GPS (Global Positioning System)

The Global Positioning System is a series of satellites owned by the US government that broadcasts signals that GPS receivers on the surface of the planet can use to determine position through triangulation. The term GPS is often used to refer to a GPS receiver, such as those used in cars and sometimes found in mobile phones.

GPRS (General Packet Radio Service)

GPRS is a wireless data standard used on GSM networks. It offers theoretical data rates as high as 120kbps on the downlink side, but real world speeds are typically significantly slower.

UMA (GAN, Generic Access Network, Unlicensed Mobile Access)

Unlicensed Mobile Access is a technology that allows a UMA capable mobile phone to seamlessly switch back and forth between mobile phone networks and local wireless networks. WiFi and Bluetooth are commonly used for the local wireless part of the system. Simply possessing a UMA capable phone does not mean that a subscriber can make use of UMA services since the system requires back-end support from the carrier. UMA is particularly useful in remote areas where mobile phone coverage is poor, as well as inside of buildings where the network signal might not be able to penetrate building walls. In the US, T-Mobile was the first carrier to start offering UMA services. UMA has been officially ratified by the 3GPP and has been renamed GAN, or Generic Access Network, though most often the technology is still referred to by the UMA name.

Focal Length

The focal length of a lens determines how much magnification it provides. A lens with a shorter focal length will be able to "see" a wider view of a subject than can a lens with a longer focal length, which would see a narrower view of the scene, but at a higher level of magnification. Whether a lens seems to be a wide angle or telephoto lens depends on the size of the image sensor it is used with. As a result, one can not say that a given 15mm lens is wide, or that a 200mm lens is telephoto in nature since the size of the image sensor is not known. When speaking of lenses used on 35mm film systems, 35mm of focal length or less is typically considered wide, and 80mm or longer is generally considered telephoto. Digital cameras often refer to their lenses as being "equivalent" to a particular 35mm film camera lens in focal length to give people an idea as to how wide or telephoto it acts when paired with that particular camera's sensor.

Aperture (f-number, f-stop)

The aperture of a lens system is the opening between the actual lens elements, typically made of glass or plastic, and the camera's digital sensor that translates the light into image data. Aperture openings are referred to in terms of stops or f-stops that equate to the ratio of the lens focal length to the diameter of the opening. A lens system with a focal length of 50mm and an aperture opening that is 25mm in diameter would equate to an f-stop of 2, and would be known as a 50mm f2 lens. Some lenses have variable apertures that can be set to one of multiple f-stop values. Reducing the aperture size decreases the amount of light that makes it to the sensor as well as increases the amount of depth of field that the lens will provide.

ESN (Electronic Serial Number)

An ESN is a numeric identifier that uniquely identifies a CDMA phone in the United States. The ESN can typically be found written underneath a phone's battery and is generally written in both decimal and hexadecimal versions. The ESN is what a CDMA network uses to identify a phone and determine which subscriber's account, if any, it is linked to. Because of this, when switching from one phone to another, subscribers will have to provide the ESN of the new phone to the network carrier before it can be activated. This can often be done at the carrier's website. The ESN is slowly being phased out in favor of the MEID, a longer number that is compatible with the IMEI system used in GSM and UMTS phones. This is happening because phone manufacturers are literally running out of ESN identifiers.

DSL (Digital Subscriber Line, Digital Subscriber Loop)

DSL is a group of networking technologies that allow for WAN connections over existing telephone network wires. Originally short for Digital Subscriber Loop, DSL is more commonly referred to today as Digital Subscriber Line. Loop refers to the short-haul connection between the end user's home or business and the local telephone company office where the DSL equipment resides. Line is merely a friendlier term that more people would understand than loop. When people refer to DSL, they generally are referring to ADSL, the most commonly used of DSL technologies.

Direct Push

Direct Push is Microsoft's Push Email system for pushing email, contacts, appointments, and tasks to a mobile device in real time.

DMB (Digital Multimedia Broadcasting)

DMB stands for Digital Multimedia Broadcasting and is a suite of systems used to send television and similar media programming over the air to mobile devices. S-DMB is a version that makes use of satellites, while T-DMB uses terrestrial (ground based) transmitters. While it is running in trials in other countries, including some European ones, it is primarily used only in South Korea.

