What is a Mobile Phone?
| Mobile phone Most current mobile phones connect to a cellular network of base stations (cell sites), which is in turn interconnected to the public switched telephone network (PSTN) (the exception are satellite phones). Cellular networks were first introduced in the early to mid 1980s (the 1G generation). Prior mobile phones operating without a cellular network (the so-called 0G generation), such as Mobile Telephone Service, date back to 1945. Until the mid to late 1980s, most mobile phones were sufficiently large that they were permanently installed in vehicles as car phones. With the advance of miniaturization, currently the vast majority of mobile phones are handheld. In addition to the standard voice function of a telephone, a mobile phone can support many additional services such as SMS for text messaging, email, packet switching for access to the Internet, and MMS for sending and receiving photos and video. The world's largest mobile phone manufacturers include Audiovox, BenQ-Siemens, High Tech Computer Corporation, Fujitsu, Kyocera, LG, Motorola, NEC,[i-mate], Nokia, Panasonic (Matsushita Electric), Pantech Curitel, Philips, Sagem, Samsung, Sanyo, Sharp, Siemens SK Teletech, Sony Ericsson, T&A Alcatel, T-Mobile, and Toshiba. The world's largest mobile phone operators (based on customer totals) include China Mobile, Vodafone, and China Unicom. There are also specialist communication systems related to, but distinct from mobile phones, such as Professional Mobile Radio. Mobile phones are also distinct from cordless telephones, which generally operate only within a limited range of a specific base station. Technically, the term mobile phone includes such devices as satellite phones and pre-cellular mobile phones such as those operating via MTS which do not have a cellular network, whereas the related term cell(ular) phone does not. In practice, the two terms are used nearly interchangeably, with the preferred term varying by location. Luxembourg has the highest mobile phone penetration rate in the world, at 164% in December 2005.[1] The total number of mobile phone subscribers in the world was estimated at 2.14 billion in 2005.[1]. Around 80% of world's population have mobile phone coverage as of 2006. This figure is expected to increase to 90% by the year 2010.[2] At present, Africa has the largest growth rate of cellular subscribers in the world.[3] African markets are expanding nearly twice as fast as Asian markets.[4] The availability of Prepaid or pay as you go services, where the subscriber does not have to commit to a long term contract, has helped fuel this growth on a monumental scale, not only in Africa but on other continents as well. All European nations and most Asian and African nations have adopted GSM. In other countries, such as the United States, Australia, Japan, and South Korea, legislation does not require any particular standard, and GSM coexists with other standards, such as CDMA and iDEN. Mobile phone culture or customsIn fewer than twenty years, mobile phones have gone from being rare and expensive pieces of equipment used by businesses to a pervasive low-cost personal item. In many countries, mobile phones now outnumber land-line telephones, with most adults and many children now owning mobile phones. In the United States, 50% of children own mobile phones.[2] It is not uncommon for young adults to simply own a mobile phone instead of a land-line for their residence. In some developing countries, where there is little existing fixed-line infrastructure, the mobile phone has become widespread. According to the CIA World Factbook the UK now has more mobile phones than people [3]. With high levels of mobile telephone penetration, a mobile culture has evolved, where the phone becomes a key social tool, and people rely on their mobile phone address book to keep in touch with their friends. Many people keep in touch using SMS, and a whole culture of "texting" has developed from this. The commercial market in SMS's is growing. Many phones even offer Instant Messenger services to increase the simplicity and ease of texting on phones. Cellular phones in Japan, offering Internet capabilities such as NTT DoCoMo's i-mode, offer text messaging via standard e-mail. The mobile phone itself has also become a totemic and fashion object, with users decorating, customizing, and accessorizing their mobile phones to reflect their personality. This has emerged as its own industry. The sale of commercial ringtones exceeded $2.5 billion in 2004 [4]. The use of a mobile phone is prohibited in some rail carriagesMobile phone etiquette has become an important issue with mobiles ringing at funerals, weddings, movies, and plays. Users often speak at increased volume which has led to places like bookshops, libraries, movie theatres, doctor's offices, and houses of worship posting signs prohibiting the use of mobile phones, and in some places installing signal jamming equipment to prevent usage (although in many countries, e.g. the United States, such equipment is illegal). Transportation providers, particularly those doing long-distance services, often offer a "quiet car" where phone use is prohibited, much like the designated non-smoking cars in the past. Mobile phone use on aircraft is also prohibited, because of concerns of possible interference with aircraft radio