customer bases for both telephone and cable networks.
In theory, WiMAX can provide connectivity to users within a 31 mile radius even if there is no direct line if sight. However, actual field tests show that the practical limits seem to be just around 3 to 5 miles. According to WiMAX proponents, the technology can provide shared data rates up to 70 Mbit/s. This is enough to connect 60 T1-type connections simultaneously and over a thousand homes running at 1 Mbit/s DSL level connectivity. Practical maximum data rates in actual field tests show can only go between 500 kbit/s to 2 Mbit/s and is quite dependent on the conditions at a given site.
Despite the numbers given, there are a lot of ways to improve the speed and range of a WiMAX connection using pre-existing technology. One interesting option for companies with analog cellular network is to let WiMAX “share” a cell tower since it will not interfere with any of the function of the cellular arrays while utilizing the licensed radio frequencies of the analog cellular network to increase its speed and range. A WiMAX antenna can also be directly connected to an Internet backbone using a fiber optic cable. This is one of the means to increase bandwidth for data-intensive applications running across a wireless network or as a back-haul for cellular phone and Internet traffic from a remote area back to a backbone. WiMAX can effectively improve a wireless infrastructure in a decentralized, inexpensive and deployment-friendly manner.
WiMAX is seen as a very good alternative to expensive urban deployments of T1 back-hauls in developing countries with limited wired infrastructure and cruel geography. The cost to install a WiMAX station as a single hub or using an existing cellular tower will be very small compared to a wired solution. WiMAX’s 31-mile diametrical range also works well with the low population density and the wide flat areas common to developing countries. Some areas have skipped wired structures due to inhibitive costs and WiMAX can easily fill the gap in-between with its low-cost wireless solution.
There is no global license assigned for WiMAX although it has a very wide RF spectrum under the IEEE 802.16 specifications. The primary band used in the US for WiMAX is around 2.5 GHz although majority of the band is already assigned to Sprint Nextel. In other parts of the world, the bands used are usually around 2.3/2.5 GHz, 3.5 GHz and 5 GHz where the 2.3/2.5 GHz is widely used in Asia.
Dr. Rosalyn L. shaw – 832-297-3457 – www.dream2life.biz (click business) THE FASTEST INTERNET ACCESS JUST GOT FASTER – CLEAR WIMAX IS HERE!!! This new technology would provide: •The high speed of broadband service •Wireless rather than wired access, so it would be a lot less expensive than cable or DSL and much easier to extend to suburban and rural areas •Broad coverage like the cell phone network instead of small WiFi hotspots WiMAX has the potential to do to broadband Internet access what cell phones have done to phone access. In the same way that many people have given up their “land lines” in favor of cell phones, WiMAX could replace cable and DSL services, providing universal Internet access just about anywhere you go. ONE MODEM can be used in MANY places. Use it at home, unplug and use it on your job. NO WIRES, CABLES OR SET UP REQUIRED, JUST PLUG AND SURF. FOR LAPTOPS. NOW HAVE INTERNET ACCESS EVERYWHERE. 4G where there is 4G access. If you dont have 4G it will switch to 3G automatically; given you internet access constantly. Get 1 -the HOME modem OR MOBILE USB – 40 dollars/month Get 1 -the HOME modem AND ON THE GO MOBILE USB – 55 dollars/month Get 2 2 ON THE GO MOBILE USBs – 65 dollars/month Get 3 the HOME modem AND the ON THE GO MOBILE AND the VOICE system – 75 dollars/mo.
Service providers offering Carrier Ethernet services face the double-edged need for speed – rapidly increasing data rates (faster) combined with ultra-low transport delay (on-time delivery) – required for financial, business services and wireless backhaul applications. Learn how to attack latency and deliver best-in-class per-flow QoS by using NIDs in place of low-performance access platforms.
Mobile computing refers to the use of small and portable computing devices in wireless enabled networks that provide wireless connections to a central main server. These devices include laptops, notebook PCs, tablet PCs, palmtops, personal digital assistant (PDAs) and other hand held devices. A radio-signaling device is installed inside these devices for receiving and transmitting electronic data.
Wireless networks use Wi-Fi(wireless fidelity) technology for providing network coverage to offices, public places, and other small workplaces. A wireless access point device is used to provide wire free network coverage in the designated area. An access point device that is built on 802.11b and 802.11g IEEE (Institute of Electrical and Electronics Engineers) standards transmits data at 2.4 GHz whereas devices that comply with 802.11a standards transmit at 5 GHz.
WiMax (Wireless Interoperability for Microwave Access) technology represents the next generation of wireless networking and can transmit data up to a distance of forty-eight km. It can provide a maximum networking speed of seventy Mbps. It provides much better facilities than Wi-Fi such as higher bandwidth and high data security by using enhanced encryption schemes. It can provide service in both Line Of Sight (LOS) and Non-Line Of Sight (NLOS) locations, but range may vary accordingly. WiMax supports several communication protocols, and can act as the backbone network for an ISP(Internet service provider) as well as telecom service provider.
Mobile computing devices can use any of these networks to access the Internet or connect to a LAN( local area network) or WAN(wide area network) server. They use networking software for adjusting device settings to suit specific network requirements.
Mobile computing has enabled users to remain connected while on the move. High end users can opt for satellite based networking which provides wireless connectivity anywhere in the world. However, this technology is costly and will take many years to become as affordable as Wi-Fi and WiMax.
Posted on December 28th, 2011 by admin in wireless wimax
This is mobility management demonstration in wireless networks in OPNET. You can see packets flowing in the network and router advertisement send periodically and 7 layers of OSI model functioning collaboratively in order for this model to work. New MAC with WiFi and WiMAX was developed. Music is copyrighted to matrix movie. Thank you.