Mobile phone features
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There are many mobile phone features found in today's mobile phones that offer users many more capabilities than only voice calls or text messaging.
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[edit] General features
Mobiles are designed to work on cellular networks and contain a standard set of services that allow phones of different types and in different countries to communicate with each other.
Before the phone can be used, a subscription to a mobile phone operator (a.k.a. carrier) is required. For phones on GSM networks, the operator will issue a SIM card which contains the unique subscription and authentication parameters for that customer; alternatively, the carrier will put the customer's handset identifier into its subscriber database so that the handset can make calls on the network. Once the SIM card is inserted into the phone, services can be accessed. Many mobile phones support 'auto-roaming', which permits the same phone to be used in multiple countries. For this to work, the operators of both countries must have a roaming agreement.
Mobile phones include an alarm. Usually it still functions while the phone is turned off or in silent mode.
Mobile phones do not only support voice calls; they can also send and receive data and faxes (if a computer is attached), send short messages (or "text messages"; see SMS), access WAP services, and provide full Internet access using technologies such as GPRS. Mobile phones usually have a clock and a calculator and often one can play some games on them.
Most current models also allow for sending and receiving pictures and have a built-in digital camera, that can have resolutions as high as 5M pixels (Nokia N95). Sound and video recording is often also possible. This feature is generally referred to as MMS. This gives rise to some concern about privacy, in view of possible voyeurism, for example in swimming pools. For this reason, Saudi Arabia has entirely banned the sale of camera phones; South Korea has ordered manufacturers to ensure that all new handsets emit a beep whenever a picture is taken.
GPS receivers are starting to appear integrated or connected (i.e. using bluetooth) to cell phones, primarily to aid in dispatching emergency responders and road tow truck services. This feature is generally referred to as E911.
Push to talk, available on some mobile phones, is a feature that allows the user to talk to another by pressing the button. It functions similar to walkie-talkie.
There are also many features aimed toward personalisation, such as user defined and downloadable ring tones and logos, and interchangeable covers, which have helped in the uptake by the teenage market. Mobile phone content advertising has become massively popular but has also drawn a great deal of criticism. Usually one can choose between a ring tone, a vibrating alert, or a combination of both.
As a result of all these features packed into a tiny device, mobile phones have recently gained reputations for their poor ergonomics. Their small size, plethora of features and modes, and attempts at stylish design often make them difficult and confusing to use.
One can try features before buying the phone.[1]
[edit] Multi-mode mobile phones
A multi-mode (also known more specifically as dual, tri or quad band) mobile phone is a phone which is designed to work on more than one GSM radio frequency. The multi-mode case occurs mostly in GSM which was originally specified in the 900 MHz band, but expanded to the 1800 MHz band, later adding 1900 MHz and finally 850 MHz in the Americas. Some multi-mode phones can operate on analog networks as well (for example, dual band, tri-mode: AMPS 800 / CDMA 800 / CDMA 1900).
For a GSM phone, dual-band usually means 850 / 1900 MHz in the United States and Canada, 900 / 1800 MHz in Europe and most other countries. Tri-band means 850 / 1800 / 1900 MHz or 900 / 1800 / 1900 MHz. Quad-band means 850 / 900 / 1800 / 1900 MHz, also called a world phone, since it can work on any GSM network.
For CDMA or TDMA phones, multiple bands usually means it supports both digital and analog communications.
Multi-mode phones have been valuable to enable roaming but are now becoming most important in allowing the introduction of WCDMA without customers having to give up the wide coverage of GSM. Almost every single true 3G phone sold is actually a WCDMA/GSM dual-mode mobile. This is also true of 2.75G phones such as those based on CDMA-2000 or EDGE.
The special challenge involved in producing a multi-mode mobile is in finding ways to share the components between the different standards. Obviously, the phone keypad and display should be shared, otherwise it would be hard to treat as one phone. Beyond that, though, there are challenges at each level of integration. How difficult these challenges are depends on the differences between systems. The different variants of the GSM system have only different frequencies and so aren't even considered true multi-mode phones but rather are called multi-band phones. When talking about IS-95/GSM multi-mode phones, for example, or AMPS/IS-95 phones, the base band processing is very different from system to system. This leads to real difficulties in component integration and so to larger phones.
An interesting special case of multi-mode phones is the WCDMA/GSM phone. The radio interfaces are very different from each other, but mobile to core network messaging has strong similarities, meaning that software sharing is quite easy. Probably more importantly, the WCDMA air interface has been designed with GSM compatibility in mind. It has a special mode of operation, known as punctured mode, in which, instead of transmitting continuously, the mobile is able to stop sending for a short period and try searching for GSM carriers in the area. This mode allows for safe inter-frequency handovers with channel measurements which can only be approximated using "pilot signals" in other CDMA based systems.