communications, [5] although the airline Emirates have announced plans to allow limited celluar phone usage on some flights. Most schools in the U.S prohibit cell phones due to the high amount of class disruptions due to their use, and due to the possibility of photographing someone (without consent). Camera phones and videophones that can capture video and take photographs are increasingly being used by companies like Scoopt to cover breaking news. Stories like the London Bombings, the Indian Ocean Tsunami and Hurricane Katrina have been reported on by camera phone users on photo sharing sites like Flickr. In Japan, cellular phone companies provide immediate notification of earthquakes and other natural disasters to their customers free of charge. In the event of an emergency, disaster response crews can locate trapped or injured people using the signals from their mobile phones; an interactive menu accessible through the phone's Internet browser notifies the company if the user is safe or in distress. Mobile phone features Invented in 1997, the camera phone is now 85% of the market. Mobile phones also often have features beyond sending text messages and making voice calls—including Internet browsing, music (MP3) playback, personal organizers, e-mail, built-in cameras and camcorders, ringtones, games, radio, Push-to-Talk (PTT), infrared and Bluetooth connectivity, call registers, ability to watch streaming video or download video for later viewing, and serving as a wireless modem for a PC. In most countries, the person receiving a cellular phone call pays nothing. However, in China (including Hong Kong), Canada, and the United States, one can be charged per minute. Mobile phone forensics and evidence The UK appears to be leading the world when in comes to mobile telephone forensics and evidence. Law enforcement globally, though, relies heavily upon mobile telephone evidence. The concerns over terrorism and the use by terrorist to use technology promoted an enquiry by the UK House of Commons Home Affairs Select Committee into the use of evidence from mobile telephone devices, prompting leading mobile telephone forensic specialists to identify forensic techniques available in this area[6]. Technology Mobile phone towerMobile phones and the network they operate under vary significantly from provider to provider, and even from nation to nation. However, all of them communicate through electromagnetic radio waves with a cell site base station, the antennas of which are usually mounted on a tower, pole, or building. The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, usually 5 to 8 miles (approximately 8 to 13 kilometres) away. When the cellular phone or data device is turned on, it registers with the mobile telephone exchange, or switch, with its unique identifiers, and will then be alerted by the mobile switch when there is an incoming telephone call. The handset constantly listens for the strongest signal being received from the surrounding base stations. As the user moves around the network, the mobile device will "handoff" to various cell sites during calls, or while waiting (idle) between calls it will reselect cell sites. Cell sites have relatively low-power (often only one or two watts) radio transmitters which broadcast their presence and relay communications between the mobile handsets and the switch. The switch in turn connects the call to another subscriber of the same wireless service provider or to the public telephone network, which includes the networks of other wireless carriers. The dialogue between the handset and the cell site is a stream of digital data that includes digitized audio (except for the first generation analog networks). The technology that achieves this depends on the system which the mobile phone operator has adopted. Some technologies include AMPS for analog, and D-AMPS, CDMA2000, GSM, GPRS, EV-DO, and UMTS for digital communications. Each network operator has a unique radio frequency band. Controversy Health controversy Main article: Mobile phone radiation and health For an increase in certain types of rare tumors (cancer) in long-time, heavy users. More recently a pan-European study provided significant evidence of genetic damage under certain conditions. Some researchers also report the mobile phone industry has interfered with further research on health risks. So far, however, the World Health Organization Task Force on EMF effects on health has no definitive conclusion on the veracity of these allegations. (See also electromagnetic radiation hazard.) It is generally thought, however, that RF is incapable of producing any more than heating effects, as it is considered non-ionizing radiation; in other words, it lacks the energy to disrupt molecular bonds such as occurs in genetic mutations.