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2G (or 2-G) is short for second-generation wireless telephone technology.

The main differentiator to previous mobile telephone systems, retrospectively dubbed 1G, is that the radio signals that 1G networks use are analog, while 2G networks are digital. Note that both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

3G (or 3-G) is short for third-generation technology.

It is used in the context of mobile phone standards. The services associated with 3G provide the ability to transfer simultaneously both voice data (a telephone call) and non-voice data (such as downloading information, exchanging email, and instant messaging).

The Base Station Controller (BSC) provides communication and control behind the BTSs. Typically a BSC can have from 1 to 100 BTSs under its control. The BSC handles allocation of radio channels, receives measurements from the mobile phones, controls handovers from BTS to BTS (except in the case of an inter-MSC handover in which case control is in part the responsibility of the Mobile Switching Centre (MSC).

The Base Transceiver Station (BTS) is a Picocellular base station that provides GSM capacity and coverage. The BTS makes use of an IP connection to other parts of the PMX ensuring that it can be installed whenever and wherever GSM capabilities are required. The BTS PMN use has been designed in accordance with ETSI standards, thus guaranteeing compatibility with existing handsets. The BTS is available for the 900, 1800 or 1900MHz bands. The unit offers up to 200mW radio output power enabling cellular coverage up to several hundred metres inside a building. With a single Ethernet connection traffic and signalling can be transported over any broadband packet connection.

Digital Private Network Signalling System (DPNSS) is an industry standard interface defined between a PBX and an access network. DPNSS expands the facilities normally only available between extensions on a single PBX to all extensions on PBXs that are connected together in a private network.

DPNSS was originally derived from British Telecom's Digital Access Signalling System I (DASS I), and enhanced where necessary to meet private network requirements. DPNSS uses a 2048 kbps or 1544 kbps digital transmission system interface. DPNSS is today being steadily replaced by SIP protocol based solutions.

A gateway is a network point that acts as an entrance to another network. In a Private Mobile eXchange (PMX) deployment the gateway will typical be used to convert between the Session Initiation Protocol (SIP) and various manufacturers private branch exchanges (PBX) or the public switched telephone network (PSTN).

General Packet Radio Service (GPRS) is a mobile data service available to users of GSM mobile phones. It is often described as "2.5G". It provides moderate speed data transfer, by using unused TDMA channels in the GSM network. Originally there was some thought to extend GPRS to cover other standards, but instead those networks are being converted to use the GSM standard, so that is the only kind of network where GPRS is in use. GPRS is integrated into GSM standards releases starting with Release 97 and onwards.

GSM (Global System for Mobile communication) is a digital mobile telephone system that is widely used in Europe and other parts of the world. GSM uses a variation of time division multiple access (TDMA) and is the most widely used of the three digital wireless telephone technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It operates at either the 900 MHz or 1800 MHz frequency band.

GSM is the de facto wireless telephone standard in Europe. GSM has over 120 million users worldwide and is available in 120 countries, according to the GSM MoU Association. Since many GSM network operators have roaming agreements with foreign operators, users can often continue to use their mobile phones when they travel to other countries.

GSM Signal Interface between BSC and MSC

An International Mobile Subscriber Identity is a unique number that is associated with all GSM and Universal Mobile Telecommunications System (UMTS) network mobile phone users. The number is stored in the Subscriber Identity Module (SIM).

The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork.

The Internet Protocol Private Branch eXchange (IP PBX) is a telephone switching equipment that resides in a private business instead of the telephone company. An IP PBX delivers employees dial-tone, the ability to conference, transfer, and dial other employees by extension number as well as many other features.

A local area network (LAN) is a computer network covering a local area, like a home, office, or group of buildings. Current LANs are most likely to be based on switched IEEE 802.3 Ethernet running at 10, 100 or 1,000 Mbit/s or on Wi-Fi technology.

A wide area network or WAN is a computer network covering a broad geographical area.

WANs are used to connect local area networks (LANs) together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private. Others, built by Internet service providers, provide connections from an organization's LAN to the Internet.

The largest and most well-known example of a WAN is the Internet.

The Mobile services Switching Centre or MSC is a sophisticated telephone exchange which provides circuit-switched calling, mobility management and GSM services to the mobile phones roaming within the area that it serves. This means voice, data and fax services, as well as SMS and call divert.

In the GSM mobile phone system, in contrast with earlier analogue services, fax and data information is sent directly digitally encoded to the MSC. Only at the MSC is this re-coded into an "analogue" signal. The core intelligence in Private Mobile eXchange is contained in the MSC.

A PBX (private branch exchange) is a telephone system within an enterprise that switches calls between enterprise users on local lines while allowing all users to share a certain number of external phone lines. The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office. The PBX is owned and operated by the enterprise rather than the telephone company (which may be a supplier or service provider, however). Private branch exchanges used analogue technology originally. Today, PBXs use digital technology (digital signals are converted to analogue for outside calls on the local loop using plain old telephone service. A PBX includes:

• Telephone trunk (multiple phone) lines that terminate at the PBX
• A computer with memory that manages the switching of the calls within the PBX and in and out of it
• The network of lines within the PBX
• Usually a console or switchboard for a human operator

In some situations, alternatives to a PBX include a centrex service, in which a pool of lines are rented at the phone company's central office.