EDGE (Enhanced Data for Global Evolution)

EDGE is a data system used on top of GSM networks that provides faster data speeds than GPRS, the technology it makes obsolete. It has a theoretical maximum downlink data rate of nearly 475Kbps, which qualifies it as a 3G technology based on ITU guidelines, even if typical implementations are configured for non-3G speeds. Generally, it is referred to as 2.75G.

Dual-band

Dual-band refers to a device's ability to function on two different frequency bands. Many CDMA devices sold in North America are dual-band capable. Dual-band CDMA devices tend to offer better roaming inside of North America. Generally speaking, a dual-band GSM device sold in a non-North American market will not function in North America. Likewise, a North American dual-band GSM phone will not function in Europe and most other parts of the world. This is because North America uses two different GSM bands than do Europe and most of the rest of the world. GSM users that wish to travel internationally should look at a tri-band or quad-band device.

Dual-mode

Dual-mode devices are capable of supporting more than one network type. Examples of such are those that support both CDMA and AMPS, CDMA and GSM, or CDMA and iDEN.

DRM (Digital Rights Management)

Digital Rights Management, more commonly referred to simply as DRM, is a system that allows use of protected media to be restricted. DRM systems are most commonly found in music files and can be used to restrict the number of times a file is moved from one media player to another, or to restrict the number of times or period of time that a file can be played back. DRM is also commonly found on video media. A wide variety of different DRM systems exist today, including Apple's FairPlay and Microsoft's Windows Media DRM 10.

Windows Mobile

Windows Mobile is Microsoft's platform for PDAs and smartphones. Windows Mobile 5 is the successor to the 2003 edition of the platform. Windows Mobile 6, codenamed "Crossbow", is the release slated for the Spring of 2007. The platform generally comes in 3 flavors: Pocket PC, Pocket PC Phone Edition, and Smartphone. Pocket PC (PPC) is for PDA devices, PPC Phone Edition is for PDAs with phone functionality, and Smartphone is for devices that lack a touch screen and are more phone-centric in functionality.

Bluetooth profile

In order for two (or more) Bluetooth devices to be able to work together to accomplish a given task, such as file sharing, they need to both support the appropriate profiles. The Bluetooth SIG has defined countless profiles, such as Headset, A2DP Stereo, OBEX File Exchange, to name just a few. This is why devices such as Bluetooth keyboards are generally not usable with mobile phones - most mobile phones do not support the necessary HID Bluetooth profile.

A-GPS (Assisted GPS)

Assisted GPS is a system commonly found in CDMA mobile phones in the US that offloads some of the processing requirements of a typical GPS receiver to a central server that can perform the calculations much more quickly. This allows the A-GPS receiver to work on devices with less computing resources than would be possible otherwise. A-GPS received a boost when the US government required mobile phones to support the E911 emergency calling system, which requires the callers location to be known.

Autofocus (AF)

Autofocus refers to a camera lens' ability to adjust its configuration in order to focus properly on a subject regardless of whether it is near or far from the camera. Autofocus lenses generally provide vastly superior image quality than do their fixed focus cousins since they do not have to rely on their depth of field.

CSTN (Color Super-Twisted Nematic)

Color super-twisted nematic (CSTN) is the type of passive matrix LCD used by many early color capable mobile devices, and is still used on some current and cheaper devices. CSTN displays are prone to ghosting, or streaking, when images on the display change quickly, and offer relatively poor contrast and color saturation.

CDMA (Code Division Multiple Access)

CDMA stands for code division multiple access, a form of multiplexing that is based on mathematics rather than time slicing (used by TDMA) or frequency hopping. The term is commonly used to refer to phone networks that make use of this form of multiplexing, such as those run in the United States by Verizon, Sprint, and Alltel. CDMA phone networks make use of 1xRTT, 1xEV-DO, and 1xEV-DV for data transfer. The core CDMA technology was developed by Qualcomm.

Palm OS

Palm OS is the operating system used on the Palm Pilot and Treo lines of PDAs and smartphones sold by Palm, as well as those sold by many other companies, including Sony. ACCESS, the company that absorbed PalmSource, has renamed the product to be the Garnet OS. Palm, the hardware company, formerly palmOne, currently has a license that allows it to further develop Palm OS 5, which was commonly referred to by its development codename of Garnet. The original planned successor of Palm OS 5 was Cobalt (Palm OS 6). Cobalt has since been killed off in favor of a future system that runs on top of a mobile Linux OS.