[5] Driving controversyAnother controversial but potentially more lethal health concern is the correlation with road traffic accidents. Several studies have shown that motorists have a much higher risk of collisions and losing control of the vehicle while talking on the mobile telephone simultaneously with driving, even when using "hands-free" systems. Other studies have shown that using a mobile phone while driving poses the same risk as someone operating a vehicle while under the influence of alcohol. Four U.S. states and many countries, such as Australia, have now restricted or prohibited the use of mobile phones while driving. In Israel and nearly all European countries, driving whilst using a hand-held mobile phone is illegal. Potential danger during electrical storms In 2006, it was reported [7] that mobile phone users suffer much more serious lesions than non-users, in case of being struck by lightning during an electrical storm. Cell phones do not, however, present the danger of a land line during an electrical storm; whereas wires can carry a lightning strike to a nearby telephone user, cell phone signals are immune to such danger. Security concerns Early mobile phones were limited in their security features. Some problems with these models were "cloning", a variant of identity theft, and "scanning" whereby third parties in the local area could intercept and eavesdrop in on calls. Analogue phones could also be listened to on some radio scanners. Although more recent digital systems (such as GSM) have attempted to address these fundamental issues, security problems continue to persist. Vulnerabilities (such as SMS spoofing) have been found in many current protocols that continue to allow the possibility of eavesdropping or cloning [6]. It should be noted that on a technical level, CDMA is more secure than GSM and TDMA. This is due to the fact that all calls are separated onto their own channel and encoded with a unique encryption code. 1 Location tracking using mobile phones is also a concern. As mobile phones begin to converge with the Internet, new security concerns will exist. Early forms of mobile viruses, SPAM, adult content and socially engineered scams have begun to target Internet capable mobile phones. Users of mobile phones will be much less tolerant of such malicious activities. What is a Data Storage Device? Data storage device Recording can be done using virtually any form of energy. A storage device may hold information, process information, or both. A device that only holds information is a recording medium. Devices that process information (data storage equipment) may either access a separate portable (removable) recording medium or a permanent component to store and retrieve information. Electronic data storage is storage that requires electrical power to store and retrieve data. Most storage devices that do not require visual optics to read data fall into this category. Electronic data may be stored in either an analog or digital signal format. This type of data is considered to be electronically encoded data, whether or not it is electronically stored. Most electronic data storage media is considered permanent (non-volatile) storage, that is, the data will remain stored when power is removed from the device. In contrast, electronically stored information is considered volatile memory With the exception of barcodes and OCR data, electronic data storage is easier to revise and may be more cost effective than alternative methods due to smaller physical space requirements and the ease of replacing (rewriting) data on the same medium. However, the durability of methods such as printed data is still superior to that of most electronic storage media. The durability limitations may be overcome with the ease of duplicating (backing-up) electronic data. Terminology Devices that are not used exclusively for recording (e.g. hands, mouths, musical instruments) and devices that are intermediate in the storing/retrieving process (e.g. eyes, ears, cameras, scanners, microphones, speakers, monitors, projectors) are not usually considered storage devices. Devices that are exclusively for recording (e.g. printers), exclusively for reading (e.g. barcode readers), or devices that process only one form of information (e.g. phonographs) may or may not be considered storage devices. In computing these are known as input/output devices. An organic brain may or may not be considered a data storage device.[1] All information is data. However, not all data is information. Data storage equipment The equipment that accesses (reads and writes) storage information are often called storage devices. Data storage equipment uses either: portable methods (easily replaced), semi-portable methods requiring mechanical disassembly tools and/or opening a chassis, or inseparable methods meaning loss of memory if disconnected from the unit. The following are examples of those methods: Portable methodsHand crafting Flat surface Printmaking Photographic Fabrication Automated assembly Textile Molding (process) Solid freeform fabrication Cylindrical accessing Card reader/drive Tape drive Mono reel or reel-to-reel Cassette player/recorder Disk accessing Disk drive Disk enclosure Cartridge accessing/connecting (tape/disk/circuitry) Peripheral networking Semi-portable methods Hard drive Circuitry with non-volatile RAM Inseparable methods Circuitry with volatile RAM Chemical synapse Recording medium A recording medium is a physical material that holds data expressed in any of the existing recording formats. With electronic media, the data and the recording medium is sometimes referred to as "software" despite the more common use of the word to describe computer software. With (traditional art) static media, art materials such as crayons may be considered both equipment and medium as the wax, charcoal or chalk material from the equipment becomes part of the surface of the medium. Ancient and timeless examples Optical Any