A Private Branch eXchange Mobile (PBXM) is a mobile Private Branch eXchange Mobile

Power over Ethernet or PoE technology describes a system to transmit electrical power, along with data, to remote devices over standard twisted-pair cable in an Ethernet network.

The PSTN (public switched telephone network) is the world's collection of interconnected voice-oriented public telephone networks, both commercial and government-owned. Also referred to as the Plain Old Telephone Service (POTS), it is the aggregation of circuit-switching telephone networks that has evolved from the days of Alexander Graham Bell. Today, it is almost entirely digital in technology except for the final link from the central (local) telephone office to the user. In relation to the Internet, the PSTN actually furnishes much of the Internet's long-distance infrastructure. Because Internet service providers (ISP’s) pay the long-distance providers for access to their infrastructure and share the circuits among many users through packet switching, Internet users avoid having to pay usage tolls to anyone other than their ISPs.

Q.SIG is an ISDN-based protocol developed for networking different enterprise switching systems together and providing additional supplementary services for feature transparency. Q.SIG has its origins in standards defined originally by the European Computer Manufacturing Association (ECMA) dating back to the mid-1980s. Q.SIG was valuable at a network site when an enterprise finds itself with PBX systems from differing vendors, but have a need for more efficient communications between the sites than what public calls or analogue tie lines can offer. Q.SIG can also be useful as a means of connecting different functional units (e.g., PBX and finical turret) to save expenses by sharing public network interfaces. Q-Sig in today being steadily replaced by SIP protocol based solutions.

The routing and translation tables are software components of the PMX that provide intelligent routing of calls to and from phones on the private mobile network to the other networks or other phones on the local GSM network. The translation tables provide intelligent number translation features such as the automatic addition or subtraction of leading digits to ensure that calls are then routed the correct destination.

A Subscriber Identity Module is a smart card roughly the size of a postage stamp that securely stores the key identifying a mobile phone service subscriber, as well as subscription information, saved telephone numbers, preferences, text messages and other information.

A text-based signalling protocol, similar to HTTP and SMTP, for initiating interactive communication sessions between users. Such sessions include voice, video, chat, interactive games, and virtual reality. Also sometimes called: Session Initiated Protocol. SIP is becoming the defacto standard for enterprise communications and offers the promise of supporting a wide range of services beyond basic telephony.

Short Message Service (SMS) is a service available on most digital mobile phones (and other mobile devices, e.g. a Pocket PC, or occasionally even desktop computers) that permits the sending of short messages (also known as text messages, or more colloquially SMSes, texts or even txts) between mobile phones, other handheld devices and even landline telephones.

A Short Message Service Controller (SMSC) is a network element in the GSM telephony network which delivers SMS messages. When a text message (SMS message) is sent from one user to another user, the phone actually sends the message to the SMSC. The SMSC stores the message and then delivers it to the destination user when they are available. This is a store and forward operation. The SMSC has a configurable time limit for how long it will store the message before removing it from the store.

Time-division multiplexing (TDM) is a type of digital or (rarely) analog multiplexing in which two or more signals or bit streams are transferred apparently simultaneously as sub-channels in one communication channel, but physically are taking turns on the channel. The time domain is divided into several recurrent timeslots of fixed length, one for each sub-channel. A sample, byte or data block of sub-channel 1 is transmitted during timeslot 1, sub-channel 2 during timeslot 2, etc. One TDM frame consists of one timeslot per sub-channel. After the last sub-channel it starts all over again with a new frame, starting with the second sample, byte or data block from sub-channel 1, etc.

Voice over Internet Protocol, also called VoIP, IP Telephony, Internet telephony, Broadband telephony, Broadband Phone and Voice over Broadband is the routing of voice conversations over the Internet or through any other IP-based network.

Protocols which are used to carry voice signals over the IP network are commonly referred to as Voice over IP or VoIP protocols. They may be viewed as commercial realizations of the experimental Network Voice Protocol (1973) invented for the ARPANET.ce providers. Some cost savings are due to utilizing a single network to carry voice and data, especially where users have existing underutilized network capacity they can use for VoIP at no additional cost. VoIP to VoIP phone calls on any provider are typically free, whilst VoIP to PSTN calls generally costs the VoIP user.

There are two types of PSTN to VoIP services: DID (Direct Inward Dialing) and access numbers. DID will connect the caller directly to the VoIP user while access numbers require the caller to input the extension number of the VoIP user. Access numbers are usually charged as a local call to the caller and free to the VoIP user(citation/example needed) while DID usually has a monthly fee. There are also DID that are free to the VoIP user but is chargeable to the caller.