A final interesting case is that of mobiles covering the DS-WCDMA and MC-CDMA 3G variants of the CDMA-2000 protocol. Initially, the chip rate of these phones was incompatible. As part of the negotiations related to patents, it was agreed to use compatible chip rates. This should mean that, despite the fact that the air and system interfaces are quite different, even on a philosophical level, much of the hardware for each system inside a phone should be common with differences being mostly confined to software.
As can be deduced from the above, most mobile phone networks now use one of two standards, GSM or CDMA. A third standard, iDEN, is found in over 20 countries around the world.
[edit] Data communications
Mobile phones are now heavily used for data communications such as SMS messages, browsing mobile web sites, and even streaming audio and video files. The main limiting factors are the size of the screen, lack of a keyboard, processing power and connection speed. Most cellphones, which supports data communications, can be used as wireless modems (via cable or bluetooth), to connect computer to internet. Such access method is slow and expensive, but it can be available in very remote areas.
With newer smartphones, screen resolution and processing power has become bigger and better. Some new phone CPUs run at over 400 MHz. Many complex programs are now available for the various smartphones, such as Symbian and Windows Mobile.
Connection speed is based on network support. Originally data transfers over GSM networks were possible only over CSD (circuit switched data), it has bandwidth of 9600 bit/s and usually is billed by connection time (from network point of view, it does not differ much from voice call). Later, there were introduced improved version of CSD - HSCSD (high speed CSD), it could use multiple time slots for downlink, improving speed. Maximum speed for HSCSD is ~42 kbit/s, it also is billed by time. Later was introduced GPRS (general packet radio service), which operates on completely different principle. It also can use multiple time slots for transfer, but it does not tie up radio resources, when not transferring data (as opposed to CSD and like). GPRS usually is prioritized under voice and CSD, so latencies are large and variable. Later, GPRS was upgraded to EDGE, which differs mainly by radio modulation, squeezing more data capacity in same radio bandwidth. GPRS and EDGE usually are billed by data traffic volume. Some phones also feature real keyboards, such as the LG enV.
As of April 2006, several models, such as the Nokia 6680, support 3G communications. Such phones have access to the Web via a free download of the Opera web browser. Verizon Wireless models come with Internet Explorer pre-loaded onto the phone.
[edit] New features
There are also new means of digital communications, such as text messaging and e-mail. As of 2004, even basic phones can send and receive text messages which makes them vulnerable to attack by worms and viruses[citation needed]. Advanced phones capable of e-mail can be susceptible to viruses that can multiply by sending messages through a phone's address book[citation needed]. Of more important concern, a virus may allow unauthorized users to access a phone to find passwords or corporate data stored on the device. Moreover, they can be used to commandeer the phone to make calls or send messages at the owner's expense[citation needed]. Unlike computers that are restricted to only a few widespread operating systems, cellular phones use a variety of systems that require separate programs to be designed in order to disable each one. While reducing overall compatibility from an application design standpoint, this has the beneficial effect of making it harder to design a mass attack. However, the rise of cellular phone operating system programming platforms shared by many manufacturers such as Java, Microsoft operating systems, Linux, or Symbian OS, may in the future change this status quo.
Bluetooth is a wireless communication feature now found in many higher-end phones, and the virus Cabir hijacked this function, making Bluetooth phones infect other Bluetooth phones running the Symbian OS. In early November 2004, several web sites began offering a specific piece of software promising ringtones and screensavers for certain phones. Those who downloaded the software found that it turned each icon on the phone's screen into a skull-and-crossbones and disabled their phones, so they could no longer send or receive text messages or access contact lists or calendars. The virus has since been dubbed "Skulls" by security experts. The Commwarrior-A virus was identified in March 2005, and it attempts to replicate itself through MMS to others on the phone's contact list. Like Cabir, Commwarrior-A also tries to communicate via Bluetooth wireless connections with other devices, which can eventually lead to draining the battery. The virus requires user intervention for propagation however. Bluetooth telephones are also subject to bluejacking, which is the generally being transmission of messages from anonymous Bluetooth users. In 2004, rumors spread of using Bluetooth to arrange casual sex hookups; this activity, widely publicized in both print and online media as toothing, was revealed to be a hoax in 2005.
[edit] Video cameras
Most people do not walk around with a video camera, but do carry a phone. The arrival of video camera phones is transforming the availability of video to consumers, and is helping to fuel the idea of citizen journalism.
[edit] See also
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