object visible to the eye, used to mark a location such as a, stone, flag or skull. Any crafting material used to form shapes such as clay, wood, metal, glass, wax. Quipu Any branding surface that would scar under intense heat. Any marking substance such as paint, ink or chalk. Any surface that would hold a marking substance such as, papyrus, paper, skin. Chemical DNA Pheromone Modern examples by energy used Graffiti on a public wall. Public surfaces are being used as unconventional data storage media, often without permission. Photographic film is a photochemical data storage medium A floppy disk is a magnetic data storage medium Hitachi 2.5 inch laptop hard drive. A hard drive is both storage equipment and a storage medium Four major types of memory cards (from left to right: CompactFlash, MemoryStick, Secure Digital, and xD. Picture of a Holographic Versatile Disc by Optware.Chemical Dipstick Thermodynamic Thermometer Photochemical Photographic film Mechanical Pins and holes Punch card Paper tape Piano roll Music box cylinder or disk Grooves (See also Audio Data) Phonograph cylinder Gramophone record DictaBelt (groove on plastic belt) Capacitance Electronic Disc Magnetic storage Wire recording (stainless steel wire) Magnetic tape Floppy disk Optical storage Photo paper Hologram Projected transparency Laserdisc Magneto-optical disc Compact disc Holographic versatile disc Electrical Semiconductor used in volatile RAM microchips Floating gate transistor used in non-volatile memory cards Modern examples by shape A typical way to classify data storage media is to consider its shape and type of movement (or non-movement) relative to the read/write device(s) of the storage apparatus as listed: Paper card storage Punched card (mechanical) Tape storage (long, thin, flexible, linearly moving bands) Paper tape (mechanical) Magnetic tape (a tape passing one or more read/write/erase heads) Disk storage (flat, round, rotating object) Gramophone record (used for distributing some 1980s home computer programs) (mechanical) Floppy disk, ZIP disk (removable) (magnetic) Holographic Optical disc such as CD-ROM, CD-R, CD-RW, DVD, DVD-R, DVD-RW, DVD+R, DVD+RW, DVD-RAM, Blu-ray, Minidisc Hard disk (magnetic) Magnetic bubble memory Flash memory/memory card (solid state semiconductor memory) xD-Picture Card MMC USB Keydrive (also known as a "thumb drive") SmartMedia CompactFlash I and II Secure Digital SONY Memory stick (Std/Duo/Pro/MagicGate versions) Solid state disk Bekenstein (2003) foresees that miniaturization might lead to the invention of devices that store bits on a single atom. Memory Random access memory In contrast, other types of memory devices (such as magnetic tapes, disks, and drums) can access data on the storage medium only in a predetermined order due to constraints in their mechanical design.Connects to: Motherboard via one of Socket Integration Types: SDRAM DDR RDRAM DDR 2 DDR 3 Generally, RAM in a computer is considered main memory or primary storage: the working area used for loading, displaying and manipulating applications and data. This type of RAM is usually in the form of integrated circuits (ICs). These are commonly called memory sticks or RAM sticks because they are manufactured as small circuit boards with plastic packaging and are about the size of a few sticks of chewing gum. Most personal computers have slots for adding and replacing memory sticks. Most RAM can be both written to and read from, so "RAM" is often used interchangeably with "read-write memory." In this sense, RAM is the "opposite" of ROM, but in a more true sense, of sequential access memory. Some RAM also have a heat sink on them. Overview Computers use RAM to hold the program code and data during computation. A defining characteristic of RAM is that all memory locations can be accessed at almost the same speed. Most other technologies have inherent delays for reading a particular bit or byte. Many types of RAM are volatile, which means that unlike some other forms of computer storage such as disk storage and tape storage, they lose all data when the computer is powered down. Modern RAM generally stores a bit of data as either a charge in a capacitor, as in dynamic RAM, or the state of a flip-flop, as in static RAM. Software can "partition" a portion of a computer's RAM, allowing it to act as a much faster hard drive that is called a RAM disk. Unless the memory used is non-volatile, a RAM disk loses the stored data when the computer is shut down. Some types of RAM can detect or correct random faults called memory errors in the stored data, using RAM parity. HistoryEarly main memory systems built from vacuum tubes behaved much like modern RAM, except that they failed frequently. Core memory, which used wires attached to small ferrite electromagnetic cores, also had roughly equal access time. The term “core” is still used by some programmers to describe the RAM main memory of a computer. The basic concepts of tube and core memory are used in modern RAM implemented with integrated circuits. Alternative primary storage mechanisms usually involved a non-uniform delay for memory access. Delay line memory used a sequence of sound wave pulses in mercury-filled tubes to hold a series of bits. Drum memory acted much like the modern hard disk, storing data magnetically in continuous circular bands. (See primary storage for a greater discussion