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Dual Transfer Mode
Dual Transfer Mode (DTM) is a protocol based on the GSM standard that makes simultaneous transfer of Circuit switched (CS) voice and Packet switched (PS) data over the same radio channel (ARFCN) simpler. Without DTM, the mobile device must be capable of reception and transmission simultaneously (full-duplex) requiring complex and expensive circuitry in the mobile terminal. With DTM this requirement doesn't exist and makes the device implementation simpler and cheaper. DTM is a 3GPP feature introduced in R4 of the specification series.3GPP specification: http://www.3gpp.org/ftp/Specs/html-info/43055.htm Traditionally, GSM/EDGE device with simultaneous CS/PS capability was supported, but only for Class A GPRS devices. Due to the fact that the uplink and downlink timeslot usage was not co-ordinated between the voice and data connections, the class A devices in practice had to be capable of transmit and reception simultaneously. With DTM, a mobile phone capable can be engaged in bot ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circuit Switched
Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel ( circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit. Circuit switching originated in analog telephone networks where the network created a dedicated circuit between two telephones for the duration of a telephone call. It contrasts with message switching and packet switching used in modern digital networks in which the trunklines between switching centers carry data between many different nodes in the form of data packets without dedicated circuits. Description The defining example of a circuit-switched network is the early analog telephone network. When a call is made from one telephone to another, swit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Packet Switched
In telecommunications, packet switching is a method of grouping data into '' packets'' that are transmitted over a digital network. Packets are made of a header and a payload. Data in the header is used by networking hardware to direct the packet to its destination, where the payload is extracted and used by an operating system, application software, or higher layer protocols. Packet switching is the primary basis for data communications in computer networks worldwide. In the early 1960s, American computer scientist Paul Baran developed the concept that he called "distributed adaptive message block switching", with the goal of providing a fault-tolerant, efficient routing method for telecommunication messages as part of a research program at the RAND Corporation, funded by the United States Department of Defense. His ideas contradicted then-established principles of pre-allocation of network bandwidth, exemplified by the development of telecommunications in the Bell System. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ARFCN
In GSM cellular networks, an absolute radio-frequency channel number (ARFCN) is a code that specifies a pair of physical radio carriers used for transmission and reception in a land mobile radio system, one for the uplink signal and one for the downlink signal. ARFCNs for GSM are defined in Specification 45.005 Section 2. There are also other variants of the ARFCN numbering scheme that are in use for other systems that are not GSM. One such example is the TETRA system that has 25 kHz channel spacing and uses different base frequencies for numbering. Different frequencies (ARFCNs) are used for the frequency-based component of GSMs multiple access scheme (FDMA — frequency-division multiple access). Uplink/downlink channel pairs in GSM are identified by ARFCN. Together with the time-based component (TDMA — time-division multiple access) the physical channel is defined by selecting a certain ARFCN and a certain time slot. Note not to confuse this physical channel with the logica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nokia N95
The Nokia N95 is a smartphone produced by Nokia as part of their Nseries line of portable devices. Announced in September 2006, it was released to the market in March 2007. The N95 ran S60 3rd Edition, on Symbian OS v9.2. It has a two-way sliding mechanism, which can be used to access either media playback buttons or a numeric keypad. It was first released in silver and later on in black, with limited edition quantities in gold and purple. The launch price of the N95 was around (about , ). The N95 was a high-end model that was marketed as a "multimedia computer", much like other Nseries devices. It featured a then-high 5 megapixel resolution digital camera with Carl Zeiss optics and with a flash, as well as a then-large display measuring 2.6 inches. It was also Nokia's first device with a built-in Global Positioning System (GPS) receiver, used for maps or turn-by-turn navigation, and their first with an accelerometer. It was also one of the earliest devices in the market sup ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nokia N900
The Nokia N900 is a smartphone made by Nokia. It supersedes the Nokia N810. Its default operating system, Maemo 5, is a Linux-based OS originally developed for the Nokia 770 Internet Tablet. It is the first Nokia device based upon the Texas Instruments OMAP3 microprocessor with the ARM Cortex-A8 core. Unlike the three Nokia Internet tablets preceding it, the Nokia N900 is the first Maemo device to include phone functionality (quad-band GSM and 3G UMTS/HSDPA). The N900 functions as a mobile Internet device, and includes email, web browsing and access to online services, a 5-megapixel digital camera for still or video photography, a portable media player for music and video, calculator, games console and word processor, SMS, as well as mobile telephony using either a mobile network or VoIP via Internet (mobile or Wi-Fi). Maemo provides an X-terminal interface for interacting with the core operating system. It was launched at Nokia World on 2 September 2009 and was released in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vodafone
Vodafone Group Public limited company, plc () is a British Multinational corporation, multinational Telephone company, telecommunications company. Its registered office and Headquarters, global headquarters are in Newbury, Berkshire, England. It predominantly operates Service (economics), services in Asia, Africa, Europe, and Oceania. , Vodafone owns and operates networks in 22 countries, with partner networks in 48 further countries. Its Vodafone Global Enterprise division provides telecommunications and IT services to corporate clients in 150 countries. Vodafone has a primary listing on the London Stock Exchange and is a constituent of the FTSE 100 Index. The company has a secondary listing on Nasdaq. Name The name Vodafone comes from ''VO''ice ''DA''ta ''FONE'' (the latter a sensational spelling of "telephone, phone"), chosen by the company to "reflect the provision of voice and data services over mobile phones". History The evolution of Vodafone started in 1981 with the es ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
References
Reference is a relationship between objects in which one object designates, or acts as a means by which to connect to or link to, another object. The first object in this relation is said to ''refer to'' the second object. It is called a ''name'' for the second object. The second object, the one to which the first object refers, is called the '' referent'' of the first object. A name is usually a phrase or expression, or some other symbolic representation. Its referent may be anything – a material object, a person, an event, an activity, or an abstract concept. References can take on many forms, including: a thought, a sensory perception that is audible (onomatopoeia), visual (text), olfactory, or tactile, emotional state, relationship with other, spacetime coordinate, symbolic or alpha-numeric, a physical object or an energy projection. In some cases, methods are used that intentionally hide the reference from some observers, as in cryptography. References feature in many sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
