General Packet Radio Service

General Packet Radio Services (GPRS) is a mobile data service available to users of GSM and IS-136 mobile phones. GPRS data transfer is typically charged per megabyte of transferred data, while data communication via traditional circuit switching is billed per minute of connection time, independently of if the user actually has transferred data or been in an idle state. GPRS can be utilized for services such as WAP access, SMS and MMS, but also for Internet communication services such as email and web access. In the future, it is expected that low cost voice over IP will be made available in cell-phones.

2G cellular systems combined with GPRS is often described as "2.5G", that is, a technology between the second (2G) and third (3G) generations of mobile telephony. It provides moderate speed data transfer, by using unused TDMA channels in for example the GSM system. 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. First it was standardized by ETSI but now that effort has been handed onto the 3GPP.

Modem

A modem (from modulate and demodulate) is a device that modulates an analogue carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, from driven diodes to radio. Experiments have even been performed in the use of modems over the medium of two cans connected by a string.^{[citation needed]}

The most familiar example is a voiceband modem that turns the digital '1s and 0s' of a personal computer into sounds that can be transmitted over the telephone lines of Plain Old Telephone Systems (POTS), and once received on the other side, converts those sounds back into 1s and 0s. Modems are generally classified by the amount of data they can send in a given time, normally measured in bits per second, or "bps".

Far faster modems are used by Internet users every day, notably cable modems and ADSL modems. In telecommunications, "radio modems" transmit repeating frames of data at very high data rates over microwave radio links. Some microwave modems transmit more than a hundred million bits per second. Optical modems transmit data over optic fibers. Most intercontinental data links now use optic modems transmitting over undersea optical fibers. Optical modems routinely have data rates in excess of a billion (1x10⁹) bits per second.

Integrated Services Digital Network

Integrated Services Digital Network (ISDN) is a circuit-switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds than available with analog systems. More broadly, ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user.

In a videoconference, ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group (room) videoconferencing systems

Ethernet physical layer

The Ethernet physical layer evolved over a considerable time span and encompasses quite a few physical media interfaces and several magnitudes of speed. The speed ranges from 3 Mbit/s to 10 Gbit/s in speed while the physical medium ranges from bulky coaxial cable to twisted pair to optical fiber. In general, network protocol stack software will work identically on most of the following types.

The following sections provide a brief summary of all the official Ethernet media types (section numbers from the IEEE 802.3-2002 standard are parenthesized). In addition to these official standards, many vendors have implemented proprietary media types for various reasons—often to support longer distances over fiber optic cabling.

Many Ethernet adapters and switch ports support multiple speeds, using auto-negotiation to set the speed and duplex for the best values supported by both connected devices. If auto-negotiation fails, a multiple speed device will sense the speed used by its partner, but will assume half-duplex. A 10/100 Ethernet port supports 10BASE-T and 100BASE-TX. A 10/100/1000 Ethernet port supports 10BASE-T, 100BASE-TX, and 1000BASE-T.

GSM (disambiguation)

GSM may stand for:

• Groupe Spécial Mobile the European group set up to establish European mobile telephony protocols and which was later Anglicised to Global System for Mobiles to preserve the acronym.
• Global System for Mobile Communications the Anglicisation of Groupe Spécial Mobile above.
• Graphic Standards Manual.
• Gameshow Marathon, a 2006 series hosted by Ricki Lake.
• The ICAO code for low cost airline Flyglobespan.
• General Service Medal
• A wine blend consisting of approximately equal parts grenache, shiraz, and mourvedre.

GSM may stand for:

• Grams per square metre (an indication of the thickness of paper).
• Generalized sequential machine in automata theory.

Internet protocol suite

The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet and most commercial networks run. It is sometimes called the TCP/IP protocol suite, after the two most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were also the first two defined.

The Internet protocol suite — like many protocol suites — can be viewed as a set of layers, each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted. The original TCP/IP reference model consisted of four layers, but has evolved into a five layer model.

The OSI model describes a fixed, seven layer stack for networking protocols. Comparisons between the OSI model and TCP/IP can give further insight into the significance of the components of the IP suite, but can also cause confusion, since the definition of the layers are slightly different.

Internet protocol suite
Layer	Protocols
5. Application	DNS, TLS/SSL, TFTP, FTP, HTTP, IMAP4, IRC, POP3, SIP, SMTP, SNMP, SSH, TELNET, RTP, …
4. Transport	TCP, UDP, RSVP, DCCP, SCTP, …
3. Network	IP (IPv4, IPv6), ICMP, IGMP, ARP, RARP, …
2. Data link	Ethernet, Wi-Fi, PPP, FDDI, ATM, Frame Relay, GPRS, Bluetooth, …
1. Physical	Modems, ISDN, SONET/SDH, RS232, USB, Ethernet physical layer, Wi-Fi, GSM, Bluetooth, …

Physical Layer

Bluetooth
Bluetooth is an industrial specification for wireless personal area networks (PANs), also known as IEEE 802.15.1. Bluetooth provides a way to connect and exchange information between devices such as personal digital assistants (PDAs), mobile phones, laptops, PCs, printers, digital cameras and video game consoles via a secure, globally unlicensed short-range radio frequency.

Introduction
Bluetooth applications
Wireless control of and communication between a cell phone and a hands free headset or car kit. This is the most popular use.
Wireless networking between PCs in a confined space and where little bandwidth is required.
Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
Transfer of files between devices via OBEX.
Transfer of contact details, calendar appointments, and reminders between devices via OBEX.
Replacement of traditional wired serial communications in test equipment, GPS receivers and medical equipment.

The next version of Bluetooth technology, currently code-named Lisbon, includes a number of features to increase security, usability and value of Bluetooth. The following features are defined:

• Atomic Encryption Change - allows encrypted links to change their encryption keys periodically, increasing security, and also allowing role switches on an encrypted link.

• Extended Inquiry Response - provides more information during the inquiry procedure to allow better filtering of devices before connection. This information includes the name of the device, and a list of services, with other information.

• Sniff Subrating - reducing the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mice and keyboards increasing the battery life from 3 to 10 times those currently used.

• QoS Improvements - these will enable audio and video data to be transmitted at a higher quality, especially when best effort traffic is being transmitted in the same piconet.

• Simple Pairing - this improvement will radically improve the pairing experience for Bluetooth devices, while at the same time increasing the use and strength of security. It is expected that this feature will significantly increase the use of Bluetooth.