of these alternatives and others.) Recent developments Currently, several types of non-volatile RAM are under development, which will preserve data while powered down. The technologies used include carbon nanotubes and the magnetic tunnel effect. In summer 2003, a 128 kB magnetic RAM chip was introduced, which was manufactured with 0.18 µm technology. The core technology of MRAM is based on the magnetic tunnel effect. In June of 2004, Infineon Technologies unveiled a 16 MB prototype again based on 0.18 µm technology. As for carbon nanotube memory, a high-tech startup Nantero built a functioning prototype 10 GB array in 2004. The Memory Wall The term "memory wall", first officially coined in Hitting the Memory Wall: Implications of the Obvious (PDF), refers to the growing disparity between CPU and memory speed. From 1986 to 2000, CPU speed improved at an annual rate of 55% while memory speed only improved at 10%. Given these trends, it was expected that memory latency would become an overwhelming bottleneck in computer performance. Currently, CPU speed improvements have slowed significantly partly due to major physical barriers and partly because current CPU designs have already hit the memory wall in some sense. Intel summarized these causes in their Platform 2015 documentation (PDF): "First of all, as chip geometries shrink and clock frequencies rise, the transistor leakage current increases, leading to excess power consumption and heat (more on power consumption below). Intel's new Tri-Gate could solve this problem. Secondly, the advantages of higher clock speeds are in part negated by memory latency, since memory access times have not been able to keep pace with increasing clock frequencies. Third, for certain applications, traditional serial architectures are becoming less efficient as processors get faster (due to the so-called Von Neumann bottleneck), further undercutting any gains that frequency increases might otherwise buy. In addition, resistance-capacitance (RC) delays in signal transmission are growing as feature sizes shrink, imposing an additional bottleneck that frequency increases don't address." The RC delays in signal transmission were also noted in Clock Rate versus IPC: The End of the Road for Conventional Microarchitectures which projects a maximum of 12.5% average annual CPU performance improvement between 2000 and 2014. The data on Intel Processors clearly shows a slowdown in performance improvements in recent processors. However Intel's new processors, Core 2 (codenamed Conroe) shows a significant improvement over previous Pentium 4 processors. Shadow RAM Shadow RAM is RAM whose contents are copied from read-only memory (ROM) to allow shorter access times [1], as ROM is in general slower than RAM. The original ROM is disabled and the new location on the RAM is write-protected. This process is called shadowing. DRAM packaging For economical reasons, the large (main) memories found in personal computers, workstations, and non-handheld game-consoles (such as playstation and xbox) normally consists of dynamic RAM (DRAM). Other parts of the computer, such as cache memories and data buffers in hard disks, normally use static RAM (SRAM). Common DRAM packages General DRAM packaging formats Dynamic random access memory (DRAM) is produced as integrated circuits (ICs) bonded and mounted into plastic packages with metal pins for connection to control signals and buses. Today, these DRAM packages are in turn often assembled into plug-in modules for easier handling. Some standard module types are: DRAM chip (Integrated Circuit or IC) Dual in-line Package (DIP) DRAM (memory) modules Single In-line Pin Package (SIPP) Single in-line memory module (SIMM) Dual in-line memory module (DIMM) Rambus modules are technically DIMMs, but are usually referred to as RIMMs due to their proprietary slot. Small outline DIMM (SO-DIMM). Smaller version of the DIMM, used in laptops. Comes in versions with: 72 pins (32-bit) 144 pins (64-bit) 200 pins (72-bit) Small outline RIMM (SO-RIMM). Smaller version of the RIMM, used in laptops. Stacked v. non-stacked RAM modules Stacked RAM chips use two RAM wafers that are stacked on top of each other. This allows large module (like a 512mb or 1Gig SO-DIMM) to be manufactured using cheaper low density wafers. Stacked chip modules draw more power. Common DRAM modules Common DRAM packages as illustrated to the right, from top to bottom: DIP 18-pin (DRAM chip, usually pre-FPRAM) SIPP (usually FPRAM) SIMM 30-pin (usually FPRAM) SIMM 72-pin (so-called "PS/2 SIMM", usually EDO RAM) DIMM 168-pin (SDRAM) DIMM 184-pin (DDR SDRAM) DIMM 240-pin (DDR2 SDRAM - not pictured) DRAM-module manufacturers Company name Website Corsair Memory http://www.corsairmemory.com/ Crucial Technology http://www.crucial.com/ EDGE Memory http://www.edgememory.com/ GEIL http://www.geilusa.com/ G.Skill http://www.gskill.com/ Hynix http://www.hynix.com/ Infineon Technologies now http://www.qimonda.com/ Kingston Technology http://www.kingston.com/ Legend http://www.legendmemory.com/ Micron Technology http://www.micron.com/ Mushkin http://www.mushkin.com/ OCZ Technology http://www.ocztechnology.com Samsung http://www.samsung.com/ SimpleTech http://www.simpletech.com/ Super Talent Technology http://www.supertalent.com/ Ultra Products http://www.ultraproducts.com/ Wintec Industries http://www.wintecind.com/ | |
