Phone Call Recorder

General Packet Radio Service

General Packet Radio Service (GPRS) is a mobile data service available to users of GSM mobile phones. It 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 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. First it was standardised by ETSI but now that effort has been handed onto the 3GPP. GPRS is different from the older Circuit Switched Data (or CSD) connection included in GSM standards releases before Release 97 (from 1997, the year the standard was feature frozen). In CSD, a data connection establishes a circuit, and reserves the full bandwidth of that circuit during the lifetime of the connection. GPRS is packet-switched which means that multiple users share the same transmission channel, only transmitting when they have data to send. This means that the total available bandwidth can be immediately dedicated to those users who are actually sending at any given moment, providing higher utilisation where users only send or receive data intermittently. Web browsing, receiving e-mails as they arrive and instant messaging are examples of uses that require intermittent data transfers, which benefit from sharing the available bandwidth. Usually, GPRS data are billed per kilobytes of information transceived while circuit-switched data connections are billed per second. The latter is to reflect the fact that even during times when no data are being transferred, the bandwidth is unavailable to other potential users. GPRS originally supported (in theory) IP, PPP and X.25 connections. The latter has been typically used for applications like wireless payment terminals although it has been removed as a requirement from the standard. X.25 can still be supported over PPP, or even over IP, but doing this requires either a router to do encapsulation or intelligence built into the end terminal. Packet-switched data under GPRS is achieved by allocating unused cell bandwidth to transmit data. As dedicated voice (or data) channels are setup by phones, the bandwidth available for packet switched data shrinks. A consequence of this is that packet switched data has a poor bit rate in busy cells. The theoretical limit for packet switched data is approx. 160.0 kbit/s (using 8 time slots and CS-4). A realistic bit rate is 30-80 kbit/s, because it is possible to use max 4 time slots for downlink. A change to the radio part of GPRS called EDGE (sometimes called EGPRS or Enhanced GPRS) allows higher bit rates of between 160 and 236.8 kbit/s. The maximum data rates are achieved only by allocation of more than one time slot in the TDMA frame. Also, the higher the data rate, the lower the error correction capability. Generally, the connection speed drops logarithmically with distance from the base station. This is not an issue in heavily populated areas with high cell density, but may become an issue in sparsely populated/rural areas. Class A - Can be connected to GPRS service and GSM service (voice, SMS), using both at the same time. No such devices are known to be available today. Class B - Can be connected to GPRS service and GSM service (voice, SMS), but using only one or the other at a given time. During GSM service (voice call or SMS), GPRS service is suspended, and then resumed automatically after the GSM service (voice call or SMS) has concluded. Most GPRS mobile devices are Class B. Class C - Are connected to either GPRS service or GSM service (voice, SMS). Must be switched manually between one or the other service. Transfer speed depends also on the channel encoding used. The least robust (but fastest) encoding scheme (CS-4) is available near the Base Transceiver Station (BTS) while the most robust encoding scheme (CS-1) is used when the Mobile Station (MS) is further away from the BTS. Using the CS-4 it is possible to achieve a user speed of 20.0 kbit/s per time slot. However, using this scheme the cell coverage is 25% of normal. CS-1 can achieve a user speed of only 8.0 kbit/s per time slot, but has 98% of normal coverage. Newer network equipment can adapt the transfer speed automatically depending on the mobile location. Like CSD, HSCSD establishes a circuit and is usually billed per minute. For an application such as downloading, HSCSD may be preferred, since circuit-switched data are usually given priority over packet-switched data on a mobile network, and there are relatively few seconds when no data are being transferred. GPRS is packet based. When TCP/IP is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone during cell handover (when you move from one cell to another). A radio noise induced pause can be interpreted by TCP as packet loss, and cause a temporary throttling in transmission speed. Telephone operators have priced GPRS relatively cheaply (compared to older GSM data transfer, CSD and HSCSD) in many areas, such as Finland. Most mobile phone operators don't offer flat rate access to the Internet (with the notable exceptions of T-Mobile in both United States and Europe, and Cingular in the United States), instead basing their tariffs on data transferred, usually rounded off per 100 kilobyte. Typical rates vary wildly, ranging from EUR _1 per megabyte to over _20 per megabyte. In the U.S., T-Mobile offers US$30 per month unlimited GPRS. In India, BPL Mobile (Bombay) offers unlimited GPRS for Rs.500 (USD 11) per month. AirTel offers nation-wide unlimited GPRS and EDGE for Rs. 600 (USD 13.5). In Pakistan, Mobilink is also offering unlimited GPRS service on its post paid connections for Rs 500 (US$ 8.33). Orange (UK) offers a 1 Gigabyte package for _128 a month, and a ?1 per day unlimited use package for pre-paid users. In Poland, Era GSM offers a 2 Gigabyte package of GPRS and UMTS transmission under Blueconnect brand for _30 a month and Plus GSM offerts a 1 Gigabyte package for _15 a month. GPRS Data on pre-paid packages is usually expensive, and limited to WAP and MMS. Full internet access, allowing Web browsing, access to POP/IMAP mail, FTP and other mainstream Web applications is usually restricted to contract packages, and are made available at lower cost. The maximum speed of a GPRS connection (as offered in 2003) is the same as modem connection in an analog wire telephone network, about 4-5 kB/s (depending on the phone used). Latency is very high; a round-trip ping being typically about 600-700 ms and often reaching one second round trip time. GPRS is typically prioritised lower than speech, and thus the quality of connection varies greatly. In order to set up a GPRS connection, a user needs to specify Access Point Name (APN), user name and password, and very often an IP address, all provided by the network operator.

List of telephony terms:

3gpp - a-law - abbreviated dialing - adsl - ani - answering machine - apn - automatic ring back - b-channel - baud - bell 202 modem - bit rate - bonding - bri - busy signal - cable modem - call-progress tones - call accounting - call capture - call forwarding - call originator - call park - call pick-up - call transfer - call waiting - call waiting deluxe - called party - caller id - caller id spoofing - calling party - carrier wave - cbr - ccitt - cdma - cdma2000 - cellular repeater - celp - channel - clec - clock rate - codec - collect call - conference - conference call - crc - csd - d-channel - data compression - device driver - dial-up - dial - dial tone - direct-inward-dialing - direct distance dialing - distinctive ring - dnis - dsl - dsp - dtmf - dtr - duplex - echo cancellation - edge - extension - fax - fcc - fdma - fidonet - follow-me - g.711 - g.723.1 - g.723 - g.726 - g.lite - gprs - gps - gsm - h.323 - harmonic - headphones - hscsd - hspda - iad - idsn - internet call waiting - isp - ivr - jack plug - local loop - long distance - microcontroller - mobile phone - modem - modulation - mu-law - music-on-hold - night service - off-hook - on-hook - pabx - pager - payphone - pbx - pcm - pots - prank call - precise tone plan - pstn - pulse dialling - push to talk - ring modulation - ring tone - ringback - ringing signal - rj11 - roaming - serial communications - serial port - signal noise - sim - simplex - sit - sms - softmodem - switchboard operator - tapi - tdma - telecommunications - telemarketing - telephone - telephone call - telephone card - telephone company - telephone exchange - telephone line - telephone number - telephone numbering plan - telephone operator - telephone switchboard - telephony - tts - twisted pair - umts - v.32 - v.32bis - v.34 - v.42bis - vbr - vertical service code - voicemail - voip - vox - wap - wav - wi-fi - wimax - wire