CSD (Circuit-Switched Data)

CSD, or Circuit-Switched Data, was a system used on early GSM networks to provide data access to mobile devices by allowing them to place a data call. CSD was capable of uplink and downlink rates of up to 9.6kbps. Later replaced by the faster HSCSD variant, circuit-switched data on wireless networks were eventually made completely obsolete by packet based networks such as GPRS and EDGE.

AMPS (Advanced Mobile Phone System)

North America's AMPS and its variants used elsewhere in the world are the antiquated analog cellular phone networks used before the advent of digital technologies such as GSM and CDMA. AMPS was first used in North America in the early 1980s and is still used today, though mostly in rural areas.

CCD (Charge-Coupled Device)

A CCD is a type of image sensor used in digital cameras. When speaking of low cost devices, CCD image sensors tend to provide better image quality than comparable CMOS models, though they require more power to utilize. As such, devices such as mobile phones tend to use CMOS sensors. Further refinements of CMOS image sensor technology will likely lead to CCD technology eventually being abandoned as far as cameras are concerned.

A2DP

The Advanced Audio Distribution Profile is a Bluetooth profile that allows for the wireless transmission of stereo audio from an A2DP source (typically a phone or computer) to an A2DP receiver (a set of Bluetooth headphones or stereo system). Such devices typically also support the AVRCP profile as well in order to allow for track selection and such. A common misconception is that A2DP support is available on all Bluetooth 2.0 devices, which is not the case, and that A2DP is only available on Bluetooth 2.0 devices, which is also not true. A2DP support can exist in older versions of Bluetooth, it just was not commonly supported.

WiMAX

WiMAX is a wireless technology put forth by the WiMAX Forum that is considered by many to be the likely technology to be used as the basis of future 4G applications. It can be used in both point to point and WAN type configurations such as those used by 2G and 3G mobile network carriers. Its formal name is IEEE standard 802.16.

Bluetooth

Bluetooth is a wireless technology developed by Ericsson that is designed to be a cable replacement. It operates on the 2.4GHz frequency band, like WiFi, and is officially known as IEEE standard 802.15.1. It is most commonly used with wireless headsets and car kits, but can also be used for network access, moving files from one device to another, or with wireless input devices such as a mouse and keyboard - among many other uses. These other uses are dependent on the Bluetooth profiles that are supported by the devices in question. There are multiple versions of the Bluetooth specification in use, and in order for full functionality to be possible, the devices on both sides of a connection must be of the same version. This is not to say that a Bluetooth 1.1 headset, for example, will not work with a Bluetooth 2.0 phone - it will. It is only to say that in order to enjoy the benefits of Bluetooth 2.0's features, such as faster connection times, a Bluetooth 2.0 (or later) headset would have to be used.

802.11b

IEEE standard 802.11b defines a Wireless LAN (WLAN) technology that is capable of achieving up to 11Mbps of bandwidth between two devices. It is part of the 802.11 group of technologies that define WiFi.

WiFi (Wi-Fi)

A brand of wireless LAN (WLAN) technologies defined by the IEEE 802.11 group of standards. The two WiFi standards most commonly used by personal computers and mobile devices, such as phones, are 802.11b and 802.11g.

3G (Third Generation)

3G, or Third Generation, is a somewhat generic term for network technologies that the ITU classifies as part of their IMT-2000 specification. Generally, wireless network technologies must be able to provide a mobile device with a downlink connection speed of 384kbps in order to be considered a 3G technology. The most used 3G technologies are WCDMA, CDMA 1xEV-DO, and, technically, EDGE and CDMA 1xRTT.

EV-DO

Commonly known simply as EV-DO, CDMA 1xEV-DO is a 3G technology add-on for CDMA networks that allows for theoretical download speeds as fast as 2.4576Mbps, though actual rates tend to be far slower. Originally known as CDMA Evolution Data Only, EV-DO is today generally regarded as standing for Evolution Data Optimized for what are likely marketing purposes. 1xEV-DV (Evolution Data Voice) is the technology that was originally destined to handle the future 3G voice and data needs of CDMA networks, but has failed to catch on in North America. Instead, 1xEV-DO Rev A has been developed, which allows for faster uplink speeds than the original EV-DO spec, which relies on the older, and much slower, 1xRTT system for uplink connections.